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Abstract Background Endothelial cells (ECs) play a major role in malaria pathogenesis, as a point of direct contact of parasitized red blood cells to the blood vessel wall. The study of cytoskeleton structures of ECs, whose main functions are to maintain shape and provide strength to the EC membrane is important in determining the severe sequelae of Plasmodium falciparum malaria. The work investigated the cytoskeletal changes (microfilaments-actin, microtubules-tubulin and intermediate filaments-vimentin) in ECs induced by malaria sera (Plasmodium vivax, uncomplicated P. falciparum and complicated P. falciparum), in relation to the levels of pro-inflammatory cytokines. Methods Morphology and fluorescence intensity of EC cytoskeleton stimulated with malaria sera were evaluated using immunofluorescence technique. Levels of tumour necrosis factor (TNF) and interferon (IFN)-gamma (γ) were determined using enzyme-linked immunosorbent assay (ELISA). Control experimental groups included ECs incubated with media alone and non-malaria patient sera. Experimental groups consisted of ECs incubated with malaria sera from P. vivax, uncomplicated P. falciparum and complicated P. falciparum. Morphological scores of cytoskeletal alterations and fluorescence intensity were compared across each experiment group, and correlated with TNF and IFN-γ. Results The four morphological changes of cytoskeleton included (1) shrinkage of cytoskeleton and ECs with cortical condensation, (2) appearance of eccentric nuclei, (3) presence of “spiking pattern” of cytoskeleton and EC membrane, and (4) fragmentation and discontinuity of cytoskeleton and ECs. Significant damages were noted in actin filaments compared to tubulin and vimentin filaments in ECs stimulated with sera from complicated P. falciparum malaria. Morphological damages to cytoskeleton was positively correlated with fluorescence intensity and the levels of TNF and IFN-γ. Conclusions ECs stimulated with sera from complicated P. falciparum malaria showed cytoskeletal alterations and increased in fluorescence intensity, which was associated with high levels of TNF and IFN-γ. Cytoskeletal changes of ECs incubated with complicated P. falciparum malaria sera can lead to EC junctional alteration and permeability changes, which is mediated through apoptotic pathway. The findings can serve as a basis to explore measures to strengthen EC cytoskeleton and alleviate severe malaria complications such as pulmonary oedema and cerebral malaria. In addition, immunofluorescence intensity of cytoskeleton could be investigated as potential prognostic indicator for malaria severity.

Abstract Background Kheaw Hom remedy is a traditional Thai medicine used to treat fever. Some plants used in the Kheaw Hom remedy show promising in vitro antimalarial activity. This study prepared novel formulations of plants from the Kheaw Hom remedy and evaluated their antimalarial and toxicological activities. Methods Seven new formulations were prepared by combining at least three herbs of six selected plants from the Kheaw Hom remedy, namely Mammea siamensis Kosterm., Mesua ferrea L., Dracaena loureiroi Gagnep., Pogostemon cablin (Blanco) Benth., Kaempferia galanga L, and Eupatorium stoechadosmum Hance. In vitro antimalarial activities of each formulation’s aqueous and ethanolic extracts were evaluated using the parasite lactate dehydrogenase (pLDH) assay. Cytotoxicity in Vero and HepG2 cells was assessed using the MTT assay. An extract with good antimalarial potency and selectivity index (SI) was selected for in vivo antimalarial activity using Peter’s 4-day suppressive test and acute oral toxicity test in mice. In addition, bioactive compounds were identified using Gas chromatography-mass spectrometry (GC-MS) analysis. Results Among the seven new formulations, ethanolic extracts of CPF-1 (Formulation 1) showed the highest activity with an IC50 value of 1.32 ± 0.66 µg/ml, followed by ethanolic extracts of Formulation 4 and Formulation 6 with an IC50 value of 1.52 ± 0.28 µg/ml and 2.48 ± 0.34 µg/ml, respectively. The highest SI values were obtained for the ethanolic extract of CPF-1 that was selected to confirm its in vivo antimalarial activity and toxicity. The results demonstrated a significant dose-dependent reduction in parasitemia. Maximum suppressive effect of the extract (72.01%) was observed at the highest dose administered (600 mg/kg). No significant toxicity was observed after the administration of 2000 mg/kg. Using GC-MS analysis, the most abundant compound in the ethanolic extract of CPF-1 was ethyl p-methoxycinnamate (14.32%), followed by 2-propenoic acid, 3-phenyl-, ethyl ester, (E)- (2.50%), and pentadecane (1.85%). Conclusion The ethanolic extract of CPF-1 showed promising in vitro and in vivo antimalarial efficacy, with no toxic effects at a dose of 2000 mg/kg, suggesting that the ethanolic extract of CPF-1 may serves as a new herbal formulation for the treatment of malaria. Additional research is required for safety and clinical pharmacology studies.

