Phenolic composition and antioxidant activity of Thai and Eri silk sericins

The present study investigates the phenolic contents and antioxidant activities of silk sericin extracted (SSE) from Thai mulberry silkworms (Bombyx mori) and non-mulberry silkworm (Samia ricini). The SSE from all strains revealed the mainly presence of flavonoid compounds including (+)-catechin (20.63-145.64 mg/100 g), quercetin (7.89-35.95 mg/100 g), and (-)-epicatechin (3.36-44.19 mg/100 g). The antioxidant activity of the SSE with water from Chokumnoui 1 was found to have low EC50 values (0.96 mg/mL), the concentrations of the SSE that exhibit 50% reduction in DPPH, and highest scavenging of ABTS(center dot +) radicals (1.73 mg TEAC/g) and highest reduce TPRZ-Fe (III) complex to TPTZ-Fe (II) (8.03 mg Fe(II)/g), thus indicating high antioxidant activities. Total phenolic content and total flavonoid content of the SSE showed positive correlated to the scavenging activity of DPPH and ABTS(center dot +) radicals and the ferric reducing ability (FRAP assay).