DPPH antioxidant assay revisited
Scavenging of DPPH free radical is the basis of a common antioxidant assay. A number of protocols have been followed for this assay resulting in variation in the results of different laboratories. We present a perspective of the protocols followed by different workers with incongruity in their results and recommend a standard procedure within the sensitivity range of spectrophotometry. Three common standard antioxidants viz. ascorbic acid, BHT and propyl gallate have been used in this study. The IC50 values for ascorbic acid and propyl gallate were 11.8μM and 4.4μM in methanol and 11.5μM and 4.7μM in buffered methanol as reaction medium, respectively. The free radical scavenging by BHT was markedly influenced by the reaction medium. The IC50 values were 60.0μM and 9.7μM when the reaction was done in methanol and buffered methanol, respectively.