Characterization of oat protein fraction, antioxidant and tyrosinase inhibitory properties of their hydrolysates

 Albumin, glutelin and globulin protein fractions were sequentially extracted from oat brans and characterized. The protein content of each fraction was 83.8%, 53.1% and 67.7%, respectively. The molecular characteristics from SDS-PAGE analysis under reducing conditions showed that all fractions content subunits of 12 globulin at about 20 and 35 kDa but with differences in concentrations. In addition, the albumin fraction had a band at 10 kDa while the glutelin fraction had 52 and 150 kDa bands. Proteomic analysis (LC-MS/MS) of the pepsin-pancreatin hydrolysates confirmed the presence of 11S and 12S globulin subunits in the three fractions. MS/MS data also showed that oat enzymes (e.g. peroxygenases, amylase-types) and avenins were mostly present in the albumin fraction while the glutenin also contained avenin-type polypeptides and endochitinase. The pepsin-pancreatin hydrolysates of the protein fractions were assayed for biological activities. Data from antioxidant tests revealed that the globulin hydrolysate has higher ABTS•+ radicals scavenging activity (31.1 ± 6.1 μmolTrolx equivalents (TE)/g) and a higher inhibition of the formation of HO• radicals (48.0 ± 6.4%). In the peroxyl radical scavenging activity, the albumin hydrolysate was the most active (339.0 ± 39. μmol TE/g). Preliminary data on the inhibition of tyrosinase showed that the glutelin hydrolysate is a better inhibitor as its IC50 (12.4 ± 3.9 μg/mL) is significantly lower compared to those of albumin and globulin hydrolysates. The difference in activities of the hydrolysates is likely due to the nature and concentrations of their peptides.