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β-Arbutin, a natural glucoside hydroquinone derivative known for its skin-whitening properties through tyrosinase inhibition in melanin synthesis, may pose potential risks of allergy and carcinogenicity due to the release of hydroquinone during use. This study explores the inhibitory effects of phenyl-β-D-pyranoglucoside (compound 1), 4-methoxyphenyl-β-D-pyranoglucoside (compound 2), 4-hydroxymethylphenyl-β-D-pyranoglucoside (compound 3), and β-arbutin (compound 4) on tyrosinase using enzyme kinetics, molecular docking, and molecular dynamics simulations. Results show compounds 1, 3, and 4 exhibit competitive inhibition, while compound 2 shows mixed inhibition. Docking analysis reveals phenyl rings of all compounds interact with the enzyme's active site, with compound 3 forming a metal bond with copper ions. MD simulations indicate high stability for compounds 2, 3, and 4, with compound 3 showing the lowest RMSD and compact Rg, suggesting stronger binding. Compound 1 is less stable and less inhibitory. These insights are valuable for designing effective tyrosinase inhibitors., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

Arbutin and 6'- O -caffeoylarbutin (CA) from Vaccinium dunalianum Wight are known for their ability to inhibit melanin synthesis. To boost the production of arbutin and CA, precursor feeding with hydroquinone (HQ) was studied in V. dunalianum suspension cells. The effect of HQ on the biosynthesis of arbutin and CA in the suspension cells was investigated using high-performance liquid chromatography (HPLC), and possible molecular mechanisms were analyzed using metabolomics and transcriptomics analyses. HPLC analysis only showed that the addition of HQ significantly enhanced arbutin synthesis in cells, peaking at 15.52 ± 0.28 mg·g -1 after 0.5 mmol·L -1 HQ treatment for 12 h. Subsequently, metabolomics identified 78 differential expression metabolites (DEMs), of which arbutin and CA were significantly up-regulated metabolites. Moreover, transcriptomics found a total of 10,628 differential expression genes (DEGs). The integrated transcriptomics and metabolomics revealed that HQ significantly enhanced the expression of two arbutin synthase (AS) genes (Unigene0063512 and Unigene0063513), boosting arbutin synthesis. Additionally, it is speculated that CA was generated from arbutin and 3,4,5-tricaffeoylquinic acid catalyzed by caffeoyl transferase, with Unigene0044545, Unigene0043539, and Unigene0017356 as potentially associated genes with CA synthesis. These findings indicate that the precursor feeding strategy offers a promising approach for the mass production of arbutin and CA in V. dunalianum suspension cells and provides new insights for CA biosynthesis in V. dunalianum .

Que Zui tea (QT) is an important herbal tea in the diet of the 'Yi' people, an ethnic group in China, and it has shown significant antioxidant, anti-inflammatory, and hepatoprotective effects in vitro. This study aims to explore the protective effects of the aqueous-ethanol extract (QE) taken from QT against ᴅ-galactose (ᴅ-gal)-induced oxidative stress damage in mice and its potential mechanisms. QE was identified as UHPLC-HRMS/MS for its chemical composition and possible bioactive substances. Thus, QE is rich in phenolic and flavonoid compounds. Twelve compounds were identified, the main components of which were chlorogenic acid, quinic acid, and 6'- O -caffeoylarbutin. Histopathological and biochemical analysis revealed that QE significantly alleviated brain, liver, and kidney damage in ᴅ-gal-treated mice. Moreover, QE remarkably attenuated oxidative stress by activating the Nrf2/HO-1 pathway to increase the expression of antioxidant indexes, including GSH, GSH-Px, CAT, SOD, and T-AOC. In addition, QE administration could inhibit the IL-1β and IL-6 levels, which suppress the inflammatory response. QE could noticeably alleviate apoptosis by inhibiting the expressions of Caspase-3 and Bax proteins in the brains, livers, and kidneys of mice. The anti-apoptosis mechanism may be related to the upregulation of the SIRT1 protein and the downregulation of the p53 protein induced by QE in the brain, liver, and kidney tissues of mice. Molecular docking analysis demonstrated that the main components of QE, 6'- O -caffeoylarbutin, chlorogenic acid, quinic acid, and robustaside A, had good binding ability with Nrf2 and SIRT1 proteins. The present study indicated that QE could alleviate ᴅ-gal-induced brain, liver and kidney damage in mice by inhibiting the oxidative stress and cell apoptosis; additionally, the potential mechanism may be associated with the SIRT1/Nrf2 signaling pathway.

Vaccinium dunalianum leaf buds make one of the most commonly used herbal teas of the Yi people in China, which is used to treat articular rheumatism, relax tendons, and stimulates blood circulation in the body. In addition, 6'- O -caffeoylarbutin (CA) is a standardized extract of V. dunalianum , which has been found in dried leaf buds, reaching levels of up to 31.76%. Because of the uncommon phenomenon, it is suggested that CA may have a potential therapeutic role in hyperlipidemia and thrombosis. This study was designed to study the efficacy of CA on treating hyperlipidemia and thrombosis and the possible mechanisms behind these effects. Hyperlipidemia and thrombosis zebrafish models were treated with CA to observe variations of the integrated optical density within the vessels and the intensity of erythrocyte staining within the hearts. The possible mechanisms were explored using network pharmacology and molecular docking. The results demonstrate that CA exhibits an excellent hypolipidemic effect on zebrafish at concentrations ranging from 3.0 to 30.0 μg/mL and shows thrombosis inhibitory activity in zebrafish at a concentration of 30.0 μg/mL, with an inhibition rate of 44%. Moreover, network pharmacological research shows that MMP9, RELA, MMP2, PRKCA, HSP90AA1, and APP are major targets of CA for therapy of hyperlipidemia and thrombosis, and may relate to pathways in cancer, chemical carcinogenesis-receptor activation, estrogen signaling pathway, and the AGE-RAGE signaling pathway in diabetic complications.

