Angiotensin I-Converting Enzyme Inhibitory Action of Fish Sauce

The angiotensin I-converting enzyme (ACE) inhibitory activity of fish sauce, the product with the strongest ACE inhibitory activity among liquid fermented foods, was fractionated into 2 fractions with ethanol treatment. The major part of the inhibitory substance was contained in the supernatant fraction (S-fraction) and its intraperitoneal administration had a hypotensive effect on spontaneously hypertensive rat (SHR). By octadecyl-silane column chromatography and two successive kinds of gel filtration, the inhibitory activity of the S-fraction was further separated into several fractions indicating that the strong inhibitory activity of the fish sauce is caused by a combined action of various kinds of inhibitory substances present. From the fraction with the lowest 50% inhibition concentration IC50 value, three kinds of dipeptides, glycyl-tryptophan, isoleucyl-tryptophan and valyl-tryptophan, were isolated as the ACE inhibitory compounds. Oral administration of these peptides to SHR showed a hypotensive effect.