7-Hydroxy-2-octenoic acid-ethyl ester mixture as an UV protectant secondary metabolite of an endolichenic fungus isolated from Menegazzia terebrata

Enodolichenic fungi (ELF) are considered a promising bio-resource since they produce a variety of novel secondary metabolites with bioactivities. Ultraviolet (UV) radiation in sunlight containing UVA and UVB can cause acute and chronic skin diseases, and the demand for UV protectants in sunscreens has been increasing. Such situations evoke the strong interest of researchers in seeking effective UV protectants from natural products. In this study, we obtained partially purified 7-hydroxy-2-octenoic acid-ethyl ester (7E) from the secondary metabolites of ELF000548, which has UVA absorption activity. The antioxidant properties were performed by in vitro tests. The superoxide anion scavenging activity and inhibition of linoleic acid peroxidation of the 7E mixture were higher than ascorbic acid (ASA) and butyl hydroxyl anisole (BHA). Furthermore, the compound recovered the damage caused by UVB irradiation and inhibited melanin synthesis. Additionally, the 7E mixture exhibited no cytotoxicity toward the mouse melanoma cell lines, B16F1 and B16F10, except for the normal cell line, HaCaT. In general, these results are the first report about bioactivities of 7E, and those demonstrated that this compound might be a UV protectant to go further study.