Preclinical Toxicological Assessment of 2-(Benzoxazol-2-yl)[(2-hydroxynaphthyl)diazenyl]phenol Derivatives for Blue Light and UV Radiation Photoprotection Applications

Abstract

The widespread use of electronic devices has led to increased blue light exposure, highlighting the need for effective radiation blockers with blue light protection. Two synthetic 2-(2′-hydroxyphenyl)benzoxazole derivatives named azo-4′-benzoxazole and azo-5′-benzoxazole have shown an unprecedented blue light absorption capacity but had not been subjected to a safety evaluation. This study aimed to evaluate the cytotoxic, genotoxic, and mutagenic activities of these compounds. The cytotoxic and genotoxic activities were evaluated using MTT assay and comet assay in L929 fibroblast cells. Salmonella/microsome assay and micronucleus test were performed to detect gene and chromosomal mutations. The IC₅₀ was 87.9 μg/mL for azo-4′-benzoxazole and 79.5 μg/mL for azo-5′-benzoxazole. In the Salmonella/microsome assay, the azo-5′-benzoxazole compound induced frameshift mutations in the TA97a strain in the presence of metabolic activation (S9 mix), while azo-4′-benzoxazole did not show mutagenic activities in all five strains tested. The azo-5′-benzoxazole showed genotoxic and mutagenic effects in L929 cells that were probably associated to the cleavage of azo-5′ into its analogs 2-(4′-amino-2′-hydroxyphenyl)benzoxazole and 2-amino-1-naphthol. In conclusion, the azo-substituted group at the 5′ position of the phenyl ring appears to have greater toxicological risks than substituents at the 4′ position of 2-(phenyl)benzoxazole. The findings warrant further preclinical studies to ensure the safety of these compounds for use as blue light filters.