Antioxidant properties of EPC-K1: a study on mechanisms

Scavenging effects of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2- (4,8,12-trimethytridecyl)-2 H-1-benzopyran-6-yl-hydrogen phosphate] potassi um salt (EPC-K1) on hydroxyl radicals, alkyl radicals and lipid radicals we re studied with ESR spin trapping techniques. The inhibition effects of EPC -K1 on lipid peroxidation were assessed by TBA assay. The kinetics of EPC-K 1 reacting with hydroxyl radicals and linoleic acid radicals were studied b y pulse radiolysis. The active site of EPC-K1 and the structure-antioxidati ve activity relationships were discussed. The superoxide radicals scavengin g capacity of the brain homogenate of EPC-K1-treated rats was measured. The results revealed that in comparison with Trolox and vitamin C, EPC-K1 show ed better overall antioxidative capacity in vitro and in vivo. EPC-K1 was a moderate scavenger on hydroxyl radicals and alkyl radicals, a potent scave nger on lipid radicals, and an effective inhibitor on lipid peroxidation. E PC-K1 could react with hydroxyl radicals with a rate constant of 7.1 x 10(8 ) dm(3) mol(-1) s(-1) and react with linoleic acid radicals with a rate con stant of 2.8 x 10(6) dm(3) mol(-1) s(-1). The active site of EPC-K1 was the enolic hydroxyl group. After administration of EPC-K1, the ability of rat brain to scavenge superoxide radicals was significantly increased. The pote nt scavenging effects of EPC-K1 on both hydrophilic and hydrophobic radical s were relevant with its molecular structure, which consisted of both hydro philic and hydrophobic groups. (C) 1999 Elsevier Science B.V. All rights re served.