Structural activity remodeling of wheat protein peptides during simulated gastrointestinal digestion: insights into antioxidant and enzyme inhibitory functionalities

Abstract

Bioactive food peptides demonstrate potential in chronic disease intervention, yet their structure–activity dynamics during digestion remain poorly understood. This study overcomes the limitations of static assessment by elucidating the remodeling mechanisms of wheat protein peptides during simulated gastrointestinal digestion. Six molecular weight fractions (<1 kDa, 1–3 kDa, 3–5 kDa, 5–10 kDa, 10–20 kDa, >50 kDa) were analysed using Fourier transform infrared and Ultraviolet–Visible spectrophotometry. Results indicate that digestion induces rearrangement of peptide hydrogen-bond networks and conformational changes, leading to a general decline in antioxidant activity. However, low-molecular-weight peptides (<1 kDa) retained a significant advantage post-digestion, exhibiting higher DPPH radical scavenging efficiency (68.3% vs. 42.1%), hydroxyl radical scavenging rate (72.5% vs. 45.8%), and total reducing power (1.8 mmol Fe²⁺ per g vs. 0.9 mmol Fe²⁺ per g) were significantly higher than those of the >50 kDa fraction. A notable finding was that the α-glucosidase inhibition rate of the 1–3 kDa fraction increased by 71.49% after intestinal digestion, indicating its trypsin-dependent activation property. Environmental response studies revealed that peptide activity was optimal at 36 °C and pH 7.0, while metal ions (particularly K⁺) significantly inhibited activity in the <1 kDa fraction. Compared to previous studies, this research innovatively constructed a dynamic digestion–activity remodeling model spanning six molecular weight gradients, elucidating multi-environmental regulatory mechanisms and providing novel insights into the bioavailability and stability of wheat protein peptides. These findings support the development of targeted peptide-based functional foods for managing oxidative stress and diabetes, conferring unique value to this study.