title: Thermodynamic versus kinetic control of antioxidant synergism between β-carotene and (iso)flavonoids and their glycosides in liposomes.
abstract: Antioxidant synergism (or antagonism) between plant (iso)flavonoids (daidzein, baicalein, and quercetin) or their glycosides (puerarin, baicalin, and rutin) and β-carotene in phosphatidylcholine liposomes (pH 7.4) with oxidation initiated thermally by the lipophilic free radical initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) and followed by the formation of conjugated dienes did not depend simply on the bond dissociation enthalpy (BDE) of the phenol O-H bond or the HOMO/LUMO energy gap based on density functional theory (DFT) calculations. Rate of regeneration of β-carotene from the β-carotene radical cation as the one-electron oxidation product of the lipid phase antioxidant by the monoanion form of the (iso)flavonoids in homogeneous (1:9 v/v methanol/chloroform) solution, as studied by laser flash photolysis and occurring on a microsecond time scale with biphasic kinetics, was in better agreement with the observed nonadditive antioxidative effects. However, correcting the observed (pseudo)-first-order rate constant for β-carotene regeneration for water/lipid distribution of the (iso)flavonoids provided an almost correct ordering of the (iso)flavonoids, according to the nonadditive effects with β-carotene on lipid oxidation.
authors.affiliation: Department of Chemistry, Renmin University of China, Beijing 100872, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Liang
authors.forename: Chang-Hui
authors.initials: CH
authors.lastname: Chen
authors.forename: Rui-Min
authors.initials: RM
authors.lastname: Han
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Zhang
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D006027:Glycosides / Q000494:pharmacology*; D007700:Kinetics; D008081:Liposomes; D010084:Oxidation-Reduction; D013816:Thermodynamics; D019207:beta Carotene / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D006027:Glycosides; D008081:Liposomes; D019207:beta Carotene