Purification and identification of novel antioxidant peptides from silkworm pupae (Bombyx mori) protein hydrolysate and molecular docking study

Crude proteins from the pupae of two indigenous strains of silkworm (Bombyx mori), Nangnoi and Nangsew were hydrolyzed by alcalase, papain and trypsin. Protein hydrolysate of Nangnoi strain prepared by alcalase showed the highest antioxidant activities. In addition, the DNA damage protection ability of this protein hydrolysate was evaluated. Subsequently, this protein hydrolysate was purified by passing through a 3 kDa MW cut-off membrane followed by reverse phase high performance liquid chromatography (RP-HPLC). Amongst eight fractions obtained after RP-HPLC purification, fraction S3 showed interesting antioxidant activities with the IC50 values toward ABTS and DPPH radicals of 4.78 ± 0.08 and 7.83 ± 0.02 μg/mL, respectively. Potentially antioxidant peptides, AAEYPA and AKPGVY were identified in the S3 fraction after analysis by LC-MS/MS. ABTS and DPPH radicals scavenging activities of both synthesized peptides were investigated. These results suggest that both hexapeptides are potential antioxidants that can be used in the food and cosmetic industries.