Physiological Functionality of Purple-Fleshed Sweet Potatoes Containing Anthocyanins and Their Utilization in Foods

Studies on the physiological functionality of purple-fleshed sweet potatoes and their dominant anthocyanin pigments are described. The purple-fleshed sweet potato cultivar ‘Ayamurasaki’ contained anthocyanins, which consisted of mono- or di-acylated forms of cyanidin (YGM-1a, -1b, -2 and -3) and peonidin (YGM-4b, -5a, -5b and -6). It was also rich in anthocyanins with peonidin aglycon. The ‘Ayamurasaki’ extract and the purified YGM exhibited multiple physiological functions such as radical-scavenging, antimutagenic, angiotensin I-converting enzyme-inhibitory, and α-glucosidase-inhibitory activities in vitro. Moreover, they also showed an ameliorative effect on carbon tetrachloride-induced liver injury and decreased postprandial blood glucose levels in rats. In addition, their role in restoring the liver function and blood pressure levels to normal in volunteers with impaired hepatic function and/or hypertension was also confirmed. The acylated anthocyanins, which were the major radical scavengers in ‘Ayamurasaki’, were directly absorbed into the blood stream of rats and were present as intact acylated forms in the plasma, and could also enhance the plasma antioxidative capacity. Based on these evidences, the purple-fleshed sweet potato can be recommended as a superior source for the production of foods with health benefits. Some foods and beverages in Japan that utilize these characteristics of anthocyanin pigments are also introduced in this paper.