Abstract
Two sericins of high and low molecular weight (HS and LS) were prepared from commercial silkworm cocoon silk with a boiling water and Ca(OH)2 solution with ultrasonic treatments, respectively. This study first investigated the release concentration of the two abovementioned sericins in simulated saliva, gastric juice, and intestinal juice (pH 6.8, 2.0, and 7.4, respectively) within 10 h. The results showed that the order of sericin release rate and its amount in the simulated environment was gastric juice > saliva > intestinal juice. Second, the molecular weights of both sericin metabolites formed by in vitro enzymatic degradation were lower than 15 kDa. The α-glucosidase inhibitory activities of both sericins and their analog metabolites were positively correlated with their concentrations. The IC50 values of the HS- and LS-derived metabolites were 1.02 ± 0.12 mg/mL and 0.91 ± 0.15 mg/mL, respectively, which were five to seven times lower than those of both original sericins. The total antioxidant capacities and hydroxyl radical scavenging capacities of both metabolites were enhanced by one- to three-fold compared with HS and LS. These results indicate that both sericins, regardless of molecular size, have significantly enhanced antioxidant, superoxide free radical scavenging, and glycosidase inhibitory activities after simulated metabolism, and that LS is better than HS regardless of simulated digestion. These results confirm that sericin is important in the sustainable development and utilization of silk resources, especially the reduction in environmental pollution, and provides new ideas for the development of adjuvant treatments for diabetes and the development of foods with anti-hyperglycemic functions.
Highlights
Accepted: 18 January 2022Since 2010, the annual output of silkworm cocoons in China alone has exceeded600,000 tons, accounting for about 70% of the total global output
We found that the sericin obtained by the Ca(OH)2 degumming method has a lower molecular weight and higher in vitro antioxidant capacity, ultraviolet (UV) resistance, and inhibitory activity against α-glycosidase [11]
In order to investigate the drug accumulation effect of sericin in different organs, this experiment utilized the dialysis bag method to determine the cumulative concentrations of two sericins (HS and LS) in simulated saliva, gastric juice, and intestinal juice within 12 h
Summary
Accepted: 18 January 2022Since 2010, the annual output of silkworm cocoons in China alone has exceeded600,000 tons, accounting for about 70% of the total global output. During the production of cocoon silk, about 40,000 to 50,000 tons of sericin globally are discharged in alkaline liquid waste every year. This causes serious environmental pollution and poor water quality, and wastes a considerable amount of natural protein resources [1,2]. Most commonly used in the laboratory are the solvent method, physical method, and biological enzymatic method. Alkaline solutions such as sodium hydroxide and sodium carbonate are the most commonly used solvents at present. It is difficult to separate these from sericin because the sodium salt formed later is soluble
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