| Abstract
| - To study the antioxidant activity of quercetin 3-O-β-d-glucuronide (Q3GA), which is one of thequercetin metabolites in the blood after intake of quercetin-rich food, the inhibitory effect of Q3GAon lipid peroxidation was estimated using phosphatidylcholine large unilamellar vesicles (PC LUV)as a biomembrane model. Iron ion, an aqueous peroxyl radical generator, a peroxynitrite generator,or lipoxygenase was used as the inducer of lipid peroxidation. In all cases, Q3GA inhibited lipidperoxidation significantly, although its inhibitory effect was lower than that of quercetin aglycon.The ultrafiltration of PC LUV containing Q3GA revealed that Q3GA has low but significant affinitywith the membranes of phospholipid bilayers. It is therefore likely that Q3GA acts as an efficientantioxidant in membranous lipid peroxidation through its localization in the phospholipid bilayer.This conjugated quercetin metabolite seems to retain the ability to protect cellular and subcellularmembranes from peroxidative attack by reactive oxygen species and peroxidative enzymes. Keywords: Quercetin 3-O-β-d-glucuronide; flavonoids; large unilamellar vesicles; biomembrane;lipid peroxidation
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