Tyrosinase is vital in fruit and vegetable browning and melanin synthesis, crucial for food preservation and pharmaceuticals. We investigated 6'- O -caffeoylarbutin's inhibition, safety, and preservation on tyrosinase. Using HPLC, we analyzed its effect on mushroom tyrosinase and confirmed reversible competitive inhibition. UV_vis and fluorescence spectroscopy revealed a stable complex formation with specific binding, causing enzyme conformational changes. Molecular docking and simulations highlighted strong binding, enabled by hydrogen bonds and hydrophobic interactions. Cellular tests showed growth reduction of A375 cells with mild HaCaT cell toxicity, indicating favorable safety. Animal experiments demonstrated slight toxicity within safe doses. Preservation trials on apple juice showcased 6'- O -caffeoylarbutin's potential in reducing browning. In essence, this study reveals intricate mechanisms and applications of 6'- O -caffeoylarbutin as an effective tyrosinase inhibitor, emphasizing its importance in food preservation and pharmaceuticals. Our research enhances understanding in this field, laying a solid foundation for future exploration.

Que Zui tea (QT), a traditional herbal tea in China, has a significant hepatoprotective effect. 6'- O -Caffeoylarbutin (CA) is the most abundant chemical compound in the QT. However, the hepatoprotective effect of CA has not been investigated. This study is aimed to evaluate the protective effect of CA on acetaminophen (APAP) induced hepatotoxicity in vivo and in vitro and its possible underlying mechanism. In APAP-induced HepG-2 cells, CA inhibited intracellular ROS accumulation and cell apoptosis, and improved the expression of antioxidants including SOD, CAT and GSH. In APAP-administrated mice, CA pretreatment remarkably ameliorated the histopathological damage and inflammatory response, and antioxidant enzyme activity in the serum and liver tissues. Moreover, the immunohistochemistry and immunofluorescence assay results revealed that the CA markedly reduced ROS production and apoptosis, and activated antioxidant transcription factor Nrf2 in the liver. Meanwhile, molecular docking results showed that the strong binding force of CA and PI3K was due to the higher number of hydrogen- and π-bonds with active site residues. Notably, CA pretreatment significantly regulated the expression of PI3K, Akt, Nrf2, NQO1, HO-1, Bcl-2, Bax, caspase-3, and caspase-9 proteins in APAP-treated liver tissues. These data demonstrated that CA had a protective effect against APAP-induced hepatotoxicity via regulating the PI3K/Akt and Nrf2 signaling pathway.

DeoxyArbutin (dA) is a tyrosinase inhibitor that has effective skin-lightening activity and has no obvious cytotoxicity toward melanocytes. With the aim of directly evaluating the effects of microemulsions containing dA on cells, we developed oil-in-water (O/W) microemulsions with relatively lower cytotoxicities by using polysorbate-series surfactants. Measurement of the transparent properties and particle size analysis at different storage time periods revealed that the developed microemulsions were stable. Moreover, the developed microemulsions had direct effects on B16-F10 mouse melanoma cells. The anti-melanogenesis activities of dA-containing microemulsions were evidently better than that of the free dA group. The results demonstrated that the developed microemulsion encapsulating dA may allow the use of deoxyArbutin instead of hydroquinone to treat dermal hyperpigmentation disorders in the future.

Background: Hydroquinone, which is considered the gold standard skin depigmenting agent, has been associated with multiple side effects. Lately, deoxyarbutin has been suggested to be an alternative of hydroquinone with better safety profile., Objective: To compare the depigmenting effect of 2% deoxyarbutin and 4% hydroquinone sera., Methods: This double-blind randomized controlled study was done on the right and left arms of healthy participants. Subjects were instructed to apply either 2% deoxyarbutin or 4% hydroquinone serum on each arm, which were randomly labeled as group A and B, every day for 12 weeks. Chromameter and mexameter analysis were done every 2 weeks to assess the color change. Paired and independent t-tests were used to assess the color change within and between both groups, respectively., Results: A total of 59 females participated in this study. Both groups showed significant improvement in skin depigmentation as shown by the chromameter (increase in L* value) and mexameter (decrease in melanin index) analysis at the end of the study (p < 0.05). No significant difference in both parameters was observed between both groups (p > 0.05). No side effects were reported in either groups., Conclusion: 2% deoxyarbutin and 4% hydroquinone sera showed comparable depigmenting efficacy., (© 2021 Wiley Periodicals LLC.)

