Chebulin: Terminalia chebula Retz. fruit-derived peptide with angiotensin-I-converting enzyme inhibitory activity.

Angiotensin-I-converting enzyme (ACE) plays an important role in blood pressure regulation. In this study, an ACE-hexapeptide inhibitor (Asp-Glu-Asn-Ser-Lys-Phe) designated as chebulin was produced from the fruit protein of Terminalia chebula Retz. by pepsin digestion, ultrafiltrated through a 3 KDa cut-off membrane, a reverse-phase high-performance liquid chromatography, and nano-liquid chromatography tandem mass spectrometry analysis. Chebulin was found to inhibit ACE in a noncompetitive manner, as supported by the structural model. It bounds to ACE by the hydrogen bond, hydrophobic and ionic interactions via the interactions of C-terminal Phe (Phe-6), and N-terminal residues (Asp-1 and Glu-2) with the amino acid residues on noncatalytic sites of the ACE. The results showed that chebulin derived from fruits of T. chebula Retz. is a potential ACE-peptide inhibitor that could be used as a functional food additive for the prevention of hypertension and as an alternative to ACE inhibitor drug.