Inhibition of Human Low-Density Lipoprotein Oxidation in Relation to Composition of Phenolic Antioxidants in Grapes (Vitis vinifera)

Antioxidant activities of phenolic extracts from fourteen different types of fresh grapes were investigated by measuring the inhibition of human low-density lipoprotein (LDL) oxidation in vitro . The inhibition of LDL oxidation ranged from 22% to 60% at 10 μM gallic acid equivalents (GAE) of total phenols and from 62% to 91% at 20 μM GAE. The antioxidant activities were thus comparable to those previously found for wines. The relative LDL antioxidant activity correlated with the concentration of total phenols ( r = 0.89, p < 0.01), with the level of anthocyanins ( r = 0.56, p < 0.05) and flavonols ( r = 0.54, p < 0.05) in the grape extracts as analyzed by high-performance liquid chromatography (HPLC). When seed crushing and longer extraction times were employed, high amounts of flavan-3-ols and hydroxybenzoates were extracted. With these extracts relative LDL antioxidant activity correlated highly with the levels of flavan-3-ols ( r = 0.86, p < 0.01), total phenols ( r = 0.79, p < 0.05), and hydroxybenzoates ( r = 0.77, p < 0.05).