Natural antioxidants in grapes and wines

The concentrations of phenolics of three grape varieties and two red wines were determined. The red grape variety and the red wines contain phenolics at concentrations of 920 mg/kg and 1800 and 3200 mg/L, respectively. The antioxidative effects of wine phenolics on the catalysis of lipid peroxidation by biological catalysts such as myoglobin, cytochrome c, iron ascorbate, and copper ions were estimated. Lipid peroxidation catalyzed by myoglobin, cytochrome c, and iron ascorbate was inhibited (I50) by wine phenolics at concentrations of 0.2, 0.35, and 0.9 micrograms of phenolics/mL. The antioxidative effects of wine phenolics were determined also in a system containing low-density lipoproteins (LDL) oxidized ex vivo by Cu2+ ions. The inhibition of LDL oxidation by wine phenolics was compared with that by alpha-tocopherol. The results show I50 inhibitions of less than 1 micromolar for wine phenolics and 2 micromolar for alpha-tocopherol, respectively. The nutritional implications of natural antioxidants at high concentration in grapes, wines, and byproducts, and their utilization in foods, are discussed