Photoprotective Activity of Vulpinic and Gyrophoric Acids Toward Ultraviolet B-Induced Damage in Human Keratinocytes

Vulpinic and gyrophoric acids are known as ultraviolet filters for natural lichen populations because of their chemical structures. However, to the best of our knowledge, there has been no reference to their cosmetic potential for skin protection against ultraviolet B (UVB)-induced damage and, consequently, we propose to highlight their photoprotective profiles in human keratinocytes (HaCaT). Therefore, vulpinic acid and gyrophoric acid were isolated from acetone extracts of Letharia vulpina and Xanthoparmelia pokornyi, respectively. Their photoprotective activities on irradiated HaCaT cells and destructive effects on non-irradiated HaCaT cells were compared through in vitro experimentation: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays, 4',6-diamino-2-phenylindole and tetramethylrhodamine B isothiocyanate-phalloidin staining protocols. Both of the lichen substances effectively prevented cytotoxic, apoptotic and cytoskeleton alterative activities of 2.5 J/cm(2) UVB in a dose-dependent manner. Moreover, vulpinic and gyrophoric acids showed no toxic, apoptotic or cytoskeleton alterative effects on non-irradiated HaCaT cells, except at high doses (≥400 μM) of gyrophoric acid. The findings suggest that vulpinic and gyrophoric acids can be promising cosmetic ingredients to photo-protect human skin cells and should therefore be further investigated by in vitro and in vivo multiple bioassays.