Isolation of angiotensin I converting enzyme (ACE) inhibitor from fermented oyster sauce, Crassostrea gigas

Angiotensin I converting enzyme (ACE) inhibitor was isolated from fermented oyster sauce (FOS) and purified. Oyster was fermented with 25% NaCl (w/w) at 20 °C for 6 months. FOS was passed through a 40-mesh sieve, desalted using an electrodialyzer and then lyophilized. ACE inhibitory activity of FOS was investigated, and the IC50 value was determined to be 2.45 mg/ml. ACE inhibitor from FOS was purified using SP-Sephadex C-25 ion exchange chromatography, Sephadex G-50 gel chromatography, high-performance liquid chromatography (HPLC) on a gel permeation chromatography (GPC) column and reversed-phase HPLC on a C18 column. The purified inhibitor had an IC50 value of 0.0874 mg/ml, and it exhibited competitive inhibition against ACE. The purified peptide was evaluated for its antihypertensive effect in spontaneously hypertensive rats (SHRs) following oral administration. Rat blood pressure significantly decreased after inhibitor injection.