Antioxidant Activity of Berry Phenolics on Human Low-Density Lipoprotein and Liposome Oxidation

The antioxidant activity of phenolic compounds present in berries was investigated by two copper-catalyzed in vitro oxidation assays: human low-density lipoproteins (LDL) and lecithin liposomes. The amount of total phenolics varied between 617 and 4350 mg/kg in fresh berries, as gallic acid equivalents (GAE). In LDL at 10 μM GAE, berry extracts inhibited hexanal formation in the order: blackberries > red raspberries > sweet cherries > blueberries > strawberries. In lecithin liposomes, the extracts inhibited hexanal formation in the order: sweet cherries > blueberries > red raspberries > blackberries > strawberries. Red raspberries were more efficient than blueberries in inhibiting hydroperoxide formation in lecithin liposomes. HPLC analyses showed high anthocyanin content in blackberries, hydroxycinnamic acid in blueberries and sweet cherries, flavonol in blueberries, and flavan-3-ol in red raspberries. The antioxidant activity for LDL was associated directly with anthocyanins and indirectly with flavonols, and for liposome it correlated with the hydroxycinnamate content. Berries thus contribute a significant source of phenolic antioxidants that may have potential health effects. Keywords: Berries; antioxidants; LDL oxidation; liposomes; flavonoids; hydroxycinnamates; anthocyanins; flavan-3-ols; flavonols