Purification, identification, and in vivo activity of angiotensin I-converting enzyme inhibitory peptide, from ribbonfish (Trichiurus haumela) backbone.

Ribbonfish (Trichiurus haumela) backbone is normally discarded as an industrial waste from fish processing. A method of developing angiotensin I-converting enzyme inhibitory (ACEI) peptides from ribbonfish backbone was previously optimized. The purposes of the study were to characterize the active peptides in the hydrolysate and to evaluate its in vivo activity. Ribbonfish backbone protein hydrolysate prepared by acid protease was fractionated into 4 fractions (I, MW < 1 kDa; II, MW = 1 to 5 kDa; III, MW = 5 to 10 kDa; and IV, MW > 10 kDa) through ultrafiltration membranes. Fraction I, showing the highest ACEI activity, was further purified using consecutive chromatographic techniques including gel filtration and reversed phase high-performance liquid chromatography. The purified ACE inhibitory peptide was determined to have a molecular weight of 317.25 Da, with a sequence of Leu-Trp and an IC₅₀ value of 5.6 μM. Systolic blood pressure of spontaneously hypertensive rats was significantly decreased from 181 ± 2.0 to 161.3 ± 2.3 mm Hg after 4 h of oral administration of Leu-Trp at a dose of 10 mg/kg of body weight. These results indicated that ribbonfish backbone protein could be used for development of antihypertensive agent.