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Rheumatoid arthritis (RA) is a persistent autoimmune disorder predominantly affecting the joint structures, eliciting inflammatory responses, and ultimately leading to degenerative changes without proper medical intervention. Ultimately, this can severely impair joint function and impact the patient's quality of life. Current treatment approaches include disease-modifying anti-rheumatic drugs, non-steroidal anti-inflammatory drug, corticosteroids, and biologic therapies for RA management. The current study contributes to the ongoing advancements in RA treatment. d-Limonene is a monocyclic monoterpene. It is present in essential oils of various aromatic plants, such as Lippia alba and Artemisia dracunculus, and in citrus fruits such as lemon and orange. It has reported anti-inflammatory and anti-nociceptive properties and was selected for the current study as a potential anti-arthritic candidate. It was administered at three dosages (25, 50, 100 mg/kg, b.w., p.o) in Complete Freund's adjuvant-induced arthritic rats over 28 days. The efficacy of the compound was compared to piroxicam, a widely used standard drug for treating RA. The anti-arthritic activity of the compound was assessed by measuring arthritic scoring and plethysmometry at both baseline and post-intervention stages. Additional confirmation of the investigation was sought by performing biochemical and hematological activities. Moreover, quantitative polymerase chain reaction was employed to determine the levels of messenger RNA expression for transcription factors such as tumor necrosis factor-α, interleukin (IL)-1β, nuclear factor-κB, matrix metalloproteinase-3, IL-6, and IL-4 in the blood. The levels of PGE2 were evaluated by enzyme-linked immunosorbent assay. The histopathological and radiographic studies were also carried out for further confirmation. The results of these findings supported our assertion regarding the anti-arthritic potential of the compound., (© 2024 Deutsche Pharmazeutische Gesellschaft.)

The excessive use of conventional medications to treat coccidiosis has led to concerns regarding drug residues in tissues and the emergence of multidrug resistance. Essential oils with anti-inflammatory and antioxidant activities may also have anticoccidial effects. The present study investigated the efficacy of D-limonene and its nanoemulsion form against Eimeria tenella in chickens. An in vitro study was conducted to evaluate the sporulation inhibitory effects of D-limonene on Eimeria tenella oocysts. Five D-limonene concentrations (0.625, 1.25, 2.5, 5, and 10% v/v) were tested alongside positive (10% formalin) and negative (2.5% potassium dichromate) controls. Each ELISA plate well was inoculated with 1200 unsporulated oocysts and incubated at 30 °C for 24, 48, and 72 h. Subsequently, samples were microscopically examined to assess sporulation inhibition and calculate the percentage of sporulated oocysts. For the in vivo study, 125 eight-day-old broiler chicks were divided into five groups of 25 birds each. The control negative group remained uninfected and untreated. The control positive group was challenged with 5 × 10 4 sporulated Eimeria tenella oocysts. The diclazuril group received 0.2 mg/kg diclazuril in their diet two days prior to, and until 10 days post infection. The D-limonene (DL) and D-limonene nanoemulsion (DLN) groups were challenged with 5 × 10 4 sporulated E. tenella oocysts at 18 days of age and administered 150 mg/L of their respective treatments in drinking water from day eight until the end of the experiment. Results from the in vitro study demonstrated that D-limonene suppressed oocyst sporulation by 50.83% at its highest concentration of 10%. In the in vivo study, both DL and DLN treated groups exhibited a significant reduction in oocyst output per gram of feces (OPG), along with increased body weight and decreased parasite stages in the cecal tissue. Furthermore, these treatments were associated with elevated levels of antioxidant enzymes such as glutathione peroxidase (GPX), catalase (CAT), and superoxide dismutase (SOD), accompanied by a decrease in malondialdehyde (MDA) and nitric oxide (NO) levels. Particularly, DLN treatment remarkably increased the number of goblet cells. In conclusion, D-limonene and its nanoemulsion represent promising alternatives for managing coccidiosis in poultry. They not only effectively control parasites but also promote intestinal health and boost antioxidant defenses., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

D-limonene extracted from citrus peels possesses an inhibitory effect on methanogenic archaea. This study is aimed to bridge the research gap on the influence of D-limonene on volatile fatty acids (VFA) production from waste activated sludge (WAS) and to address the low VFA yield in standalone anaerobic fermentation of WAS. When the initial pH was not controlled, 1.00 g/g TSS D-limonene resulted in a VFA accumulation of 1175.45 ± 101.36 mg/L (174.45 ± 8.13 mgCOD/gVS). When the initial pH was controlled at 10 and the D-limonene concentration was 0.50 g/g TSS, the VFA accumulation reached 2707.44 ± 183.65 mg/L (445.51 ± 17.10 mgCOD/gVS). The pH-regulated D-limonene treatment enhanced solubilization and acidification, slightly inhibited hydrolysis, and significantly suppressed methanogenesis. D-limonene under alkaline conditions can increase the relative abundance of Clostridium_sensu_stricto, significantly enhancing acidification. Moreover, it markedly inhibited methanogenesis by particularly reducing the relative abundance of Methanothrix that was responsible for acetate consumption, thus favoring the accumulation of VFA. The research reveals the potential mechanism of pH regulation and D-limonene on anaerobic fermentation acid production, providing a theoretical basis for improving the acid production performance of the anaerobic fermentation of WAS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Bioaccumulation of d-Limonene in environment due to the aggrandised usage of their natural sources like citrus food wastes and industrial day to day life products has raised concern to their biotoxicity to environment biotic health. Moreover, their after-usage discharge to aquatic system has enhanced the distress of posing threat and needs attention. This study entails mechanistic and molecular evaluation of in-vivo biotoxicity of d-Limonene in zebrafish embryo models. Experimental analysis excavated the controlled concentration-dependent morphological, physiological and cellular in-vivo impact of d-Limonene in zebrafish embryos through significant changes in oxidative stress, steatosis and apoptosis regulated via 6-fold and 5-fold mRNA expression change in p53 and Sod1 genes. Computational evaluation deduced the cellular mechanism of d-limonene biotoxicity as irregularities in oxidative stress, apoptosis and steatosis due of their intrinsic interaction with metabolic proteins like Zhe1a (-4.8 Kcal/mol), Sod1(-5.3 Kcal/mol), p53, caspase3 and apoa1 leading to influential change in structural and functional integrity of the metabolic proteins. The study unravelled the measured in-vivo biotoxicity of d-Limonene at cellular and molecular level to advocate the controlled usage of d-Limonene related natural and industrial product for a sustainable environmental health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

D-limonene is a widely used flavouring additive in foods, beverages and fragrances due to its pleasant lemon-like odour. This study aimed to investigate the effects of D-limonene on the central nervous system when subjected to chronic restraint stress in rats for 21 days. Forty rats were randomly divided into five groups: i) control, ii) D-limonene, iii) restraint stress, iv) restraint stress+D-limonene and v) restraint stress+fluoxetine. Following the induction of restraint stress, the sucrose preference test, the open field test, the novel object recognition test and the forced swimming test were performed. The levels of BDNF, IL-1β, IL-6 and caspase-1 were measured from hippocampal tissue using the ELISA method. Sucrose preference test results showed an increase in consumption rate in the stress+D-limonene and a decrease in the stress group. The stress+D-limonene group reversed the increased defensive behaviour observed in the open-field test compared to the stress group. In the novel object recognition test, the discrimination index of the stress+D-limonene group increased compared to the stress group. BDNF levels increased in the stress+limonene group compared to the stress group. In contrast, IL-1β and caspase-1 levels increased in the stress group compared to the control and decreased in the stress+limonene group compared to the stress group. In this study, D-limonene has been found to have antidepressant-like properties, reducing anhedonic and defensive behaviours and the impairing effects of stress on learning and memory tests. It was observed that D-limonene showed these effects by alleviating neuroinflammation induced by chronic restraint stress in rats., (© 2024 The Author(s). European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

The Pichia kluyveri , a proliferation commonly found in Sichuan pickles (SCPs), can accelerate the growth and reproduction of spoilage bacteria, causing off-odor development and decay. Although D-limonene, a common natural preservative, effectively restricts P. kluyveri , its inhibitory mechanism remains unclear. This study aimed to elucidate this molecular mechanism by investigating the impact on basic P. kluyveri metabolism. The findings revealed that D-limonene inhibited P. kluyveri growth and disrupted the transcription of the genes responsible for encoding the enzymes involved in cell wall and membrane synthesis, oxidative phosphorylation, glycolysis, and the tricarboxylic acid (TCA) cycle pathway. The results indicated that these events disrupted crucial metabolism such as cell wall and membrane integrity, adenosine triphosphate (ATP) synthesis, and reactive oxygen species (ROS) balance. These insights provided a comprehensive understanding of the inhibitory effect of D-limonene on the growth and reproduction of P. kluyveri while highlighting its potential application in the SCP industry.

