Hydroalcoholic extract of Spartium junceum L. flowers inhibits growth and melanogenesis in B16-F10 cells by inducing senescence

Background: Ultraviolet light exposure generates, in human tissues, radical species, which represent the main cause of photo-aging, DNA damage and skin cancer onset. On the other hand, Mediterranean plants, being continuously subjected to high solar radiation levels, are naturally adapted to take on this type of abiotic stress, thanks to the production of antioxidant secondary metabolites. For these reasons, several plant extracts were documented to be excellent antineoplastic drugs. Purpose: We investigated the potential antitumor activity of the flower extract obtained by Spartium junceum L., a Mediterranean shrub, correlating it with the plant metabolic profile. Study design: After selecting the best extraction method to obtain as more secondary metabolites as possible from S. junceum flowers, we characterized the extract metabolic content. Then, by in vitro analyses, the antioxidant profile and the antineoplastic activity on B16-F10 murine melanoma cell of our extract were investigated. Methods: Spectrophotometric assays, HPLC-DAD and GC-MS analyses provided us information about flower extract composition and antioxidant activity. MTT assay and Trypan Blue exclusion test were performed to assess the extract toxicity and the viability, after treatments, of B16-F10 cancer cells and of C2C12 murine myoblasts. In vitro experiments (i.e. cytofluorimetry, protein analysis and qPCR) allowed us to analyze the effect of the plant extract on B16-F10 cell redox state, melanogenesis and cell cycle. Senescence induction was investigated by using a specific kit. Results: We observed that the hydroalcoholic extract of S. junceum flowers (HFE) strongly inhibited B16-F10 murine melanoma cell proliferation, while just a feeble effect was observed on C2C12 murine myoblasts. Moreover, we found that HFE exerted a pro-oxidant activity on melanoma cells, inhibited melanogenesis and caused cell cycle arrest in G2/M phase, inducing senescence. These anti-cancer properties of HFE could be related to the rich metabolic profile of the extract that we characterized by HPLC-DAD and GC-MS analyses. Conclusion: This evidence suggests that S. junceum phytocomplex can be used as a selective, nontoxic, economic and easily available anticancer drug.