Abstract Background Drug resistance exists in almost all antimalarial drugs currently in use, leading to an urgent need to identify new antimalarial drugs. Medicinal plant use is an alternative approach to antimalarial chemotherapy. This study aimed to explore potent medicinal plants from Prabchompoothaweep remedy for antimalarial drug development. Methods Forty-eight crude extracts from Prabchompoothaweep remedy and its 23 plants ingredients were investigated in vitro for antimalarial properties using Plasmodium lactate dehydrogenase (pLDH) enzyme against Plasmodium falciparum K1 strain and toxicity effects were evaluated in Vero cells. The plant with promising antimalarial activity was further investigated using gas chromatography-mass spectrometry (GC-MS) to identify phytochemicals. Antimalarial activity in mice was evaluated using a four-day suppressive test against Plasmodium berghei ANKA at dose of 200, 400, and 600 mg/kg body weight, and acute toxicity was analyzed. Results Of the 48 crude extracts, 13 (27.08%) showed high antimalarial activity against the K1 strain of P. falciparum (IC50

Abstract Background: The emergence of antimalarial drug resistance encourages the search for new antimalarial agents. Mammea siamensis belongs to the Calophyllaceae family, which is a medicinal plant that is used in traditional Thai preparations. The hexane and dichloromethane extracts of this plant were found to have potent antimalarial activity. Therefore, this study aimed to isolate active compounds from M. siamensis flowers and evaluate their antimalarial potential and their interactions with Plasmodium falciparum lactate dehydrogenase (PfLDH). Methods: The compounds from M. siamensis flowers were isolated by chromatographic techniques and evaluated for their antimalarial activity against chloroquine (CQ)-resistant P. falciparum (K1) strains using a parasite lactate dehydrogenase (pLDH) assay. Interactions between the isolated compounds and the PfLDH enzyme were investigated using a molecular docking method. Results: The isolation produced the following thirteen compounds: two terpenoids, lupeol (1) and a mixture of β-sitosterol and stigmasterol (5); two mammea coumarins, mammea A/AA cyclo D (6) and mammea A/AA cyclo F (7); and nine xanthones, 4,5-dihydroxy-3-methoxyxanthone (2), 4-hydroxyxanthone (3), 1,7-dihydroxyxanthone (4), 1,6-dihydroxyxanthone (8), 1-hydroxy-5,6,7-trimethoxyxanthone (9), 3,4,5-trihydroxyxanthone (10), 5-hydroxy-1-methoxyxanthone (11), 2-hydroxyxanthone (12), and 1,5-dihydroxy-6-methoxyxanthone (13). Compound 9 exhibited the most potent antimalarial activity with an IC50 value of 9.57 µM, followed by 10, 1, 2 and 13 with IC50 values of 15.48, 18.78, 20.96 and 22.27 µM, respectively. The molecular docking results indicated that 9, which exhibited the most potent activity, also had the best binding affinity to the PfLDH enzyme in terms of its low binding energy (-7.35 kcal/mol) and formed interactions with ARG109, ASN140, and ARG171. Conclusion: These findings revealed that isolated compounds from M. siamensis flowers exhibited antimalarial activity. The result suggests that 1-hydroxy-5,6,7-trimethoxyxanthone is a possible lead structure as a potent inhibitor of the PfLDH enzyme.

