Isolation, purification and identification of two antioxidant peptides from water hyacinth leaf protein hydrolysates (WHLPH).

In order to find novel natural antioxidant peptides, the water hyacinth leaf protein was hydrolyzed by Protamex at optimum condition to prepared water hyacinth leaf protein hydrolysate (WHLPH). And antioxidant properties of WHLPH were evaluated dependent on several in vitro antioxidant systems, including superoxide anion radical-scavenging activity, ABTS cation radical-scavenging activity, reducing power, and metal chelating capacity. WHLPH showed 86.37% of superoxide anion radical-scavenging activity at 1.0 mg/mL, and 56.51% of ABTS cation radical-scavenging activity at 100 μg/mL. At 1.0 mg/mL, the reducing power of WHLPH was 0.92, and the metal chelating capacity was 68.54%. Subsequently, the WHLPH was subjected to consecutive isolation and purification by macroporous resin, gel filtration chromatography, and reverse-phase high-performance liquid chromatography, and two peptide fractions with higher radical-scavenging activity were acquired. Finally, the two peptide fractions were identified to be Phe-Phe-Glu and Leu-Phe, respectively, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Considering the two peptides' amino acid composition, their antioxidant properties may be due to the hydrophobic and/or aromatic acid residues in their sequences. The results indicated that the isolated antioxidant peptides from WHLPH would find widespread application in food, cosmetics, and pharmaceutical industry because of their high potency, safety, low cost and abundant source. [ABSTRACT FROM AUTHOR]