In the DPPH assay, the antioxidant was able to
reduce the stable radical DPPH to the yellow coloured
diphenyl-picrylhydrazine. The method is based on the
reduction of alcoholic DPPH solution in the presence of a
hydrogen-donating antioxidant due to the formation of the
non-radical form DPPH–H by the reaction (Oyaizu, 1986).