Abstract Background In response to the persistent problem of malaria resistance, medicinal herbal plants can be used as a source of potential novel antimalarial agents. Therefore, the aim of this study was to evaluate the in vivo antimalarial activity and toxicity of an ethanolic seed extract of Spondias pinnata (L.f.) Kurz (S. pinnata). Methods Qualitative phytochemical screening of the extract was performed using standard procedures, and the constituents were determined by gas chromatography–mass spectrometry (GC–MS). The in vivo antimalarial activity was assessed against the Plasmodium berghei ANKA strain in mice based on 4-day suppressive, curative and prophylactic tests. In addition, the acute toxicity of the extract was evaluated after oral administration of a single dose of 2,000 mg/kg body weight. Results Phytochemical screening tests on the ethanolic S. pinnata seed extract revealed the presence of terpenoids, tannins, and coumarins. GC–MS analysis of the extract led to the identification of twenty-nine phytochemical compounds, including oleic acid amide, β-sitosterol, linoleic acid, oleic acid, protocatechuic acid, syringic acid and gallic acid. The results of the 4-day suppressive test revealed that mice treated with 250, 500, 600 and 800 mg/kg doses of the ethanolic S. pinnata seed extract showed significant parasitemia suppression in a dose-dependent manner, with 22.94, 49.01, 60.67 and 66.82% suppression, respectively, compared to that of the negative control group. All the doses of the ethanolic seed extract significantly suppressed parasitemia (P

Abstract Background Novel potent antimalarial agents are urgently needed to overcome the problem of drug-resistant malaria. Herbal treatments are of interest because plants are the source of many pharmaceutical compounds. The Mahanil-Tang-Thong formulation is a Thai herbal formulation in the national list of essential medicines and is used for the treatment of fever. Therefore, this study aimed to evaluate the antimalarial activity of medicinal plants in the Mahanil-Tang-Thong formulation. Methods Nine medicinal plant ingredients of the Mahanil-Tang-Thong formulation were used in this study. Aqueous and ethanolic extracts of all the plants were analyzed for their phytochemical constituents. All the extracts were used to investigate the in vitro antimalarial activity against Plasmodium falciparum K1 (chloroquine-resistant strain) by using the lactate dehydrogenase (pLDH) method and cytotoxicity in Vero cells by using the 3-(4,5-dimethylthiazol2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, an extract with potent in vitro antimalarial activity and no toxicity was selected to determine the in vivo antimalarial activity with Peters’ 4-day suppressive test against the Plasmodium berghei ANKA strain. Acute toxicity was evaluated in mice for 14 days after the administration of a single oral dose of 2000 mg/kg. Results This study revealed that ethanolic extracts of Sapindus rarak DC., Tectona grandis L.f., Myristica fragrans Houtt. and Dracaena loureiri Gagnep. exhibited potent antimalarial activity, with half-maximal inhibitory concentration (IC50) values of 2.46, 3.21, 8.87 and 10.47 μg/ml, respectively, while the ethanolic of the formulation exhibited moderate activity with an IC50 value of 37.63 μg/ml and its aqueous extract had no activity (IC50 = 100.49 μg/ml). According to the in vitro study, the ethanolic wood extract of M. fragrans was selected for further investigation in an in vivo mouse model. M. fragrans extract at doses of 200, 400, and 600 mg/kg body weight produced a dose-dependent reduction in parasitemia by 8.59, 31.00, and 52.58%, respectively. No toxic effects were observed at a single oral dose of 2000 mg/kg body weight. Conclusion This study demonstrates that M. fragrans is a potential candidate for the development of antimalarial agents.

