Antioxidant activity of water and ethanol extracts from roots of Cassine transvaalensis Burtt-Davy from Botswana

Several studies have described the antioxidant properties of medicinal plants rich in phenolic compounds. Botswana, a country with a strong history of traditional healing, hosts a variety of plant species with therapeutic reputation. There is however, very little or scanty information regarding the phytochemical composition of medicinal plants of Botswana. In this work, water and ethanol extracts of roots from Cassine transvaalensis Burtt-Davy (Celastraceae) were assessed for in vitro antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay. The ethanolic extract exhibited higher free radical scavenging effect than the water extract at all tested concentrations. Above 100µg/mL, the ethanolic extract showed 80% scavenging activity, similar to control antioxidant compounds quercetin, rutin and L-ascorbic acid. The water extract reached a similar level of activity (80%) at 200µg/mL. Between 25–50µg/mL, 4'-O-methyl-epigallocatechin isolated by bioassay directed fractionation exhibited (65%) scavenging activity greater than that of either the ethanolic or aqueous extract. However, at concentrations above 50µg/mL, the scavenging activity of the ethanolic extract exceeded that of 4'-O-methyl-epigallocatechin. This shows that there are additional active compounds than the isolate. The results suggest that extracts from the roots of Cassine transvaalensis have strong antioxidant activity. These findings support the ethnomedical use of this plant to promote good health.

Acknowledgements: Botswana College of Agriculture for funding. King's College, London Pharmacognosy Research Laboratory.