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Isolation and determination of anthocyanins in seed coats of black soybean (Glycine max (L.) Merr.)

Choung, M.G., Baek, I.Y., Kang, S.T., Han, W.Y., Shin, D.C., Moon, H.P., Kang, K.H.
Journal of agricultural and food chemistry 2001 v.49 no.12 pp. 5848-5851
soybeans, color, anthocyanins, glucosides, chemical composition, chemical structure, varieties, testa
Anthocyanin pigments in seed coats of black soybean (Glycine max (L.) Merr.) were extracted with 1% HCl-CH3OH, and the crude anthocyanin extract was purified by Sephadex LH-20 and Lichroprep RP-18 open-column chromatography. Three major anthocyanins were isolated, and their chemical structures were identified by spectroscopic methods (UV-visible, FABMS, 1H and 13C NMR, and by TLC). The complete structures of these anthocyanins were elucidated as delphinidin-3-glucoside, cyanidin-3-glucoside, and petunidin-3-glucoside. Among them, petunidin-3-glucoside was identified as a new anthocyanin in black soybeans. On the basis of RP-HPLC with a UV-vis detector, the contents of delphinidin-3-glucoside, cyanidin-3-glucoside, petunidin-3-glucoside, and total anthocyanins in seed coats of 10 black soybeans were found in the ranges of 0-3.71, 0.94-15.98, 0-1.41, and 1.58-20.18 mg/g, respectively. The results obtained in this study imply that the seed coats of black soybean can be used as a good source for cyanidin-3-glucoside and delphinidin-3-glucoside.