Aim of the study: Five South African medicinal plants, Bulbine alooides (L.) Willd. (Asphodelaceae), Crinum macowani Baker (Amaryllidaceae), Hypoxis sobolifera var. sobolifera (Jacq.) Nel (Hypoxidaceae), Leonotis leonurus (L.) R.Br. (Lamiaceae) and Tulbaghia violacea 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.NKR-CCR5 cells, and against HIV-1 reverse transcriptase (RT) and HIV-1 protease (PR). Results: In CEM.NKR-CCR5 cells, ethanol extracts of Leonotis leonurus inhibited HIV-1 significantly (33% reduction in HIV-1 p24, P < 0.05). HIV-1 RT inhibition (≥50%) was shown for extracts of Bulbine alooides (aqueous and ethanol), Hypoxis sobolifera (aqueous and ethanol) and Leonotis leonurus (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 Leonotis leonurus (ethanol). Only ethanolic extracts of Bulbine alooides and Leonotis leonurus retained HIV-1 PR inhibition after dereplication with IC50 of 94 μg/ml and 120 μg/ml, respectively. Conclusion: The dereplicated ethanolic extracts of Leonotis leonurus and Bulbine alooides showed the greatest anti-HIV potential in this study through inhibition of HIV-1 PR. © 2009 Elsevier Ireland Ltd. All rights reserved.
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