title: Identification and Relative Quantification of Bioactive Peptides Sequentially Released during Simulated Gastrointestinal Digestion of Commercial Kefir.
abstract: Health-promoting effects of kefir may be partially caused by bioactive peptides. To evaluate their formation or degradation during gastrointestinal digestion, we monitored changes of the peptide profile in a model of (1) oral, (2) gastric, and (3) small intestinal digestion of kefir. Matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy analyses revealed clearly different profiles between digests 2/3 and kefir/digest 1. Subsequent ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry identified 92 peptides in total (25, 25, 43, and 30, partly overlapping in kefir and digests 1, 2, and 3, respectively), including 16 peptides with ascribed bioactivity. Relative quantification in scheduled multiple reaction monitoring mode showed that many bioactive peptides were released by simulated digestion. Most prominently, the concentration of angiotensin-converting enzyme inhibitor β-casein203-209increased approximately 10 000-fold after combined oral, gastric, and intestinal digestion. Thus, physiological digestive processes may promote bioactive peptide formation from proteins and oligopeptides in kefir. Furthermore, bioactive peptides present in certain compartments of the gastrointestinal tract may exert local physiological effects.
authors.affiliation: Department of Chemistry and Pharmacy, Food Chemistry Unit, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , Schuhstraße 19, 91052 Erlangen, Germany.
authors.forename: Yufang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Pharmacy, Food Chemistry Unit, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , Schuhstraße 19, 91052 Erlangen, Germany.
authors.forename: Monika
authors.identifier: http://orcid.org/0000-0003-3465-4179
authors.initials: M
authors.lastname: Pischetsrieder
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000378:metabolism; D000818:Animals; D002364:Caseins / Q000737:chemistry; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004063:Digestion; D041981:Gastrointestinal Tract / Q000378:metabolism*; D006801:Humans; D000070716:Kefir / Q000032:analysis*; D008954:Models, Biological; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002364:Caseins; D010455:Peptides
keywords: bioactive peptides; gastrointestinal digestion; kefir; peptide profile