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-(NL4.3) replication with dose-dependence and without concomitant cytotoxicity. C sieberiana and V. doniana extracts inhibited HIV-1 replication by 50% at 84.8 mu g/mL and at 25 mu g/mL, respectively, while C megalobotrys extracts inhibited HIV-1 replication by a maximum of 45% at concentrations as low as 0.05 mu g/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. (C) 2016 Elsevier Ireland Ltd. All rights reserved.