What SARS-CoV-2 Variants Have Taught Us: Evolutionary Challenges of RNA Viruses.

Since its discovery in 2019, SARS-CoV-2 still makes the headline news [...].

Alpha-mangostin, piperine and beta-sitosterol as hepatitis C antivirus (HCV): In silico and in vitro studies.

Hepatitis C is still a serious liver case of health. Up to now the development of anti-Hepatitis C Virus (HCV) drugs is challenging, especially the development of natural material compounds as anti-HCV. In the present study, we evaluated the probability of α-mangostin, piperine, and ß-sitosterol as anti-HCV with the in silico and in vitro approaches. Molecular docking was performed between nonstructural protein 5B (NS5B, PDB ID 3FQL) with α-mangostin, piperine, and ß-sitosterol by Autodock Tools® and BIOVIA Discovery Studio®. Subsequently, molecular dynamics simulations were conducted for 200 ns, evaluating the dynamic interaction between the ligands and the viral protein NS5B. Furthermore, compound characterization at the hepatocarcinoma cell line was employed. α-Mangostin with NS5B complex demonstrated the most negative binding free energy value based on MM-PBSA calculation with a value of -9.13 kcal/mol. In vitro test showed that IC50 of α -mangostin was 2.70 ± 0.92 µM, IC50 of piperine was 52.18 ± 3.21 µM, IC50 of ß-sitosterol was >100 µM. α-Mangostin can serve as a valuable lead compound for further development of the anti-HCV.

Microscopic and physicochemical evaluation of Ruta angustifolia leaves.

Background: There are thousands of species of known medicinal plants in the world. Ruta angustifolia L. has been widely used in traditional medication for jaundice and liver disease. Previous studies have shown that R. angustifolia leaves can inhibit the hepatitis C virus in Huhit culture cells, reduce the value of NS3 protein, and possess a synergistic effect in combination with antiviral drugs. Therefore, this plant is potential to be developed as a drug candidate. Characteristics of plants including microscopic, physicochemical properties, and phytochemical profiles are necessary information to ensure the quality of raw material in drug development. Objective: This study was carried out to examine the microscopic and physicochemical including the standardized parameter of R. angustifolia leaves to fulfil the quality raw materials as traditional medicine. Methods: Simplicia of R. angustifolia leaves obtained from Jombang, East Java, were observed under a microscope and determined its physicochemical properties referred to the Materia Medica Indonesia V. The TLC and HPLC profiles of extract were determined as well. Results: Microscopic analysis were conducted by transfection sections and the presence of epidermis cells, palisade, mesophyll with stomata, and Ca-oxalate crystal were found. The standard parameter obtained value of loss of drying, extractive value in water and ethanol, and ash value. The TLC and HPLC profiles of leaves extract demonstrated to contain with flavonoid, terpenoids, and alkaloids. Conclusion: Ruta angustifolia obtained from Jombang, east Java, has a specific character in microscopic analysis. The physicochemical properties analysis of R. angustifolia leaves as a raw material met the requirements according to Materia Medica Indonesia V.

Promising alkaloids and flavonoids compounds as anti-hepatitis c virus agents: a review.

Background: Virus infections are presently seen as a major public health problem. Hepatitis C Virus (HCV) is recognized as a "silent killer" because the acute infection has no symptoms, and it develops as a chronic infection that causes hepatocellular carcinoma and liver damage. The World Health Organization (WHO) predicts that between 130-170 million people are estimated to have chronic Hepatitis C. Plants have various phytochemical compounds such as alkaloids and flavonoids that have prominent antiviral effects especially anti-HCV. The current HCV treatment still has limitations related to side effects and can lead to viral resistance. Therefore, it is necessary for the discovery and development of novel anti-HCV drugs for alternative and complementary medicine. Objective: This review intends to evaluate the alkaloids and flavonoids that have the potential to be used against HCV by looking at their classification and their mechanism of action. Methods: Twenty-one articles from 2010 to 2022 obtained from PUBMED database using keywords such as isolated compounds, alkaloids, flavonoids, hepatitis C virus. Results: 21 alkaloids and 37 flavonoids reported active against HCV. Alkaloids include quinoline, quinolizidine and isoquinoline. In addition, flavanone, flavonol, flavone, flavan-3-ol, flavonolignan, anthocyanidin and proanthocyanidin comprise flavonoids. The berberine alkaloids and eriodictyol 7-O-(6″-caffeoyl)-ß-Dglucopyranoside flavonoids had the lowest IC50 with values of 0.49 mM and 0.041 nM. Conclusions: Alkaloids and flavonoids compound had good activity against HCV with various mechanisms. Our results provide information of alkaloids and flavonoids to the researcher for the development of alternative and complementary medicine of hepatitis C.

