Purification Of Antihypertensive And Hypocholesterolemic Peptides From Soybean

The limited enzymatic hydrolysis of soybean proteins is an effective approach for the preparation of functional soybean peptides. The functional activities for ACE inhibitory activity and micellar solubility of cholesterol inhibitory activity of different preparation of soy peptides were investigated. After hydrolysis with selected enzymes and controlled degree of hydrolysis, peptides were separated and purified by macroporous adsorption resin chromatography, gel filtration chromatography, ion exchange chromatography and reverse phase high performance liquid chromatography (RP-HPLC). Amino acid sequences of the single peptides with high activity were identified by LC-MS.Soybean protein isolate hydrolysates, which were produced with Alcalase, were found to have functional activities of hypocholesterolemia (DH18%) and antihypertensive (DH14%). After Alcalase hydrolysis both peptide fractions were desalted by adsorption on a macroporous resin and then eluted with ethanol at different concentrations. The results showed that both the highest hypocholesterolemic and antihypertensive activity fractions were eluted with 75% ethanol and had inhibitory ratios of 63.53% and 56.52% respectively. The two active fractions were farther separated on Sephadex G-15, the most effective elution was with 0.01 mol/L HCl as a buffer for the hypocholesterolemic peptide and 1 mol/L HAc as buffer for ACE inhibitory peptide. The second fraction had the most hypocholesterolemic activity with an inhibitory ratio of 73.21%, The fifth fraction had the most ACE inhibitory activity with an inhibitory ratio 69.57%.Soybean antihypertensive peptides that were eluted with 75% ethanol from the macroporous adsorption resin were farther separated by SP-Sephadex C-25 cation exchange choromatography. The optimaizaed loading parameters for peptides on SP-Sephadex C-25 was 0.004 g/mL IE with a starting buffer of 1 M HAc. These conditions provided the largest adsorption ratio of 61.19%. An elution buffer with 1 M NaCl was able to elute all the adsorbed peptides from the ion exchange column. Fraction 5 was the most active peptide and its inhibitory ratio was 62.75%, while fraction 4 and fraction 6 also showed high inhibitory activity whose ratios were 61.76% and 60.78%, respectively. All three fractions exhibited high ACE inhibitory activity, it was difficulty to choose the best one. Thus, comparing with Sephadex G-15, SP-Sephadex C-25 has lower efficiency for the separation of soybean active peptides.