Angiotensin I-converting enzyme inhibitory activity and antioxidant capacity of bioactive peptides derived from enzymatic hydrolysis of buffalo milk proteins

Buffaloes' milk, which is consumed in many parts of the world, is a little-explored source of bioactive peptides. The angiotensin converting enzyme (ACE)-inhibitory activity and the antioxidant capacity of peptides from buffaloes' milk were examined. A retentate from buffaloes' skimmed milk was hydrolysed using papain, pepsin or trypsin. The papain hydrolysate showed the highest ACE-inhibitory activity and radical scavenging capacity and was fractionated by size exclusion chromatography (SEC) and characterized by LC-MS analysis. A SEC-fraction with intermediate peptide size showed very high ACE-inhibitory activity, while two fractions with small peptides exhibited the strongest antioxidant activity. Peptide identification by ultra-performance liquid-chromatography-tandem mass spectrometry showed that these active fractions contained known bioactive sequences, in addition to novel peptides with supposed ACE-inhibitory (FPGPIPK, IPPK, IVPN, and QPPQ) and antioxidant (YPSG, HPFA and KFQ) activities. The results obtained showed the potential of buffaloes' milk proteins to release ACE-inhibitory and antioxidant peptides.