In silico screening of potential compounds from begonia genus as 3CL protease (3Cl pro) SARS-CoV-2 inhibitors.

Background: The emergence of Coronavirus disease (COVID-19) has been declared a pandemic and made a medical emergency worldwide. Various attempts have been made, including optimizing effective treatments against the disease or developing a vaccine. Since the SARS-CoV-2 protease crystal structure has been discovered, searching for its inhibitors by in silico technique becomes possible. Objective: This study aims to virtually screen the potential of phytoconstituents from the Begonia genus as 3Cl pro-SARS-CoV- 2 inhibitors, based on its crucial role in viral replication, hence making these proteases "promising" for the anti-SARS-CoV-2 target. Methods: In silico screening was carried out by molecular docking on the web-based program DockThor and validated by a retrospective method. Predictive binding affinity (Dock Score) was used for scoring the compounds. Further molecular dynamics on Desmond was performed to assess the complex stability. Results: Virtual screening protocol was valid with the area under curve value 0.913. Molecular docking revealed only ß-sitosterol- 3-O-ß-D-glucopyranoside with a lower docking score of - 9.712 kcal/mol than positive control of indinavir. The molecular dynamic study showed that the compound was stable for the first 30 ns simulations time with Root Mean Square Deviation <3 Å, despite minor fluctuations observed at the end of simulation times. Root Mean Square Fluctuation of catalytic sites HIS41 and CYS145 was 0.756 Å and 0.773 Å, respectively. Conclusions: This result suggests that ß-sitosterol-3-O-ß-Dglucopyranoside might be a prospective metabolite compound that can be developed as anti-SARS-CoV-2.

Acacia mangium: A promising plant for isolating anti-hepatitis C virus agents.

Background: Medicinal plants are potential resources for isolating drug candidates. Various plants have been reported to possess pharmacological effects including anti-hepatitis C activities. The current study examined the anti-hepatitis C virus (HCV) activities of Acacia mangium extracts in solvents with various polarities and further evaluated the mechanism of action of the extracts using Western blotting and combination treatment models. Methods: The leaves of A. mangium were extracted in two phases, first in ethanol and then in solvents with different polarities (n-hexane, dichloromethane, and methanol). HCV-infected Huh7it-1 cells were treated with the extracts at concentrations of 0.01, 0.1, 1, 10, 50, and 100 µg/mL. Results: The results revealed the strong anti-HCV activities of the extracts. The 50% inhibition concentrations (IC 50s) of the ethanol, n-hexane, dichloromethane and methanol extracts were of 4.6 ± 0.3, 2.9 ± 0.2, 0.2 ± 0.3, and 2.8 ± 0.2 µg/mL, respectively, and no cytotoxic effect was detected. These extracts displayed stronger effects than the positive control ribavirin. The mode of action of the ethanol extract was evaluated at 30 µg/mL, revealing that the inhibitory effect was stronger on the post-entry step than on the entry step. Western blotting revealed that the extracts decreased NS3 protein expression, indicating that virus replication was suppressed. Further evaluation illustrated that combined treatment with the ethanol extract enhanced the anti-viral activity of simeprevir. Conclusions: These results indicated that A. mangium leaves could represent sources of anti-HCV agents.

An in vitro study of an Artocarpus heterophyllus substance as a hepatitis C antiviral and its combination with current anti-HCV drugs.

