A novel deep eutectic solvent-based green extraction and purification of DPP-IV inhibitory peptides from tilapia ( Oreochromis niloticus ) viscera hydrolysate

The use of green and low-cost techniques to produce bioactive peptides with anti -diabetic properties from protein -rich fish waste is a sustainable way to manage agro-fishery and food industrial waste. This study investigated a novel ultrasound (UL) assisted deep eutectic solvent (DES) based extraction approach to recover bioactive protein -rich extracts from tilapia fish viscera waste under optimized conditions (52.52% ultrasound amplitude, 1:4 DES molar ratio, 25 min extraction time). The aqueous two-phase system (ATPS) method successfully concentrated the crude proteins in the top phase and back -extracted proteins to the bottom phase with a high recovery yield. Hydrolysis by Alcalase produced tilapia viscera protein hydrolysate (TVPH) with low molecular weight (MW) peptides and low dipeptidyl peptidase (DPP) -IV half -maximal inhibitory concentration (IC 50 ) value of 1.57 +/- 0.16 mg/mL. Notably, TVPH-3 fraction and TVPH-3-2 sub -fraction exhibited appreciable DPP -IV IC 50 values of 1.36 +/- 0.08 mg/mL and 0.42 +/- 0.01 mg/mL, respectively. Ultrafiltration combined with RP-HPLC enriched the DPP -IV inhibitory concentration of the individual protein fractions. TVPH-3-2 sub -fraction contained hydrophobic amino acids and peptide sequences with typical DPP -IV inhibitory peptide sequence motifs. The results presented in this study indicate that tilapia viscera biomass is a potential source for protein recovery aided with a green extraction approach, and tilapia viscera protein -derived hydrolysates have potential applications as a potent functional food ingredient for the management of metabolic diseases like type -2 diabetes.