Effects of Sutherlandia frutescens Extracts on Normal T-Lymphocytes In Vitro

Abstract

Sutherlandia frutescens (SF), a popular traditional medicinal plant found in various parts of southern Africa, is used for treatment or management of HIV/AIDS and other diseases including cancer. However, its toxicity profile has not been fully established. The aims of this study were to examine the effects of 70% ethanol (SFE) and deionised water (SFW) extracts on normal isolated human T cells. An experimental study on normal human lymphocytes treated with doses SF extract doses ranging from 0.25 to 2.5 mg/ml. Untreated, vehicle-treated (Ethanol) and camptothecin (CPT) treated normal T cells were used as controls. Induction of cell death, changes in intracellular ATP, caspase-3/-7 activity and nuclear changes were analysed using flow cytometry, luminometry and nuclear staining (Hoechst) respectively. The highest concentration (2.5 mg/ml) of SFE extract induced significant necrosis (95%), depletion of ATP (76%), and inhibition of caspase-3/-7 activity (11%) following a 24 hour incubation period (p< 0.001). The 2.5 mg/ml concentration of SFW showed the same trend but were less effective (necrosis- 26%, ATP- 91%, & caspase-3/-7- 15%). These effects showed a time-dependence over 48 hours of incubation, with high doses of SFE extracts eliminating viable cells by necrosis, depleting ATP levels and decreasing caspase-3/-7 activity (p< 0.001). The activity of SFE extract was independent of ethanol. The SFW extract dilutions were less toxic than the SFE extracts. Significant DNA fragmentation as demonstrated by Hoechst staining was also seen over 48-hour incubation for high doses of both types of SF extracts. These results showed that although high concentrations of SF extracts can be toxic to normal T cells in vitro, SFW fractions were relatively safe for use.

Keywords: Sutherlandia frutescens, T lymphocytes, flow cytometry, luminometry, necrosis, apoptosis