Screening of twenty-four South African Combretum and six Terminalia species (Combretaceae) for antioxidant activities.

The dried leaves of Combretum and Terminalia species (Combretaceae) were extracted with acetone, hexane, dichloromethane and methanol. Thin layer chromatography (TLC) plates were developed under saturated conditions and sprayed with 0.2% 2,2-diphenyl-1-picryl hydrazyl (DPPH) in methanol for antioxidant screening. Visualization of separated bands exhibiting antioxidant activities enabled the localization and the subsequent identification of the potential active compounds. The acetone and methanol extracts displayed the presence of antioxidant activity after spraying the chromatogram with DPPH. Hexane and dichloromethane extracts did not have any antioxidant activity. C. hereroense had the highest number of active compounds, followed by C. collinum ssp. taborense, which were 16 and 10, respectively. Acetone extracts of all tested Combretum species had 53 active bands and methanol had 55. All Terminalia species extracted with acetone and methanol had antioxidant activity. T. gazensis and T. mollis methanol extracts had 11 and 14 active compounds respectively in one of the solvent systems used. The qualitative DPPH assay on TLC was successfully used in this study to systematically assess the total antioxidant activity of the Combretum and Terminalia species extracts.