Evaluation of toxicological aspects of three new benzoxazole compounds with sunscreen photophysical properties using in silico and in vitro methods.

Sunscreening chemicals protect against damage caused by sunlight most absorbing UVA or UVB radiations. In this sense, 2-(2'-hydroxyphenyl)benzoxazole derivatives with amino substituents in the 4' and 5' positions have an outstandingly high Sun Protection Factor and adequate photostability, but their toxicity is not yet known. This study aimed to evaluate the toxicity of three synthetic 2-(2'-hydroxyphenyl)benzoxazole derivatives for their possible application as sunscreens. In silico tools were used in order to assess potential risks regarding mutagenic, carcinogenic, and skin sensitizing potential. Bioassays were performed in L929 cells to assess cytotoxicity in MTT assay and genotoxic activities in the Comet assay and micronucleus test. Also, the Salmonella/microsome assay was performed to evaluate gene mutations. The in silico predictions indicate a low risk of mutagenicity and carcinogenicity of the compounds while the skin sensitizing potential was low or inconclusive. The 2-(4'-amino-2'-hydroxyphenyl)benzoxazol compound was the most cytotoxic and genotoxic among the compounds evaluated in L929 cells, but none induced mutations in the Salmonella/microsome assay. The amino substituted at the 4' position of the phenyl ring appears to have greater toxicological risks than substituents at the 5' position of 2-(phenyl)benzoxazole. The findings warrant further studies of these compounds in cosmetic formulations.

A study on 2-(2'-hydroxyphenyl) benzoxazoles derivatives as potential organic UV filters, Part I

Abstract Damage resulting from the incidence of ultraviolet (UV) radiation on the skin is common nowadays, with UVB (290-320 nm) and UVA (320-400 nm) radiation responsible for photoaging, sunburn and carcinogenesis. For this reason, sunscreens represent products of growing interest to prevent such damage. However, there are few organic filters marketed worldwide with photostability and effectiveness at wavelengths greater than 340 nm (long UVA), which justifies the exploration for new compounds. In this work, we determined the photostability and sun protection factor (SPF) of three 2-(2'-hydroxyphenyl)benzoxazole derivative dyes in order to develop new organic UV filters. UV-vis spectrophotometry has high level of reproducibility when compared with in vivo human clinical methods. Solubility determinations were performed in different solvents. The compounds absorbed UVA and UVB radiation, with maximum absorption wavelengths ranging from 336 to 374 nm. Photostability was evaluated using a solar simulator (3 J.m2.s-1 UVA radiation) for a maximum of 3 h. The 2-(amino-2'-hydroxyphenyl) benzoxazoles showed higher photostability than the acetylated derivative under the evaluated conditions. The three benzoxazoles presented SPF values of around 40 and preliminary results indicate that they show suitable properties to act as good chemical filters in photoprotective formulations.