Abstract— Quercetin, quercitrin and rutin suppressed lipid photoperoxidation in spinach chloroplasts in the presence of 100 μM carbonylcyanide m‐chlorophenylhydrazone (CCCP) or 100 μM methyl viologen (MV). Fifty percent inhibition of lipid peroxidation by quercetin was observed between 30 and 50 μM. Concentrations of quercetin and rutin higher than 100 μM were required to obtain 50% inhibition. Ouercitrin was more effective than rutin in the suppression of lipid photoperoxidation. Photooxidation of the flavonols by chloroplasts in the presence of MV was suppressed by superoxide dismutase (SOD) more than 90%, and the rates of the oxidation decreased in order of quercetin, quer citrin and rutin suggesting that the reactivity of the flavonols with O2‐decreased in that order. The photooxidation of the flavonols by CCCP‐poisoned chloroplasts was partially suppressed by SOD. Radicals generated in the course of lauroyl peroxide degradation also oxidized the flavonols and the oxidation was insensitive to SOD. In these experiments, oxidation rate of quercetin was faster than those of its glycosides. The results obtained suggest that flavonols can function as antioxidants in chloroplasts by scavenging both O2‐and the radicals formed during lipid peroxidation.
Photochemistry & Photobiology – Wiley
Published: Sep 1, 1983