Free and conjugated phenolic compounds and their antioxidant activities in regular and non-darkening cranberry bean (Phaseolus vulgaris L.) seed coats

摘要

Postharvest darkening in dry bean (Phaseolus vulgaris L.) negatively impacts consumer preference. Regular-darkening (RD) and non-darkening (ND) cranberry beans were profiled for seed coat phenolics using HPLC-DAD/LC-ESI-MSn and assessed for antioxidant activity using oxygen radical absorbing capacity (ORAC) and ferric-reducing antioxidant power (FRAP) assays. Flavonoids were exclusive to free phenolic extracts of RD beans. Total phenolic content (TPC) was significantly higher (p < 0.05) in RD seed coats (52.41-56.43 mg GAE/g) compared to ND seed coats (2.00-2.06 mg GAE/g). Alkaline hydrolysis revealed the presence of phenolic acids and flavonoid conjugates in RD beans. Only p-coumaric and ferulic acids were found in ND beans. Overall antioxidant activity was stronger in RD seed coats (125.28-287.87 mu mole TE/g and 20.71-54.01 mu mole AAE/g) compared to ND seed coats (2.11-10.09 mu mole TE/g and 0.73-1.88 mu mole AAE/g). This is the first report of specific flavonoids in cranberry beans. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.