Novel synthetic UV screen compounds inspired in mycosporine-like amino acids (MAAs): Antioxidant capacity, photoprotective properties and toxicity

The combination of environmental stress on the ozone layer, climate change and a greater sun exposure due to outdoor habits has led to an increase in skin cancer cases and other health issues related with UV radiation. Researchers are searching for new alternative UV filters that could protect our skin from the deleterious effects of UV radiation while also presenting low toxicity and biodegradable character (unlike the UV filters currently available in the market). In this work, two compounds inspired in the natural oxo-mycosporine-like amino acids (MAAs) have been synthesized and their antioxidant and photoprotective properties, as well as their in vitro and in vivo toxicity effects were evaluated. Both compounds featured a strong UV-B absorption together with a high antioxidant capacity, close to 50 μmol TE g^-1 DW in the ABTS assay. Compound 1 presented an absorption peak at 285-300 nm, whereas compound 2 showed a wider band with a peak around 295-305 nm and two shoulders at 318 and 342 nm. The addition of 5 % of compound 2 to galenic formulas increased the photoprotection, reaching SPF values of 4. Both compounds were stable under UV radiation exposure. Regarding toxicity, the synthetic compounds did not show cytotoxic activity against healthy human cell lines or significant toxicity over zebrafish embryos. Compound 1 showed a complete lack of toxicity over zebrafish, although compound 2 showed slight, not-significant effects on viability, hatching, pericardial stability or body axis formation over 5 mg mL^-1. Moreover, compound 1 presented relatively antitumoral activities against HCT-116 cells (selective index:1.49). The relevant antioxidant and photoprotective ability together with the great advantage provided by the reduced toxicity to health cells or zebrafish embryos, make these compounds promising candidates to be exploited as functional ingredients with specific applications in the biotechnological or pharma sector.