BACKGROUND: Current therapy of chronic hepatitis C virus (HCV) with direct-acting antivirals (DAAs) has dramatically improved the sustained virologic response (SVR) of affected patients; however, treatment with DAAs remains expensive, and drug-resistant HCV variants remain a threat. As a result, there is still a need to continue to develop affordable and effective drugs for the treatment of HCV. Previously, we have demonstrated that a crude extract from Artocarpus heterophyllus leaves is a potential anti-HCV candidate. In this study, we have further purified this crude extract, examined which sub-fraction possesses the highest antiviral activity, and then explored its efficacy at different HCV life cycle stages. We also assessed synergistic antiviral effects between the A. heterophyllus extract and commercially available anti-HCV drugs. METHODS: We used vacuum liquid chromatography (VLC) and high-performance liquid chromatography (HPLC) to fractionate a dichloromethane extract of A. heterophyllus leaves. We then examined the anti-HCV activity of the fractions using HCV genotype 2a, JFH1a; the antiviral mode of action was determined by exploring adding the treatments at different times. We examined the antiviral effects on the viral entry stage through a virucidal activity test, viral adsorption examination, and pretreatment of cells with the drug. The effects on the post-viral entry stage were determined by the levels of HCV protein expression and HCV RNA expression in infected cells. RESULTS: Through activity guided purification, we identified the sub-fraction FR3T3 as possessing the most robust anti-HCV activity with an IC50 value of 4.7 ± 1.0 µg/mL. Mode-of-action analysis revealed that FR3T3 inhibited post-viral entry stages such as HCV NS3 protein expression and HCV RNA replication with marginal effects on the viral entry stage. Thin-layer Chromatography (TLC) indicated that FR3T3 contained terpenoids and chlorophyll-related compounds. We also found a synergistic antiviral activity when the DCM extract of A. heterohyllus was used in combination therapy with commercial anti-HCV drugs; Ribavirin, Simeprevir, Cyclosporin A. CONCLUSIONS: The extract of A. heterophyllus and its sub-fraction, FR3T3, presented here have anti-HCV activities and could be candidate drugs for add-on-therapy for treatment of chronic HCV infections.

Phyllanthin and hypophyllanthin, the isolated compounds of Phyllanthus niruri inhibit protein receptor of corona virus (COVID-19) through in silico approach.

OBJECTIVES: Phyllanthus niruri has been known as an immunomodulator and also reported to possess an antiviral activity against several RNA viruses, such as hepatitis B virus and hepatitis C virus by inhibiting viral entry and replication. Since the current situation of Coronavirus Disease 2019 (COVID-19) which infected among the world and caused severe disease and high morbidity, it urgently needed to find new agents against COVID-19. Therefore, in silico screening against COVID-19 receptors is carried out as an initial stage of drug discovery by evaluating the activity of phyllanthin and hypophyllanthin, an isolated from Phyllanthus niruri, in inhibiting spike glycoprotein (6LZG) and main protease (5R7Y) which play as target receptors of COVID-19. METHODS: Molegro Virtual Docker 6.0 used to determine the best binding energy through the rerank score which shows the total energy bonds calculation. RESULTS: Phyllanthin and hypophyllanthin demonstrated to possess greater binding affinity toward the COVID-19 inhibition sites than their native ligand. The rerank score of phyllanthin and hypophyllanthin are lower than the native ligands 6LZG and 5R7Y. This result indicated that phyllanthin and hypophyllanthin have a stronger interaction than the native ligands both in spike glycoprotein (entry inhibitor) and main protease (translation and replication inhibitor). CONCLUSIONS: In conclusion, phyllanthin and hypophyllanthin are predicted to have strong activity against COVID-19 through inhibiting spike glycoprotein and main protease under in silico study. Further research is needed to support the development of P. niruri as inhibitor agents of COVID-19 through bioassay studies.

Antiplasmodial activity of Ethanolic extract of Cassia spectabilis DC leaf and its inhibition effect in Heme detoxification.

