Angiotensin-I-converting enzyme (ACE)-inhibitory and antihypertensive properties of squid skin gelatin hydrolysates

Gelatin extracted from squid (Dosidicus eschrichitii Steenstrup) skin was hydrolysed with pepsin to prepare Angiotensin-I-Converting Enzyme (ACE) inhibitory peptide. The ACE-inhibitory activity was measured by spectrophotometric assay. The hydrolysate was fractionated into three ranges of molecular weight (6 kDa < HSSG-I < 10 kDa, 2 kDa < HSSG-II < 6 kDa, HSSG-III < 2 kDa) using an ultrafiltration unit. The HSSG-III showed the most potent ACE inhibitory activity in vitro with IC50 of 0.33 mg/ml. Renovascular hypertensive rats (RHR) model was made with two-kidney one clip assay, and antihypertensive effects were studied in RHR treated with HSSG-III for 30 days by oral administration. Arterial blood pressure were measured respectively. The HSSG-III remarkably reduced the arterial blood pressure of RHR. These results suggested that hydrolysate of squid skin gelatin obtained by treatment with pepsin was a good source of peptides with ACE-inhibitory activity and had an antihypertensive effect by oral administration.