Polypodium leucotomos extract inhibits trans-urocanic acid photoisomerization and photodecomposition

Abstract In this report, we demonstrate a possible molecular mechanism by which a hydrophilic extract of the leaves of the fern Polypodium leucotomos (Fernblock ® , PL) blocks ultraviolet (UV)-induced skin photodamage. The extract inhibits UVA and UVB light induced photoisomerization of trans -urocanic acid ( t -UCA), a common photoreceptor located in the stratum corneum, and also blocks its photodecomposition in the presence of oxidizing reagents such as H 2 O 2 , and titanium dioxide (TiO 2 ). PL protects in vitro human fibroblasts from UV-induced death as well. These results suggest the potential of employing the PL extract as a component of sunscreen moistures in order to prevent photodecomposition of t -UCA, to inhibit UV-induced deleterious effects of TiO 2 and to protect skin cells and endogenous molecules directly involved in skin immunosurveillance.