Measurement of superoxide dismutase-like activity of natural antioxidants

The superoxide dismutase (SOD)-like activity of natural antioxidants was evaluated by measuring the inhibition of pyrogallol autoxidation that is catalyzed by the superoxide radical. Among 22 water-soluble antioxidants tested, L-ascrobic acid, L-ascorbic acid 6-palmitate, glutathione (reduced form), (+)-catechin, and (-)-epicatechin showed effective SOD-like activity. To analyze lipophilic antioxidants, an optically clear organic system composed of diethyl ether, surfactant (dioctyl sulfosuccinate, AOT) and water, called reverse micelles, was developed. The optimum concentrations of AOT, water and pyrogallol for determining SOD-like activity were found to be 50 mM, 1.3 M, and 40 mM, respectively. After proving that pyrogallol autoxidation was mediated by the superoxide anion in that system, the SOD-like activity of 24 lipophilic antioxidants was measured. Cinnamon oil, gamma-oryzanol, extract of rosemary leaf, L-alpha-lecithin, and L-alpha-cephalin exhibited activity, although the activity of some antioxidants could not be measured because of the intense color or low solubility.