A comparative review of natural and synthetic UV filters: Gadusol and benzophenone-3 as representative examples

Abstract

The need for extra protection to mitigate the harmful effects of ultraviolet (UV), such as direct or indirect DNA damage, has become of great importance in the last decades. Synthetic photoprotectors, commonly used in sunscreen formulations, are associated with a large number of genotoxic, photoallergic, and environmental problems. Thus, the interest of both scientific research and industry has notably increased, aiming to advance in new developments that will improve effectiveness, minimizing detrimental effects. Nevertheless, due to the high benefit-risk ratio of synthetic photoprotectors, there is still a dilemma between either continuing their use or replacing them with more sustainable alternatives. In this regard, natural photoprotectors emerged as promising substitutes to synthetic ones, although they cannot usually be obtained on a large scale, and do not always represent an adequate option. Most of the scientific literature is biased towards natural or synthetic photoprotectors, and therefore a rigorous comparison between them is necessary to access a more accurate and critical view. In this work, a comprehensive one-to-one comparison was made between benzophenone-3 (oxybenzone) and gadusol, chosen as representative models of synthetic and natural photoprotectors, respectively. The review of their physicochemical properties allows an in-depth understanding of their behavior under UV solar radiation exposure and their environmental fate. Even though synthetic sunscreens cannot be completely replaced by natural ones immediately, the information provided in this work seeks to set a starting point for studies that aim the development of more efficient sunscreens.