Screening and phytochemical characterization of a South African herbal concoction for anti-HIV-1 activity
Hlatshwayo, Vincent Nkosinathi
In South Africa, the anti-HIV-1 activity of various indigenous plants has not been studied extensively. Most of the phytochemical screening work has focused on anti-cancer activity with less attention given to infectious diseases. A large proportion of South Africans (70-80%) still rely on traditional medicines for treatment of various ailments. And, therefore, there is a need to evaluate and validate the effectiveness of the traditional medicines. The aim of this study was to identify, screen, phytochemically characterize and isolate bioactive compounds from a South African herbal extract that exhibit the best anti-HIV-1 activity. Three extracts were prepared: an ethanol extract, a dereplicated ethanol extract and an aqueous extract from a herbal concoction comprised of a mixture of six plants. These herbal concoctions were investigated for anti-HIV-1 subtype C activity. Phytochemical profiling of the ethanol- and dereplicated ethanol- extracts from the herbal concoctions showed the presence of intermediate polar compounds (flavonoids, alkaloids, sugars and terpenes) for both extracts, while the aqueous extract contained predominantly highly polar compounds. Anti-HIV-1 screening of the three extracts showed that the ethanol and dereplicated ethanol herbal- extracts had the best anti-reverse transcriptase activity. The ethanol extract had mean IC50 values of 56.53, 53.96 and 55.39 μg/ml against MJ4, Du179 and CM9 HIV-1 subtypes C isolates, respectively. The dereplicated ethanol extract had mean IC50 values of 51.87, 47.56 and 52.81 μg/ml against MJ4, Du179 and CM9 HIV-1 isolates, respectively. The aqueous extract was inactive against HIV-1 activity. Moreover, both the ethanol- and dereplicated ethanol- extracts showed activity against HIV neutralization. The ethanol- and dereplicated ethanol- extracts had mean IC50 values of 36.33 and 32.06 μg/ml, respectively. Furthermore, they also potently neutralized Vesicular stomatitis virus (VSV) yielding mean IC50 values of 24.91 and 20.82 μg/ml for ethanol- and dereplicated ethanol- extracts, respectively. All extracts were inactive against Murine leukemia virus (MLV). The isolation and phytochemical characterization of the bioactive compound(s) was done by utilizing various chromatographic and spectroscopic methods. Four homoisoflavanoids were isolated and tested for anti-HIV-1 subtype C activity. Three compounds (1, 3a and 3b) were inactive while compound 2 was found to be bioactive against HIV-1 reverse transcriptase (RT) and yielded mean IC50 values of 7.23 ± 1.88, 12.83 ± 0.41 & 12.81 ± 0.10 μg/ml for MJ4, CM9 and Du179 HIV-1 subtype C isolates, respectively. Compound 2 had a mean CC50 value of 23.08 ± 0.1981 μg/ml against HEK293T cells. Overall, the data suggested that ethanol- and dereplicated ethanol- herbal extracts possess direct and indirect anti-HIV-1 activity. They possess a cocktail of phytochemicals that can inhibit HIV-1 RT, HIV-1 entry. Furthermore, these extracts possess phytochemicals that can lower the activation of inflammatory responses during an infection and, hence, reduction in the number new cells infected during the course of HIV-1 infection. Moreover, they possess phytochemicals that have antioxidant activity which, in relation to HIV infection, results in a boosted immune system response in order to ward off the virus.
A dissertation submitted to the Faculty of Science under the School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master in Science. Johannesburg, June 2017.
Hlatshwayo, Vincent Nkosinathi (2017) Screening and phytochemical characterization of a South African herbal concoction for anti-HIV-1 activity, University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/23466>