Anti HIV, Immunomodulatory and antimicrobial activities of extracts of some plant species from Bukoba, Tanzania

Certain plant species are used in traditional medicines to treat illnesses including those caused by highly infectious agents like HIV. In this study, aqueous and ethyl acetate extracts from eight plant species were screened against inhibition of HIV-1 protease, cytotoxicity, antioxidant activity, immune-modulating effects and activity against opportunistic infections. The inhibitory effect of the extracts against HIV-1 protease was tested using a fluorogenic assay. Cytotoxicity was assessed using the 2,3-bis-(2-methoxy-4-nitro-5-Sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) viability assay and confirmed by using real time cell electronic sensing technology (RT-CES). Antioxidant activity was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and cupric reducing antioxidant capacity (CUPRAC) assays. Inflammatory activities were measured by using the nitric oxide colorimetric assay while antimicrobial activities were assessed using disc diffusion assay. Three out of eight aqueous extracts showed HIV protease inhibition with IC50 values ranging between 22.4 and 32.8 µg/ml. Aqueous extracts showed no cytotoxicity whereas only two ethyl acetate extracts were cytotoxic with CC50 values of 30.6 and 52.2 µg/ml. The antioxidant activity was higher for water extracts with EC50 values ranging from 1.894 to 23.46 µg/ml. The nitric oxide (NO) assay revealed that some aqueous extracts supported the production of the inflammatory mediator, NO, from peripheral blood mononuclear cells while others reduced or inhibited its production. Extracts were found to have moderate antimicrobial activities with MICs ranging from 3.1 to 100 mg/ml. Preliminary phytochemical screening of the aqueous extracts showed the presence of saponins, tannins and alkaloids. Findings of this study support the regular usage of these plant species for medical purposes against HIV/AIDS. Further studies, especially testing more HIV-1 enzymes, in vivo studies and characterization of the active chemical compounds responsible for the observed activity are recommended.