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 β-casein (β-CN). The gastrointestinal digest possessed an important angiotensin converting enzyme (ACE)-inhibitory activity with an IC50 of 273.0 ± 27.9 μg mL−1. The β-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 μm. To our knowledge, this is the first time that a bioactive peptide from donkeys’ milk has been reported.