Stability and composition ratio of anthocyanin pigments from Ipomoea batatas Poir.

Abstract

Anthocyanin pigments (AN) were extracted and purified from sweet potatoes (Ipomoea batatas Poir.) of Ayamurasaki, Yamagawamurasaki, Kankei-55, Tanegashimamurasaki, Y-617, Y-637, Beniazuma (skin) and Beniimo, and examined yields, spectrum characteristics, composition ratios and stabilities. (1) A positive correlation was observed between Emaxs of the extracts and yields of ANs provided from various sweet potatoes, and the yield of Ayamurasaki AN was the highest in the eight sweet potatoes. (2) Structures of Ayamurasaki ANs were estimated as 3-caffeoylsophoroside-5-glucosides, 3-caffeoylcaffeoylsophoroside-5-glucosides, 3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucosides, and 3-caffeoylferuloylsophoroside-5-glucosides of cyanidin and peonidin by LC/MS. (3) ANs of Ayamurasaki and Yamagawamurasaki were peonidin type ANs, and Kankei-55, Tanegashimamurasaki, Y-617, Y-637 and Beniimo ANs were cyanidin type ANs. ANs in skin of Beniazuma were different at the kind and the composition ratio from ANs inner part of the tuberous root. (4) Sweet potato ANs were stabler than the pigments of red cabbage, shiso, strawberry and apple for heating, ultraviolet rays irradiation either. Major ANs of Ayamurasaki decreased in heating and ultraviolet rays irradiation either. New ANs were detected when irradiated with ultraviolet rays.