Identification of peptides from edible silkworm pupae (Bombyx mori) protein hydrolysates with antioxidant activity

Silkworm (Bombyx mori) pupae is a by-product from the silk industry which is rich in protein. Hydrolysates from  silkworm pupae generated using Alcalase®, Prolyve®, Flavourzyme® and Brewers Clarex® proteolytic prepa?rations were characterised. The antioxidant activity of the hydrolysates was investigated using in vitro antioxi?dant assays and an in situ assay for reactive oxygen species (ROS) reduction using hepatic HepG2. Overall,  Alcalase and Prolyve hydrolysates had highest scavenging activities, however, Flavourzyme and Brewers Clarex  hydrolysates had enhanced ferric reducing antioxidant power (FRAP) activity compared to the other samples.  Furthermore, the Flavourzyme hydrolysate significantly reduced ROS by 40% compared to untreated control  HepG2 cells. Peptides identified by LC-MS/MS were synthetised and then tested for their in vitro and in situ  antioxidant activity. Peptides SWFVTPF and NDVLFF showed highest antioxidant activity (ROS reduction, su?peroxide dismutase (SOD) expression and glutathione (GSH) production activity) in HepG2 cells, and therefore  may have potential as natural antioxidants.