BACKGROUND: In previous studies, Cassia spectabilis DC leaf has shown a good antiplasmodial activity. Therefore, this study is a follow-up study of the extract of leaf of C. spectabilis DC on its in vitro and in vivo antiplasmodial activity and mechanism as an antimalarial. METHODS: The extract was fractionated, sub-fractionated and isolated to obtain the purified compound. In vitro antiplasmodial activity test against Plasmodium falciparum to find out the active compound. In vivo test against P. berghei ANKA-infected mice was conducted to determine prophylactic activity and antiplasmodial activity either alone or in combination with artesunate. The inhibition of heme detoxification test as one of the antimalarial mechanisms was carried out using the Basilico method. RESULTS: The results showed that active antimalarial compound isolated from C. spectabilis DC leaf had a structural pattern that was identical to (-)-7-hydroxycassine. Prophylactic test of 90% ethanolic extract of C. spectabilis DC leaf alone against P. berghei ANKA-infected mice obtained the highest percentage inhibition was 68.61%, while positive control (doxycycline 13 mg/kg) was 73.54%. In combination with artesunate, 150 mg/kg three times a day of C. spectabilis DC (D0-D2) + artesunate (D2) was better than the standard combination of amodiaquine + artesunate where the inhibition percentages were 99.18 and 92.88%, respectively. The IC50 of the extract for the inhibitory activity of heme detoxification was 0.375 mg/ml which was better than chloroquine diphosphate (0.682 mg/ml). CONCLUSION: C. spectabilis DC leaf possessed potent antiplasmodial activity and may offer a potential agent for effective and affordable antimalarial phytomedicine.

Alkaloid and benzopyran compounds of Melicope latifolia fruit exhibit anti-hepatitis C virus activities.

BACKGROUND: New agents for developing alternative or complementary medicine to treat the hepatitis C virus (HCV) are still needed due to high rates of HCV infection globally and the current limitations of available treatments. Treatment of HCV with a combination of direct acting antivirals have been shown to be approximately 90% effective but will be limited in the future due to the emergence of drug resistance and high cost. The leaves of Melicope latifolia have previously been reported to have anti-HCV activity and are a potential source of bioactive compounds for future novel drug development. This study aimed to evaluate the efficacy of the extract of M. latifolia fruit to treat HCV and to isolate its active compounds. METHOD: M. latifolia fruit was extracted using methanol and purified using vacuum liquid chromatography (VLC) and Radial Chromatography. The anti-HCV activity was analyzed using cell culture lines Huh7it-1 and JFH1 (genotype 2a). Time-of-addition and immunoblotting studies were performed to identify the mode of action of the isolated active compounds. The structures of the active compounds were determined using nuclear magnetic resonance (NMR) spectra, UV, IR, and Mass Spectra. RESULTS: Six known compounds were isolated from M. latifolia fruit: O-methyloktadrenolon, alloevodionol, isopimpinellin, alloxanthoxyletin, methylevodionol, and N-methylflindersine. N-methylflidersine was the most active compound with IC50 value of 3.8 µg/ml while methylevodionol, isopimpinellin, and alloevodionol were less active. O-methyloktadrenolon and alloxanthoxyletin were moderately active with IC50 values of 10.9 and 21.72 µg/ml, respectively. N-methylflidersine decreased level of HCV NS3 protein expression in the cells. CONCLUSION: The alkaloid compound, N-methylflindersine which was isolated from M. latifolia possesses anti-HCV activity through post-entry inhibition and suppressed NS3 protein expression.

Synergistic anti-hepatitis C virus activity of Ruta angustifolia extract with NS3 protein inhibitor.

Background Medicinal plants are known to perform many pharmacological actions due to their chemical metabolites, which include antiviral effects. Previously, the extract of Ruta angustifolia was shown to have potential anti-hepatitis C virus (HCV) activity without any cytotoxicity, with a 50% inhibitory concentration of 3.0 µg/mL and a 50% cytotoxicity concentration of >100 µg/mL. Furthermore, the combination of medicinal plants and current anti-HCV agents, such as a direct-acting antiviral agent, was shown to potentiate their overall effectiveness. In the course of this study, the ethanolic extract of R. angustifolia was evaluated for its anti-HCV effects; specifically, the mechanism of action on HCV NS3 and NS5A protease was investigated. Methods Analysis of the use of this extract in conjunction with current NS3 inhibitor drugs, simeprevir (SMV) and telaprevir (TVR), was performed. Anti-HCV activity was performed by in vitro culture of hepatocyte cells. The cells were infected and treated with various concentrations of the sample. HCV inhibition was calculated and CompuSyn software analysis was used to determine the synergistic effect of the combination. Results Results demonstrated that R. angustifolia extract inhibited the post-entry step and decreased the protein levels of HCV NS3 and NS5A. The combination of extract and SMV and TVR mediated a synergistic effect. Conclusions These findings suggest that combining R. angustifolia extract with current anti-HCV drugs should be considered when developing alternative and complementary anti-HCV medicines.

