Antioxidative Effect of Quercetin and Its Equimolar Mixtures with Phenyltin Compounds on Liposome Membranes

Abstract

Our earlier studies have shown that the compounds diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) in the presence of UVC radiation enhanced the degree of phosphatidylcholine liposome membrane oxidation (J. Agric. Food Chem. 2005, 53, 76-83). The prooxidative behavior of the compounds has now been confirmed with the electron paramagnetic resonance method, which proved the possibility that the studied compounds can exist in free radical forms. The present work investigates the possibility of the protective action of quercetin on phosphatidylcholine liposome membranes exposed to the prooxidative action of DPhT and TPhT induced by UV radiation (lambda = 253.7 nm). The concentrations of quercetin and its equimolar mixtures with DPhT and TPhT were determined (and compared with well-known antioxidants as standards-trolox and butylated hydroxytoluene, also in the presence of phenyltins) as those that induce 50% inhibition in oxidation of liposomes radiated with UV. They are 5.1 +/- 0.10, 2.9 +/- 0.12, and 1.9 +/- 0.08 microM (differences between the values are statistically significant), constituting the following sequence of antioxidative activity: quercetin:TPhT > quercetin:DPhT > quercetin. This relation is confirmed by the results on the antiradical ability of quercetin and its mixtures with DPhT and TPhT toward the free radical 1,1-diphenyl-2-pricrylhydrazil. Similar sequences obtained in both studies suggest a possible mechanism of the antiradical action of the mixtures as free radical scavengers. We suggested that (i) quercetin's ability, documented by spectrophotometric, infrared attenuated total reflectance spectroscopy, (1)H NMR, and molecular modeling methods, to form complexes with phenyltins indicates a possible way of protection against the peroxidation caused by the free radical forms of phenyltins and (ii) the differentiation in the action of the quercetin/TPhT and quercetin/DPhT associates (statisticaly significant) may result from a different localization in the liposome membrane, which is indicated by the results of the fluorimetric studies.

Antifungal and Antioxidant Activities of Pyrrolidone Thiosemicarbazone Complexes

“…The metal complexes used in the study showed good activities as a radical scavenger compared to the scavenging ability of ascorbic acid, which was used as a standard (Figure 5). These results were in agreement with previous studies of metallic complexes [32, 33] in which the ligand has antioxidant activity and it is expected that the metal moiety will increase its activity.…”

Antimicrobial and Antioxidant Activities of New Metal Complexes Derived from 3-Aminocoumarin

“…The metal complexes showed good activities as a radical scavenger compared with ascorbic acid, Figure 9. These results were in agreement with previous metallic complexes studies where the ligand has the antioxidant activity and it is expected that the metal moiety will increase its activity [44,45,46]. …”

Antioxidant Activity of Butyl- and Phenylstannoxanes Derivedfrom 2-, 3- and 4-Pyridinecarboxylic Acids

“…There are literature reports of metallic complexes where the ligand has antioxidant activity and it is expected that the metal moiety will increase its activity [26,29,44,45,46]. In this case, the three heterocarboxylic acid isomers show a moderated antioxidant activity even though, their use in diverse applications has been reported, for example, ligand II is an antihyperlipidemic drug and its widely used in patients with atherosclerosis [47]; also for ligand III , some authors refer its wide biological applications but these do not include antioxidant activity [48].…”

“…Gabrielska et al . [29] found that the addition of Ph 2 SnCl 2 to quercetin increased its antioxidant activity. In our research, ligand II did show a moderate antioxidant activity towards the DPPH stable free radical, but the complex derived from this ligand and Ph 2 SnCl 2 (Figure 2, compound 5 ) did show a high percentage of scavenging activity (Figure 5).…”

“…Some authors have indicated that the antioxidant capacity of some flavonoids, like quercetin, is increased when it is complexed with a metallic moiety, for example Cu(II) [26], Cr(III) [27] or Co(II) [28]. There is little information however on a similar trend of Sn(IV) compounds; although there is information where authors refer that an equimolar mixture of the kaempeferol or quercetin (natural antioxidants) with diphenyltin dichloride (Ph 2 SnCl 2 ) or triphenyltin chloride (Ph 3 SnCl) resulted in a higher antioxidant activity than that of kaempeferol or quercetin alone [29,30]. …”