Background: SARS-CoV-2, an emerging strain of coronavirus, has affected millions of people from all the continents of world and received worldwide attention. This emerging health crisis calls for the urgent development of specific therapeutics against COVID-19 to potentially reduce the burden of this emerging pandemic., Purpose: This study aims to evaluate the anti-viral efficacy of natural bioactive entities against COVID-19 via molecular docking and molecular dynamics simulation., Methods: A library of 27 caffeic-acid derivatives was screened against 5 proteins of SARS-CoV-2 by using Molegro Virtual Docker 7 to obtain the binding energies and interactions between compounds and SARS-CoV-2 proteins. ADME properties and toxicity profiles were investigated via www.swissadme.ch web tools and Toxtree respectively. Molecular dynamics simulation was performed to determine the stability of the lead-protein interactions., Results: Our obtained results has uncovered khainaoside C, 6-O-Caffeoylarbutin, khainaoside B, khainaoside C and vitexfolin A as potent modulators of COVID-19 possessing more binding energies than nelfinavir against COVID-19 M pro , Nsp15, SARS-CoV-2 spike S2 subunit, spike open state and closed state structure respectively. While Calceolarioside B was identified as pan inhibitor, showing strong molecular interactions with all proteins except SARS-CoV-2 spike glycoprotein closed state. The results are supported by 20 ns molecular dynamics simulations of the best complexes., Conclusion: This study will hopefully pave a way for development of phytonutrients-based antiviral therapeutic for treatment or prevention of COVID-19 and further studies are recommended to evaluate the antiviral effects of these phytochemicals against SARS-CoV-2 in in vitro and in vivo models., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Vaccinium dunalianum Wight, usually processed as a traditional folk tea beverage, is widely distributed in the southwest of China. The present study aimed to investigate the antioxidant, α-glucosidase and pancreatic lipase inhibitory activities of V. dunalianum extract and isolate the bioactive components. In this study, the crude extract (CE) from the buds of V. dunalianum was prepared by the ultrasound-assisted extraction method in 70% methanol and then purified with macroporous resin D101 to obtain the purified extract (PM). Five fractions (Fr. A-E) were further obtained by MPLC column (RP-C18). Bioactivity assays revealed that Fr. B with 40% methanol and Fr. D with 80% methanol had better antioxidant with 0.48 ± 0.03 and 0.62 ± 0.01 nM Trolox equivalent (TE)/mg extract for DPPH, 0.87 ± 0.02 and 1.58 ± 0.02 nM TE/mg extract for FRAP, 14.42 ± 0.41 and 19.25 ± 0.23 nM TE/mg extract for ABTS, and enzyme inhibitory effects with IC 50 values of 95.21 ± 2.21 and 74.55 ± 3.85 for α -glucosidase, and 142.53 ± 11.45 and 128.76 ± 13.85 µg/mL for pancreatic lipase. Multivariate analysis indicated that the TPC and TFC were positively related to the antioxidant activities. Further phytochemical purification led to the isolation of ten compounds (1-10). 6- O -Caffeoylarbutin (7) showed significant inhibitory effects on α -glucosidase and pancreatic lipase enzymes with values of 38.38 ± 1.84 and 97.56 ± 7.53 µg/mL, and had the highest antioxidant capacity compared to the other compounds.

Excessive melanin formation has been linked to various skin disorders such as hyperpigmentation and skin cancer. Tyrosinase is the most prominent target for inhibitors of melanin production. In this study, we investigated whether arbutin and its prodrug, arbutin undecylenic acid ester, might inhibit phenoloxidase (PO), a tyrosinase-like enzyme. Molecular docking simulation results suggested that arbutin and arbutin undecylenic acid ester can bind to the substrate-binding pocket of PO. Arbutin undecylenic acid ester with an IC 50 6.34 mM was effective to inhibit PO compared to arbutin (IC 50 29.42 mM). In addition, arbutin undecylenic acid ester showed low cytotoxicity in Drosophila S2 cells and the compound inhibited the melanization reaction. Therefore, the results of this study have demonstrated that arbutin undecylenic acid ester as a potential inhibitor of PO. We successfully designed a new platform utilizing Drosophila melanogaster and Bombyx mori as animal models propounding fast, cheap, and high effectiveness in method to screen tyrosinase inhibitors., 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 © 2021 Elsevier Inc. All rights reserved.)

Arbutin, a natural polyphenol isolated from the bearberry plant Arctostaphylos uvaursi, possesses whitening and anticancer properties. The effects of arbutin on melanogenesis and its pro-apoptotic effect on B16 murine melanoma cells have not yet been reported. In the present study, acetylated arbutin was prepared in order to improve the biological effects of arbutin, and it was found to significantly inhibit the biosynthesis of melanin and tyrosinase activity compared with parent arbutin in B16 murine melanoma cells. Interestingly, only acetylated arbutin strongly inhibited B16 murine melanoma cell migration in a dose-dependent manner. Both arbutin and acetylated arbutin significantly reduced cell viability, promoted cell apoptosis, caused G1 cell cycle arrest and induced mitochondrial disruption in B16 murine melanoma cells. Furthermore, reduced expression of B-cell lymphoma‑extra large (Bcl-xL) and Bcl-2 were observed in arbutin- and acetylated arbutin-treated cells. Therefore, arbutin and acetylated arbutin were found to exert pro-apoptotic effects on B16 murine melanoma cells, mediated through the mitochondrial pathway. The findings of the present study also support the use of acetylated arbutin as a new potential candidate agent for skin whitening and melanoma treatment.

A new arbutin derivative, namely dunalianosides J (1), along with six known compounds, arbutin (2), robustaside A (3), 6'-O-caffeoylarbutin (4), dunalianoside D (5), kaempferol 3-O-β-D-glucopyranoside (6) and kaempferol 3-O-β-D-sambubioside (7) were isolated from the leaves of Vaccinium dunalianum Wight (Ericaceae). The structure of 1 was elucidated by extensive 1D and 2D NMR, HR-MS and CD spectroscopic analyses. In which, kaempferol 3-O-β-D-sambubioside (7) was isolated from the genus Vaccinium for the first time.

