Evaluation of Anti-Melanogenic and Cytotoxic Activities of Phlomis caucasica on Human Melanoma SKMEL-3 Cells

Background Under normal physiological condition, melanosomal melanin acts as a natural UV photoprotective filter. However, after long exposure to UV radiation, melanin has shown to involve in reactive oxygen species (ROS) generation and increases the risk of developing ageing, melasma and melanoma skin cancers. A number of plant polyphenols influenced the melanin biosynthesis and growth of various melanoma cells through their anti-tyrosinase activity as well as antioxidant effect. Objective In this study, we evaluated the anti-melanogeneic and cytotoxic effects of methanol extract of Phlomis caucasica (Lamiaceceae) on human melanoma SKMEL-3 cells. Methods The level of antioxidant and anti-tyrosinase capacity of MeOH extract from P. caucasica (MPc) were evaluated in vitro by DPPH radical scavenging and mushroom tyrosinase activity assays, respectively. Moreover, the effects of MPc on the melanin content, cellular tyrosinase activity and cytotoxicity (using MTT assay) on human melanoma SKMEL-3 cells were determined 72 hours after the treatment. Results The results showed that MPc weakly inhibited DPPH radicals and mushroom tyrosinase activity with SC₅₀ = 1.037 mg/mL and IC₅₀ = 1.316 mg/mL, respectively. The cytotoxicity assay showed that its IC₅₀ value was approximately 0.134 mg/mL (0.09791 to 0.1834) on SKMEL-3 cells. The extract had no effect on the melanin content at concentrations of ≤ 0.1 mg/mL. Additionally, no effect on cellular tyrosinase activity was observed at concentrations ranging from 0.001 to 0.25 mg/mL of MPc. Conclusions The results obtained suggest that the P. caucasica extract can reveal cytotoxic effect on human melanoma SKMEL-3 cells at higher concentrations of 0.1 mg/mL. Therefore, it can be considered as a good candidate for anti-melanoma therapy.