The correlation between active oxygens scavenging and antioxidative effects of flavonoids.

Abstract The abilities of 15 flavonoids as a scavenger of active oxygens (hydroxyl radical and superoxide anion) were studied. Hydroxyl radical ( . OH) 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. (+)-Catechin, (−)-epicatechin, 7,8-dihydroxy flavone, and rutin showed the . OH scavenging effect 100–300 times superior to that of mannitol, a typical . OH scavenger. The other flavonoids showed no . OH scavenging effect at their concentrations up to 50 μM. Baicalein, quercetin, morin, and myricetin unexpectedly increased the . OH production in the Fenton system. The flavonoids tested now, except monohydroxy flavones, were more or less inhibitive to the superoxide anion (O 2 ) 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 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 nor O 2 − scavenging effect, but was a strong antioxidant.