Peptide fragments from β-casein f(134-138), HLPLP, generated by the action of rat blood plasma peptidases show potent antihypertensive activity

The intact absorption of a β-casein peptide, HLPLP, into rat blood circulation after oral administration was recently demonstrated. In addition to the parent peptide, several derived fragments were detected in rat plasma. The aim of the present work is to elucidate whether these fragments retain antihypertensive activity and if their activity is mediated by angiotensin-converting-enzyme inhibition. The penta-peptide was incubated in rat plasma in order to identify and quantify the fragments generated by the action of plasmatic peptidases on HLPLP, using tandem mass spectrometry. Peptides HLPL, LPLP and HLP were generated within seconds of incubation. The parent peptide, HLPLP, and all possible derived peptides showed potent antihypertensive activity in spontaneously hypertensive rats and caused inhibition of vascular contraction elicited by angiotensin-I. It can be concluded that the antihypertensive effect of HLPLP can be produced by the concomitant action of the parent peptide and several novel derived fragments.