2001 Volume 47 Issue 5 Pages 357-362
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 [EGC], epicatechin gallate [ECg], epigallocatechin gallate [EGCg], myricetin, quercetiji, apigenin, kaempferol, and luteolin) toward 1, 1-Biphenyl-2-picryl-hydrazyl [DPPH]. After 20 min of incubation, EGCg was the most effective DPPH radi-cal scavenger, luteolin being the least active of this flavonoid group. The mutual antioxidant effect of flavonoids with a-tocopherol (a-toc) on LDL oxidizability was investigated by using the lipophilic azo radical initiator 2, 2'-azobis(4-methoxy-2, 4-dimethylvaleronitrile) [AMVN-CH3O]. 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 a-toc (6 mg/100 mL) was re-stored 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 a-toc radical; fur-thermore, by interaction with a-toc, they have a greater potential to delay the oxidation of LDL.