title: Effect of naturally occurring flavonoids on lipid peroxidation and membrane permeability transition in mitochondria.
abstract: The ability of eight structurally related naturally occurring flavonoids in inhibiting lipid peroxidation and mitochondrial membrane permeability transition (MMPT), as well as respiration and protein sulfhydryl oxidation in rat liver mitochondria, was evaluated. The flavonoids tested exhibited the following order of potency to inhibit ADP/ Fe(II)-induced lipid peroxidation, estimated with the thiobarbituric acid assay: 3'-O-methyl-quercetin > quercetin > 3,5,7,3',4'-penta-O-methyl-quercetin > 3,7,3',4'-tetra-O-methyl-quercetin > pinobanksin > 7-O-methyl-pinocembrin > pinocembrin > 3-O-acyl-pinobanksin. MMPT was estimated by the extent of mitochondrial swelling induced by 10 microM CaCl2 plus 1.5 mM inorganic phosphate or 30 microM mefenamic acid. The most potent inhibitors of MMPT were quercetin, 7-O-methyl-pinocembrin, pinocembrin, and 3,5,7,3',4'-penta-O-methyl-quercetin. The first two inhibited in parallel the oxidation of mitochondrial protein sulfhydryl involved in the MMPT mechanism. The most potent inhibitors of mitochondrial respiration were 7-O-methyl-pinocembrin, quercetin, and 3'-O-methyl-quercetin while the most potent uncouplers were pinocembrin and 3-O-acyl-pinobanksin. In contrast 3,7,3',4'-tetra-O-methyl-quercetin and 3,5,7,3',4'-penta-O-methyl-quercetin showed the lowest ability to affect mitochondrial respiration. We conclude that, in general, the flavonoids tested are able to inhibit lipid peroxidation on the mitochondrial membrane and/or MMPT. Multiple methylation of the hydroxyl substitutions, in addition to sustaining good anti-lipoperoxidant activity, reduces the effect of flavonoids on mitochondrial respiration, and therefore, increases the pharmacological potential of these compounds against pathological processes related to oxidative stress.
authors.affiliation: Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Ribeirão Preto, Brazil.
authors.forename: A C
authors.initials: AC
authors.lastname: Santos
authors.forename: S A
authors.initials: SA
authors.lastname: Uyemura
authors.forename: J L
authors.initials: JL
authors.lastname: Lopes
authors.forename: J N
authors.initials: JN
authors.lastname: Bazon
authors.forename: F E
authors.initials: FE
authors.lastname: Mingatto
authors.forename: C
authors.initials: C
authors.lastname: Curti
mesh_terms: D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects*; D005419:Flavonoids / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects*; D015227:Lipid Peroxidation / Q000187:drug effects*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D008933:Mitochondrial Swelling / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D005419:Flavonoids; D013438:Sulfhydryl Compounds