Our ear
lier studies have shown that the compounds dipheny
ltin dich
loride (DPhT) and tripheny
ltinch
loride (TPhT) in the presence of UVC radiation enhanced the degree of phosphatidy
lcho
line
liposomemembrane oxidation (
J. Agric. Food Chem. 2005,
53, 76-83). The prooxidative behavior of thecompounds has now been confirmed with the e
lectron paramagnetic resonance method, which provedthe possibi
lity that the studied compounds can exist in free radica
l forms. The present work investigatesthe possibi
lity of the protective action of quercetin on phosphatidy
lcho
line
liposome membranesexposed to the prooxidative action of DPhT and TPhT induced by UV radiation (<
IMG SRC="/images/gifchars/
lambda.gif" BORDER=0 > = 253.7 nm). Theconcentrations of quercetin and its equimo
lar mixtures with DPhT and TPhT were determined (andcompared with we
ll-known antioxidants as standards-tro
lox and buty
lated hydroxyto
luene, a
lso inthe presence of pheny
ltins) as those that induce 50% inhibition in oxidation of
liposomes radiatedwith UV. They are 5.1 ± 0.10, 2.9 ± 0.12, and 1.9 ± 0.08
M (differences between the va
lues arestatistica
lly significant), constituting the fo
llowing sequence of antioxidative activity: quercetin:TPhT> quercetin:DPhT > quercetin. This re
lation is confirmed by the resu
lts on the antiradica
l abi
lity ofquercetin and its mixtures with DPhT and TPhT toward the free radica
l 1,1-dipheny
l-2-pricry
lhydrazi
l.Simi
lar sequences obtained in both studies suggest a possib
le mechanism of the antiradica
l actionof the mixtures as free radica
l scavengers. We suggested that (i) quercetin's abi
lity, documented byspectrophotometric, infrared attenuated tota
l ref
lectance spectroscopy,
1H NMR, and mo
lecu
larmode
ling methods, to form comp
lexes with pheny
ltins indicates a possib
le way of protection againstthe peroxidation caused by the free radica
l forms of pheny
ltins and (ii) the differentiation in the actionof the quercetin/TPhT and quercetin/DPhT associates (statistica
ly significant) may resu
lt from adifferent
loca
lization in the
liposome membrane, which is indicated by the resu
lts of the f
luorimetricstudies.