Antioxidative activities of caffeoyl-proline dipeptides

The benefits of antioxidants in treating degenerative diseases, delaying ageing and preserving food, have been extensively studied. In our previous study, we found that caffeoyl-Pro-His dipeptide (CA-Pro-His-NH2) showed the highest antioxidative activity among the histidine- containing caffeic acid dipeptides (CA-His-Xaa-NH2 and CA-Xaa-His-NH2). We assumed that the addition of proline to the CA-Pro-His-NH2 structure may synergistically enhance its antioxidative activity. Therefore, we synthesised twenty different caffeoyl-proline dipeptides (CA-Pro-Xaa-NH2), and evaluated their antioxidative activities with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and lipid peroxidation inhibition tests. Some of the CA-Pro-Xaa-NH2 showed higher free radical scavenging activities than CA, and even CA- CA-Pro-His-NH2. However, CA-Pro-His-NH2 still exhibited the highest antioxidative activity in reducing lipid peroxidation.