Scavenging Effects of Dihydric and Polyhydric Phenols on Superoxide Anion Radicals, Studied by Electron Spin Resonance Spectrometry

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We investigated the scavenging effects of dihydric, trihydric phenols and related polyphenols on superoxide anion radicals (O^-_2) generated form the hypoxanthine-xanthine oxidase system by ESR (electron spin resonance) spin trapping technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a trapping reagent.The O^-_2 scavenging activities of non-substituted dihydric phenols were in the order of pyrocatechol≫hydroquinone≫resorcinol.Trihydric phenols, pyrogallol and gallic acid, which have phenolic OH groups at ortho positions, had stronger activities than pyrocatechol; phloroglucinol, on the other hand, which has phenolic OH groups at meta positions, had much weaker effect. Polyhydric phenols like quercetin and hematoxylin, which have catechol groups, had significant O^-_2 scavenging activities. In order to clarify the physico-chemical property of these phenolic compounds which determines their O^-_2 scavenging acivities, we investigated the effects of six 4-substituents of pyrocatechol on O^-_2 scavenging effects. The effects of these substituents were well correlated with their redox potentials, indicating that O^-_2 scavenging activities of catechol derivatives are controlled by their electron donor activities.We also observed the scavenging effects of these phenolic compounds on O^-_2 from a defferent source : potassium superoxide (KO_2) solubilized in dimethyl sulfoxide by 18-crown-6. ESR analysis in this system revealed that one-electron oxidized products of these compounds were concomitantly formed accompanied by the reduction of O^-_2. The results revealed that phenolic compounds directly react with O^-_2 to form stable radicals, which account for the O^-_2 scavenging activities of the compounds.
公益社団法人日本薬学会の論文
1992-02-25

Scavenging Effects of Dihydric and Polyhydric Phenols on Superoxide Anion Radicals, Studied by Electron Spin Resonance Spectrometry

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