Antioxidative activity of 3,4-dihydroxyphenylacetic acid and caffeic acid in rat plasma.
The purpose of the present paper is to study and compare in vitro the inhibitory effect of 3,4-dihydroxyphenylacetic acid (DOPAC) and caffeic acid (CA) on lipid peroxidation in rat plasma. Rat plasma was oxidized at 37 degrees C by the radical initiators 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) or 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (MeO-AMVN). The consumption of endogenous alpha-tocopherol (alpha-TOH) and the accumulation of conjugated diene hydroperoxides were measured by high-performance liquid chromatography and by ultraviolet spectroscopy, respectively. Alpha-TOH was consumed at the same rate in the presence of 20 mM AAPH or 2 mM MeO-AMVN. DOPAC and CA suppressed the alpha-TOH consumption in a dose-dependent manner. A concentration of 50 microM of both phenolic acids was sufficient to induce a lag phase and to delay the rate of alpha-TOH consumption. The effect was more pronounced in rat plasma oxidation by AAPH than by MeO-AMVN. CA spared vitamin E more effectively than DOPAC in both oxidations. DOPAC and CA suppressed the formation of conjugated diene hydroperoxides. DOPAC and CA at concentration 50 microM suppressed alpha-TOH consumption during oxidation of soybean phosphatidylcholine (2.8 mM) multilamellar vesicles containing 15 microM alpha-TOH, in which the lipophilic initiator 2,2'-azobis (2,4-dimethylvaleronitrile) (6 mM) was incorporated. In conclusion, we demonstrated that DOPAC and CA in micromolar concentrations have antioxidant activity in rat plasma, a medium very close to the conditions in vivo, suggesting that supplementation with the phenolic acids will provide significant antioxidant protection.
Raneva
V
V
First Department of Biochemistry, Teikyo University School of Medicine, Tokyo, Japan. villy@med.teikyo-u.ac.jp
Shimasaki
H
H
Ishida
Y
Y
Ueta
N
N
Niki
E
E
D015102:3,4-Dihydroxyphenylacetic Acid / Q000097:blood / Q000494:pharmacology*; D000578:Amidines / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001391:Azo Compounds / Q000494:pharmacology; D002109:Caffeic Acids / Q000097:blood / Q000494:pharmacology*; D004492:Edetic Acid / Q000494:pharmacology; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects*; D008055:Lipids / Q000097:blood; D008081:Liposomes / Q000737:chemistry; D008297:Male; D000432:Methanol / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley; D024502:alpha-Tocopherol / Q000097:blood
D000578:Amidines; D000975:Antioxidants; D001391:Azo Compounds; D002109:Caffeic Acids; D008055:Lipids; D008081:Liposomes; D009570:Nitriles; D015102:3,4-Dihydroxyphenylacetic Acid; C109522:V 70; C046728:2,2'-azobis(2-amidinopropane); D004492:Edetic Acid; D024502:alpha-Tocopherol; C040048:caffeic acid; D000432:Methanol