Antiviral Activity of Cananga odorata Against Hepatitis B Virus.

Chronic hepatitis B virus (HBV) infection can lead to liver cirrhosis and hepatocellular carcinoma. Current therapeutic drugs for chronic hepatitis B using pegylated interferons and nucleos(t)ide analogs have limited efficacy. Therefore, the development of novel and safe antivirals is required. Natural products including medicinal plants produce complex and structurally diverse compounds, some of which offer suitable targets for antiviral screening studies. In the present study, we screened various crude extracts from Indonesian plants for anti-HBV activity by determining their effects on the production of extracellular HBV DNA in Hep38.7-Tet cells and HBV entry onto a HBV-susceptible cell line, HepG2-NTCP, with the following results: (1) In Hep38.7-Tet cells, Cananga odorata exhibited the highest anti-HBV activity with a 50% inhibitory concentration (IC50) of 56.5 µg/ml and 50% cytotoxic concentration (CC50) of 540.2 µg/ml (Selectivity Index: 9.6). (2) The treatment of HepG2-NTCP cells with Cassia fistula, C. odorata, and Melastoma malabathricum at concentrations of 100 µg/ml lowered the levels of HBsAg production to 51.2%, 58.0%, and 40.1%, respectively, compared to untreated controls, and IC50 and CC50 values of C. odorata were 142.9 µg/ml and >400 µg/ml. In conclusion, the C. odorata extract could be a good candidate for the development of anti-HBV drugs.

DETERMINATION OF EFFECTIVE DOSE OF ANTIMALARIAL FROM CASSIA SPECTABILIS LEAF ETHANOL EXTRACT IN PLASMODIUM BERGHEI-INFECTED MICE.

BACKGROUND: The preliminary study on antimalarial activity of the ethanol extract of Cassia spectabilis leaves against Plasmodium berghei has been carried out by in vivo experiment. It was demonstrated that ethanol extract of C. spectabilis leaves could inhibit growth of rodent malaria parasite P. berghei by 59.29 % (at a dose of 100 mg/kg bodyweight). However, further investigation is required to determine an effective dose of the administered extract for a higher inhibitory effect and increasing effectiveness of the extract. MATERIAL AND METHODS: To determine the effective dose of ethanol extract of C. spectabilis leaves, a "4-day suppressive test" of Peter was performed with some modifications. The extract was administered orally to P. berghei-infected mice in multiple doses (twice and thrice daily) and single dose (once daily) with dose ranging from 50 - 250 mg/kg body weight. Antimalarial activities were determined by analyzing suppression of parasitaemia of treated mice. RESULTS: The results showed that oral administration of the ethanol extract of C. spectabilis leaves at dose of 150mg/kg bodyweight thrice daily possessed higher inhibition (62.42%) compared to those twice daily (52.58%) and once daily (46.25%). CONCLUSION: These results suggested that ethanol extract of C. spectabilis is promising candidate for development of antimalarial drugs. The effective dose of the ethanol extract is 150 mg/kg bodyweight with thrice administration daily.

Promising Anti-Hepatitis C Virus Compounds from Natural Resources.

Hepatitis C virus (HCV) infection is a major worldwide problem, which involves approximately 170 million people. High morbidity of patients is caused by chronic infection, which leads to liver cirrhosis, hepatocellular carcinoma and other HCV-related diseases. The sustained virological response (SVR) has been markedly improved to be >90% by the current standard interferon (IFN)-free treatment regimens with a combination of direct-acting antiviral agents (DAAs) targeting the viral NS3 protease, NS5A multi-function protein and NS5B RNA-dependent RNA polymerase, compared with 50-70% of SVR rates achieved by the previous standard IFN-based treatment regimens with or without an NS3 protease inhibitor. However, the emergence of DAA-resistant HCV strains and the limited access to the DAAs due to their high cost could be major concerns. Also, the long-term prognosis of patients treated with DAAs, such as the possible development of hepatocellular carcinoma, still needs to be further evaluated. Natural resources are considered to be good candidates to develop anti-HCV agents. Here, we summarize anti-HCV compounds obtained from natural resources, including medicinal plant extracts, their isolated compounds and some of their derivatives that possess high antiviral potency against HCV.

