Identification and Characterization of Novel DPP-IV Inhibitory Peptides from Limnospira platensis Hydrolysates: Stability and Intestinal Permeability Evaluation

As the prevalence of type 2 diabetes increases rapidly, the demand for natural origin dipeptidyl peptidase-IV (DPP-IV) inhibitors with fewer side effects is increasing. In this study, protein-rich Limnospira platensis was investigated as a source of bioactive peptides to enhance its value as a functional food ingredient. Hydrolysates were prepared using three food-processing proteases, individually and in two-step combinations, followed by in silico analysis and peptide identification via liquid chromatography–tandem mass spectrometry. Subsequently, the thermal stability, gastrointestinal resistance, and intestinal permeability (using Caco-2 cells) of the identified peptides were evaluated. It was revealed that the Orientase 22BF digest exhibited high DPP-IV inhibitory activity. From the digest, three novel peptides—SPSPN (IC50 = 144.1 ± 2.2 μM), VPSV (IC50 = 93.6 ± 5.8 μM), and IPIGG (IC50 = 13.4 ± 2.3 μM)—were identified, exhibiting DPP-IV inhibitory potencies comparable to or higher than previously reported Limnospira-derived peptides. Although VPSV exhibited low epithelial permeability (Papp = 4.02 ± 0.69 × 10−8 cm/s), it remained stable under simulated gastrointestinal digestion conditions, suggesting potential local luminal inhibitory activity within the small intestine. Overall, these findings highlight Limnospira-derived VPSV as a promising functional ingredient candidate with high bioactivity and digestive stability.