Changes in polyphenols, anthocyanins, and DPPH radical-scavenging activities in sweetpotato (Ipomoea batatas L.) during tuber growth

Anthocyanins and polyphenols in the sweetpotato (Ipomoea batatas L.) have attracted attention due to their multiple physiological functions. Therefore, sweetpotato breeders have focused on increasing the anthocyanin and polyphenol contents. In this study, we investigated the diversity of anthocyanins, polyphenols, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activities in sweetpotato genotypes. We also assessed how the anthocyanin and polyphenol contents and compositions were related to DPPH radical-scavenging activities during tuber growth in several cultivars of sweetpotatoes. In six purple-fleshed cultivars, the percentage of acylated anthocyanins that were evaluated was high (92.0-98.5 %), whereas in 'Fukumurasaki' this percentage was particularly low (63.6 %). Moreover, the percentages of anthocyanins that were acylated in the purple-fleshed cultivars 'Tanegashimamurasaki', 'Purple Sweet Lord', and 'Akemurasaki' had already reached high levels in the early stage of tuber development. On the other hand, these three cultivars with high anthocyanin contents had high DPPH radical-scavenging activities, and the activities during tuber growth showed a high correlation with total anthocyanin content. Elucidating the changes in acylated anthocyanin content and in antioxidant activities during tuber growth can help promote high-quality sweetpotato cultivation and breeding.