## 4 Discussion  
In this study we hydrolyzed SLC to produce ESLC using commercial enzymes alkaline, bromelain, and viscozyme. We measured the NPN content, which is a nitrogenous compound produced by protein degradation due to hydrolysis, and observed that the NPN content of ESLC was remarkably increased by enzyme treatment. In addition, the SLC and ESLC amino acid composition were analyzed to determine the amino acid changes induced by enzymatic treatment. The SLC and ESLC amino acid composition were not significantly different, indicating that enzymatic treatment effectively hydrolyzed the proteins in SLC without affecting the amino acid composition. Polyphenolic compounds are aromatic compounds with hydroxyl groups that are observed in large amounts in leafy vegetables and fruits [32]. The hydroxyl groups of polyphenols can easily combine with various compounds and exhibit antioxidant activity, which inhibits oxidation by donating hydrogen to alkyl radicals or alkyl peroxy radicals to scavenge radicals [33]. The increase in bioactive substance content due to enzymatic treatment is because compounds bound to polymeric substances, such as polysaccharides and proteins, are degraded and converted into small-molecule phenolic compounds during enzymatic treatment. In addition, [PERSON] and [PERSON] [34] reported that the polyphenol content of extracts might increase as polyphenolic compounds bound to polysaccharides and proteins are released by enzymatic treatment [35]. The polyphenol content of ESLC extracts developed using enzymatic treatment was remarkably higher than that of SLC (\(p<0.05\)). This was similar to the findings of [PERSON] et al. [21], who reported that the hydrolysis of silkworm powder by enzymatic treatment increased the total polyphenol content. The SOD-like activity and ABTS radical scavenging capacity are commonly used to investigate the antioxidant effects of functional materials. The antioxidant activity of ESLC was highest against the ABTS radical, while there was no significant difference in efficacy against the DPPH radical. The difference is that ABTS radical scavenging  
Figure 7: Effect of ESLC on MAPK signaling pathway in SH-SYSY cells impaired by H\({}_{2}\)O\({}_{2}\) treatment. (A) p-ERK/ERK; (B) p-JNK/JNK; (C) p-p38/p38. Values are means \(\pm\) SEM. Significant differences (\(p<0.01\)) were observed among the groups, as indicated by the different letters (a,b) above the bars in the one-way ANOVA with [PERSON]’s multiple range test. CON, control; ESLC, enzymatic hydrolyzate from silkworms fed the leaves of _Cudrania tricuspidata_. ERK, extracellular signal-regulated kinase; JNK, c-Jun N-terminal kinase; p-ERK, phospho-extracellular signal-regulated kinase; p-JNK, phospho-c-Jun N-terminal kinase; p-p38, phospho-p38. activity can be determined for both polar and non-polar samples, whereas DPPH can only be determined for non-polar materials. In addition, DPPH tests with free radicals whereas ABTS tests with cationic radicals, and the nature of the substrates is different, so the ABTS test may have a wider range of applications than the DPPH test. The ABTS radical scavenging capacity can be analyzed to measure the oxidative capacity of the extract because the antioxidants in the sample react with the ABTS radicals generated by the reaction of the ABTS solution with potassium persulfate. The blue-green color of the radicals is decolorized, indicating a change in absorbance [36]. SOD is an enzyme involved in the scavenging of superoxide formed in the body and converts ROS formed by rancidity into H\({}_{2}\)O\({}_{2}\), which is converted into harmless water and oxygen molecules to protect cells from ROS [37]. Polyphenol content and antioxidants are positively correlated, and that polyphenol extracts can effectively increase SOD activity by reducing oxidative stress in cells [33; 38]. Furthermore, enzymatic hydrolysis increased the polyphenol content of the sample and enhanced its antioxidant effects [26].