Long-term exposure to arsenic can lead to testicular damage and lower sperm quality in males, which is mediated by increased arsenic-induced oxidative stress and other damage mechanisms. D-Limonene, which is rich in oranges, lemons, oranges, grapes and other natural fruits, can relieve doxorubicin (DOX)-induced kidney injury and CCL 4 -induced cardiac toxicity by inhibiting oxidative stress and inflammatory response. The antioxidant and anti-inflammatory properties of D-limonene motivate us to further explore whether it can reduce arsenic-induced testicular injury. To verify this scientific hypothesis, testicular pathology, testicular oxidative stress levels and sperm motility were determined after intervention with D-limonene in rats chronically exposed to arsenic. As expected, long-term arsenic exposure caused testicular tissue structure disturbances, increased levels of oxidative stress, and decreased sperm activation, all of which were significantly inhibited due to treatment with D-limonene. In conclusion, our data reveal a previously unproven beneficial effect of D-limonene, namely that D-limonene can inhibit arsenic-induced testicular injury, and also provide theoretical and experimental basis for the application of D-limonene in the treatment of arsenic-induced testicular injury., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Cancer is a fatal disease that severely affects humans. Designing new anticancer strategies and understanding the mechanism of action of anticancer agents is imperative., Hypothesis/purpose: In this study, we evaluated the utility of metformin and D-limonene, alone or in combination, as potential anticancer therapeutics using the human liver and breast cancer cell lines HepG2 and MCF-7., Study Design: An integrated systems pharmacology approach is presented for illustrating the molecular interactions between metformin and D-limonene., Methods: We applied a systems-based analysis to introduce a drug-target-pathway network that clarifies different mechanisms of treatment. The combination treatment of metformin and D-limonene induced apoptosis in both cell lines compared with single drug treatments, as indicated by flow cytometric and gene expression analysis., Results: The mRNA expression of Bax and P53 genes were significantly upregulated while Bcl-2, iNOS, and Cox-2 were significantly downregulated in all treatment groups compared with normal cells. The percentages of late apoptotic HepG2 and MCF-7 cells were higher in all treatment groups, particularly in the combination treatment group. Calculations for the combination index (CI) revealed a synergistic effect between both drugs for HepG2 cells (CI = 0.14) and MCF-7 cells (CI = 0.22)., Conclusion: Our data show that metformin, D-limonene, and their combinations exerted significant antitumor effects on the cancer cell lines by inducing apoptosis and modulating the expression of apoptotic genes., (© 2024. The Author(s).)

Purpose: Ticks infestation has a negative impact against human and animal health through blood sucking, transmission of blood-borne diseases and also caused economic losses., Methods: In the present study the adulticidal, ovicidal and larvicidal activity of D-limonene nanoemulsion (DLN) were evaluated against two tick species; Rhipicephalus annulatus and Rhipicephalus sanguineus. Nanoemulsion form of D-limonene was prepared, and its characteristics were evaluated using a UV spectrophotometer and zeta droplet size measurement. Acetylcholinesterase activity was determined., Results: The results revealed significant adulticidal effect with low LC50 and LC90 for D-limonene pure form (DL) against both adult tick spp. (R. annulatus and R. sanguineus) ((0.958 and 1.559%) and (2.26 and 3.51%), respectively). DLN LC50 and LC90 values were ((1.277 and 2.396) and (3.97 and 7.28), respectively) against R. annulatus and R. sanguineus, respectively. DL and DLN showed significant ovicidal effect against R. sanguineus at high concentrations (10 and 5%). In larval packet test, LC50 and LC90 values of DL were ((1.53 and 2.22%) and (6.81 and 12.07%), respectively) against R. annulatus and R. sanguineus, respectively, while LC50 and LC90 values of DLN were ((6.48 and 11.26%) and (7.82 and 13.59%), respectively) against R. annulatus and R. sanguineus, respectively. Significant acetylcholinesterase inhibition percentage was detected for both ticks spp. which treated by DL and DLN., Conclusion: Pure DL is more effective than DLN form against R. annulatus and R. sanguineus., (© 2023. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

Oxidative status is important in reproductive performance and using two natural antioxidants is more beneficial than one in nulliparous rabbits. The goal, effect of vitamin E (VitE), D-limonene (DL), and VitE+DL on maternal LBW (MLBW), conception (CR), pregnancy (PR), and kindling rates (KR), gestation length (GL), total litter size at birth (TLSB) and weaning (TLSW), live kits at birth (LKB) and weaning (LKW), dead kits at birth (DKB) and weaning (DKW), kits mortality rate at weaning (KMRW), Kit weight at birth (KWB) and weaning (KWW), total kit weight at birth (TKWB) and weaning (TKWW), and concentrations of progesterone (P4) and Malondialdehyde (MDA), during first two pregnancies. A total of 24 healthy female WNZ rabbits were randomly selected and assigned into four groups (6/each). Control (animals injected with 1.0 mL propylene glycol), VitE (60 mg IM injection/animal, 2X/week pre-mating and 3X post-mating until mid-pregnancy, DL (20 mg IM injection/animal, 2X/week pre-mating and 1X at mating, and VitE+DL (IM injection/animal with the same doses and times applied in VitE and DL groups. All animals were treated during 1st pregnancy only. The results confirmed that animals treated with VitE+DL gained significant maternal LBW in 1st pregnancy, reduced dead kit number at birth and kit mortality rate at weaning, increased live kits and total kit weight at birth and weaning in the two pregnancies, and also increased significantly kit weight at birth and weaning in the treatments than controls in the two pregnancies, and DL was greater in 1st pregnancy. Progesterone concentrations in mid-pregnancy rose significantly in VitE+DL during 1st pregnancy and DL in 2nd pregnancy. Malondialdehyde concentrations dropped significantly in VitE and VitE+DL in mid-pregnancy in the two pregnancies. Eventually, the integration of VitE and DL displayed their unique properties for improving productive and reproductive performance in nulliparous rabbits., Competing Interests: Declaration of Competing Interest On behalf of my colleagues, I declare that no one has any interest or relationships with individuals or organizations that affect in our work., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this work, seven Citrus aurantium essential oils (EOs) derived from flavedo of cultivars 'Canaliculata', 'Consolei', 'Crispifolia', 'Fasciata', 'Foetifera', 'Listata', and 'Bizzaria' were investigated. EOs were also combined in 1:1 ( v / v ) ratio to identify possible synergism or antagonism of actions. GC-MS analysis was done to investigate Eos' phytochemical profiles. The antioxidant activity was studied by using a multi-target approach based on FRAP, DPPH, ABTS, and β-carotene bleaching tests. A great difference was observed in EOs' phytochemical profiles. d-limonene (33.35-89.17%) was the main monoterpene hydrocarbon, and α-Pinene, β-myrcene, and β-linalool were identified in almost all samples. Among EOs, only C3 showed high quantitative and qualitative variability in its chemical composition. The chemical diversity of EOs was also demonstrated by PCA and HCA statistical analysis. Samples C2, C4, C5, C6, and C7 were statistically similar to each other, while C1 and C3 were characterized as having a different amount of other compounds and oxygenated monoterpenes, respectively, with respect to the other EOs mentioned. The global antioxidant score (GAS) revealed that among the tested EOs, C. aurantium 'Fasciata' EO had the highest antioxidant potential, with a GAS value of -0.47, whereas among combinations, the EO obtained by mixing 'Canaliculata' + 'Bizzaria' was the most active. Comparison by theoretical and real data on inhibitory concentration (IC 50 ) and FRAP values did not reveal any significant effect of synergism or antagonism of actions to be valid in all biological applied tests. These findings, considered together, represent an important starting point to understand which compounds are responsible for the activities and their future possible industrial application.