Deoxyarbutin, a potent inhibitor of tyrosinase, could act as substrate of the enzyme. Oxytyrosinase is able to hydroxylate deoxyarbutin and finishes the catalytic cycle by oxidizing the formed o-diphenol to quinone, while the enzyme becomes deoxytyrosinase, which evolves to oxytyrosinase in the presence of oxygen. This compound is the only one described that does not release o-diphenol after the hydroxylation step. Oxytyrosinase hydroxylates the deoxyarbutin in ortho position of the phenolic hydroxyl group by means of an aromatic electrophilic substitution. As the oxygen orbitals and the copper atoms are not coplanar, but in axial/equatorial position, the concerted oxidation/reduction cannot occur and the release of a copper atom to bind again in coplanar position, enabling the oxidation/reduction or release of the o-diphenol from the active site to the medium. In the case of deoxyarbutin, the o-diphenol formed is repulsed by the water due to its hydrophobicity, and so can bind correctly and be oxidized to a quinone before being released. Deoxyarbutin has been characterized with: [Formula: see text] = 1.95 ± 0.06 s-1 and [Formula: see text] = 33 ± 4 μM. Computational simulations of the interaction of β-arbutin, deoxyarbutin and their o-diphenol products with tyrosinase show how these ligands bind at the copper centre of tyrosinase. The presence of an energy barrier in the release of the o-diphenol product of deoxyarbutin, which is not present in the case of β-arbutin, together with the differences in polarity and, consequently differences in their interaction with water help understand the differences in the kinetic behaviour of both compounds. Therefore, it is proposed that the release of the o-diphenol product of deoxyarbutin from the active site might be slower than in the case of β-arbutin, contributing to its oxidation to a quinone before being released from the protein into the water phase.

Deoxyarbutin (DeoxyArbutin, dA), a natural compound widely used in skin lighting, displayed selectively cytotoxicity in vitro. In the study, we found that dA significantly inhibited viability/proliferation of B16F10 melanoma cells, induced tumour cell arrest and apoptosis. Furthermore, dA triggered its pro-apoptosis through damaging the mitochondrial function (membrane potential loss, ATP depletion and ROS overload generation etc.) and activating caspase-9, PARP, caspase-3 and the phosphorylation of p38. Treatment with p38 agonist confirmed the involvement of p38 pathway triggered by dA in B16F10 cells. The in vivo finding also revealed that administration of dA significantly decreased the tumour volume and tumour metastasis in B16F10 xenograft model by inhibiting tumour proliferation and inducing tumour apoptosis. Importantly, the results indicated that dA was specific against tumour cell lines and had no observed systemic toxicity in vivo. Taken together, our study demonstrated that dA could combate tumour in vitro and in vivo by inhibiting the proliferation and metastasis of tumour via a p38-mediated mitochondria associated apoptotic pathway.

Arbutin (Arb) and deoxyArbutin (dA) are both effective hypopigmentation agents. However, they are glucoside derivatives of hydroquinone (HQ), which may be decayed into HQ under higher energy environments. Therefore, safety and toxicity are very important issues when considering the usage of these compounds. However, no study has verified the properties of Ultra-Violet B (UVB)-irradiated Arb and dA. In this work, we investigated the cytotoxicity and hypopigmentation effects of UVB-irradiated Arb and dA in Detroit 551 human fibroblast cells and B16-F10 mouse melanoma cells. The results showed that UVB-irradiated Arb and dA have strong cytotoxicity for the fibroblast cells, especially for dA, the caspase-3 is also activated by the treatment of UVB-irradiated dA in Detroit 551 cells. The results correlated with the produced HQ. In addition, UVB-irradiated Arb and dA suppressed the production of melanin in melanoma cells; this is due to the release of HQ that compensates for the UVB triggered Arb and dA decomposition.

Safe and effective ingredients capable of removing undesired hyperpigmentation from facial skin are urgently needed for both pharmaceutical and cosmetic purposes. Deoxyarbutin (4-[(tetrahydro-2H-pyran-2-yl) oxy] phenol, D-Arb) is a glucoside derivative of hydroquinone. Here, we investigated the toxicity and efficacy of D-Arb at the sub-cellular level (directly on melanosomes) and skin pigmentation using in vivo and in vitro models to compare with its parent compound hydroquinone (1,4-benzenediol, HQ). At first, we examined the ultrastructural changes of melanosomes in hyperpigmented guinea pig skin induced by 308-nm monochromatic excimer lightand/or treated with HQ and D-Arb using transmission electron microscopy. The results showed that prominent changes in the melanosomal membrane, such as bulb-like structure and even complete rupture of the outer membranes, were found in the skin after topical application of 5% HQ for 10 days. These changes were barely observed in the skin treated with D-Arb. To further clarify whether membrane toxicity of HQ was a direct result of the compound treatment, we also examinedultrastructural changes of individual melanosomes purified from MNT1 human melanoma cells. Similar observations were obtained from the naked melanosome model in vitro. Finally, we determined the effects of melanosomal fractions exposed to HQ or D-Arb on hydroxyl radical generation in the Fenton reaction utilizing an electron spin resonance assay. D-Arb-treated melanosomesexhibit a moderate hydroxyl radical-scavenging activity, whereas HQ-treated melanosomessignificantly generate more hydroxyl free radicals. This study suggests that D-Arb possesses a potent ability in skin lightening and antioxidation with less melanosome cytotoxicity., Competing Interests: The authors have declared that no competing interests exist.

