Screening of alpine plant extracts as protective agents against UV-induced skin damage

Incidence of skin cancer has increased in the last few years. High sun protection factors (SPF) in suncare products allow the consumer to expose himself to sunlight for longer periods, but they do not fully protect the skin from harm. Therefore, it is important to develop novel cosmetic formulations which can efficiently fight the negative effects of UV rays, such as production of reactive oxygen species, subsequent cell damages, and ultimately skin cancer. Alpine plants used in medicine and nutrition represent an attractive source for the development of new products with skin-protective effects. Plants growing at high altitudes have developed natural defense mechanisms including the synthesis of secondary metabolites protecting against exposure to high UV doses.

In this context, we screened more than 30 plant extracts for antiradical and anti-inflammatory activities in vitro. Plants collected in the Valais region were extracted with ethanol. Cyclooxygenase-2 inhibitory activity was measured through COX-2 catalyzed prostaglandin synthesis in Mono Mac 6 cells. The formation of 6-keto PGF_1a was determined by ELISA. Absence of cytotoxicity was controlled by assessing cell mytochondrial activity (resazurin and MTT bioassays) in Mono Mac 6 cell line. The strongest COX-2 inhibition was observed for the extracts of Antennaria dioica (Asteraceae), Athamanta cretensis (Apiaceae), Satureja montana (Lamiaceae) and Sisymbrium irio (Brassicaceae) with 22.7, 26.4, 25.0 and 21.9% inhibition at 100 µg/mL, respectively. In addition, the extracts were screened for free radical scavenging activity against the DPPH radical. In this assay, Geum montanum (Rosaceae) (IC₅₀ 17 µg/mL) was the most active, followed by Helianthemum nummularium (Cistaceae) (IC₅₀ 49 µg/mL), Salix reticulata (Salicaceae) (IC₅₀ 53 µg/mL), and Satureja montana (IC₅₀ 65 µg/mL). Investigations to identify the active constituents of the most promising candidates are ongoing.