Purification, identification and characterization of two novel antioxidant peptides from finger millet (Eleusine coracana) protein hydrolysate

Antioxidant peptides were successfully identified from a finger millet protein hydrolysate. The trypsin hydrolysate showed a higher degree of hydrolysis (17.47 +/- 0.63%) than the pepsin hydrolysate, was further fractionated by ultrafiltration membrane [< 31cDa (UF3), 3-10 kDa (UF2) and > 10 kDa (UF1)]. UF3 with higher antioxidant activity (48.41 +/- 0.21%) was further fractionated into five fractions (GF(A), GE(E), GF(C), GF(D) and GF(E)) using gel filtration. Fraction GF(B) possessed the highest antioxidant activity (61.79 +/- 0.08%) and was purified by reverse-phase ultra-flow liquid chromatography. Two potential antioxidant peptides were identified as TSSSLNMAVRGGLTR and STTVGLGISMRSASVR. Synthetic peptides with the same sequence were synthesized and characterized for their antioxidant activity. Molecular docking studies revealed that potential antioxidant activity from both peptides resulted from the interaction of serine and threonine residues with free radicals. The current study suggested that natural peptides identified from finger millet have potent antioxidant activity and regarded as a promising source for a functional food ingredient.