Effects of an ace-inhibitory agent, Katsuobushi oligopeptide, in the spontaneously hypertensive rat and in borderline and mildly hypertensive subjects

It has been previously documented that the thermolysin digest of "Katsuobushi," or dried bonito, a traditional Japanese food, potently inhibits the angiotensin I-converting enzyme (ACE). This hydrolyzate "Katsuobushi oligopeptide (KO)" has antihypertensive effects in hypertensive subjects at a dose of 3 g/day. In order to reduce the amount of KO required to produce an effect, we obtained a stronger KO (S-type KO) by ultra-filtration. The S-type KO had two-fold higher ACE-inhibitory activity, and also showed two-fold higher antihypertensive activity in the spontaneously hypertensive rat after oral administration, compared with the original KO. In a human study, the antihypertensive effects of 1.5 g/day of S-type KO were monitored against a placebo in a double-blind, randomized, cross-over study in 61 borderline and mildly hypertensive subjects. S-type KO showed antihypertensive activity without any side-effects. Thus, the ACE-inhibitory S-type KO demonstrated more potent antihypertensive effects than the original formulation. (C) 2001 Elsevier Science Inc. All rights reserved.