Anthocyanins in Purple Sweet Potato (Ipomoea batatas L.) Varieties

Anthocyanins from purple sweet potatoes can serve as natural colorants due to their high heat and light stability and are commonly used in juices, alcoholic beverages, jams, confectioneries, bread, snacks and noodles. There are several commercially available varieties of purple sweet potatoes, which can vary in storage root size, shape, and color. During the last decade sweet potato cultivars with purple flesh were mainly grown in Japan and new varieties with high contents of anthocyanins have been developed due to the low anthocyanin accumulation in indigenous purple-fleshed sweet potatoes. Among them, important cultivars are the 'Yamagawamurasaki' and 'Ayamurasaki' varieties. Chromatographic analyses show a very complex anthocyanin composition. Ten major pigments with non-, monoor diacylated structures of 3-O-(2-O-D-glucopyranosyl-D-glucopyranoside)-5-O-D-glucosides of cyanidin and peonidin were characterized by ESI-MS and NMR analyses. A comparison of different Japanese purple sweet potato cultivars shows a remarkable variation of anthocyanin profile. According to this, they can be categorized into two groups (blue and red dominant) based on the shade of color and the peonidin/cyanidin ratio. By means of the four Japanese cultivars 'Chiran murasaki', 'Tanegashima murasaki', 'Naka murasaki' and 'Purple Sweet' the differences in anthocyanin composition will be discussed in detail. _____________________________________________________________________________________________________________