Anthocyanins as antioxidants on human low-density lipoprotein and lecithin-liposome systems

The antioxidant activity of several anthocyanins was tested in vitro on human low-density lipoproteins (LDL) and on a lecithin-liposome system. Samples were incubated at 37 degrees C, and the extent of oxidation was measured by determining the formation of conjugated diene and hexanal. The inhibition of oxidation increased with concentration of the antioxidant. In the LDL system, when the oxidation was catalyzed with 10 mu M copper, malvidin was the best oxidation inhibitor, followed by delphinidin, cyanidin, and pelargonin. When the oxidation was catalyzed with 80 mu M copper, the order of antioxidant activity changed and decreased in the following order at all concentrations tested: delphinidin, cyanidin, malvidin, and pelargonin. In the liposome system, catalyzed with either 3 or 10 mu M copper, malvidin was the best inhibitor of both conjugated diene and hexanal formation. At 3 mu M copper, delphinidin, cyanidin, and pelargonin showed prooxidant activity. At 10 mu M copper, pelargonin followed malvidin in antioxidant potency, and cyanidin and delphinidin were prooxidants. Several antioxidant mechanisms may explain the effect; of anthocyanins, including hydrogen donation, metal chelation, and protein binding.