Aim of the study: Five South African medicinal plants, Bulbine alooides (L.) Willd. (Asphodelaceae), Crinummacowani Baker (Amaryllidaceae), Hypoxis sobolifera var. sobolifera (Jacq.) Nel (Hypoxidaceae), Leonotisleonurus (L.) R.Br. (Lamiaceae) and Tulbaghiaviolacea Harv (Liliaceae) used for the treatment of various ailments, including infectious diseases, were screened for activity against human immunodeficiency virus (HIV).
Materials and methods: Aqueous and ethanol extracts were tested for inhibitory activity in HIV-1 infected CEM.NK(R)-CCR5 cells, and against HIV-1 reverse transcriptase (RT) and HIV-1 protease (PR).
Results: In CEM.NK(R)-CCR5 cells, ethanol extracts of Leonotisleonurus inhibited HIV-1 significantly (33% reduction in HIV-1 p24, P<0.05). HIV-1 RT inhibition (> or =50%) was shown for extracts of Bulbine alooides (aqueous and ethanol), Hypoxis sobolifera (aqueous and ethanol) and Leonotisleonurus (aqueous), but inhibitory activity was lost upon dereplication for removal of non-specific tannins/polysaccharides. HIV-1 PR inhibition was observed for extracts of Hypoxis sobolifera (aqueous), Bulbine alooides (aqueous and ethanol) and Leonotisleonurus (ethanol). Only ethanolic extracts of Bulbine alooides and Leonotisleonurus retained HIV-1 PR inhibition after dereplication with IC50 of 94 microg/ml and 120 microg/ml, respectively.
Conclusion: The dereplicated ethanolic extracts of Leonotisleonurus and Bulbine alooides showed the greatest anti-HIV potential in this study through inhibition of HIV-1 PR.