Exploration of potential antihypertensive peptides derived from farmed Chinese giant salamander (Andrias davidianus)

The alcalase digestate of farmed Chinese giant salamander meat powder (FCGSMP) demonstrated antihypertensive properties through inhibition of angiotensin-I-converting enzyme (ACE), with an ACE IC₅₀ value of 22.8 ± 1.8 µg/mL. Initiated by a zwitterionic hydrophilic interaction liquid chromatography solid-phase extraction (ZIC HILIC-SPE) fractionation, FCGSMP alcalase hydrolysate was fractionated, and fraction H1 from the ZIC HILIC-SPE fractionation showed the highest angiotensin-I-converting enzyme inhibitory (ACEI) activity (ACE IC₅₀ = 21.3 ± 0.2 µg/mL). Fraction H1 from the ZIC HILIC-SPE fractionation was further separated using a reversed-phase C₁₈ solid-phase extraction (RP-SPE). Fraction S2 from the RP-SPE fractionation exhibited the highest ACEI activity (ACE IC₅₀ = 7.7 ± 0.2 µg/mL) among the six RP-SPE fractions. Using synthetic peptides, twenty identified peptides from fraction S2 were confirmed to have ACEI activity. The ACE IC₅₀ values of the four most potent ACEI peptides (LLPGW, PLYE, KLW, and LGEW) were calculated to be 9.1 ± 0.1, 67.2 ± 1.5, 92.5 ± 2.9, and 98.2 ± 4.7 µM, respectively. LLGPW (LW5) exhibited the strongest ACEI activity compared to the others. Furthermore, the study of its inhibitory mechanism using the Lineweaver-Burk plot suggested that LW5 acts as a competitive inhibitor. Molecular docking simulation of LW5 with human tACE (1O8A.pdb) indicated that LW5 can form interactions with the ACE catalytic site. Subsequently, LW5 was categorized as an ACE true-inhibitor type and remained unaltered during simulated gastrointestinal digestion. To the best of our knowledge, this is the first report of exploration into angiotensin-I-converting enzyme inhibitory peptides derived from farmed Chinese giant salamander meat.