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Title: Characterization of anthocyanins and anthocyanidins in purple-fleshed sweetpotatoes by HPLC-DAD and LC-ESI/MS-MS

Author
item Truong, Van Den
item DEIGHTON, NIGEL - North Carolina State University
item Thompson, Roger
item McFeeters, Roger
item Dean, Lisa
item PECOTA, KENNETH - North Carolina State University
item YENCHO, G. CRAIG - North Carolina State University

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2009
Publication Date: 1/25/2010
Citation: Truong, V., Deighton, N., Thompson, R.L., Mcfeeters, R.F., Dean, L.L., Pecota, K.V., Yencho, G. 2010. Characterization of anthocyanins and anthocyanidins in purple-fleshed sweetpotatoes by HPLC-DAD and LC-ESI/MS-MS. Journal of Agriculture and Food Chemistry. 58:404-410.

Interpretive Summary: Purple-fleshed sweetpotatoes (PFSP) have attractive reddish-purple color with high levels of anthocyanins, total phenolics and antioxidant activities. Recent research on nutraceutical properties of PFSP indicated that the extracted anthocyanins have a potential capacity for reducing the risks of several chronic diseases. In the United States, there is a growing interest in the sweetpotato industry in exploring the market opportunities for PFSP as a healthy food choice and potential source for natural food colorants. Breeding efforts to develop PFSP genotypes suitable for local growing conditions, postharvest handling practices and marketing systems have been carried out. Processing technologies have been developed to convert PFSP into frozen and aseptic purees for various food applications. Therefore, characterization of anthocyanin pigments in PFSP is important for breeding programs and development of value-added products. In this study, seventeen anthocyanins in three varieties grown in the U.S. were identified by HPLC and LC-MS/MS. Cyanidin and peonidin, which were the major anthocyanidins in the acid hydrolyzed extracts, were well separated and quantified by HPLC with external standards. Cyanidin and peonidin, which contribute to the blue and red hues of PFSP, can be simply quantified by HPLC after acid hydrolysis of the anthocyanins. Steam cooking had no significant effect on total anthocyanin content or the anthocyanin composition.

Technical Abstract: Purple-fleshed sweetpotatoes (PFSP) can be a healthy food choice for consumers and a potential source for natural food colorants. This study aimed to identify anthocyanins and anthocyanidins in PFSP, and to evaluate the effect of thermal processing on these polyphenolic compounds. Freeze-dried powder of raw and steamed samples of three PFSP varieties were extracted with acidified methanol using a Dionex ASE 200 accelerated solvent extractor. The extract was acid hydrolyzed at 100ºC for anthocyanidin analysis. Anthocyanins and anthocyanidins were characterized by HPLC-DAD and LC-ESI/MS-MS. Seventeen anthocyanins were identified for Carolina Purple and NC 415 varieties with five major compounds: cyanidin 3-caffeoylsophoroside-5-glucoside (A), peonidin 3-caffeoylsophoroside-5-glucoside, cyanidin-3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucoside, peonidin 3-caffeoyl-p-hydroxybenzoyl-sophoroside-5-glucoside, and peonidin-caffeoyl-feruloylsophoroside-5-glucoside. Okinawa variety showed 12 pigments with 3 major peaks identified as (A), cyanidin 3-(6'', 6'''-dicaffeoylsophoroside)-5-glucoside and cyanidin 3-(6''-caffeoyl-6'''-feruloylsophoroside)-5-glucoside. Steam cooking had no significant effect on total anthocyanin content or the anthocyanin pigments. Cyanidin and peonidin, which were the major anthocyanidins in the acid hydrolyzed extracts, were well separated and quantified by HPLC with external standards. Cyanidin and peonidin, which contribute to the blue and red hues of PFSP, can be simply quantified by HPLC after acid hydrolysis of the anthocyanins.