Novel α-glucosidase inhibitory peptide derived from Cyperus esculentus meal protein hydrolysates: Screening, inhibition mechanism and stability

Abstract

Cyperus esculentus meal, a major by-product of Cyperus esculentus oil extraction, is rich in proteins and represents a valuable source of bioactive peptides. This study aimed to prepare peptides with α-glucosidase inhibitory activity from Cyperus esculentus meal proteins by dual enzyme hydrolysis (Alkaline protease and Trypsin). The hydrolysate was separated and purified by ultrafiltration and reverse high-performance liquid chromatography (RP-HPLC) to obtain the best inhibitory fraction (F₂). Three novel α-glucosidase inhibitory peptides (AAGF, QPTM and QGSM) were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and computerized screening. The inhibition kinetics and molecular docking revealed that AAGF and QPTM were mixed inhibitors of α-glucosidase and QGSM was anticompetitive inhibitor, and all three peptides inhibited α-glucosidase activity through hydrogen bonding. Furthermore, the three α-glucosidase inhibitory peptides were stable by heat treatment (65、100 °C), acidic or neutral conditions (pH 2.0–7.0), metal ions (Mg^2 +、K⁺、 Na⁺ 、Ca²⁺) and simulated gastrointestinal digestion. However, strong alkaline conditions (pH > 9.5) and Zn²⁺ metal ions should be avoided during processing. This study demonstrates that Cyperus esculentus meal protein hydrolysate can be used as a natural source of hypoglycemic substances by inhibiting the activity of α-glucosidase. The identified peptides AAGF, QPTM and QGSM hold significant potential for development in functional foods and antidiabetic therapeutics.