Antioxidant activity of caffeic acid and dihydrocaffeic acid in lard and human low-density lipoprotein

Caffeic acid (CA) has been implied as an important source of natural antioxidants in various agricultural products. We compared the antioxidative activity of CA and dihydrocaffeic acid (HCA) in lard and the low-density lipoprotein (LDL) system to know the role of the 2,3-double bond on the appearance of its antioxidative property. HCA was more effective than CA in enhancing oxidative stability of lard at 60 degrees C. Inhibition by HCA of copper ion-induced oxidation of human LDL was less effective than that by CA, whereas there was no significant difference, between the two compounds in the capacity of 1,1-diphenyl-2-picrylhydrazyl radical scavenging and the activity of lipid peroxyl radical scavenging in solution. It can be concluded that the 2,3-double bond in the structure of CA affects the efficiency of antioxidative activity depending on the environment where the oxidation happens, although it is rarely responsible for its inherent activity.