In vitro simulated gastrointestinal digestion of donkeys' milk. Peptide characterization by high performance liquid chromatography-tandem mass spectrometry

Donkeys' milk was subjected to in vitro simulated gastrointestinal digestion using pepsin and a mixture of pancreatic enzymes. Analysis of the hydrolysate by high pressure liquid chromatography coupled to tandem mass spectrometry allowed the identification of 46 peptides, of which 30 peptides belonged to beta-casein (beta-CN). The gastrointestinal digest possessed an important angiotensin converting enzyme (ACE)-inhibitory activity with an IC50 of 273.0 +/- 27.9 mu g mL(-1). The beta-CN fragment f(176-185) [VAPFPQPVVP], one of the most abundant peptides in the hydrolysate, was synthesized and its ACE-inhibitory activity measured. This peptide showed very potent activity with an IC50 of 48.8 +/- 2.3 mu M. To our knowledge, this is the first time that a bioactive peptide from donkeys' milk has been reported. (C) 2011 Elsevier Ltd. All rights reserved.