Chemical Characterization and Bioactivities of Sericin Extracted from Silkworm Cocoons from Two Regions of Portugal

Sericin has been characterized as demonstrating a variety of bioactivities, establishing it as a valuable resource for biomedical and pharmaceutical applications. The diverse biological activities of sericin are likely linked to its unique biochemical composition and properties. This study aimed to assess the effect of origin, seasonality, and amino acid composition on the bioactivity of sericin samples from two Portuguese regions compared to commercial sericin. The amino acid profile was analyzed using HPLC-FLD. Moreover, several bioactivities were assessed through in vitro assays, including antiproliferative effects, cell migration, antimicrobial activity, anticoagulant properties, antioxidant capacity, and anti-inflammatory effects. The results obtained in this work revealed that the origin and season affect the sericin amino acid profile. In its pure state, sericin exhibited a low content of free amino acids, with tyrosine being the most abundant (53.42-84.99%). In contrast, hydrolyzed sericin displayed a higher amino acid content dominated by serine (54.05-59.48%). Regarding bioactivities, the sericin tested did not demonstrate antioxidant or anti-inflammatory potential in the conducted tests. Notwithstanding, it showed antiproliferative activity in contact with human tumor cell lines at a minimum concentration of 0.52 mg/mL. Regarding antimicrobial activity, sericin had the capacity to inhibit the growth of the bacteria and fungi tested at concentrations between 5 and 10 mg/mL. Additionally, sericin demonstrated its capacity to prolong the coagulation time in pooled human plasma, indicating a potential anticoagulant activity. In addition, the origin and season also revealed their impact on biological activities, and sericin collected in Bragança in 2021 (S3) and 2022 (S4) demonstrated higher antiproliferative, antibacterial, and anticoagulant potentials. Future studies should focus on optimizing sericin's bioactivities and elucidating its molecular mechanisms for clinical and therapeutic applications.