Evaluation of selected South African medicinal plants for inhibitory properties against human immunodeficiency virus type 1 reverse transcriptase and integrase.

Abstract Seventeen aqueous and methanol extracts from nine South African medicinal plants, ethnobotanically selected, were screened for inhibitory properties against HIV-1 reverse transcriptase (RT). Isolated compounds were additionally evaluated on HIV-1 integrase (IN). The strongest inhibition against the RNA-dependent-DNA polymerase (RDDP) activity of RT was observed with the methanol extract of the stem-bark of Peltophorum africanum Sond. (Fabaceae) (IC 50 3.5 μg/ml), while the methanol extract of the roots of Combretum molle R.Br. ex G. Don (Combretaceae) was the most inhibitory on the ribonuclease H (RNase H) activity (IC 50 9.7 μg/ml). The known compounds bergenin and catechin, and a red coloured gallotannin composed of meta -depside chains of gallic and protocatechuic acids esterified to a 1- O -isobutyroly-β- d -glucopyranose core, were isolated from the methanol extract of the roots and stem-bark of Peltophorum africanum . The gallotannin inhibited the RDDP and RNase H functions of RT with IC 50 values of 6.0 and 5.0 μM, respectively, and abolished the 3′-end processing activity of IN at 100 μM. Catechin showed no effect on RT but had a moderate activity on HIV-1 IN. Bergenin was inactive on both enzymes. The aqueous and methanol extracts were non-toxic in a HeLaP4 cell line at a concentration of 400 μg/ml.