Phenolic profile of whole seeds and seed fractions of lentils and its impact on antioxidant activity

Seed color and size are the major traits influencing consumer's acceptability and market class of lentils worldwide. In this paper we assessed the in vitro antioxidant capacity of whole seeds, hulls, and cotyledons of five lentil varieties in relation to their phenolic profile. The samples were evaluated for total polyphenol content and different phenolic classes, such as condensed tannin content, total monomeric anthocyanins, and phenolic acids. Individual phenolic compounds, including flavonols, flavanols, flavones, anthocyanins, and phenolic acids, were further quantitatively investigated by HPLC-DAD. Total antioxidant capacity was evaluated by ABTS and ORAC assays, and a direct measurement (ABTSdir) was used to evaluate the antioxidant capacity of the bioactive compounds present in the whole-meal flours without extraction. The five genotypes showed considerable variations in their phenolic content and profile as well as antioxidant activities. The results showed a preferential accumulation of phenolic compounds with antioxidant activity in the hulls compared to cotyledons. Delphinidin and cyanidin were the most abundant flavonoids in the hulls, while epicatechin and catechin were the most concentrated in the cotyledons. A highly significant correlation was observed between ABTS, ORAC and ABTSdir and total polyphenols. The antioxidant capacities were highly correlated with several individual phenolics detected in hulls and cotyledons. The overall results showed that the lentil fractions and extracts with higher phenolics had also higher antiradical activity which was independent on seed size and color. Identifying lentil genotypes with diverse phenolic profile in cotyledons and whole seeds could meet diverse consumers preferences and health requirements.