Background: Besides being a potential component of (some species of) colophonium, D-limonene is also used as a tackifier in the production of adhesives. Hydroperoxides of limonene are well-known skin sensitizers., Objectives: To show that D-limonene may be present in colophonium-containing but also colophonium-free ("hypoallergenic") adhesives, and that patients suffering from allergic contact dermatitis (ACD) from both types of adhesives might display positive patch test reactions to limonene hydroperoxides in this regard., Methods: Five patients with suspected ACD from adhesives were patch tested to the baseline series (containing limonene hydroperoxides 0.3 and 0.2% pet.), additional series and, if available, to the culprit adhesives. The adhesives labelled as containing colophonium (n = 3) or free from it (n = 2) were analysed with gas chromatography - mass spectrometry (GC-MS) for the presence of D-limonene., Results: All five patients sensitised to adhesives had (strong) positive patch test reactions to limonene hydroperoxides. The presence of D-limonene, and/or related components, could be demonstrated in all three colophonium-containing and, surprisingly, also in two colophonium-free ("hypoallergenic") tapes., Conclusions: D-limonene may be present in both regular and "hypoallergenic" adhesives, with limonene hydroperoxides potentially contributing to ACD from such medical devices. The use of fragrance chemicals in adhesives deserves further research., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Recently, Pickering emulsions have been considered as an efficient method to maintain and protect the functional properties of essential oils against the harsh conditions. In this research, the encapsulation of d-limonene, as an aromatic component with several distinct properties, was conducted through optimizing the production of Pickering emulsions stabilized by chitosan nanoparticles (CSNPs) and using the response surface methodology; independent variables were different concentrations of CSNPs (0.43, 0.25, and 0.07% w/v) and ratio of d-limonene to Pickering emulsions (5, 15, and 25%). The stability of the emulsions increased at higher contents of the CSNPs. By increasing the concentration of CSNPs and ratio of d-limonene to Pickering emulsion, viscosity of Pickering emulsions was considerably increased. Considering the chemical interactions, thermal behaviors, and crystallinity of samples, CSNPs can be used as an appropriate stabilizer for d-limonene-loaded emulsions and a food grade delivery carrier for the bioactive compounds., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: D-limonene and its derivatives have demonstrated potential chemopreventive and anticancer activity in preclinical and clinical studies. The aim of this scoping review was to assess and critically appraise current literature on the effect of these bioactive citrus peel compounds on breast cancer in human trials and to identify knowledge gaps for exploration in future studies., Methods: This study followed a scoping review framework. Peer-reviewed journal articles were included if they reported the effect of d-limonene or its derivatives on breast cancer in human subjects. Articles were retrieved from academic databases - PubMed, EMBASE, CINAHL, Web of Science, and Cochrane reviews - and iteratively through review of bibliographies of relevant manuscripts. Titles and abstracts were appraised against the aforementioned inclusion criteria in a first round of screening. Through consensus meetings and full article review by authors, a final set of studies were selected. Results were reported according to the PRISMA extension for scoping reviews., Results: Our search strategy yielded 367 records. Following screening and adjudication, five articles reporting on phase 1(n = 2), phase 2 (n = 2) and both trial phases (n = 1) were included as the final dataset for this review. Trials evaluating the effect of d-limonene (n = 2) showed it was well tolerated in subjects. One study (n = 43 participants) showed d-limonene concentrated in breast tissue (mean 41.3 μg/g tissue) and reduction in tumor cyclin D1 expression, which is associated with tumor proliferation arrest. This study did not show meaningful change in serum biomarkers associated with breast cancer, except for a statistically significant increase in insulin-like growth factor-1 (IGF-I) levels. While elevation of IGF-I is associated with increased cancer risk, the clinical implication of this study remains uncertain given its short duration. Trials with perillyl alcohol (n = 3) showed low tolerance and no effect on breast cancer., Conclusion: This review demonstrated a dearth of clinical studies exploring the effect of d-limonene and its derivatives on breast cancer. Limited literature suggests d-limonene is safe and tolerable in human subjects compared to its derivative, perillyl alcohol. Our review demonstrates the need for additional well-powered placebo-controlled trials that assess d-limonene's efficacy on breast cancer compared to other therapies., (© 2021. The Author(s).)

Purpose: The main goal of the research was to determine whether commercially available common dietary phytochemical supplements (curcumin, andrographolide, and d-limonene) have radiomodulatory effects on p53-competent human colonic epithelial cells., Methods: Clonogenic survival assays were used to characterize effects of the phytochemicals on cultured colonic epithelial cells (HCT116 p53 +/+ ) in direct irradiation or upon receipt of irradiated-cell conditioned media (for bystander effects). In direct irradiation, feeding regimen experiments included compound administration pre- and post-irradiation, which was used as a basis to define effects as radioprotective and radiomitigative, respectively. In the bystander effect experiments, either donor or recipient cell cultures were fed with the phytochemicals and bystander-induced clonogenic cell death was quantitatively evaluated. Dose challenge was in the range of 0.5 - 5 Gy using the gamma source (Cs-137)., Results: Curcumin, andrographolide, and d-limonene appeared to not exhibit radioprotective and radiomitigative properties in HCT116 p53 +/+ cells. D-limonene was found to induce radiosensitization in post-irradiation administration. All three compounds appeared not to modulate the radiation-induced bystander signal production and response in HCT116 p53 +/+ cells., Conclusions: Curcumin, andrographolide, and d-limonene are known to have many chemoprotective benefits. This work shows that they, however, did not protect colonic epithelial HCT116 p53 +/+ cells from radiation killing. As HCT116 p53 +/+ cells are tumourigenic in nature, this finding implies that these three dietary compounds would not reduce the killing efficacy of radiation in gastrointestinal tumorigenesis. The post-irradiation radiosensitizing effect of d-limonene was an intriguing observation worth further investigation.

The molecular target and mechanism by which d-limonene induces LC3 lipidation and autophagosome formation remain elusive. Here, we report that this monoterpene rapidly enhances Ca 2+ levels in SH-SY5Y cells; yet this effect does not lead to calpain- or caspase-mediated proteolysis of α-spectrin, nor calpain activity is required for the established enhancement of LC3-II levels by d-limonene. However, d-limonene rapidly reduced vimentin levels, an unexpected effect also induced by the autophagy inhibitor chloroquine (CQ). The magnitude of vimentin reduction parallels accumulation of LC3-II caused by a brief incubation with d-limonene or CQ. For longer exposure (48 h), d-limonene does not reduce vimentin, nor it increases LC3-II levels; conversely, a clear reduction of vimentin along with a massive accumulation of LC3-II is evident in cells treated with CQ. Vimentin participates in organelle positioning and in other cellular processes that have linked this intermediate filament protein to various diseases, including cancer, inflammatory and autoimmune disorders, and to virus replication and internalization. Our findings suggest an inverse relationship between vimentin reduction and LC3-II accumulation, whose causal link needs to be examined. Further experiments are needed to dissect the role of vimentin reduction in the mechanisms through which CQ impairs fusion of autophagosome with lysosomes as well as in other effects of this drug., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Epilepsy is a chronic neurological disorder characterized by the recurrence of seizures. One-third of patients with epilepsy may not respond to antiseizure drugs., Purpose: We aimed to examine whether D-limonene, a cyclic monoterpene, exhibited any antiseizure activity in the pentylenetetrazole (PTZ)-induced kindling mouse model and in vitro., Methods: PTZ kindling mouse model was established by administering PTZ (30 mg/kg) intraperitoneally to mice once every 48 h. We performed immunoblot blots, immunohistochemistry (IHC), and high-performance liquid chromatography (HPLC) analysis after the behavioral study., Results: An acute injection of PTZ (60 mg/kg) induced seizure in mice, while pretreatment with D-limonene inhibited PTZ-induced seizure. Repeated administration of PTZ (30 mg/kg) increased the seizure score gradually in mice, which was reduced in D-limonene (10 mg/kg)-pretreated group. In addition, D-limonene treatment increased glutamate decarboxylase-67 (GAD-67) expression in the hippocampus. Axonal sprouting of hippocampal neurons after kindling was inhibited by D-limonene pretreatment. Moreover, D-limonene reduced the expression levels of Neuronal PAS Domain Protein 4 (Npas4)-induced by PTZ. Furthermore, the adenosine A2A antagonist SCH58261 and ZM241385 inhibited anticonvulsant activity and gamma-aminobutyric acid (GABA)ergic neurotransmission-induced by D-limonene., Conclusion: These results suggest that D-limonene exhibits anticonvulsant activity through modulation of adenosine A2A receptors on GABAergic neuronal function.

