Proteolytic hydrolysis of cowpea proteins is able to release peptides with hypocholesterolemic activity

Abstract

This study aimed to assess the hypocholesterolemic activity of peptides obtained by in vitro simulated human digestion of cowpea bean proteins; moreover, we have screened the bioactive peptides through chromatographic separation by RP-HPLC of the 3kDa molecular mass cut-off fraction of hydrolyzed isolated cowpea protein. Micellar solubility of cholesterol was measured after adding 35μgmL−1 of each fraction on in vitro prepared intestine-like micelles. The inhibiting activity of each fraction (50μgmL−1) also was tested on the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase). The whole hydrolysate was analyzed by ‘de novo’ mass spectrometry peptide sequencing (RP-HPLC-MS2) and the top score candidate peptide sequences were further analyzed by computational modeling. All collected fractions inhibited the initial HMG-CoA reductase activity by 47.8 to 57.1%. They also reduced cholesterol micellar solubilization, with fraction 1 being the most effective (71.7%). The peptide conserved domains may interact with the phosphatidylcholine added in the reaction of the cholesterol micelles. According with a computational prediction, the only peptide able to bind significantly the HMG-CoA reductase was GCTLN. This is the first report of peptide fractions from cowpea bean protein released by human digestion enzymes (pepsin followed by pancreatin) assigned to its cholesterol-lowering effect. These routes may define their action in lipid metabolism.