Impact of bioprocessing on phenolic content and antioxidant activity of soy seed to improve hypoglycemic functionality

Hyperglycemia, a condition characterized by an abnormal excess of sugar in the blood, has been linked to the onset of type 2 diabetes mellitus and associated to oxidation-linked vascular complications. Medicinal plants and legumes have been shown to exert their hypoglycemic effect by several mechanisms which include the inhibition of the key enzymes, pancreatic α-amylase and intestinal α-glucosidase. The aim of the present study was to investigate the enrichment of soy seed (Glycine max) substrates with phenolic antioxidants via fungal-based solid-state bioconversion (SSB) system by dietary fungus (Rhizopus oligosporus) and its effect on the inhibition of above enzymes. Total phenol content (Lowry’s method) and antioxidant activity (DPPH) were determined. Inhibition of α- amylase and α-glucosidase activities were measured using starch and p-nitrophenyl-α-D-glucopyranoside as substrates respectively. Protein and total phenol content of the seed extracts increased with fungal incubation time. The extract indicated high antioxidant activity (85±0.6%), during early growth stage (days 4-6) followed by reduced activity during later growth stage (days 8-10). A direct association between higher phenolic contents during early growth stage (days 4-6) and antioxidant activity suggested a link to mobilization of polymeric and hydrophobic phenolic forms. SSB process substantially improved in vitro α-amylase inhibition activity in soy seed extracts to 75% on day 4 which is compared to higher levels of antioxidant activity. It is concluded that SSB is a good strategy to improve the phenolic content of above seed for enhanced functionality with improved antioxidant activity that contributes to α-amylase inhibition relevant to potential diabetes management.

Author(s): Debasmita Maiti and *Mala Majumdar

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