D-Limonene, a cyclized monoterpene, possesses citrus-like olfactory property and multi-physiological functions, which can be used as a bioactive compound and flavor to improve the overall quality of alcoholic beverages. In our previous study, we established an orthogonal pathway of D-limonene synthesis by introducing neryl diphosphate synthase 1 (tNDPS1) and D-limonene synthase (tLS) in Saccharomyces cerevisiae. To further increase D-limonene formation, the metabolic flux of the mevalonate (MVA) pathway was enhanced by overexpressing the key genes tHMGR1, ERG12, IDI1, and IDI1 WWW , respectively, or co-overexpressing. The results showed that strengthening the MVA pathway significantly improved D-limonene production, while the best strain yielded 62.31 mg/L D-limonene by co-expressing tHMGR1, ERG12, and IDI1 WWW genes in alcoholic beverages. Furthermore, we also studied the effect of enhancing the MVA pathway on the growth and fermentation of engineered yeasts during alcoholic beverage fermentation. Besides, to further resolve the problem of yeast growth inhibition, we separately investigated transporter proteins of the high-yielding D-limonene yeasts and the parental strain under the stress of different D-limonene concentration, suggesting that the transporters of Aus1p, Pdr18p, Pdr5p, Pdr3p, Pdr11p, Pdr15p, Tpo1p, and Ste6p might play a more critical role in alleviating cytotoxicity and improving the tolerance to D-limonene. Finally, we verified the functions of three transporter proteins, finding that the transporter of Aus1p failed to transport D-limonene, and the others (Pdr5p and Pdr15p) could improve the tolerance of yeast to D-limonene. This study provided a valuable platform for other monoterpenes' biosynthesis in yeast during alcoholic beverage fermentation.

Background: Limonene (LIM) and its main metabolite perillyl alcohol (POH) are ingredients found in food with promising chemical entities due to their pharmacological profile. In this study, we hypothesized that LIM and POH are two molecules capable of accelerating the regenerative process and alleviating neuropathic pain., Methods: Animals were treated daily (LIM, POH and saline) for 28 days and during this period evaluated for mechanical hyperalgesia, astrocyte participation by immunofluorescence for GFAP, and ELISA was used to quantify IL-1β and TNF-α in the spinal cord. Western blot analysis of the following proteins was also performed: GFAP, GAP-43, NGF and ERK. For motor deficit analysis, tests were performed to assess hind paw muscle strength and footprints through gait (SFI)., Results: Both POH and LIM accelerated the regenerative process and improved motor deficits comparing to positive control; however, POH was more effective, particularly between the 2nd and 3rd week after the nerve injury, increasing GAP-43, NGF and the phosphorylated ERK immunocontent. Moreover, POH and LIM were able to reduce hyperalgesia and astrocytosis., Conclusions: Both substances, LIM and POH, improved the regeneration process and sensory and motor function recovery in the PNI model in mice by mitigating the inflammatory reactions and up-regulating the neurotrophic process., (Copyright © 2020 Elsevier B.V. All rights reserved.)

d-Limonene, a cyclic monoterpene, possesses citrus-like olfactory property and multi-physiological functions. In this study, the d-limonene synthase (tLS) from Citrus limon was codon-optimized and heterologously expressed in Saccharomyces cerevisiae. The metabolic flux of canonical pathway based on overexpressing endogenous geranyl diphosphate synthase gene (ERG20) and its variant ERG20 F96W-N127W was strengthened for improvement d-limonene production in Chinese Baijiu. To further elevate production, we established an orthogonal pathway by introducing neryl diphosphate synthase 1 (tNDPS1) from Solanum lycopersicum. The results showed that expressing ERG20 and ERG20 F96W-N127W could enhance d-limonene synthesis, while expressing heterologous NPP synthase gene significantly increase d-limonene formation. Furthermore, we constructed a tLS-tNDPS1 fusion protein, and the best strain yielded 9.8 mg/L d-limonene after optimizing the amino acid linker and fusion order, a 40% improvement over the free enzymes during Chinese Baijiu fermentation. Finally, under the optimized fermentation conditions, a maximum d-limonene content of 23.7 mg/L in strain AY12α-L9 was achieved, which was the highest reported production in Chinese Baijiu. In addition, we also investigated that the effect of d-limonene concentration on yeast growth and fermentation. This study provided a meaningful insight into the platform for other valuable monoterpenes biosynthesis in Chinese Baijiu fermentation.

The stress-induced hormone corticosterone initiates oxidative stress and inflammatory responses, culminating in cell apoptosis and neurological changes. We assessed the effects of d-Limonene on a PC12 cellular model of corticosterone-induced neurotoxicity, and whether these effects involved the AMP-activated protein kinase (AMPKα) pathway. PC12 cells were treated with corticosterone with or without d-limonene for 24 h. Western blots were performed to measure activation of AMPK pathway members [Silent mating type information regulation 2 homolog-1 (SIRT1), AMPKα, and nuclear factor (NFκB)], reactive oxygen species, inflammatory cytokines, and markers of apoptosis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) was used to measure cell death after treatment. d-Limonene reversed the effects of corticosterone on PC12 cells: it decreased the levels of malondialdehyde (MDA) and nitric oxide (NO), activities of NADPH oxidase (p67-phox and p47-phox), expression of pro-inflammatory markers [inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α)], and expression of pro-apoptotic proteins [Bcl2 associated with X protein (Bax) and cleaved caspase-3)]. d-Limonene also increased levels of the antioxidant enzymes superoxide dismutase 1 (SOD1) and heme oxygenase 1 (HO-1) and the anti-apoptotic protein Bcl-2 while decreasing the number of TUNEL-positive cells. d-limonene significantly activated AMPKα and suppressed NF-κB nuclear translocation through up-regulation of SIRT1. Addition of compound C, an AMPK inhibitor, severely weakened these neuroprotective effects of d-limonene. d-Limonene has a neuroprotective effect on corticosterone-induced PC12 cell injury induced by activating the AMPKα signaling pathway, and thereby inhibiting reactive oxygen species and inflammatory factors. These data suggest that d-limonene might protect against neuronal death to improve depressive symptoms., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The aim of the present study was to develop a method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) to determine and quantify the d-limonene in mouse plasma and tissue samples. This new method was validated for the quantification of d-limonene with the linearity ranges 1.0-1000.0 ng/mL (r 2  > 0.9952) for plasma samples and 5.0-5000.0 ng/g (r 2  > 0.9940) for tissue samples. The intra- and inter-day assay of precisions in plasma and tissues were <13.4% and the accuracies were within 91.1-105.8%. In the oral/inhalation administration pharmacokinetics and tissue distribution studies, the main pharmacokinetic parameters were the peak concentration = (97.150 ± 34.450)/(4336.415 ± 1142.418) ng/mL, the area under the curve = (162.828± 27.447)/(2085.721 ± 547.787) h ng/mL and the half-life = (3.196 ± 0.825)/(0.989 ± 0.095) h. The tissue distribution of d-limonene in mice after oral/inhalation administration demonstrated a decreasing tendency in different tissues (liver > kidney > heart > lung > spleen)., (© 2019 John Wiley & Sons, Ltd.)

