Bioactive properties of peptides from silkworm pupa protein

Enzymatic hydrolysates of silkworm pupa (Bombyx mori) protein isolate were prepared by treatment with three different gastrointestinal proteases: pepsin, trypsin and α-chymotrypsin. The protein hydrolysates with a 33.6% degree of hydrolysis were fractionated by ultrafiltration showing a high concentration of short chain peptides (SPBP-1), which exhibited significantly higher antioxidant and antihypertensive capacities than fractions with higher molecular weights (SPBP-2, SPBP-3). All hydrolysates presented antioxidant properties with EC50 values on DPPH• from 1.7 to 5.2 mg/ml, HO• from 2.5 to 4.3 mg/ml, O2−• from 2.8 to 3.2 mg/ml, ABTS• from 2.9 to 9.5 mg/ml, respectively. All hydrolysates showed antihypertensive capacity with IC50 values from 0.75 to 2.48 mg/ml and SPBP-1 was the peptides with the highest ACE-inhibitory capacity. Finally, their antitumor capacities were evaluated through cell viability assay. These results verified that silkworm pupa proteins may represent a useful source of bioactive peptides after gastrointestinal enzymatic hydrolysis.