Mulberry leaf extract inhibits the oxidative modification of rabbit and human low density lipoprotein

In a previous study, we demonstrated that the intake of mulberry leaves or their 1-butanol extract (MLBE) reduced the concentration of serum lipids an d atheromatous thickening of arterial intima in hypercholesterolemic rabbit s. In the present study, we investigated the antioxidative activity of MLBE and isoquercitrin, the main component of MLBE. First, we determined the ef fect on a stable radical agent, finding that quercetin, isoquercitrin and M LBE scavenged the DPPH radical. We then determined the copper-induced oxida tive modification of rabbit and human low-density lipoprotein (LDL). Oxidat ion of LDL was spectrophotometrically monitored by changes in absorbance at 234 nm accompanied by the formation of conjugated dienes, and measured the formation of thiobarbituric acid reacting substances (TBARS). Quercetin, a n aglycone of isoquercitrin, inhibited the formation of conjugated dienes a nd TBARS by copper-induced oxidative modification of rabbit and human LDLs, MLBE and isoquercitrin also inhibited the oxidation of LDL. These results indicate that mulberry leaves inhibit the oxidative modification of LDL and suggest that mulberry leaves may had prevent atherosclerosis.