Characteristics of Caffeic Acid Derivatives in Okinawan Sweet Potato (Ipomoea batatas L.) Leaves and the Anti-LDL Oxidation Activity

The constituents of functional polyphenols, such as caffeic acid (CA), chlorogenic acid (ChA), 4,5 -di-caffeoylquinic acid (4, 5-diCQA), 3, 5-diCQA, 3, 4-diCQA and 3, 4, 5-triCQA, in 9 cultivars of Okinawan sweet potato leaves (Ipomoea batatas L.) and two comparable sweet potato cultivars were examined. The total amounts of caffeic acid derivatives correlated with the polyphenol contents (r=0.94), and were the main polyphenol constituents of sweet potato leaf. 4, 5-diCQA and 3, 5-diCQA were the main components in all cultivars, and were higher in harukogane, koganeyutaka and nagomasari than in the other cultivars. The inhibition of LDL-oxidation of the sweet potato leaf extracts was correlated with the total amounts of caffeic acid derivatives, suggesting that sweet potato leaves may prevent atherosclerosis via reducing early atherogenesis. This study demonstrated that Okinawan sweet potato leaves have potential as a functional food.