Angiotensin I converting enzyme (ACE) inhibitory peptides derived from alfalfa (Medicago sativa L.) leaf protein and its membrane fractions

摘要

Alfalfa leaf proteins (ALP) were extracted through the method of alkali solubilizationand acid precipitation, and the six different ALP hydrolysates were obtained by hydrolysisof papain, Alcalase, Neutrase, trypsin, pepsin, and Flavourzyme, respectively.The results showed that alfalfa leaf protein hydrolysate (ALPH) prepared by papainexhibited the highest angiotensin I converting enzyme (ACE) inhibitory activity of79.69% ± 2.77% at the same concentration. Hence, papain ultimately was used to hydrolyzeALP for producing ACE inhibitory activity peptides. The hydrolysis conditionsof hydrolysis temperature, enzyme to substrate ratio (E/S), and pH were optimizedby using response surface methodology (RSM). We obtained the maximum ACE inhibitoryrate of 92.33% ± 0.30% under E/S of 3%, pH of 7.5 and hydrolysis temperatureof 55 ºC. Finally, the hydrolysate was separated into four ranges of molecularweight (ALPH-1,>30 kDa; ALPH-2,30–10kDa; ALPH-3,10–5kDa; ALPH-4,<5 kDa)through different ultrafiltration membranes. Among them, ALPH-4showed the maximumACE inhibitory activity of 93.85% ± 1.09%, implying that ALPH-4should beconsidered as a potential source of natural ACE inhibitor.