Mechanistic insights in the use of a Polypodium leucotomos extract as an oral and topical photoprotective agent.

Photoprotection is essential to prevent the deleterious effects of ultraviolet (UV) light, including skin cancer, photoaging and immunosuppression. Photoprotective agents can be classified according to their main mechanism of action. Some of them absorb or deflect UV photons (sunscreens), whereas others prevent or fix the deleterious effects of UV exposure. Here, we review recent evidence on the cellular and molecular mechanisms underlying the photoprotective effect of a Polypodium leucotomos fern extract (PL). PL is a natural mixture of phytochemicals endowed with powerful antioxidant properties. Its short-term effects include inhibition of reactive oxygen species production induced by UV radiation, DNA damage, isomerization and decomposition of trans-urocanic acid, prevention of UV-mediated apoptosis and necrosis, as well as degradative matrix remodeling, which is the main cause of photoaging. These short-term effects translate into long-term prevention of photoaging and photocarcinogenesis. A striking property is that PL can exert its effect when administered orally. Together, these effects postulate PL as a natural photoprotective agent and a potential adjuvant to phototherapy for various skin diseases.