Inhibitory Effect of a Quercetin Metabolite, Quercetin 3-O-β-d-Glucuronide, on Lipid Peroxidation in Liposomal Membranes

Abstract

To study the antioxidant activity of quercetin 3-O-beta-D-glucuronide (Q3GA), which is one of the quercetin metabolites in the blood after intake of quercetin-rich food, the inhibitory effect of Q3GA on 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 lipid peroxidation 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 affinity with the membranes of phospholipid bilayers. It is therefore likely that Q3GA acts as an efficient antioxidant in membranous lipid peroxidation through its localization in the phospholipid bilayer. This conjugated quercetin metabolite seems to retain the ability to protect cellular and subcellular membranes from peroxidative attack by reactive oxygen species and peroxidative enzymes.

The neuroprotective potential of flavonoids: a multiplicity of effects

“…Circulating metabolites of flavonoids, such as glucuronides, sulphates and conjugated O-methylated forms, or intracellular metabolites like flavonoid-GSH adducts, have significantly reduced antioxidant potential relative to the forms found in plants [102]. Indeed, studies have indicated that although such conjugates and metabolites may participate antioxidant reactions and may scavenge reactive oxygen and nitrogen species in the circulation, their effectiveness to do so is reduced compared to their parent aglycones [22,70,94,117,132].…”

The interactions of flavonoids within neuronal signalling pathways

“…Circulating metabolites of flavonoids, such as glucuronides, sulphates and conjugated O-methylated forms, or intracellular metabolites like flavonoid-GSH adducts, have greatly reduced antioxidant potential [160]. Indeed, studies have indicated that although such conjugates and metabolites may participate directly in plasma antioxidant reactions and in scavenging reactive oxygen and nitrogen species in the circulation, their effectiveness is reduced relative to their parent aglycones [41,122,152,170,189].…”

High-yield production of scutellaria radix flavonoids (baicalein, baicalin and wogonin) by liquid-culture of Scutellaria baicalensis root-derived cells

“…Considering the present results with baicalein and baicalin, the lower activity observed in baicalin suggested that a disappearance of 7-hydroxyl group by glucosylation weakened the radical-scavenging power of the compound. Shirai et al (2001) reported that the introduction of a glucuronide group to the 3-position contributed to an increase of affinity toward lipid, resulting decrease of the antioxidative activity. The effect of glucosylation of hydroxyl group at 7-position on affinity toward lipid was studied by van Dijk et al (2000), and it was shown that the glucosylation at 7-position resulted in increase of affinity.…”