Inhibition of endothelial cell-mediated oxidation of low-density lipoprotein by rosemary and plant phenolics

Plant-derived phenolic compounds possess antioxidant activity that may be applicable to such diverse areas as human health and the preservation of food lipids. The potential antioxidant activities of a variety of plant phenolics were investigated using human aortic endothelial cells (HAEC) to mediate the oxidation of low-density lipoprotein(LDL). Carnosic acid, carnosol, and rosmarinic acid, present in rosemary extract, and thymol, carvacrol, and zingerone, present in thyme, origanum, and ginger, were individually incubated with HAEC and LDL for 12 h. The extent of oxidation was determined spectrophotometrically by measuring absorbance (at 234 nn) of conjugated dienes. All antioxidants produced dose-dependent inhibition of LDL oxidation. Their relative antioxidant activities decreased in the order carnosol > carnosic acid approximate to rosmarinic acid >>> thymol > carvacrol > zingerone. The antioxidant activity of these plant phenolics in the HAEC system suggests that they may have potential benefits in human health.