THE CORRELATION BETWEEN ACTIVE OXYGENS SCAVENGING AND ANTIOXIDATIVE EFFECTS OF FLAVONOIDS

The abilities of 15 flavonoids as a scavenger of active oxygens (hydroxyl radical and superoxide anion) were studied. Hydroxyl radical ((OH)-O-.) was generated by the Fenton system, and assayed by the determination of methanesulfinic acid (MSA) formed from the reaction of dimethyl sulfoxide (DMSO) with (OH)-O-.. (+)-Catechin, (-)-epicatechin, 7,8-dihydroxy flavone, and rutin showed the (OH)-O-. scavenging effect 100-300 times superior to that of mannitol, a typical (OH)-O-. scavenger. The other flavonoids showed no (OH)-O-. scavenging effect at their concentrations up to 50 mu M. Baicalein, quercetin, morin, and myricetin unexpectedly increased the (OH)-O-. production in the Fenton system. The flavonoids tested now, except monohydroxy flavones, were more or less inhibitive to the superoxide anion (Oz) generation in the hypoxanthine-xanthine oxidase system. A great part of this inhibitory effect was likely owing to suppression of xanthine oxidase activity by the flavonoids. The flavonoids, which scavenged (OH)-O-. or O-2(-) , were necessarily antioxidants to the peroxidation of methyl linoleate. However, there was a type of flavonoid such as morin, which have neither (OH)-O-. nor O-2(-) scavenging effect, but was a strong antioxidant.