Croton megalobotrys Müll Arg. and Vitex doniana (Sweet): Traditional medicinal plants in a three-step treatment regimen that inhibit in vitro replication of HIV-1.

ETHNOPHARMACOLOGICAL RELEVANCE: Human Immunodeficiency Virus (HIV) strains resistant to licensed anti-retroviral drugs (ARVs) continue to emerge. On the African continent, uneven access to ARVs combined with occurrence of side-effects after prolonged ARV therapy have led to searches for traditional medicines as alternative or complementary remedies to conventional HIV/AIDS management. AIM OF THE STUDY: Here we characterize a specific three-step traditional HIV/AIDS treatment regimen consisting of Cassia sieberiana root, Vitex doniana root, and Croton megalobotrys bark by combining qualitative interviews of traditional medical knowledge users in Botswana with in vitro HIV replication studies. MATERIALS AND METHODS: Crude extracts from a total of seven medicinal plants were tested for in vitro cytotoxicity and inhibition of wild-type (NL4.3) and ARV-resistant HIV-1 replication in an immortalized GFP-reporter CD4+ T-cell line. RESULTS: C. sieberiana root, V. doniana root, and C. megalobotrys bark extracts inhibited HIV-1NL4.3 replication with dose-dependence and without concomitant cytotoxicity. C. sieberiana and V. doniana extracts inhibited HIV-1 replication by 50% at 84.8µg/mL and at 25µg/mL, respectively, while C. megalobotrys extracts inhibited HIV-1 replication by a maximum of 45% at concentrations as low as 0.05µg/mL. Extracts did not interfere with antiviral activities of licensed ARVs when applied in combination and exhibited comparable efficacies against viruses harboring major resistance mutations to licensed protease, reverse-transcriptase, or integrase inhibitors. CONCLUSIONS: We report for the first time a three-step traditional HIV/AIDS regimen, used alone or in combination with standard ARV regimens, where each step exhibited more potent ability to inhibit HIV replication in vitro. Our observations support the "reverse pharmacology" model where documented clinical experiences are used to identify natural products of therapeutic value.

Old plants newly discovered: Cassia sieberiana D.C. and Cassia abbreviata Oliv. Oliv. root extracts inhibit in vitro HIV-1c replication in peripheral blood mononuclear cells (PBMCs) by different modes of action.

ETHNOPHARMACOLOGICAL RELEVANCE: Despite advances in anti-retroviral therapy which has transformed HIV/AIDS from a fatal to a manageable chronic disease, increasing viral drug resistance, side effects and uneven access to anti-retroviral drugs remain considerable therapeutic challenges. Partly as a consequence of these shortcomings and partly based on the fact that HIV/AIDS gives rise to opportunistic infections whose symptoms have been managed in Africa in an HIV/AIDS-independent context by traditional healers for centuries, many HIV/AIDS patients use herbal medicines. The aim of this study was to screen selected medicinal plants from Botswana, used by traditional healers to treat/manage HIV/AIDS, for inhibitory activities on HIV replication. MATERIALS AND METHODS: Based on an ethnomedical survey, ethanolic tannin-containing and tannin-free extracts from 10 medicinal plants were tested for inhibitory properties against a clone of HIV-1c (MJ(4)) measuring cytopathic effect protection and levels of viral p24 antigen in infected PBMCs. RESULTS: Cassia sieberiana D.C., Cassia abbreviata Oliv. Oliv. and Plumbago zeylanica L. extracts showed significant inhibition of HIV-1c (MJ(4)) replication. The inhibitory activity of the Plumbago zeylanica extract could be attributed to its tannin content. Anti-HIV activity of Cassia sieberiana root and bark extracts, and Cassia abbreviata root extracts occurred in a concentration-dependent manner with an effective concentration (EC(50)) of 65.1µg/ml, 85.3µg/ml and 102.8µg/ml, respectively. Experiments to elucidate possible mechanism(s) of action revealed that Cassia sieberiana root and bark extracts blocked HIV replication at its binding- (EC(50)=70.2µg/ml and 90.8µg/ml, respectively) and entry stage (EC(50)=88.9µg/ml and 100.5µg/ml, respectively) while Cassia abbreviata extracts did not. CONCLUSIONS: We report here for the first time a direct inhibitory effect on HIV-1c replication of extracts from two extremely popular medicinal plants, Cassia sieberiana and Cassia abbreviata. Considering the traditional uses of both Cassia species, our findings strongly suggest pilot clinical observational studies involving traditional healers to further evaluate the therapeutic potential of the Cassia extracts.