Antioxidant activity of nasunin, an anthocyanin in eggplant peels

The free radical scavenging activities and inhibitory effect of lipid peroxidation of a delphinidin derivative in eggplant were investigated, Delphinidin-3-(p-coumaroylrutinoside)-5-glucoside (nasunin), an anthocyanin, was isolated as purple colored crystals from eggplant peels, Using electron spin resonance spectrometry and 5.5-dimethyl-1-pyrroline-N-oxide (DMPO), hydroxyl radicals ((OH)-O-.) or super-oxide anion radicals (O-2(.-)) generated by the Fenton reaction or the hypoxanthine-xanthine oxidase system were measured as DMPO-OH or DMPO-OOH spin adducts. L-Ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6yl-hydrogen phosphate] potassium salt (EPC-K1) and bovine erythrocyte superoxide dismutase (SOD) were used as standards for (OH)-O-. and O-2(.-) scavengers, respectively. Nasunin showed potent O-2(.-) scavenging (143 +/- 8 SOD-equivalent U/mg) and (OH)-O-. scavenging (0.65 +/- 0.07 EPC-K1-equivalent mu mol/mg) activities, Then, by changing the concentration of DMPO to vary the trapping late of (OH)-O-., the presence of a competitive reaction between nasunin and (OH)-O-. was studied. The 50% inhibition dose (ID50) obtained from the inhibition curve did not change, indicating (OH)-O-. scavenging of nasunin is not due to direct scavenging but inhibition of (OH)-O-. generating system by chelating ferrous ion, Nasunin protection against H2O2-induced lipid peroxidation in rat brain homogenate was measured at 586 nm using the indicator of malonaldehyde and 4-hydroxyalkenals. Nasunin ( < 50 mu M) protected against lipid peroxidation of brain homogenates, The findings suggest that nasunin is a potent O-2(.-) scavenger and has protective activity against lipid peroxidation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.