Inhibition of hepatitis C virus replication by chalepin and pseudane IX isolated from Ruta angustifolia leaves.

Hepatitis C virus (HCV) infection is highly prevalent among global populations, with an estimated number of infected patients being 170 million. Approximately 70-80% of patients acutely infected with HCV will progress to chronic liver disease, such as liver cirrhosis and hepatocellular carcinoma, which is a substantial cause of morbidity and mortality worldwide. New therapies for HCV infection have been developed, however, the therapeutic efficacies still need to be improved. Medicinal plants are promising sources for antivirals against HCV. A variety of plants have been tested and proven to be beneficial as antiviral drug candidates against HCV. In this study, we examined extracts, their subfractions and isolated compounds of Ruta angustifolia leaves for antiviral activities against HCV in cell culture. We isolated six compounds, chalepin, scopoletin, γ-fagarine, arborinine, kokusaginine and pseudane IX. Among them, chalepin and pseudane IX showed strong anti-HCV activities with 50% inhibitory concentration (IC50) of 1.7 ± 0.5 and 1.4 ± 0.2 µg/ml, respectively, without apparent cytotoxicity. Their anti-HCV activities were stronger than that of ribavirin (2.8 ± 0.4 µg/ml), which has been widely used for the treatment of HCV infection. Mode-of-action analyses revealed that chalepin and pseudane IX inhibited HCV at the post-entry step and decreased the levels of HCV RNA replication and viral protein synthesis. We also observed that arborinine, kokusaginine and γ-fagarine possessed moderate levels of anti-HCV activities with IC50 values being 6.4 ± 0.7, 6.4 ± 1.6 and 20.4 ± 0.4 µg/ml, respectively, whereas scopoletin did not exert significant anti-HCV activities at 30 µg/ml.

Anti-hepatitis C virus compounds obtained from Glycyrrhiza uralensis and other Glycyrrhiza species.

Development of complementary and/or alternative drugs for treatment of hepatitis C virus (HCV) infection is still much needed from clinical and economic points of view. Antiviral substances obtained from medicinal plants are potentially good targets to study. Glycyrrhiza uralensis and G. glabra have been commonly used in both traditional and modern medicine. In this study, extracts of G. uralensis roots and their components were examined for anti-HCV activity using an HCV cell culture system. It was found that a methanol extract of G. uralensis roots and its chloroform fraction possess anti-HCV activity with 50%-inhibitory concentrations (IC(50)) of 20.0 and 8.0 µg/mL, respectively. Through bioactivity-guided purification and structural analysis, glycycoumarin, glycyrin, glycyrol and liquiritigenin were isolated and identified as anti-HCV compounds, their IC(50) being 8.8, 7.2, 4.6 and 16.4 µg/mL, respectively. However, glycyrrhizin, the major constituent of G. uralensis, and its monoammonium salt, showed only marginal anti-HCV activity. It was also found that licochalcone A and glabridin, known to be exclusive constituents of G. inflata and G. glabra, respectively, did have anti-HCV activity, their IC(50) being 2.5 and 6.2 µg/mL, respectively. Another chalcone, isoliquiritigenin, also showed anti-HCV activity, with an IC(50) of 3.7 µg/mL. Time-of-addition analysis revealed that all Glycyrrhiza-derived anti-HCV compounds tested in this study act at the post-entry step. In conclusion, the present results suggest that glycycoumarin, glycyrin, glycyrol and liquiritigenin isolated from G. uralensis, as well as isoliquiritigenin, licochalcone A and glabridin, would be good candidates for seed compounds to develop antivirals against HCV.

Antiviral activities of Indonesian medicinal plants in the East Java region against hepatitis C virus.

