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

Chen, P.X., Bozzo, G.G., Freixas-Coutin, J.A., Marcone, M.F., Pauls, K.P., Tang, Y., Zhang, B., Liu, R., and Tsao, R. (2015). "Free and conjugated phenolic compounds and their antioxidant activities in regular and non-darkening cranberry bean (Phaseolus vulgaris L.) seed coats.", Journal of Functional Foods, 18(part B), pp. 1047-1056. doi : 10.1016/j.jff.2014.10.032  Access to full text

Abstract

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 µmole TE/g and 20.71–54.01 µmole AAE/g) compared to ND seed coats (2.11–10.09 µmole TE/g and 0.73–1.88 µmole AAE/g). This is the first report of specific flavonoids in cranberry beans.

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