Antihypertensive Effect of Peptide-Enriched Soy Sauce-Like Seasoning and Identification of Its Angiotensin I-Converting Enzyme Inhibitory Substances

We have developed a peptide-enriched soy sauce-like seasoning termed Fermented Soybean Seasoning (FSS), by modifying the process of soy sauce brewing. The FSS has a 2.7-fold higher concentration of total peptides than regular soy sauce. The angiotensin I-converting enzyme (ACE) inhibitory activity of FSS (IC50 = 454 mu g/mL) was greater than that of regular soy sauce (IC50 = 1620 mu g/mL). The FSS demonstrated anti hypertensive effects both in spontaneously hypertensive rats and in Dahl salt-sensitive rats during continuous feeding. The ACE inhibitory substances were purified from FSS by reversed-phase chromatography. Ala-Trp (IC50 = 10 mu g/mL), Gly-Trp (30 mu g/mL), Ala-Tyr (48 mu g/mL), Ser-Tyr (67, mu g/mL), Gly-Tyr (97 mu g/mL), Ala-Phe (190 mu g/mL), Val-Pro (480 mu g/mL), Ala-Ile (690 mu g/mL), Val-Gly (1100 mu g/mL), and a nonprotein amino acid, nicotianamine (0.26 mu g/mL), were identified. The concentrations of these substances in the FSS were revealed to be higher than that of regular soy sauce through quantitative LC-MS/MS analysis.