Characterization of the dietary fiber extract from corn (Zea mays L.) and cooked common bean (Phaseolus vulgaris L.) flours and evaluation of their inhibitory potential against enzymes associated to lipid and glucose metabolism in vitro

Nutritionally low diets have led to the increase of chronic non-communicable diseases (NCDs), particularly obesity and type II diabetes. Corn (Zea mays L.) and common beans (Phaseolus vulgaris L.) mixture have been tested as proper ingredients to manufacture healthy food products. However, but most of their biological potential reducing the risk of NCDs is mainly concentrated on its dietary fiber (DF), particularly for its content of phenolic compounds and its derived antioxidant capacity. This research aimed to characterize DF-aqueous extracts from nixtamalized corn and cooked common bean flour blends, evaluating their inhibitory potential against lipid and glucose metabolism in vitro. Two nixtamalized white corn flours (commercial: A; Northwestern white population, NWP: B) and one cooked common bean flour (Bayo Madero cultivar, C) were assessed on different proportions (80:20 and 70:30 corn:bean). An aqueous fiber extraction was conducted, and insoluble (IDF), soluble (SDF), and total dietary fiber (TDF) were quantified. IDF exhibited the highest total phenolics (30-45 µg eq. gallic acid/g sample), whereas SDF from 8020AC/8020BC displayed the highest content of condensed tannins. Chlorogenic and ellagic acids and (+)-catechin were the main identified phenolics by HPLC-DAD in the fiber extracts. SDF showed the highest antioxidant capacity levels (ABTS/DPPH), α-amylase, and pancreatic lipase inhibitions (20-25 %) among the fiber types. IDF exhibited the highest α-glucosidase inhibitions (up to ~75 %). In silico simulations indicated that epigallocatechin gallate had the highest binding affinity against the three assayed enzymes (-6.10 to -5.70 kcal/mol). Results suggested that DF extracts from nixtamalized NWP corn and cooked Bayo Madero common bean flours could be used as functional ingredients but incorporating these flours in suitable food products is required to validate their technological potential.