Bio-functional, antibacterial, ACE and DPP-IV inhibitory activities of thyme, flax and apple pollen-peptides by controlled enzymolysis

In recent years, the chemical composition, bioactive compounds, and high nutritional value of flower pollen have made it known as "perfect health food". Therefore, in this study, the effects of different enzymes (Al-Alcalase, Pe-pepsin, Pa-pancreatin and Tr-trypsin) on nutritional value, the composition of amino acids, antioxidant properties, ACE, DPP-IV inhibitory and antibacterial activity of pollen protein of thyme (TP), flax (FP) and apple (AP) flowers were evaluated. Structural characteristics (conformational changed and amide regions of proteins) were identified by FTIR spectroscopy. The composition of antioxidant (∼20–24 %), and hydrophobic (∼36–40 %) amino acids, the ratio of EAA/TAA (∼45 %) and PER index (AP = 1.2–1.2; TP = 1.61–1.71 and FP = 1.68–1.81) were influenced by primary protein and enzyme type. The highest degree of hydrolysis (DH 34.4 %), inhibiting DPPH (86.1 %), ABTS (2.4 mM Trolox), OH (60.9 %), NO (33.6 %) radicals, reducing power (1.29), total antioxidant (1.83) and the chelation of Fe 2+ (76.7 %) and Cu 2+ (31.5 %) ions, ACE (67.9 %) and DPP-IV (64.6 %) inhibition were affected by the type of enzyme. Also, the greatest inhibition of the growth of Escherichia coli (∼24.7 mm) and Bacillus cereus (∼21.7 mm) was related to FP protein. Finally, TP-hydrolyzed with Alcalase can be considered as a suitable option for the production of beneficial products and the fortification of dietary supplements. • Enzymolysis of pollen proteins of thyme, flax and apple flowers was done with different proteases. • The composition of essential amino acids and nutritional indices were affected by the origin of proteins. • Enzyme type and composition of amino acids played a key role in the antioxidant, ACE, DPP-IV inhibitory of peptides. • Flax pollen peptides showed the highest antibacterial activity against E. Coli and B. cereus.