Conclusion of the Opinion: Although on the basis of the provided scientific data the use of deoxyarbutin as such can be considered safe for consumers in cosmetic products in a concentration up to 3% in face creams, hydroquinone will be formed at levels which raise concerns with regard to the safety of such products during life-cycle of the product (e.g. storage conditions and stability under in-use conditions). Therefore, the overall conclusion of the SCCS is that the use of deoxyarbutin up to 3% in face creams is not safe., (Copyright © 2015. Published by Elsevier Inc.)

Arbutin (1), chlorogenic acid (2) and 6'-O-caffeoylarbutin (3) are three major components in Vaccinium dunalianum Wight with various promising bioactivities. A reliable, reproducible and accurate method for simultaneous and quantitative determination of 1-3 is developed by RP-HPLC analysis. This method should be appropriate for the quality assurance of unprocessed and processed materials of V. dunalianum. The contents of 1-3 in different parts of V. dunalianum from different origins were analysed. The content of 3 was much higher than those of 1 and 2, accounting for up to 31.76% in the dried leaf buds. Moreover, the leaf buds, flower buds and leaves showed a tendency towards higher contents of 1-3 than the other plant parts.

From the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Grevillea robusta, new arbutin derivatives and related compounds, named grevillosides J-Q (1-8), together with eight known compounds (9-18) were isolated. Various kind of acyl groups were attached to β-D-glucose at the 6-position through an ester linkage. Their structures were mainly elucidated from one- and two-dimensional NMR spectroscopic data. For exploitation as skin-lightening and anti-chloasma agents, the inhibitory activities of the isolated compounds as well as ones isolated in previous experiments (19-31) toward tyrosinase and melanin-producing B16 cells were assayed. Several compounds showed promising activity.

6'-O-Caffeoylarbutin, an arbutin derivative, is a naturally occurring glucoside of hydroquinone from Vaccinium dunalianum. On anti-melanogenic effect assay, 6'-O-caffeoylarbutin expressed a stronger anti-melanin activity in a dose-dependent manner with about a two-fold more than that of arbutin, but with less toxicity about a two-fold lower than that of arbutin. In addition, melanin synthesis could be fully recovered after the removal of 6'-O-caffeoylarbutin. The result suggested that 6'-O-caffeoylarbutin could be a candidate natural product to serve as a skin-whitening ingredient with the merits of potent melanin inhibition, less toxicity and reversible melanin synthesis after stopping use.

Arbutin and deoxy arbutin may release hydroquinone under some conditions. We therefore investigated the photostability of arbutin and deoxy arbutin in an aqueous solution. The results revealed arbutin and deoxy arbutin to be photolabile in an aqueous solution. Deoxy arbutin was less stable than arbutin when exposed to UV radiation. The hydroquinone concentration was also increased during the radiation period in both solutions. Benzophenone-4 could clearly improve the photostability of arbutin during the period of UV radiation, but only slightly enhance the photostability of deoxy arbutin.

Safety is a major concern in developing commercial skin-lightening agents. Here, we report the modulating effects of deoxyArbutin (dA) and its second-generation derivatives - deoxyFuran (dF), 2-fluorodeoxyArbutin (fdA), and thiodeoxyArbutin (tdA) - on tyrosinase, and consequently, on melanization. Results demonstrate that dA and its derivatives inhibit tyrosine hydroxylase and dopa oxidase activity of tyrosinase. The inhibition is dose-dependent, thereby inhibiting melanin synthesis in intact melanocytes, when used at concentrations that retain 95% viability of the treated cells in culture. Herein we demonstrate that dA, and its second-generation derivatives dF, fdA, and tdA, exhibit dose-dependent reductions in melanocyte cell number, primarily due to inhibition of proliferation rather than initiation of apoptosis as exemplified by hydroquinone (HQ), ie, cytostatic as opposed to cytotoxic. Human and murine melanocytes with functional mutations in either tyrosinase or tyrosinase-related protein 1 (Tyrp1) are less sensitive to the cytostatic effects of dA and its derivatives. Minimal amounts of reactive oxygen species (ROS) were generated upon treatment with dA and its derivatives, in contrast to a dramatic amount of ROS induced by HQ. This increase in ROS subsequently induced the expression of the endogenous antioxidant catalase in treated melanocytes. Treatment with exogenous antioxidants provided protection for melanocytes treated with HQ, but not dA and its derivatives, suggesting that HQ exerts more oxidative stress. These studies demonstrate that dA and its derivatives are relatively safe tyrosinase inhibitors for skin lightening or for ameliorating hyperpigmented lesions.

A new arbutin derivative, madhuglucoside (1), along with three known arbutin derivatives were isolated from the seeds of Madhuca latifolia in addition to seven other known constituents. Their structures were established on the basis of spectral analysis. Compounds 1a, 2a and 3a were obtained in a pure state after acetylation of the mother fraction and characterized as their acetyl derivatives.

The skin-whitening agent, deoxyArbutin, is a potent tyrosinase inhibitor that is safer than hydroquinone and arbutin. However, it is thermolabile in aqueous solutions, where it decomposes to hydroquinone. Pharmaceutical and cosmetic emulsions are normally oil-in-water (o/w) or water-in-oil (w/o) systems; however, emulsions can be formulated with no aqueous phase to produce an anhydrous emulsion system. An anhydrous emulsion system could offer a stable vehicle for compounds that are sensitive to hydrolysis or oxidation. Therefore, to enhance the stability of deoxyArbutin in formulations, we chose the polyol-in-silicone, anhydrous emulsion system as the basic formulation for investigation. The quantity of deoxyArbutin and the accumulation of hydroquinone in both hydrous and anhydrous emulsions at various temperatures were analyzed through an established high performance liquid chromatographic (HPLC) method. The results indicated that water increased the decomposition of deoxyArbutin in the formulations and that the polyol-in-silicone, oil-based, anhydrous emulsion system provided a relatively stable surrounding for the deoxyArbutin that delayed its degradation at 25 °C and 45 °C. Moreover, the composition of the inner hydrophilic phase, containing different amounts of glycerin and propylene glycol, affected the stability of deoxyArbutin. Thus, these results will be beneficial when using deoxyArbutin in cosmetics and medicines in the future.

