Study of low-density lipoprotein oxidizability indexes to measure the antioxidant activity of dietary polyphenols

Oxidation of low-density lipoprotein (LDL) may be important in the pathogen esis of atherosclerosis. Recent studies have reported that specific polyphe nols play a role as antioxidants inhibiting lipid peroxidation, LDL oxidati on and scavenging oxygen radicals. To investigate the mechanism by which di etary antioxidants may reduce the risk of atherosclerosis by inhibiting oxi dative damage of lipoproteins, low-density lipoprotein oxidizability indexe s were studied to measure the antioxidant activity of dietary polyphenols a nd a modification in the CLT50 parameter was proposed. This parameter measu re the concentration of antioxidant that increase the Lag time to 50% great er than that of the control, and the proposed modification eliminate the ef fects of the LDL status in the oxidation induced with Cu2+. The lower the C LT50, the higher antioxidant activity in the inhibition of LDL oxidation. P olyphenols with different structures such as condensed tannins (tannin acid ), flavonols (catechin, quercetin, rutin), cinnamic acids (caffeic and feru lic acid), stilbenes (resveratrol), benzoic acids (gallic acid), anthocyani dins (malvidin); a synthetic phenol (3-tert-butyl-4-hydroxyanisole, BHA) an d two vitamins (ascorbic acid vitamin C- and DL-alpha-tocopherol -vitamin E -) were studied. All antioxidants tested showed dose-dependent inhibition o f LDL oxidation. In general, it was suggested that dietary polyphenols are better antioxidants than other common antioxidants, such as vitamin C and E . An adequate study of the low-density lipoprotein oxidizability indexes co uld determine the serum antioxidant status within different subjects, and/o r evaluate the antioxidant efficiency of different antioxidants in the inhi bition of human LDL oxidation. (C) 2000 Elsevier Science Inc.