Multi-target mechanisms of diabetic inhibitory peptides derived from longan seed protein hydrolysate

Abstract

This research sought to examine the diabetic inhibitory potential of bioactive peptides derived from longan seed protein hydrolysates (LSH). These hydrolysates were produced using pepsin and pancreatin to simulate gastrointestinal digestion, and upon testing were revealed to inhibit α-amylase (IC50 = 196.91 μg/mL), α-glucosidase (IC50 = 25.29 μg/mL), and dipeptidyl peptidase-IV (DPP-IV) enzymes (IC50 = 116.10 μg/mL). Results from ultrafiltration revealed the strongest inhibition was achieved by the smallest peptide fraction. Nine active fractions were classified via RP-HPLC purification, and the most effective inhibitors were found to be the fractions F1, F4, and F8. LC-Q-TOF MS/MS was carried out to identify a total of seven peptide sequences, with SSYYPFKGFA (SA-10) and VKGPGLYSDI (VI-10) providing the strongest inhibitory properties according to the molecular docking analysis. Both peptides exhibited antidiabetic effects, as demonstrated by in vitro and enzymatic kinetic assays. SA-10 showed competitive, uncompetitive, and mixed-type inhibition against α-amylase, α-glucosidase, and DPP-IV, respectively. Conversely, VI-10 exhibited uncompetitive inhibition of α-amylase and mixed-type inhibition of both α-glucosidase and DPP-IV. Preliminary ADMET predictions of pharmacokinetic properties suggest that LSH peptides may exhibit adequate solubility and minimal toxicity. However, further in vivo studies and clinical trials are essential to gain comprehensive insight and clarify their actual efficacy, safety, and pharmacokinetic profile in diabetes treatment. Overall, the multi-targeted approach of longan seed peptides suggested a potential avenue in the control of diabetes and postprandial hyperglycemia, since SA-10 and V-I10 demonstrated useful abilities in boosting insulin secretion and slowing the digestion of carbohydrates.