Tyrosinase is the key and rate-limiting enzyme responsible for the conversion of tyrosine into melanin. Competitive inhibition of tyrosinase enzymatic activity results in decreased or absent melanin synthesis by melanocytes in human skin. DeoxyArbutin (4-[(tetrahydro-2H-pyran-2-yl)oxy]phenol), a novel skin whitening agent, was synthesized through the removal of hydroxyl groups from the glucose side-chain of arbutin. DeoxyArbutin not only shows greater inhibition of tyrosinase activity but is also safer than hydroquinone and arbutin. Hence, deoxyArbutin is a potential skin whitening agent for cosmetics and depigmenting drugs; however, stability of this compound under some conditions remains a problem. The lack of stability poses developmental and practical difficulties for the use of deoxyArbutin in cosmetics and medicines. Improving the thermostability of deoxyArbutin is an important issue for its development. In this research, we established an analytical procedure to verify the amount of deoxyArbutin in solutions using a high performance liquid chromatographic (HPLC) method. The results indicate that this novel skin whitening agent is a thermolabile compound in aqueous solutions. Additionally, the rate constant for thermodegradation (k) and the half-life (t(1/2)) of deoxyArbutin were determined and can be used to understand the thermodegradation kinetics of deoxyArbutin. This information can aid in the application of deoxyArbutin for many future uses.

Direct and regioselective acylation of arbutin with aromatic or aliphatic acid using a lipase obtained from Candida antarctica in an organic solvent was investigated. We achieved the enzymatic synthesis of feruloyl arbutin and lipoyl arbutin without the need of vinyl ferulate and vinyl lipoate as acyl donors, respectively., ((c) 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

A high performance liquid chromatography (HPLC) method for the determination of two optical isomers of arbutin (alpha-arbutin and beta-arbutin) and niacinamide in cosmetics was developed. The samples were extracted by the mixture of salt water and chloroform (2:1, v/v). The separation was performed on an ODS-BP column (200 mm x 4.6 mm, 5 microm, Elite) with methanol-water (10:90, v/v) as the mobile phase at a flow rate of 0.5 mL/min and 25 degrees C. The detection wavelength was set at 220 nm and the sample injection volume was 20 microL. There were good linear relationships between the mass concentration and the peak areas of alpha-arbutin, beta-arbutin and niacinamide in the ranges of 0.07-50, 0.06-50 and 0.05-50 mg/L, respectively. The relative standard deviations (RSDs, n = 7) of alpha-arbutin, beta-arbutin and niacinamide were 1.65%, 1.73% and 1.33%, respectively. The proposed method has been applied for the determination of alpha-arbutin, beta-arbutin and niacinamide in cosmetics with recoveries of 91.7%-109.6%. This method is rapid, simple and suitable for the detection of whitening ingredients in cosmetic.

Acyl arbutin was synthesized through the condensation of arbutin with a saturated fatty acid (C6-18) by the immobilized lipase in a batch reaction. The conversion at 10 and 20 g/l-solvent of immobilized lipase reached 45% over 2 d, but the initial reaction rate per amount of immobilized lipase decreased at 20 g/l-solvent. The radical scavenging activity of acyl arbutin in an ethanol solution was independent of the acyl chain length, although the rate constant, k, estimated for the oxidation of methyl linoleate in a bulk system with acyl arbutin by using the Weibull equation, decreased as the acyl chain length increased. This indicates the antioxidative ability of acyl arbutin with a long acyl chain to be due to its lipophilicity. Furthermore, it is suggested that dodecanoyl arbutin mainly acted on the interface between the oil and water phases in an O/W emulsion, and effectively suppressed the oxidation induced at the interface.

Background and Objective: The biosafety of hydroquinone and its derivatives as skin whitening agent remains controversial. Here, we investigated the effects of hydroquinone, arbutin, and deoxyarbutin (d-arb) on melanogenesis and antioxidation using cultured melan-a melanocytes in the presence or absence of ultraviolet A (UVA)-induced oxidative stress and determined whether d-arb enables to be an alterative to hydroquinone and arbutin for skin whitening use., Methods: d-arb was synthesized in this study by removing all hydroxyl groups from the glucose side-chain of arbutin. Tyrosinase activity was measured by (14)C-tyrosine incorporation, the intracellular reactive oxygen species (ROS) level was monitored by H(2)DCFDA fluorescence labeling, and the cell viability was determined by MTT assay in murine melan-a melanocytes treated with hydroquinone, arbutin and deoxyarbutin in the presence or absence of UVA-induced oxidative stress., Results: The cytotoxicity of hydroquinone and arbutin except for d-arb was increased while the cells exposed to a nontoxic dose (3J/cm(2)) of UVA irradiation. Suppressed ROS generation was noted by the treatment of d-arb to compare with arbutin and hydroquinone. All three compounds had a similar inhibition on tyrosinase activity in dose-dependent manners with two- to three-fold decreases over the untreated control. There was no change in expression of tyrosinase protein in cells treated with arbutin or hydroquinone, but a decreased protein expression of tyrosinase was seen in deoxyarbutin-treated cells., Conclusions: Deoxyarbutin exerts potent tyrosinase inhibition, lessened cytotoxicity, and certain antioxidation potential, may serve as an effective and safe alternative to hydroquinone for use in skin whitening.