Novel fibers containing different ratios of PVA and d-limonene were fabricated using electrospinning for antibacterial active packaging applications. The PVA/d-limonene fibers were thoroughly characterized using a scanning electron microscope, fourier-transform infrared spectrometry, thermal gravimetry, differential scanning calorimetry, tensile tests, and oxygen permeability tests. The results of these analyses showed that the highest tensile strength and elongation at break values of 3.87 ± 0.25 MPa and 55.62 ± 2.93%, respectively, were achieved for a PVA/d-limonene ratio of 7:3 ( v / v ) and an ultrasonication time of 15 min during processing. This material also showed the lowest oxygen permeation and the best degradability and bacteriostatic properties of all samples.

This study deals with the application of different monoterpenes as relatively green bio-based solvents for low density-dispersive liquid-liquid microextraction (LD-DLLME) of different non-steroidal anti-inflammatory drugs (NSAIDs) from aqueous samples in comparison with conventional halogenated solvents. Results indicated that D-limonene could extract the hydrophobic compounds with higher %recovery compared with other bio-based and halogenated solvents. The LD-DLLME procedure was optimized by applying one-factor-at-a-time (OFAT) followed by central composite face-centered design (CCF) of the response surface methodology (RSM). Under the optimal conditions, the method exhibited good linearity with r ≥ 0.9950 with low LOD as well as LOQ levels in the range of 0.11 to 0.81 and 0.36 to 2.69 ng/mL, respectively. The method was efficiently applied to a variety of real aqueous samples. Finally, the green aspect of our procedure was compared with some reported methods using two green metric tools.

Diabetes mellitus is a major public health problem worldwide. Oxidative stress plays a pivotal role in the pathogenesis of diabetes as it is one of the inevitable outcomes of the cellular process. The present study aims to investigate the putative antihyperglycemic, antihyperlipidemic and antioxidant efficacy of limonene and vitamin E in comparison with metformin, a standard drug for therapy of diabetes. Diabetes was induced by a single intraperitoneal injection of 150 mg/kg of alloxan. There was a significant (P<0.05) increase in body weight of rats treated with limonene, vitamin E and combinatory therapy of limonene and vitamin E compared to the untreated diabetic group which showed decrease in weight. Combinatory therapy treatment of limonene and vitamin E showed significant difference (P<0.05) when compared with the groups treated with limonene, vitamin E and metformin. The combinatory therapy also reduced blood glucose levels, significantly (P < 0.05) compared to non-diabetic treated group treated with limonene and the group treated with metformin. Treatment with limonene and vitamin E, significantly (P< 0.05) ameliorated diabetic effect on MDA concentration and SOD activity. Pathological lesions observed in the pancreas treated with limonene, vitamin E and combinatory therapy of limonene and vitamin E showed normal tissue architecture compared to group treated with metformin. It was concluded that limonene and vitamin E exerted significant anti-diabetic and anti-hyperglycaemic effects in alloxan-induced diabetic rats. [ABSTRACT FROM AUTHOR]

Transglutaminase (TG) cross-linked whey proteins are used to prepare a D -limonene emulsion, which can solve the problems of easy oxidation and poor water solubility of D -limonene. TG cross-linking can improve the emulsion stability of whey protein isolate (WPI). SDS PAGE results showed that TG cross-linked WPI and limonene were emulsified under high-pressure homogenization to form the emulsion (WPI-TG-Oil), which had more molecular polymers. The adsorption rate of interfacial protein of the WPI-TG-Oil emulsion was significantly increased by 5.15 % compared to the WPI limonene emulsion cross-linked with TG (WPI-Oil-TG). After a 10-day storage interval, the CDs and POV showed that the WPI-TG-Oil emulsion had the strongest oxidation stability and a thickened interfacial layer. It was also noted that WPI-TG-Oil was difficult to hydrolyze during the digestion process due to the large degree of cross-linking and many high molecular weight polymers. The WPI-TG-Oil emulsion was more stable with a high molecular weight and improved the overall properties. Moreover, these findings provide basic theoretical and technical support for improving the stability of D -limonene emulsions. The most suitable processing method was TG-crosslinked WPI to form a stable emulsion, which improved the physiochemical and emulsifying properties of its emulsion for potential uses in food, cosmetics, and other industries. [Display omitted] • TG cross-linking and emulsification were crucial for D -limonene emulsion. • WPI-TG-Oil had more molecular polymers than WPI-Oil-TG. • WPI-TG-Oil emulsion had the strongest oxidation stability. [ABSTRACT FROM AUTHOR]

[Display omitted] Enhancement of skin permeation of drugs is affected by the simultaneous co-permeation of excipients that hinder the predictivity of in vitro tests. The collaborative effects of two permeation enhancers (ethanol and d-limonene) of a lipophilic drug (alprazolam) have been simultaneously assessed in human skin under different in vitro conditions: integrated setups of diffusion cell experiments with selective concentration gradients of permeants (asymmetric) or without (symmetric) have been combined with coadministration dosages (all-in-one) at different concentrations or short-time skin pretreatment to scrutiny this mutual performance. Findings: Drug permeation is increased under moderated supersaturation but reaches a stationary level above 33 % of its solubility. Ethanol in absence of a concentration gradient increases ca. 5 times basal drug permeation. Limonene until 20 % permeates human skin proportionally to its donor concentration but its effect does not depend on ethanol in symmetric conditions and is based on skin imbibition rather than on a carry-on effect. Simultaneous permeation of ethanol and limonene reaches a stationary state after 1.5 h, enough time to achieve maximal enhancement of alprazolam permeation. Additive enhancement is based on ethanol solubilisation maximized by skin saturation of terpene. Complementary analyses of skin disruption published in the literature are in line with these assessments and consolidate them. [ABSTRACT FROM AUTHOR]

Background and Objective: Reactive oxygen species are the main factors involved in kidney damage during renal ischemia-reperfusion (RIR). Since D-limonene has antioxidant, anti-diabetic, anti-apoptotic, and lipid peroxidation effects, it prevents mitochondrial dysfunction and inhibits ROS, this study was conducted to evaluate the effects of pretreatment with D-limonene on oxidative stress and antioxidant activity in RIR injury. Methods: In this experimental study, 24 male Wistar rats were randomly divided into 3 groups: control, RIR (ischemia was induced by clamping of renal pedicles for 45 minutes and reperfusion was considered 24 hours after ischemia), and RIR+D-limonene (100 mg/kg by oral gavage for 12 days). Serum and kidney were used to evaluate malondialdehyde (MDA), myeloperoxidase (MPO), paraoxonase1 (PON1), glutathione (GSH), catalase (CAT), glutathione peroxidase (GPX), and nitric oxide (NO). Findings: Serum and renal levels of MDA ([18.2±98.77 vs. 9.21±1.77] and [19.85±3.39 vs. 9.84±1.65]) and MPO ([67.25±32.67 vs. 40.21±6.1] and [18.44±2.86 vs. 10.42±1.68]) and serum level of NO (31.3±36.1 vs. 27.88±2.6) significantly increased in the RIR group compared with the control group (p<0.05). Serum and kidney levels of GSH, activities of CAT and GPX in serum and kidney, and serum activity of PON1 significantly decreased in the RIR group compared with the control group (p<0.05). Pretreatment with D-limonene could significantly ameliorate serum and renal levels of MDA, serum levels of GSH and NO, and serum activity of CAT in rats pretreated with D-limonene in comparison with RIR rats (p<0.05). Conclusion: This study indicated that pretreatment with D-limonene could ameliorate RIR injuries in rats through its antioxidant activities. [ABSTRACT FROM AUTHOR]

