Isolation and characterization of angiotensin I-converting enzyme inhibitor dipeptides derived from Allium sativum L (garlic)

A concentrate of an aqueous extract of Allium sativum L. (garlic) was fractionated rising ion exchange and gel filtration to isolate fractions with angiotensin I-converting enzyme (ACE) inhibitory activity. Fractions with high ACE inhibitory activity were combined and further chromatographed on a reverse-phase column to yield seven dipeptides with ACE inhibitory properties. These dipeptides were identified by sequence analysis and fast atom bombardment mass spectrometry as Ser-Tyr, Gly-Tyr, Phe-Tyr, Asn-Tyr, Ser-Phe, Gly-Phe, and Asn-Phe, with IC50 (the amount of peptide needed to inhibit ACE activity) values of 66.3, 72.1, 3.74, 32.6, 130.2, 277.9, and 46.3 mu M, respectively. Each dipeptide was synthesized and its antihypertensive activity was determined after oral administration in spontaneously hypertensive rats. The blood pressure lowering activity of the dipeptides was lower than that of captopril. However, the presence of these dipeptides in garlic suggests that these compounds may, at least in part, be responsible for the observed antihypertensive effect of garlic (or garlic extracts) in animals and humans. Further, long-term use of dietary garlic may have a protective effect against rise in blood pressure. (J. Nutr. Biochem. 9:415-419, 1998) (C) Elsevier Science Inc. 1998.