2,2-diphenyl-1-picrylhydrazyl (DPPH*) test demonstrates antiradical activity of Dorstenia psilurus and Dorstenia ciliata plant extracts

Plants of the Dorstenia genus, used in traditional medicine and as food ingredient in Africa, are rich in polyphenolic compounds which can be involved in prevention of disease and food spoilage through their antioxidant activity. The antiradical activities of extracts of Dorstenia psilurus. D. ciliata and a phenolic compound (6-prenylapigenin) from D. ciliata were evaluated with the 2,2-diphenyl-1-picrylhydrazyl (DPPH*) test. D. psilurus chloroform and D. ciliata ethyl acetate extracts were shown to exhibit antiradical activities, with slow kinetic action. The efficient concentrations at different kinetic times "EC50,t" for the D. ciliata extract: 699, 479, 311 and 251 g/kg after 30, 60, 120 and 180 min, respectively, were always much lower than for the D. psilurus extract: 2341, 2312, 1672 and 1281 g/kg at the same times. The antiradical activity of 6-prenylapigenin was weak compared to the extracts. These results suggest the antioxidant activities of Dorstenia extracts and might help to understand their traditional use. We propose "EC50, t", calculated on the curves obtained with DPPH test, as a parameter to screen and compare antiradical activities of plant extracts with slow kinetic behaviour.