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 fractio ns with angiotensin I-converting enzyme (ACE) inhibitory activity. Fra ctions with high ACE inhibitory activity were combined and further chr omatographed on a reverse-phase column to yield seven dipeptides with ACE inhibitory properties. These dipeptides were identified by sequenc e 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 dipeptid e was synthesized and its antihypertensive activity was determined aft er oral administration in spontaneously hypertensive rats. The blood p ressure lowering activity of the dipeptides was lower than that of cap topril. However, the presence of these dipeptides in garlic suggests t hat these compounds may, at least in part, be responsible for the obse rved antihypertensive effect of garlic (or garlic extracts) in animals and humans. Further, long-term use of dietary garlic may have a prote ctive effect against rise in blood pressure. (J. Nutr. Biochem. 9:415- 419, 1998) (C) Elsevier Science Inc. 1998.