Antioxidant ability of various flavonoids against DPPH radicals and LDL oxidation

• Published in: Journal of Nutritional Science and Vitaminology 2001, Vol.47(5), pp.357-362
• Main Authors: Hirano, R. (National Defense Medical Coll., Tokorozawa, Saitama (Japan)), Sasamoto, W, Matsumoto, A, Itakura, H, Igarashi, O, Kondo, K
• Format: Article
• Language: English
• Subjects: antioxidant; ANTIOXIDANTS; Antioxidants - administration & dosage; Antioxidants - pharmacology; Arteriosclerosis - metabolism; Arteriosclerosis - prevention & control; Biological and medical sciences; Biphenyl Compounds; Catechin - administration & dosage; Catechin - analogs & derivatives; Catechin - pharmacology; Dose-Response Relationship, Drug; Feeding. Feeding behavior; flavonoid; FLAVONOIDS; Flavonoids - administration & dosage; Flavonoids - pharmacology; free radical; Free Radical Scavengers - administration & dosage; Free Radical Scavengers - pharmacology; Fundamental and applied biological sciences. Psychology; Humans; In Vitro Techniques; Indicators and Reagents - metabolism; LDL oxidation; LIPOPROTEINS; Lipoproteins, LDL - metabolism; OXIDATION; Oxidation-Reduction; Phenols; Picrates - metabolism; Polymers; tocopherol; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0301-4800; 1881-7742
• DOI: 10.3177/jnsv.47.357

Flavonoids, a group of polyphenolic compounds, exist naturally and serve as antioxidants in vegetables, fruits, and so on. The inhibition of low density lipoprotein (LDL) oxidation may be an effective way to prevent or delay the progression of atherosclerosis. In the present study, we analyzed the radical scavenging capacity of 10 flavonoids (catechin, epicatechin [EC], epigallocatechin [EGG], epicatechin gallate [ECg], epigallocatechin gallate [EGCg], myricetin, quercetin, apigenin, kaempferol, and luteolin) toward 1,1-diphenyl-2-picryl-hydrazyl [DPPH]. After 20 min of incubation, EGCg was the most effective DPPH radical scavenger, luteolin being the least active of this flavonoid group. The mutual antioxidant effect of flavonoids with alpha-tocopherol (alpha-toc) on LDL oxidizability was investigated by using the lipophilic azo radical initiator 2,2'-azobis(4-methoxy-2, 4-dimethylvaleronitrile) [AMVN-CH30]. An inhibitory effect of flavonoids on LDL oxidation was observed in the order of luteolin>ECg>EC>quercetin>catechin>EGCg>EGC>myricetin>kaempferol>apigenin. The shortened lag time induced by higher doses of alpha-toc (6 mg/100 mL) was restored by flavonoids. These results suggest that 1) radical trapping effects of flavonoids differ according to their structure, and 2) flavonoids act as hydrogen donors to alpha-toc radical; furthermore, by interaction with alpha-toc, they have a greater potential to delay the oxidation of LDL.