The fragmentation behavior of hydroquinone glycosides involving one or two sugar groups from Fraxinus sieboldiana and their analogue arbutin was investigated systematically by electrospray ionization tandem mass spectrometry in negative ion mode. The characteristic fragmentation reaction of these compounds was through the homolytic and heterolytic cleavage of the O-glycosidic bond to produce radical aglycone ion ([Y0-H]-*) and aglycone ion (Y0-), respectively. Unambiguous differentiation between the mono-O-glycoside isomers which differ in glycosylation position was achieved by comparing the relative abundance of [Y0-H]-* and Y0- ions with the optimized collision energy. In the fragmentation of 1, 4-di-O-glycosides, only the Y0- ion was produced when the first glucosyl residue was expelled. However, both the [Y0-H]-* and Y0- ions were present when the second glucosyl residue was eliminated. In addition, an interesting [Y0-2H]- ion was present in the product ion spectra of hydroquinone glycosides with methoxy group(s) substituted at C-3 or/and C-5 positions of the benzene ring. The results of this study can facilitate the rapid determination of hydroquinone glycosides in crude plant extracts and also reveal that the systematic investigation and optimization of collision energy play an important role in the differentiation of isomers which have subtle differences in structures., (Copyright 2009 John Wiley & Sons, Ltd.)

Dunalianosides A-I (1-9), esters of arbutin and related phenolic glucosides, were isolated from the buds of Vaccinium dunalianum Wight (Ericaceae) together with 20 known compounds, and their structures were established on the basis of 1- and 2D NMR spectroscopic evidence. Dunalianosides F-H were dimers of p-hydroxyphenyl 6-O-trans-caffeoyl-beta-D-glucopyranoside (10). The latter was obtained in extraordinary high yield (22% of dry weight), and dunalianoside I (9) was found to be a conjugate of arbutin with an iridoid glucoside.

Background: Disorders, such as age spots, melasma and hyperpigmentation at sites of actinic damage, emanate from the augmentation of an increased amount of epidermal melanin., Objectives: The ineptness of current therapies in treating these conditions, as well as high cytotoxicity, mutagenicity, poor skin penetration and low stability of skin-depigmenting formulations led us to investigate new compounds that meet the medical requirements for depigmentation agents. We have shown previously that the tyrosinase inhibitor deoxyArbutin (dA) is a more effective and less toxic skin lightener than hydroquinone (HQ)., Methods: The efficacy and reversibility of dA and its derivatives on inhibiting tyrosine hydroxylase and DOPAoxidase was assessed using standard assays., Results: dA and its second-generation derivatives inhibit tyrosine hydroxylase and DOPAoxidase activities of tyrosinase dose dependently thereby inhibiting melanin synthesis in intact melanocytes, when used at concentrations that retain 95% cell viability in culture. This depigmenting effect was completely reversible when the compounds were removed. Tyrosinase inhibition was also observed in vitro when tested using human and purified mushroom tyrosinase, establishing that they are direct enzyme inhibitors. Lineweaver-Burk reciprocal plot analysis using mushroom tyrosinase illustrated that dA and its derivatives are more robust competitive inhibitors than HQ, when tyrosine is used as substrate., Conclusions: Thus, dA and its second-generation derivatives, which inhibit melanogenesis at safe concentrations by specifically acting on the tyrosinase enzyme at a post-translational level, are promising agents to ameliorate hyperpigmented lesions or lighten skin.

Three new galloyl arbutins, hyemalosides A-C (1-3), along with nine known compounds were isolated from the evergreen tree Eugenia hyemalis. The structures of compounds 1-3 were determined by analysis of NMR and MS data. Compounds 1-3 inhibited HIV-1 RNase H in vitro with IC50 values of 1.46, >18, and 1.19 microM, respectively. However, in a XTT-based cell viability assay using the human T-cell line CEM-SS infected with HIV-1 RT, none of the compounds inhibited the cytopathic effect of HIV-1 infection at the highest dose tested (20 microg/mL).

A new phenolic glucoside ester, 6'-E-(2''-methyl-2''-butenoyl) arbutin (1), was isolated from the leaves of Heliciopsis lobata. Its structure was elucidated by spectral analysis.

Transesterification of arbutin and undecylenic acid vinyl ester was catalyzed by alkaline protease, Bioprase, in dimethylformamide to get arbutin derivative having undecylenic acid at 6-position of glucose moiety, 6-O-undecylenoyl p-hydroxyphenyl beta-D-glucopyranoside. The reaction rate increased with increase of arbutin concentration, and when its concentration was 0.9 M, the conversion rate was more than 90% under addition of 2 M undecylenic acid vinyl ester. The obtained arbutin ester significantly suppressed melanin production in murine B16 melanoma cells.

A novel tyrosinase inhibitor, an arbutin derivative having undecylenic acid at the 6-position of its glucose moiety, was enzymatically synthesized. Its inhibitory activity was studied in vitro by using catechol and phenol as substrates. The IC(50) value of the arbutin ester on tyrosinase using catechol (4 x 10(-4) M) was 1% of that when arbutin (4 x 10(-2) M) was used. Using phenol, IC(50) of the arbutin ester (3 x 10(-4) M) as substrate was 10% of that of arbutin (3 x 10(-3) M). These results suggest that the arbutin ester inhibits the latter part of the tyrosinase reaction, which consists of hydroxylation and oxidation.

