Abstract
In the present study, fermented grains (Jiupei), the raw material for Baijiu distillation, were used to isolate and identify low molecular weight peptides with angiotensin-I-converting enzyme (ACE) inhibitory activities. The methods of peptides extraction from Jiupei are described as follows: ultrasonication, centrifugation and filtration. Peptide purification was performed by ultrafiltration, adsorption on a macroporous resin, gel chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). HPLC with quadrupole-time-of-flight-mass spectrometry/mass spectrometry (HPLC-Q-TOF-MS/MS) was used to identify the peptides, and the ACE inhibitory activities of the peptides were measured. Finally, the optimum peptide extraction and separation parameters were determined to be a liquid/solid (ultrapure water/Jiupei powder) ratio of 15 mL g-1, extraction temperature of 57 °C and ultrasonication time of 33 min. XAD-16 resin was used for the removal of sugars and salts. Under these conditions, the total yield of peptides extracted was 57.682 mg/1 g Jiupei. The peptides identified were Val-Asn-Pro and Tyr-Gly-Asp. Val-Asn-Pro exhibited some ACE inhibitory activity (IC50 = 38.02 μM), while Tyr-Gly-Asp showed higher ACE inhibitory activity (IC50 = 5.21 μM). These results provide an important foundation for the study of peptides in Jiupei and show a reference for the trace of peptides in Baijiu production.