Discovery of vitexin, isovitexin and catechin as hypoglycemic factors in mung bean via metabolomics combined with in vitro experiments

Abstract Mung bean (Vigna radiata L .), a food with a medium–low glycemic index, contains a variety of functionally active small molecule metabolites that exhibit hypoglycemic effects. Notably, the hypoglycemic properties of different varieties of mung beans are variable. This study employed nontargeted metabolomics to analyze mung bean varieties with distinct phenotypic differences in the estimated glycemic index (eGI), identifying vitexin, isovitexin, and catechins as significantly relevant metabolites. The functions of these metabolites on the eGI were further validated through enzyme inhibition assays in vitro. The results elucidate the digestion characteristics of mung bean starch, revealing that the three metabolites contribute to an increase in the resistant starch (RS) content and a reduction in the hydrolysis rate of starch, ultimately resulting in a decrease in the eGI. Specifically, vitexin inhibited alpha-glucosidase (AG) activity via an uncompetitive inhibition mechanism (IC 50 = 50.11 µM), whereas isovitexin functioned through a competitive inhibition mechanism (IC 50 = 116.14 µM), and catechin exhibited noncompetitive inhibition (IC 50 = 42.06 µM). Furthermore, the study revealed a notable synergistic effect among these three metabolites in the inhibition of AG activity. This research screened and identified the main metabolites exhibiting hypoglycemic potential in mung beans and confirmed their hypoglycemic effects in vitro, thereby providing a theoretical foundation for the development of functional foods aimed at hypoglycemic applications of mung beans. Graphical Abstract