Antioxidative activity of quercetin and quercetin monoglucosides in solution and phospholipid bilayers

Abstract

The antioxidative effect of quercetin, quercetin 3-O-beta-D-glucopyranoside (Q3G), quercetin 4'-O-beta-D-glucopyranoside (Q4'G) and quercetin 7-O-beta-D-glucopyranoside (Q7G) was examined in solution and liposomal phospholipid suspension. First, their peroxyl radical-scavenging activities were investigated by measuring the inhibition of hydroperoxidation of methyl linoleate initiated by a radical initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). Quercetin exhibited the highest peroxyl radical-scavenging activity judging from the rate of hydroperoxidation during the induction period (Rinh) and the length of induction period (tinh). Although Q7G showed an induction period, its Rinh was higher and its tinh was lower than that of quercetin. Neither Q3G nor Q4'G gave a clear induction period in the curve of hydroperoxide formation. The rate of hydroperoxidation in the presence of Q3G was higher than Rinh of quercetin and the oxidative loss of Q3G was much slower than quercetin or Q7G when exposed to AMVN in solution. Q4'G exerted little inhibition compared to Q3G or Q7G. Next, the antioxidative activity of quercetin and its monoglucosides in phospholipid bilayers was examined by measuring the inhibition of lipid peroxidation in large unilamellar vesicles composed of egg yolk phosphatidylcholine (PC) and a water-soluble radical initiator. They retarded the accumulation of PC-hydroperoxides and the induction period increased in the order of Q4'G < Q3G approximately Q7G < quercetin. It is therefore concluded that quercetin acts as an antioxidant more efficiently than its monoglucosides when phospholipid bilayers are exposed to aqueous oxygen radicals.

Effect of Phytochemicals on the Antioxidative Activity of Brain Lipids in High- and Low-fat-fed Mice and Their Structural Changes during <i>in vitro</i> Digestion

“…Murota and Terao [20] reported that intact flavonoid glycosides were not well absorbed by the small intestine because sugar moieties elevate their hydrophilicity, whereas flavonoid aglycone can be easily absorbed into epithelial cells in the large intestine because its lipophilicity facilitates its passage across the phospholipid bilayer of cellular membranes. [20] The results of another study [17] support our suggestion that quercetin aglycone appears to be a more active chainbreaking antioxidant than its glycoside counterparts because of its higher accessibility to the site of chaininitiating and chain-propagating free radicals in membranous phospholipid bilayers. An earlier study demonstrated that dietary quercetin could accumulate in the human circulatory system [20].…”

“…On the contrary, the increased antioxidative activity of rutin by in vitro digestion may be because rutin was changed into its aglycone form, such as quercetin. Quercetin is the aglycone form of rutin, and quercetin aglycone appears to be a more active chain-breaking antioxidant than its glycoside counterparts (e.g., rutin) because of its higher accessibility to the site of chain-initiating and chainpropagating free radicals in membranous phospholipid bilayers [17]. Most dietary polyphenols are quite stable during gastric digestion.…”

Review of anticancer mechanisms of isoquercitin

“…In vitro studies comparing the antioxidative effects of quercetin, IQ and other quercetin glycosides in liposomal phospholipid suspensions also demonstrated that the quercetin aglycone is a more efficient antioxidant than its glycoside [7,31,32] . This result should not reduce the credibility of IQ as an antioxidant compound since que rcetin (aglycone) is not the dominant form in nature and has an inferior bioavailability to Q3G [2,33] .…”

Optimization of Quercetin Extraction from Green Tea ( Camellia sinensis ) Using Central Composite Design, and the Pharmacological Activity of the Extract

“…In addition, caffeine and its metabolic products, such as theobromine and xanthine, show antioxidant properties 46 . Ioku and collaborators 47 confirmed that quercetin and its monoglucoside have also an antioxidant activity.…”