Thymol (Th) and d -limonene (L) exhibit low stability and are prone to oxidation when exposed to air, light, humidity, and high temperatures. This study examined the coencapsulation of Th and L into Ferula assafoetida gum (AFG) microparticles. Scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analyzer (TGA) were done to characterize the obtained complexes. Furthermore, the encapsulation efficiency, antibacterial properties, cytotoxicity, and anticancer properties of both the free and encapsulated forms of L and Th were measured. For all samples, by increasing the percentage of bioactive compound (L, Th, and L-Th) from 2.5 to 5 % w/w, the EE was increased. FTIR and XRD analysis results demonstrated that Th and L were successfully incorporated into the AFG. Additionally, thermogravimetric analysis showed that in the thermal graphs of all samples, the first weight loss occurred between 30 °C and 160 °C, which was due to the evaporation of water. In the free L and Th graph, a sharp reduction peak was observed in which 80 % of compounds were lost. These reduction peaks disappeared in the thermal graphs of L: AFG and Th: AFG revealing that the thermal stability of Th and L was significantly increased upon their incorporation into the AFG. The inclusion of Th into the AFG also led to an increase in its antibacterial activity, while L exhibited acceptable antibacterial activity, albeit not as high as Th. Additionally, according to the MIC results, Th: AFG had the best antibacterial activity among all compounds, especially on gram-positive bacteria. According to the result of the MTT assay, there was a significant difference between the IC 50 of free Th (123.4 μg/ml) and Th: AFG (2312 μg/ml), and free L (1762 μg/ml) and L: AFG (2480 μg/ml) showing that encapsulated Th and L into the AFG has decreased the cytotoxicity of free compounds against L929 cell line. Also, Th: AFG had the best anticancer activity against Hella and CT26 cell lines among all compounds. Finally, the flow cytometry analysis demonstrated that the encapsulated particles effectively eliminated cancer cells. The outcomes imply that AFG can be employed as a suitable delivery system to enhance the use of Th and L into the food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

Limonene is a potential candidate for the synthesis of polymers from renewable and non‐toxic sources. The synthesis of poly(limonene) via controlled photopolymerization is studied for the first time, both at an experimental and computational level. A kinetic modeling is developed and all unknown parameters are estimated by adjusting them to the experimental data (conversion, molar mass, and dispersity). The reasonable model fit indicates that the proposed mechanism can be considered valid for this process simulation. In that fashion, different reagent ratios are evaluated, as well as simulations for long polymerization times. The experiments provide less than 10% monomer conversion at 40 °C, and short times. However, it is possible to identify a reasonable polymerization control (dispersities <1.5). In a complementary way, the simulations allowed to identify a threshold of reagent ratios in order to maintain the polymerization control for conversions around 20%, and at the same time enable monomer conversions at the same level as traditional thermally‐initiated radical polymerizations at high temperatures. Therefore, this new route can be a promising alternative for the synthesis of limonene‐based polymers. [ABSTRACT FROM AUTHOR]

A large percentage of fruit mass is left as waste after the consumption or processing of citrus fruits. The inappropriate disposal of these wastes directly leads to environmental and economic concerns. However, scientific investigations have demonstrated that citrus wastes, due to their high concentration in soluble sugars, can be a source of cellulosic biomass for biogas recovery. d-Limonene, the major constituent of essential oils present in citrus wastes, is however, known to hamper the conversion process of citrus wastes to biogas. With the aim of improving biogas production, a study on the pre-treatment of lime fruit waste to reduce the effect of d-limonene was carried out. The pretreatment process was done using hexane as the solvent in a solid-liquid extraction process to leach out essential oils from lime wastes. Solid-liquid extraction was carried out in a Soxhlet apparatus with pulverized lime waste at 68 °C for 180 min; then the residue was washed and aerated. From the pre-treatment procedure, 21.3 mL of essential oil was recovered, indicating an oil yield of 3.8%. Substrates of untreated and pre-treated lime waste were digested in batches under mesophilic conditions for a period of 28 days. The biogas yield of each substrate was evaluated and the results compared. Substrate of untreated lime waste yielded 66.9 mL/g VS. biogas after the digestion period. In comparison, pre-treated lime waste gave a better biogas yield of 93.2 mL/g VS. after 28 days, indicating an improvement in biogas yield by about 40%. The findings of this research show that there is a viable recovery option of biogas from lime waste, and recommendations of this research can be further explored to develop an economically viable biogas plant process that efficiently utilizes citrus wastes. This would boost the drive of government towards alternative sources of energy and also fulfil two of the sustainable development goals presented by the United Nations. [ABSTRACT FROM AUTHOR]

By using the ramping method for humidity at a constant temperature, the release rates of d-limonene were investigated from spray-dried powders with various wall materials, such as maltodextrin (MD) (dextrose equivalent (DE) = 25 and 19), lactose (Lac), and sucrose (Suc). Spray-dried powders, which were sieved to the average powder size of 107-140 μm, contained d-limonene at about 90-97 mg/g-dry powder. d-limonene release profile was measured using a dynamic vapor sorption (DVS) system coupled gas chromatography at 30, 40, and 50 °C from 10% to 90% relative humidity (RH). The linear correlation was found between the release start humidity, sRH, of d-limonene release from the powder and the glass transition temperature of wall materials. The release rates for Suc and Lac increased rapidly at certain humidities and became the maximum rates. Then, these rates decreased gradually with increasing RH. This might have been due to the powder aggregation for Suc and to crystallization for Lac. The release behaviors significantly depended on the wall materials. [ABSTRACT FROM AUTHOR]

Objectives: The aim of current research was to formulate limonene self-nanoemulsified delivery system (SNEDS) by spontaneous emulsification method. Methods: The optimization was carried out through the construction of a pseudo-ternary phase diagram. Limonene-based self- nanoemulsifying system was optimized by evaluating its droplet characteristic; namely; size, polydispersity, zeta potential, in addition, its morphology was assessed through the use of transmission electron microscopy. Moreover, the formulation stability under different storage conditions for three months was examined. Results: The obtained results showed that the optimized limonene-based self-nanoemulsifying system was characterized by a small droplet size, low polydispersity index, high percentage transmittance and optimal zeta potential with uniform spherical droplets. The selected formulation with 50% w/w limonene, 40% w/w Tween 80 and 10% w/w propylene glycol had a droplet size of 113.3±1.18nm with bluish transparent appearance and a zeta potential value of -19.13±0.38 mV. The developed formula was stable against pH change. The stored limonene-based SNEDS showed acceptable stability at 4°C and 0°C compared to 25°C. Conclusion: The formulated self-nanoemulsifying system showed an improved aqueous dispersibility, patient acceptability and stability of limonene, representing a promising carrier for lipophilic drugs. [ABSTRACT FROM AUTHOR]

There are two chemotypes of Litsea cubeba (Lour.) Pers. (fam. Lauraceae) essential oils (EOs), either dominated by citral and limonene or by citronellal. L. cubeba EOs exhibits broad antimicrobial activity against bacteria and fungi with minimal inhibitory concentrations (MICs) from 0.5 to 2500 µg/mL. This antimicrobial activity is attributed to the monoterpene citral, exhibiting a broad antimicrobial spectrum against bacteria and fungi (MICs 50–1000 µg/mL). Pseudomonas aeruginosa were found most resistant, with MIC values above 1000 µg/mL. Citral's mode of action is not fully investigated. At biocidal concentrations, it affects membrane structure and cell respiration, leading to rapid energy depletion and cell death. Involvement of intracellular reactive oxygen species has not been verified. Limonene exhibits insignificant antimicrobial activity. MICs of d-limonene range from 1 to 20 mg/mL. Citral and L. cubeba EOs were also subjects of food application studies. Promising results have been reported for fresh produce or fruit-juice. [ABSTRACT FROM AUTHOR]

Highlights • d -Limonene is the major compound in Citrus microcarpa essential oil. • Quantification of d -limonene present in essential oil revealed 98.1%w/w. • Essential oil exhibits cytotoxicity against breast cancer cell line, MCF-7. • Essential oil is twice toxic to cancer (MCF-7) than normal (AA8) cell line. Abstract The development of drug resistance is widespread in today's arsenal of chemotherapeutic agents and this has brought renewed interest in the use of natural products. Calamansi (Citrus microcarpa B.) is an essential oil-rich citrus from the Philippines popularly used in beverages and condiments. Calamansi wastes from processing plants are underutilized and may pose environmental concerns if not properly processed. This study aims to determine the volatile composition, d -limonene content, and cytotoxicity of calamansi essential oil. The calamansi essential oil was prepared by steam distillation and characterized using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy and Gas Chromatography analysis. Cytotoxicity on human mammary tumor cell line MCF-7 and Chinese hamster ovary non-tumor cell line AA8 were assessed by MTT assay. Gas Chromatography-Mass Spectrometry qualitative analysis results revealed that d -limonene is the major constituent of calamansi essential oil comprising at least 92.67% of the total oil. Quantification of d -limonene in essential oil using a reference standard by Gas Chromatography-Flame Ionization Detector has shown 98.1% w/w. The IC 50 of calamansi essential oil on MCF-7 and AA8 cells were identified to be 7.98 ± 1.77 and 16.15 ± 8.35 μg/mL respectively. Our findings suggest that calamansi essential oil has greater cytotoxic activity on MCF-7 than AA8 and this activity can be directly attributed to the high amount of d -limonene and perhaps the presence of other terpenes that may also have synergistic effects with d -limonene. Calamansi essential oil can be a good candidate for a natural low-cost chemopreventive and chemotherapeutic agent. These findings are of considerable economic interest to Philippine calamansi industry which produces large amount of calamansi pericarp waste. [ABSTRACT FROM AUTHOR]

