In vitro simulated gastrointestinal digestion and identification of novel antidiabetic peptides from isolated peanut protein

This work aimed to discover potential peptides with antidiabetic properties by inhibiting the enzymes α-amylase and α-glucosidase. After undergoing simulated gastrointestinal digestion (SGID), the protein digestion rate was determined to be 66.98%. SDS-PAGE analysis demonstrated that SGID effectively promoted the digestion of peanut protein, leading to the formation of smaller peptides. The digested protein exhibited significant inhibition of α-amylase and α-glucosidase. The inhibitory activity of both enzymes was higher in the FIII fraction (< 3 kDa) obtained through ultrafiltration. This fraction was further purified using gel filtration chromatography to produce sub-fractions (SF). Among these SFs, FIII-SF5 exhibited the highest activity (p < 0.05) in terms of inhibiting α-amylase (IC₅₀ of 9.48 mg/mL) and α-glucosidase (IC₅₀ of 7.52 mg/mL). It was subsequently purified using RP-HPLC to produce sub-sub-fractions (SSF), and FIII-SF5-SSF3 was identified as the most active (p < 0.05) with IC₅₀ of 1.80 mg/mL for α-amylase and 1.23 mg/mL for α-glucosidase. LC–MS/MS was then utilized to determine the peptide sequences. In this study, two novel peptides, Asp-Asn-Leu-Pro (458.19 Da, IC₅₀ of 1.37 and 0.95 mg/mL) and Gln-Leu-Pro (357.18 Da, IC₅₀ of 1.96 and 1.57 mg/mL), were successfully discovered as α-amylase and α-glucosidase inhibitors. Additionally, both peptides demonstrated antiglycation activity, with IC₅₀ values of 280.46 and 110.39 μg/mL, respectively. These results indicate that peptides derived from peanut protein are promising natural components for diabetes management applications and could serve as a novel source of antidiabetic peptides, offering potential benefits in the functional and health food sector.