Delphinidine-3-(p-coumaroylrutinoside)-5-glucoside (nasunin), an anthocyani
n was isolated as purple colored crystals from eggplant peels, Solanum melo
ngena L. 'Chouja'. Using an electron spin resonance spectrometer and 5,5-di
methyl-1-pyrroline-N-oxide (DMPO), spin trapping, hydroxyl (. OH) or supero
xide anion radicals (O2(.-)) generated by the Fenton reaction or the hypoxa
nthine-xanthine oxidase system were measured as DMPO-OH or DMPO-OOH spin ad
ducts. L-Ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,l 2-trimet
hyltridecyl)-2H-1-benzopyran-6yl-hydrogen phosphate] potassium salt (EPC-K1
) and bovine erythrocyte superoxide dismutase (SOD) were used as standards
for OH and O2(.-), respectively. Nasunin directly scavenged O2(.-) with a p
otency of 143+/-8 SOD-equivalent units/mg), and inhibited formation of DMPO
-OH (0.65+/-0.07 EPC-K1 mu mol/mg). A spectrophotometric study showed that
nasunin formed an iron complex with a molar ratio of nasunin : Fe3+ of 2 :
1. Therefore, hydroxyl radical scavenging by nasunin is not due to direct r
adical scavenging but inhibition of OH generation by chelating iron. Nasuni
n (1 mu M) significantly protected against lipid peroxidation of brain homo
genates (p<0.001) as measured by malonaldehyde and 4-hydroxyalkenals. These
findings demonstrate that nasunin is a potent O2(.-) scavenger and iron ch
elator which can protect against lipid peroxidation.