In Vitro Evaluation of the Photoprotective Potential of Quinolinic Alkaloids Isolated from the Antarctic Marine Fungus Penicillium echinulatum for Topical Use.

Marine-derived fungi proved to be a rich source of biologically active compounds. The genus Penicillium has been extensively studied regarding their secondary metabolites and biological applications. However, the photoprotective effects of these metabolites remain underexplored. Herein, the photoprotective potential of Penicillium echinulatum, an Antarctic alga-associated fungus, was assessed by UV absorption, photostability study, and protection from UVA-induced ROS generation assay on human immortalized keratinocytes (HaCaT) and reconstructed human skin (RHS). The photosafety was evaluated by the photoreactivity (OECD TG 495) and phototoxicity assays, performed by 3T3 neutral red uptake (3T3 NRU PT, OECD TG 432) and by the RHS model. Through a bio-guided purification approach, four known alkaloids, (-)-cyclopenin (1), dehydrocyclopeptine (2), viridicatin (3), and viridicatol (4), were isolated. Compounds 3 and 4 presented absorption in UVB and UVA-II regions and were considered photostable after UVA irradiation. Despite compounds 3 and 4 showed phototoxic potential in 3T3 NRU PT, no phototoxicity was observed in the RHS model (reduction of cell viability < 30%), which indicates their very low acute photoirritation and high photosafety potential in humans. Viridicatin was considered weakly photoreactive, while viridicatol showed no photoreactivity; both compounds inhibited UVA-induced ROS generation in HaCaT cells, although viridicatol was not able to protect the RHS model against UVA-induced ROS production. Thus, the results highlighted the photoprotective and antioxidant potential of metabolites produced by P. echinulatum which can be considered a new class of molecules for photoprotection, since their photosafety and non-cytotoxicity were predicted using recommended in vitro methods for topical use.