Abstract:Distiller' grains are one of the by-products of the winemaking process, and rich in a variety of natural active substances. In this research, the ACE inhibition rate of the crude extract obtained by water extraction from the rice distiller's grains was 42.93%, which was 21.25% lower than that (64.52%) of the commercially available antihypertensive peptide (measured at the same time). Subsequently, the crude extracted was treated with the ethanol (90% volume fraction). Then, the resulting supernatant was filtered by ceramic membrane and nanofiltration membrane, then extracted with petroleum ether. The extracted samples were separated by 3, 0.2 μm and 5 000 u ultrafiltration membranes. The ACE inhibition rate of the 5 000 u permeate was 46.00%, which was higher than that (39.57%) of the commercially available antihypertensive peptide (difference: 6.43%). Finally, LTQ Orbitrap Velos Pro was used, with the aid of Compound Discovery software, to analyze the possible bioactive peptides. Eleven active short peptides were identified, including Val-Val-Val, Ile-Ser-Val, Val-Pro-Leu, Leu-Ser-Glu, Ph-Tyr, and Val-Arg. These peptides contained hydrophobic or aromatic amino acids that have been shown to be involved in ACE inhibition mechanism, such as Val, Phe and Tyr. The experimental results showed that the above separation methods could improve the ACE inhibition effect of the polypeptide mixture. The separation of polypeptide mixtures with high ACE inhibition activities from distiller' grains provides a theoretical basis for the processing and utilization of distiller's grains.
