In vitro activity of three selected South African medicinal plants against human immunodeficiency virus type 1 reverse transcriptase

Crude extracts of three ethnobotanically selected medicinal plants were screened for activity against two functions of human immunodeficiency type 1 reverse transcriptase. Inhibition of the RNA-dependent DNA polymerase activity was evaluated by measuring the degree of incorporation of methyl-3H thymidine triphosphate using polyadenylic acid.oligodeoxythymidylic acid as a template primer. Ribonuclease H activity was evaluated by measuring the extent of degradation of a radiolabelled RNA in an RNA/DNA hybrid by reverse transcriptase in the presence of test substance. The methanol extract of the leaves of Terminalia sericea (Combretaceae) was found to strongly inhibit the polymerase (IC sub(50) = 7.2 mu g/ml) and the ribonuclease H (IC sub(50) = 8.1 mu g/ml) activities. Isolation and characterization of a possible active molecule is warranted.