Antioxidant activity of royal jelly hydrolysates obtained by enzymatic treatment

Recently, research on the processing of raw functional materials with the aim of improving various physiological activities has been conducted. In this study, we investigated the antioxidant activity of royal jelly (RJ) hydrolysates obtained from three commercial proteases. Enzyme-treated royal jelly (ERJ), in which the RJ hydrolysates were converted into easy-to-absorb shorter chain monomers through the removal of two known allergen proteins, showed no difference in the content of (E)-10-hydroxydec-2-enoic acid (10-HDA) or the freshness parameter and showed a significant increase in total free amino acid content. The antioxidant activity of ERJ was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and chemical assays. The ERJ showed about 80% DPPH-radical scavenging activity at same concentration of ascorbic acid. The antioxidant effect of ERJ was confirmed to be due to reduction of intracellular reactive oxidative species (ROS) and nitric oxide (NO) production in LPS-treated macrophages. Moreover, ERJ significantly increased the activity of the antioxidant enzyme superoxide dismutase (SOD) and the level of the antioxidant glutathione (GSH) in a dose-dependent manner. Interestingly, these antioxidant activities of ERJ were stronger than those of non-treated RJ. These findings indicate that ERJ has high potential as an antioxidant agent for use in human and animal diets.