Limonene has a great potential to create an active paper for citrus products. The aim of this study is first to encapsulate limonone by liposome method and cyclodextrin inclusion methods and second to characterize and measure antifungal activity of hutbak papers that have active properties. Active hutbak papers are produced by dipping method with free limonene solution (H-L), encapsulated limonene containing liposome solution (H-Lp), hydroxypropyl-beta-cyclodextrin/limonene inclusion complex solutions (H-HPβCD) and beta-cyclodextrin/limonene (H-βCD) inclusion complex solutions. The effects of the production methods on the physical properties of the papers were analyzed by tensile test and color analysis. The produced active papers were stored for 30 days at 4⁰C. The amount of limonene remaining in the papers and antifungal activity analyzes against P. digitatum and P. expansium were performed on intervals of storage. The highest limonene content values were determined in H-βCD samples. Only the H-HPβCD samples showed zone diameters according to the disk diffusion method. • Limonene has a potential use as an additive in food packaging. • Encapsulation is an effective method for the production of active paper. • Impacts of encapsulation methods on hutbak paper were studied. • β-cyclodextrin significantly reduced the release of limonene from hutbak paper. • H-HPβCD samples showed better antifungal properties. [ABSTRACT FROM AUTHOR]

The valorisation of waste generated during orange juice manufacturing (OPW) by anaerobic digestion is gaining attention due to the several economic, social and environmental advantages of the process. Given that anaerobic digestion is a process that requires rigorous control to improve the biodegradability of the waste and methane production, this paper highlights the importance of modelling for adequate process monitoring. Specifically, this study fitted three sigmoidal models (Logistic, Gompertz, and Sigmoid models) to methane production from OPW. At laboratory scale, two thermophilic continuously stirred-tank reactors working in semi-continuous mode was used. d-limonene removal of 70% was previously reached by applying a pre-treatment on OPW. The results showed a biodegradability of the pre-treated waste of up to 96.7% in COD. The Logistic, Gompertz and Sigmoid models fitted adequately to cumulative methane production (R2 was 0.9691; 0.9492 and 0.9511, respectively). However, the Logistic model showed the best fit to the experimental data even under critical conditions. Specifically, the Logistic model predicted the maximum methane production rate within loads of 2.5–5.0 g COD/L. Therefore, this model might be very useful in predicting the maximum methane production rate and the maximum load that could be added without the inhibition of anaerobic digestion at real scale. [ABSTRACT FROM AUTHOR]

Purpose: d-limonene is a plant extract with widespread application, and it has been recently reported to have antiproliferative and proapoptotic effects on cancer cells. However, the mechanisms by which d-limonene achieves these effects, especially in lung cancer, are not entirely clear. Therefore, the goal of this study was to examine the effects of d-limonene on lung cancer and explore its mechanisms of action. Methods: We examined the therapeutic effects of d-limonene on lung cancer cells and in a xenograft animal model by characterizing its effects on the pathways of apoptosis and autophagy. Cell proliferation was measured using the Cell Counting Kit-8, and apoptosis was determined by flow cytometric analysis. Levels of LC3 puncta, an autophagy marker, were analyzed by laser scanning confocal microscopy. Autophagy and apoptosis-related gene expression were assessed by real-time quantitative polymerase chain reaction and Western blot. Results: d-limonene inhibited the growth of lung cancer cells and suppressed the growth of transplanted tumors in nude mice. Expression of apoptosis and autophagy-related genes were increased in tumors after treatment with d-limonene. Furthermore, the use of chloroquine, an autophagy inhibitor, and knockdown of the atg5 gene, suppressed the apoptosis induced by d-limonene. Conclusion: d-limonene may have a therapeutic effect on lung cancer as it can induce apoptosis of lung cancer cells by promoting autophagy. [ABSTRACT FROM AUTHOR]

Abstract: This study was designed to assess the potential antifibrotic effect of D‐Limonene—a component of volatile oils extracted from citrus plants. D‐limonene is reported to have numerous therapeutic properties. CCl4‐intduced model of liver fibrosis in Wistar rats is most widely used model to study chemopreventive studies. CCl4‐intoxication significantly increased serum aminotransferases and total cholesterol these effects were prevented by cotreatment with D‐Limonene. Also, CCl4‐intoxication caused depletion of glutathione and other antioxidant enzymes while D‐Limonene preserved them within normal values. Hydroxyproline and malondialdehyde content was increased markedly by CCl4 treatment while D‐Limonene prevented these alterations. Levels of TNF‐α, TGF‐β, and α‐SMA were also assessed; CCl4 increased the expression of α‐SMA, NF‐κB and other downstream inflammatory cascade while D‐Limonene co‐treatment inhibited them. Collectively these findings indicate that D‐Limonene possesses potent antifibrotic effect which may be attributed to its antioxidant and anti‐inflammatory properties. [ABSTRACT FROM AUTHOR]

Gas chromatography-mass spectrometry (GC-MS) study results, and dilution method results were compared in respect of food flavors in orange juices, which are sold in Ukrainian markets as 'natural.' It was shown that the presence of d-limonene, and benzoic acid, in commercial/industrial orange juices indicates the presence of added food flavors. New scientific evidence demonstrates the correlation between intensity of odor, represented numerically by dilution index ( p < 0.05), and GC-MS results. It was established that the comparative evaluation of dilution indexes of industrial orange juices, and freshly squeezed ones, eliminates subjectivity factor, and can be useful for rapid investigation of orange juice authenticity in respect of the presence of food flavors. For orange juices produced with, and without added food flavors, the intensity of odor was found to be 2 times higher, and 1.5-2.5 times lower, respectively, than that of freshly squeezed juice. Practical applications The rapid evaluation of orange juices and concentrates, regarding authenticity, with respect to the presence of food flavors, can be provided by dilution method. The results confirm the potential of odor index as a numerical criterion for characterization of the aroma intensity level in fruit juices and could be of practical relevance. The article is important for food producers, food inspection authorities, and scientists who are working in the area of restored fruit juices. [ABSTRACT FROM AUTHOR]

Solvent selection is a key factor in the development of processes for the extraction of bioactive compounds from natural sources such as algae. The aim of this work was the use of bio-based solvents for the selective extraction of fucoxanthin from P. tricornutum , using pressurized technologies. In this regards, the application of Hansen solubility approach reduced the list of candidate solvents for pressurized liquid extraction (PLE) to four: ethyl acetate, ethyl lactate, d-limonene and ethanol. The use of theoretical calculations narrowed the search of suitable solvents, thus making the process greener. Among the bio-based solvents proposed, d-limonene was the most selective, although it was not able to recover all the fucoxanthin present in the biomass unless a continuous extraction aided by supercritical CO 2 was used. The other three solvents tested showed good recoveries of fucoxanthin, but were less selective, following the decreasing order: ethyl acetate > ethyl lactate > ethanol. [ABSTRACT FROM AUTHOR]

