An angiotensin-I converting enzyme inhibitor from buckwheat (Fagopyrum esculentum Moench) flour.

A compound that inhibited angiotensin-I converting enzyme (ACE) activity was isolated from buckwheat powder. This compound is thought to be the hydroxy derivative of nicotianamine and its chemical structure is 2''-hydroxynicotianamine. This compound showed a very high inhibitory activity toward ACE, and the IC(50) was 0.08 microM. Only this hydroxy analog was found in buckwheat powder, at about 30 mg/100g, and no nicotianamine was detected. However, nicotianamine was detected in the buckwheat plant body. 2''-hydroxynicotianamine was also found in other polygonaceous plants.