Distribution of Nutrients and Antinutrients in Milled Fractions of Chickpea and Horse Gram: Seed Coat Phenolics and Their Distinct Modes of Enzyme Inhibition

Abstract

Milled fractions of chickpea ( Cicer arietinum L.) and horse gram ( Macrotyloma uniflorum L. Verdc.) were evaluated for their nutritional and antinutritional characteristics. Crude protein content of these fractions ranged from 22.6-23.8 g 100(-1) g in cotyledon to 7.3-9.1 g 100(-1) g in seed coat fractions. The fat content of chickpea fractions (1.6-7.8 g 100(-1) g) was higher than that of horse gram fractions (0.6-2.6 g 100(-1) g). Crude fiber content was higher in seed coat fractions of both legumes than embryonic axe and cotyledon fractions. Seed coat fractions had high dietary fiber content (28.2-36.4 g 100(-1) g), made up of mainly insoluble dietary fiber. Most of the phytic acid and oligosaccharides were located in the cotyledon fractions, whereas phenolic compounds in higher concentrations were found in seed coats. Significantly higher concentrations of proteinaceous and phenolic inhibitors of digestive enzymes were found in cotyledon and seed coat fractions, respectively. The kinetic studies, using Michaelis-Menten and Lineweaver-Burk derivations, revealed that seed coat phenolics inhibit alpha-amylase activity by mixed noncompetitive (chickpea) and noncompetitive (horse gram) inhibition mechanisms. In the case of trypsin, chickpea and horse gram seed coat phenolics showed noncompetitive and uncompetitive modes of inhibition, respectively. These results suggest the wide variability in the nutrient and antinutrient composition in different milled fractions of legumes and potential utility of these fractions as ingredients in functional food product development.