29-10 |
|
Y.-F. CHU and R. H. Liu. Dept. of Food Science, Cornell Univ., Stocking Hall, Ithaca, NY 14853 Cardiovascular disease (CVD) is the leading cause of death in the US. Oxidation of low density lipoproteins (LDL) induced by free radicals has been hypothesized to play a key role in the atherosclerotic process. Prevention of LDL oxidation thus is a primary focus in reducing the risk of CVD. The objective of this study is to develop a novel LDL oxidation model to assess the antioxidant activity of natural or synthetic, lipophilic or hydrophilic compounds based on their potency to inhibit peroxyl radical-initiated LDL oxidation at physiological conditions. LDL was isolated from human plasma by sequential ultracentrifugation. The protein concentration of LDL was determined by the Lowry method. Peroxyl radicals generated at physiological conditions were used to initiate LDL oxidation. The degree of LDL oxidation is determined by measuring the production of hexanal, a marker of lipid oxidation, by headspace GC analysis. Vitamin C, vitamin E, and apple extracts were selected to represent hydrophilic, lipophilic, and natural antioxidants. All vitamin C and E and apple extract concentrations tested resulted in increasing partial suppression of LDL oxidation; LDL oxidation was delayed at higher concentrations of antioxidants, natural or synthetic, indicating vitamin C, vitamin E, and apple extracts are potent antioxidants to prevent peroxyl radical induced LDL oxidation. The median effective dose (EC50) of vitamin C, vitamin E, and apple extracts preventing LDL oxidation were 41.2 µM, 117.4 µM, and 3.2 mg/mL, respectively. The antioxidant activity of 100 g apple against LDL oxidation is equivalent to 1,563 mg vitamin E or 224.2 mg vitamin C. In addition, both hydrophilic and lipophilic antioxidants can be evaluated by this assay. Our study shows that this assay can be used to routinely analyze antioxidants and phytochemical extracts in the prevention of LDL oxidation and further suggest dietary modifications for associated health benefits.
Session 29, Food Chemistry: Antioxidants and bioactive agents
|