Photoprotection and antioxidant activity of eumelanin from Streptomyces lasalocidi NTB 42 and its photoprotective effects on Schizosaccharomyces pombe ARC039

This study evaluated the photoprotective and antioxidant properties of eumelanin derived from Streptomyces lasalocidi NTB 42 (eumelanin NTB 42). This study also investigated the cellular-level photoprotective effects of eumelanin using Schizosaccharomyces pombe ARC039 as a model organism and its ability to enhance the Sun Protection Factor (SPF) of commercial sunscreens. The thermal and light stability and total phenolic and flavonoid contents were analyzed. Antioxidant activity was assessed using hydroxyl radicals (OH), and superoxide anions (O₂^.-) radical-scavenging assays. The efficacy of photoprotection was determined using various in vitro methods, yeast cell viability assays, and enhanced SPF values of commercial sunscreen products. Eumelanin NTB 42 exhibited both thermal and photostabilities. The total phenolic and flavonoid contents were reported as 88.82 ± 0.68 mg gallic acid equivalent (GAE)/g and 53.24 ± 2.66 mg quercetin equivalent (QE)/g, respectively, representing the first report on microbial eumelanin. Eumelanin NTB 42 demonstrated significant scavenging activity against OH and O₂^.-. It also displays notable photoprotective effects against UV-B radiation, offering broad-spectrum coverage and optimal protection against UV-A radiation. It effectively acted as a sunblock against UV-A and UV-B radiation. Furthermore, eumelanin NTB 42 enhanced S. pombe ARC039 cell viability after exposure to UV-B and UV-C for 30–90 min. It also augmented the SPF value of commercial products at a minimum concentration of 0.0025 %. These findings highlight the potential antioxidant and photoprotective properties of eumelanin NTB 42, suggesting its applicability as a raw material for sunscreen formulations in the cosmetic industry.