Chronic musculoskeletal pain is one of the main symptoms found in Fibromyalgia with unclear etiology and limited pharmacological treatment. The aim of this study was to complex LIM in β -cyclodextrin (LIM- β CD) and then evaluate its antihyperalgesic effect in an animal model of chronic musculoskeletal pain. Differential scanning calorimetry and scanning electron microscopy was used for the characterization of the inclusion complex. Male Swiss mice were used for experimental procedures where mechanical hyperalgesia, thermal hyperalgesia, muscular strength, Fos immunofluorescence was studied after induction of hyperalgesia. Mechanism of action was also investigated through tail flick test and capsaicin-induced nociception. Endothermic events and morphological changes showed that the slurry complex method was the best method for the complexation. After induction of hyperalgesia, the oral administration of LIM- β CD (50 mg/kg) significantly increased the paw withdrawal threshold compared to uncomplexed limonene. Fos immunofluorescence showed that both compounds significantly decreased the number of Fos-positive cells in the dorsal horn. In nociceptive tests, FLU was able to reverse the antinociceptive effect of LIM- β CD. After intraplantar administration of capsaicin, LIM was able to significantly decrease time to lick. LIM- β CD has antihyperalgesic action superior to its uncomplexed form, with possible action in the dorsal horn of the spinal cord. These results suggest the possible applicability of LIM, uncomplexed or complexed with β CD, in conditions such as FM and neuropathic pain, for which there are currently only limited pharmacological options. [ABSTRACT FROM AUTHOR]

Core-shell latex-based pressure-sensitive adhesives comprising n-butyl acrylate, styrene and acrylic acid were prepared via two-stage seeded semi-batch emulsion polymerization. d-Limonene (Lim) was used as a renewable chain transfer agent. Adhesive performance was modified by manipulating the microstructure of both the latex particle cores and shells. In the first stage of the polymerization, the concentrations of Lim and divinylbenzene (DVB) crosslinker were varied to alter the core microstructure and thus, the cohesive strength of the adhesive films. The particle shell microstructure was modified in the second stage of the polymerization by varying only the amount of Lim. As a result, a variety of particle microstructures and morphologies were generated. Tack and peel strength decreased with increasing Lim concentration while shear strength showed a maximum at a moderate core Lim concentration of 2 phm. Empirical models were developed using stepwise regression to correlate tack, peel strength and shear strength to Lim concentration in the core/shell and DVB concentration in the core. [ABSTRACT FROM AUTHOR]

ABSTRACT BACKGROUND D-limonene, a high-value added molecule found in the flavedo of orange peels (about 0.7% w/w), is used in the nutritional, pharmaceutical and cosmetic fields. An accelerated moderate temperature extraction was investigated in order to recover D-limonene. Furthermore, the residue from the extraction was used for energy recovery through the pyrolysis process. RESULTS The proposed extractive process was able to recover D-limonene up to 0.48 ± 0.002% w/w (on a wet basis) from orange peels at the highest investigated temperature (130 °C for 60 min). The residual matrix was then subjected to a dehydration step, which was carried out at room temperature for 10 days, in order to decrease the moisture from the porous surface, and then to a pyrolysis process. The average chemical energy recovery efficiency (91% ± 0.04) suggested that the thermochemical process is suitable for biofuel production. CONCLUSION Orange peels can be exploited for the recovery of an important bio-product and the residue can be used as feedstock for biofuels. This work has confirmed that accelerated extraction is more efficient than Soxhlet extraction (more than 68% w/w against 37% w/w of total D-limonene, respectively), and that a pyrolysis process can be successfully performed on the residue. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

D-limonene has been demonstrated to have important immunomodulatory properties, including antitumor effects, and may alleviate asthma and allergies. In the present study, the anti-inflammatory effects of D-limonene were investigated in an ulcerative colitis (UC) rat model. Healthy male Sprague-Dawley rats were randomly divided into control, untreated UC, and treatment with 50 or 100 mg/kg D-limonene UC groups. In UC rats, disease activity and colonic mucosa damage were significantly reduced by the anti-inflammatory effects of D-limonene, via suppression of matrix metalloproteinase (MMP)-2 and -9 gene expression. In addition, treatment with D-limonene significantly increased antioxidant, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression levels in UC rats. A decrease in prostaglandin E2 (PGE2) production, transforming growth factor-β (TGF-β) gene expression and an increase phosphorylated-extracellular signal regulated kinase (ERK) 1/2 expression levelswere observed in UC rats treated with D-limonene. In conclusion, D-limonene reduced MMP-2 and -9 mRNA expression levels via regulation of the iNOS, COX-2, PGE2, TGF-β and ERK1/2 signaling pathways in a UC rat model, indicating its potential antioxidant and anti-inflammatory properties. [ABSTRACT FROM AUTHOR]

Salmonella Senftenberg is a pathogen agent causative of foodborne disease and it is considered the most heat-resistant serovar within this genus. Food industries use heat treatment and chemical antimicrobials in order to eliminate this microorganism in food, but consumers prefer natural antimicrobials as essential oils and their components. This study evaluates the combined effect of thermal treatments and different concentrations of D-limonene nanoemulsion on the inactivation of Salmonella (S.) Senftenberg. The results showed an important effect of the nanoemulsified D-limonene on the heat resistance of S. Senftenberg. The δ50°C value was reduced by 85%, 96% and 98% when 0.1, 0.5 and 1 mM of nanoemulsified D-limonene was added to the heating medium. The effect was kept along all the heating temperatures researched and the shape of the survival curves did not change with the addition of the antimicrobial. The results obtained in this research could be very useful for food industries for optimizing or improving heat treatments applied to food. [ABSTRACT FROM AUTHOR]

The aim of this study was to design and develop simultaneous optimal transinvasome formulations (OTV) to enhance the transdermal delivery of capsaicin. Using a central composite experimental design with duplicate centroids, 10 model formulations of transinvasomes (TVs) were demonstrated. The lipid compositions of the TV formulations were determined as formulation factors (Xn) and response variables (Yn), respectively. TV formulations containing a constant concentration of phosphatidylcholine, cholesterol, 0.15% capsaicin, and various percentages ofd-limonene (X1) and cocamide diethanolamine (X2) were prepared. The physicochemical characteristics, e.g. the vesicle size, size distribution, zeta potential, entrapment efficiency, and skin permeability, of the TV formulations were experimentally investigated. The relationship among the formulation factor, the response variables, and the OTV was predicted using Design Expert®software. The accuracy and reliability of the OTV predicted using computer software were experimentally confirmed and investigated as an experimental transinvasome formulation (ETV). The results indicated that the skin permeability of the ETV was close to the OTV and was significantly higher than that of conventional liposomes and commercial products. The response surfaces estimated by the computer software were helpful in understanding the complicated relationship among the formulation factor, the response variables, and the stability of the TV formulation. [ABSTRACT FROM AUTHOR]

The essential oils obtained from citric fruits have been used as aromatizing agents in various foods. However, the addition of orange essential oil, d-limonene, to cocoa butter (CB) has been shown to have an influence on its crystallization behavior. The objective of this study was to evaluate the influence of adding d-limonene at concentrations of 1.5 and 5% w/w on the polymorphic transitions in Brazilian CB and in a commercial cocoa butter equivalent (CBE). X-ray diffraction (XRD) was used to identify the polymorphic forms in the samples over 27 days of storage at 25°C. The results showed that d-limonene addition was able to accelerate the polymorphic transition in CB and CBE. The addition of 5% w/w d-limonene to Brazilian CB accelerated the complete transition from βV to the more stable βVI polymorphic form in only 11 days. Under the same conditions, pure CB remained in βV form and the transition was not completed in CBE samples. The polymorphic transition of CBE samples appeared to be governed by the characteristics of the triacylglycerol (TAG) profile and only intensified with d-limonene incorporation. Practical applications: d-Limonene is an essential oil that has been used industrially to give orange flavor in chocolate products. Our results showed that d-limonene addition to CB and CBE accelerates the polymorphic transition from polymorphic form V to VI in a short period. As the polymorphic form VI is more stable than form V, the addition of d-limonene to chocolates and the like allows them to keep their melting properties and sensorial quality for long storage periods. Changes of d-spacing values and Powder X-ray diffraction patterns of Brazilian cocoa butter and cocoa butter equivalent samples containing 5% d-limonene stored for 27 days (4 [d4], 11 [d11], 27 [d27] days) at 25°C. [ABSTRACT FROM AUTHOR]