Background: Aging is closely associated to several deleterious conditions and cognitive impairment. Administration of low-dose paracetamol (APAP) has previously been reported to improve cognitive performance in both human and animal studies. However, the altered cognitive effects of low-dose APAP treatment in the aging brain have not been elucidated. Objectives: The purpose of this study was to determine whether low-dose APAP treatment improves cognitive dysfunction in a d-galactose (d-gal)-induced aging model. Materials and methods: APAP (15 and 50 mg/kg p.o.) and vitamin E (Vit E 100 mg/kg p.o.) were administered once daily to d-gal-injected mice (200 mg/kg s.c.) for 6 weeks. The elevated plus maze (EPM), open field, novel object recognition (NOR), and Morris water maze (MWM) tests, respectively, were used to measure altered neurobehavioral functions, including anxiety-like behavior and exploratory locomotor activity, as well as learning and memory performance. The gene transcription of brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) signaling in brain tissues was evaluated by real-time polymerase chain reaction. Results: Compared to the control, d-gal significantly decreased exploratory locomotor activity and NOR and MWM performance but did not significantly change the activity in the EPM test. However, APAP50 and Vit E significantly reversed the effects of d-gal injection on exploratory locomotor activity. In addition, low-dose APAP (15 and 50 mg/kg) and Vit E significantly improved the reduction in NOR and MWM performance induced by d-gal. Real-time polymerase chain reaction analysis revealed that the mRNA expression of BDNF, neurotrophic tyrosine receptor kinase (NTRK), which is the gene coding TrkB receptor, and cAMP response element-binding protein (CREB) was significantly decreased in the frontal cortex and hippocampus of the d-gal mice. However, APAP50 and Vit E significantly increased BDNF and NTRK mRNA expression in both the frontal cortex and the hippocampus. A lower dose of APAP (15 mg/kg) significantly elevated the mRNA expression of NTRK, but only in the hippocampus. Moreover, APAP50 significantly increased CREB mRNA expression in the frontal cortex and hippocampus. Conclusion: Low-dose APAP treatment has a neuroprotective effect on cognitive dysfunction in the d-gal aging model, and the underlying molecular mechanisms depend on the activation of BDNF/TrkB signaling.

The increasing resistance of parasites to antimalarial drugs and the limited number of effective drugs are the greatest challenges in the treatment of malaria. It is necessary to search for an alternative medicine for use as a new, more effective antimalarial drug. Therefore, this study aimed to evaluate the in vitro antimalarial activity and cytotoxicity of extracts from plants belonging to the Asteraceae and Rubiaceae families. The phytoconstituents of one hundred ten ethanolic and aqueous extracts from different parts of twenty-three plant species were analyzed. Evaluation of their antimalarial activities against the chloroquine (CQ)-resistant Plasmodium falciparum (K1) strain was carried out using the lactate dehydrogenase (pLDH) assay, and their cytotoxicity in Vero cells was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric method. A total of 40.91% of the extracts were active antimalarial agents. Three extracts (2.73%) exhibited high antiplasmodial activity (IC50 < 10 μg/ml), twenty-four extracts (21.82%) were moderately active with IC50 values ranging from 10–50 μg/ml, and eighteen extracts (16.36%) were mildly active with IC50 values ranging from 50–100 μg/ml. The ethanolic leaf extract of Mussaenda erythrophylla (Dona Trining; Rubiaceae) exhibited the highest activity against P. falciparum, with an IC50 value of 3.73 μg/ml and a selectivity index (SI) of 30.74, followed by the ethanolic leaf extract of Mussaenda philippica Dona Luz x M. flava (Dona Marmalade; Rubiaceae) and the ethanolic leaf extract of Blumea balsamifera (Camphor Tree; Asteraceae), with IC50 values of 5.94 and 9.66 μg/ml and SI values of 25.36 and >20.70, respectively. GC–MS analysis of these three plant species revealed the presence of various compounds, such as squalene, oleic acid amide, β-sitosterol, quinic acid, phytol, oleamide, α-amyrin, sakuranin, quercetin and pillion. In conclusion, the ethanolic leaf extract of M. erythrophylla, the leaf extract of M. philippica Dona Luz x M. flava and the leaf extract of B. balsamifera had strong antimalarial properties with minimal toxicity, indicating that compounds from these plant species have the potential to be developed into new antiplasmodial agents.

