Sceletium tortuosum demonstrates in vitro anti-HIV and free radical scavenging activity

•Commercially available Sceletium tortuosum was investigated for anti-HIV and free radical scavenging properties.•S. tortuosum extracts inhibited HIV-1 reverse transcriptase and protease.•The plant also demonstrated good antiradical activity.•Free radical scavenging has been linked to managing the pathogenesis of neuropsychiatric disorders.

Crude extracts of commercially available Sceletium tortuosum (Aizoaceae) were investigated for in vitro anti-HIV and free radical scavenging activity for the first time. In addition, the chemical profile of S. tortuosum was determined using qualitative and quantitative phytochemical analysis. Crude extracts were prepared from dried plant parts of S. tortuosum. Ethanol and ethyl acetate extracts from the plants were tested for inhibitory activity against HIV-1 enzymes; protease (PR), reverse transcriptase (RT) and integrase (IN). S. tortuosum revealed the presence of anthraquinones, terpenes, polyphenols, anthocyanin, tannins, alkaloids, glycosides, carbohydrates and coumarins. The total phenolic, flavonoid and tannin contents were 171.89 ± 0.05 mg GAE/g, 678.51 ± 0.01 mg QE/g and 903.15 ± 0.02 mg TAE/g extract, respectively. Ethanol and ethyl acetate extracts of S. tortuosum inhibited HIV-1 RT and PR respectively. HIV-1 RT inhibition testing had IC50 values of < 50 and 121.7 ± 2.5 μg/mL for ethanol and ethyl acetate extracts, respectively. In addition, both extracts also inhibited HIV-1 PR with IC50 values < 100 μg/mL. Results of the antiradical activity indicate a dose-dependent ability of the extracts to scavenge DPPH radicals. For this experiment, IC50 values of 49.0 ± 0.2 and 64.7 ± 3.1 μg/mL were obtained from the ethanolic and ethyl acetate extracts, respectively. This suggests that S. tortuosum might be a useful potential source of new lead compounds in the development of new anti-HIV and radical scavenging compounds.