Variability in the Distribution of Phenolic Compounds in Milled Fractions of Chickpea and Horse Gram: Evaluation of Their Antioxidant Properties

Seed coat, cotyledon and embryonic axe fractions of chickpea (Cicer arietinum L.) and horse gram
(Macrotyloma uniflorum L.) were evaluated for their phenolic composition in relation to antioxidant
activities. Compositional analysis of phenolics by HPLC revealed a wide variation in the distribution
of flavonols, isoflavones, phenolic acids and anthocyanins among these legume fractions. Although
cotyledon fractions of both the legumes were rich in phenolic acids, the concentrations of flavonols
such as quercetin, kaempferol, and myricetin were significantly (p < 0.05) lower than the embryonic
axe and seed coat fractions. Ferulic, chlorogenic, caffeic, and vanillic acids were the principal
phenolic acids found in cotyledons. The most striking difference was the predominance of
isoflavones in embryonic axe fractions. Although the isoflavone genistein was detected in all three
fractions of chickpea, it was present exclusively in the embryonic axe fraction of horse gram at
levels greater than daidzein. Furthermore, cyanidin, petunidin, and delphinidin were detected in
seed coat and embryonic axe fractions but not in cotyledons. In addition to these three anthocyanins,
malvidin was found only in the horse gram seed coat fraction. Seed coat fractions having
higher total phenolic indexes were found to be the most active 2,2-diphenyl-1-picrylhydrazyl (DPPH)
radical scavengers (IC50 13.1 to 18.6 μg/mL) followed by embryonic axe and cotyledon fractions
(IC50 15.4 to 34.2 μg/mL). Hydrogen peroxide (H2O2) scavenging capacities of cotyledons,
embryonic axe and seed coats were 12.3, 34.1 and 78.6% for chickpea and 15.1, 56.8 and
92.6% for horse gram, respectively. The multiple antioxidant activity of horse gram and chickpea
fractions was evident, as they also possessed reducing power and ferrous ion-chelating potency.
These results contributed to the understanding of the relationships between major phenolic
compounds and antioxidant activities of legumes and provided useful information for effective
utilization of legume-milled fractions as functional food ingredients for promoting health.