Angiotensin I-converting enzyme inhibitory activity of proteins hydrolysate from seeds Thai fruits

Abstract

Blood pressure regulation is partially dependent on the rennin-angiotensin system; renin acts on angiotensinogen to release angiotensin-I, which is further converted into the angiotensin II by the angiotensin I-converting enzyme (ACE). ACE plays a key physiological role in the regulation of blood pressure by virtue of two different reactions that it catalyzes: conversion of the inactive angiotensin I to the powerful vasoconstrictor angiotensin II, and inactivation of the vasodilator bradykinin. Crude extract and ammonium sulphate cut protein extracts, and their pepsin-pancreatin hydrolysates, from the seeds of 4 Thai fruits (i) Carica papaya L.; (papaya; unripe and ripe form), (ii) Nephelium lappaceum L. (rambutan) (iii) Dimocarpus longan Lour. subsp. (longan), and (iv) Litchi chinensis Sonn. (lychee) were screened for their in vitro angiotensin I- converting enzyme inhibitory (ACEI) activity. The highest activity of each fraction, protein hydrolysate of lychee seeds shows the highest potential of ACE inhibitors of IC50 value 0.22±0.010 mg protein/ml. The protein hydrolysate of unripe papaya seeds, longan seeds, and lychee seeds show uncompetitive and non-competitive inhibition with Ki values at 6.02, 2.82, and 5.62 mg protein/ml, with optimum pH in range of 6-8. After partial purified with ultrafiltration technique, UF-3 (below 5 kDa) of longan seeds show the highest inhibitory activity with IC50 values at 0.43±0.011 mg protein/ml. This fraction subjected to RP-HPLC, five peaks were separated, and subjected into LC/MS/MS for amino acids sequences analysis. The P1-F1, P3-F1, and P3-F4 are possibility the most inhibitory activity peptides.