Characterization of Nicotianamine Isolated from Soybeans

Angiotensin ?-converting enzyme (ACE) [EC 3.4.15.1] plays one of important roles to control the arterial blood pressure. Inhibitory activity of the enzyme has been reportedly detected in plant foods. We examined the activity in plant foods and isolated an ACE inhibitor in soybeans. The structure was identified as nicotianamine, N-[N-(3-amino-3carboxypropyl)-3-amino-3-carboxypropyl]-azetidine-2-carboxylic acid. The contents in several soybean foods were estimated using an amino acid analyzer. The chelation capacity of nicotianamine with metals was examined using a mass spectrometer. Soybean foods contained considerable amounts of nicotianamine but fermentation caused a decrease in the nicotianamine content. The (1:1) adduct formation of nicotianamine with metals was directly observed in the mass spectra.