Decreased serum sphingosine 1-phosphate (S1P) has been reported in severe malaria patients, but the expression of receptors and enzymes associated with S1P has not been investigated in the liver of malaria patients. Therefore, this study aimed to investigate the expression of sphingosine kinase (SphK) and S1P receptors (S1PRs) in the liver of malaria-infected mice. C57BL/6 male mice were divided into a control group (n = 10) and a Plasmodium berghei (PbA)-infected group (n = 10). Mice in the malaria group were intraperitoneally injected with 1×106 P. berghei ANKA-infected red blood cells, whereas control mice were intraperitoneally injected with normal saline. Liver tissues were collected on Day 13 of the experiment to evaluate histopathological changes by hematoxylin and eosin staining and to investigate SphK and S1PR expression by immunohistochemistry and real-time PCR. Histological examination of liver tissues from the PbA-infected group revealed sinusoidal dilatation, hemozoin deposition, portal tract inflammation and apoptotic hepatocytes, which were absent in the control group. Immunohistochemical staining showed significant increases in the expression of SphK1 and SphK2 and significant decreases in the expression of S1PR1, S1PR2, and S1PR3 in the endothelium, hepatocytes, and Kupffer cells in liver tissue from the PbA-infected group compared with the control group. Real-time PCR analysis showed the upregulation of SphK1 and the downregulation of S1PR1, S1PR2, and S1PR3 in the liver in the PbA-infected group compared with the control group. In conclusion, this study demonstrates for the first time that SphK1 mRNA expression is upregulated and that S1PR1, S1PR2, and S1PR3 expression is decreased in the liver tissue of PbA-infected mice. Our findings suggest that the decreased levels of S1PR1, S1PR2, and S1PR3 might play an important role in liver injury during malaria infection.

The Kheaw Hom remedy is a traditional Thai medicine widely used to treat fevers. Some plant ingredients in this remedy have been investigated for their antimicrobial, antiviral, anti-inflammatory, and antioxidant activities. However, there have been no reports on the antimalarial activities of the medicinal plants in this remedy. Therefore, this study focuses on identifying potential antimalarial drug candidates from the medicinal plant ingredients of the Kheaw Hom remedy. Eighteen plants from the Kheaw Hom remedy were extracted using distilled water and ethanol. All extracts were investigated for their in vitro antimalarial activity and cytotoxicity. An extract that exhibited good in vitro antimalarial activity and low toxicity was selected for further investigation by using Peter’s 4-day suppressive test and an acute oral toxicity evaluation in mice. Based on the in vitro antimalarial activity and cytotoxicity studies, the ethanolic extract of Globba malaccensis rhizomes showed promising antimalarial activity against the Plasmodium falciparum K1 strain (IC50 = 1.50 µg/mL) with less toxicity to Vero cells (CC50 of >80 µg/mL). This extract exhibited a significant dose-dependent reduction in parasitemia in P. berghei-infected mice. The maximum suppressive effect of this extract (60.53%) was observed at the highest dose administered (600 mg/kg). In a single-dose acute toxicity test, the animals treated at 2000 mg/kg died within 48 h after extract administration. In conclusion, our study indicates that the ethanolic extract of G. malaccensis rhizomes exhibited in vitro and in vivo antimalarial activities, which could serve as a promising starting point for antimalarial drug.