BACKGROUND: Hepatitis C virus (HCV) is a major cause of liver disease and a potential cause of substantial morbidity and mortality worldwide. The overall prevalence of HCV infection is 2%, representing 120 million people worldwide. Current standard treatment using pegylated interferon and ribavirin is effective in only 50% of the patients infected with HCV genotype 1, and is associated with significant side effects. Therefore, it is still of importance to develop new drugs for treatment of HCV. Antiviral substances obtained from natural products, including medicinal plants, are potentially good targets to study. In this study, we evaluated Indonesian medicinal plants for their anti-HCV activities. METHODS: Ethanol extracts of 21 samples derived from 17 species of medicinal plants explored in the East Java region were tested. Anti-HCV activities were determined by a cell culture method using Huh7.5 cells and HCV strains of 9 different genotypes (1a to 7a, 1b and 2b). RESULTS: Four of the 21 samples tested showed antiviral activities against HCV: Toona sureni leaves (TSL) with 50% inhibitory concentrations (IC50) of 13.9 and 2.0 µg/ml against the HCV J6/JFH1-P47 and -P1 strains, respectively, Melicope latifolia leaves (MLL) with IC50 of 3.5 and 2.1 µg/ml, respectively, Melanolepis multiglandulosa stem (MMS) with IC50 of 17.1 and 6.2 µg/ml, respectively, and Ficus fistulosa leaves (FFL) with IC50 of 15.0 and 5.7 µg/ml, respectively. Time-of-addition experiments revealed that TSL and MLL inhibited both at the entry and post-entry steps while MMS and FFL principally at the entry step. TSL and MLL inhibited all of 11 HCV strains of all the genotypes tested to the same extent. On the other hand, FFL showed significantly weaker inhibitory activities against the HCV genotype 1a strain, and MMS against the HCV strains of genotypes 2b and 7a to a lesser extent, compared to the other HCV genotypes. CONCLUSIONS: Ethanol extracts of TSL, MLL, MMS and FFL showed antiviral activities against all the HCV genotypes tested with the exception that some genotype(s) showed significant resistance to FFL and to MMS to a lesser extent. These plant extracts may be good candidates for the development of anti-HCV drugs.

Synthesis and structure-activity relationships of cassiarin A as potential antimalarials with vasorelaxant activity.

Cassiarin A 1, a tricyclic alkaloid, isolated from the leaves of Cassia siamea (Leguminosae), shows powerful antimalarial activity against Plasmodium falciparum in vitro as well as P. berghei in vivo, which may be valuable leads for novel antimalarials. Interactions of parasitized red blood cells (pRBCs) with endothelium in aorta are especially important in the processes contribute to the pathogenesis of severe malaria. Nitric oxide (NO) reduces endothelial expression of receptors/adhesion molecules used by pRBC to adhere to vascular endothelium, and reduces cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 showed vasorelaxation activity against rat aortic ring, which may be related with NO production. A series of a hydroxyl and a nitrogen-substituted derivatives and a dehydroxy derivative of 1 have been synthesized as having potent antimalarials against P. falciparum with vasodilator activity, which may reduce cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 exhibited a potent antimalarial activity and a high selectivity index in vitro, suggesting that the presence of a hydroxyl and a nitrogen atom without any substituents may be important to show antimalarial activity. Relative to cassiarin A, a methoxy derivative showed more potent vasorelaxant activity, although it did not show improvement for inhibition of P. falciparum in vitro. These cassiarin derivatives may be promising candidates as antimalarials with different mode of actions.

Cassiarins C-E, antiplasmodial alkaloids from the flowers of Cassia siamea.

Three new alkaloids, cassiarins C-E (1-3), and a new chromone, 10,11-dihydroanhydrobarakol (4), which showed moderate antiplasmodial activity against Plasmodium falciparum 3D7, were isolated from flowers of Cassia siamea, and the structures of 1-4 were elucidated by 2D NMR analysis and chemical transformation. Cassiarin D (2) was a dimeric compound consisting of 5-acetonyl-7-hydroxy-2-methylchromone and cassiarin C (1), and cassiarin E (3) was a dimer of cassiarins A and C (1).