Trans-resveratrol and beta-carotene from sunscreens penetrate viable skin layers and reduce cutaneous penetration of UV-filters

Cutaneous permeation is a critical parameter when topical application of sunscreens containing antioxidants is considered. The aim of this study was to evaluate the cutaneous penetration of most marketed UV-filters combined with trans-resveratrol (RES) and beta-carotene (BTC) since few studies report skin penetration when such compounds are applied. Formulations containing octocrylene, octyl methoxycinnamate, avobenzone and bemotrizinole were prepared and supplemented or not with BTC, or with RES, or with both compounds in combination. Penetration studies were performed using Franz vertical diffusion cells and porcine ear skin as the biological membrane. The quantification of UV-filters and antioxidants in the stratum corneum (SC), viable epidermis plus dermis and receptor fluid was performed by HPLC. Results suggested that UV-filters and antioxidants did not permeate the skin but were retained for 12h post application. About 90% and 80%, respectively, of the total penetrated amount of UV-filters and antioxidants was found in the SC. Interestingly, it was observed that BTC, alone or combined with RES, reduced the skin retention of UV-filters on average by 63%. In conclusion, this study demonstrated that the combination of antioxidants and UV-filters in sunscreens is advantageous for cutaneous penetration, since BTC and BTC+RES improved sunscreen safety by reducing delivery of the four UV-filters in the study into SC and viable epidermis.