Several tyrosinase inhibitors have been developed and utilized to ameliorate various cutaneous hyperpigmentary disorders and complexion discolorations. Deoxyarbutin (dA) (i.e., 4-[(tetrahydro-2H-pyran-2-yl)oxy]phenol), designed using quantitative structure-activity relationships (QSAR), demonstrates effective inhibition of mushroom tyrosinase and skin-lightening capability (1). However, its comparative safety, effectiveness, and reversibility to other known tyrosinase inhibitors in human melanocytes had not been determined. The effect of dA was assessed in cultured human skin cells, on xenographs, and with a clinical trial. Using cultured human melanocytes, the maximum concentration of dA that allowed 95% viability was fourfold greater than for hydroquinone (HQ), indicating that dA is less cytotoxic/cytostatic than HQ. The viability of cultured human keratinocytes and fibroblasts was also less compromised by increasing concentrations of dA as opposed to HQ. At the maximum concentration allowing normal cellular viability, dA effectively inhibited tyrosinase activity and melanin content in human melanocytes, whereas HQ was marginally inhibitory. Upon removal of dA, tyrosinase activity and melanin content was normalized within five days. Topical application of dA on human xenografts resulted in a gradual and visually apparent skin lightening effect during an eight-week period. In a clinical trial, dA facilitated fading of pre-tanned skin to a statistically significant greater extent than either HQ or no treatment. These results demonstrate that dA is a potentially safe, effective, and reversible tyrosinase inhibitor.

A new phenolic glycoside, 6'-[(E)-2''-hydroxymethyl, 2''-butenoyl] arbutin (1), and two known phenolic glycosides, 6'-[(E)-4''-hydroxycinnamoyl] arbutin (2) and 6'-[(E)-3'',4''-dihydroxycinnamoyl] arbutin (3), were isolated from the leaves of Heliciopsis lobata (Merr.) Sleum. Their structures were elucidated by various spectroscopic methods including 2D NMR spectroscopy.

Modulation of melanogenesis in the melanocytes can be achieved using chemicals that share structural homologies with the substrate tyrosine and as thus competitively inhibit the catalytic function of tyrosinase. We have developed a new tyrosinase inhibitor, deoxyArbutin (dA), based on this premise. DeoxyArbutin demonstrates effective inhibition of mushroom tyrosinase in vitro with a Ki that is 10-fold lower that hydroquinone (HQ) and 350-fold lower than arbutin. In a hairless, pigmented guinea pig model, dA demonstrated rapid and sustained skin lightening that was completely reversible within 8 weeks after halt in topical application. In contrast, HQ induced a short but unsustained skin lightening effect whereas kojic acid and arbutin exhibit no skin lightening effect. Results from a panel of safety tests supported the overall establishment of dA as an actionable molecule. In a human clinical trial, topical treatment of dA for 12 weeks resulted in a significant or slight reduction in overall skin lightness and improvement of solar lentigines in a population of light skin or dark skin individuals, respectively. These data demonstrate that dA has potential tyrosinase inhibitory activity that can result in skin lightening and may be used to ameliorate hyperpigmentary lesions.

Arbutin cinnamate was synthesized from arbutin (4-hydroxyphenyl beta-D-glucopyranoside) and vinyl cinnamate by regioselective transesterification with a bacterial lipase in acetonitrile. The product was identified by NMR and FAB-MS analyses. These spectra showed that one ester bond was formed between the primary alcohol moiety of the D-glucose of arbutin and the carboxyl residue of cinnamic acid. Furthermore, plant pigments such as isoquercitrin (quercetin 3-O-beta-D-glucopyranoside) and callistephin (pelargonidin 3-O-beta-D-glucopyranoside) were also converted to their corresponding cinnamate esters in the same manner.

Six compounds have been isolated from the leaves of Pistacia chinensis, a species of Anacardiaceae family. Their structures were identified on the basis of UV, IR, NMR, and MS as gallic acid, m-digallic acid, quercetin, 6-0-galloyl arbutin-quercitrin and quercetin-3-0(6''-galloyl)-beta-D-glucosides.

In Escherichia coli, highly effective regulation controls the balanced synthesis of membrane phospholipids, important for optimal growth. Regulation is such that normally about 70% of a common pool of cytosine liponucleotide precursor is utilized by phosphatidylserine synthase and eventually converted to phosphatidylethanolamine, while about 30% is utilized by the competing enzyme phosphatidylglycerophosphate synthase and converted to phosphatidylglycerol (25%) plus cardiolipin (5%). Although the ratio of phosphatidylglycerol to cardiolipin may vary with conditions of growth, the sum of these two lipids remains relatively constant at about 30% of the total. Alternative models, postulating coordinate regulation of the two competing enzymes, or independent feedback regulation are proposed. These models were tested in experiments in which phosphatidylglycerol was continuously removed from growing cells treated with arbutin (4-hydroxyphenyl-O-beta-D-glucoside), causing its conversion to arbutinphosphoglycerol (Bohin, J.-P., and Kennedy, E.P. (1984) J. Biol. Chem. 259, 8388-8393.) The synthesis of phosphatidylglycerol was increased by a factor of 7 in cells treated with arbutin, with only small changes in phospholipid composition and with no significant change in the level of phosphatidylglycerophosphate synthase. The synthesis of phosphatidylethanolamine was not significantly increased, decisively eliminating the model that requires coordinate regulation of phosphatidylserine synthase and phosphatidylglycerophosphate synthase, and supporting the model of independent feedback inhibition, sensitive to very small changes in composition of cellular phospholipids.