3.3.3. Tyrosinase and Melanin Inhibition

The effect of the *S. perfoliata* on melanogenesis has not yet been determined. It was reported that the acetone and methanol extract of *S. stricta*, being in the same genus, exhibited 15.66 ± 0.11% and 23.29 ± 0.56% inhibition of tyrosinase, respectively, at 200 μg/mL [44]. Similar inhibition of tyrosinase was observed for the ethanol extract of *S. perfoliata* at concentrations higher than 25 μg/mL (Figure 1). However, no inhibition was observed at concentrations lower than 12.5 μg/mL. Additionally, no significant inhibition of melanin production in UCT-MEL-1 cells was observed at the highest concentration tested (200 μg/mL). The inhibitors of elastase and tyrosinase enzymes can potentially have applications as skin hyperpigmentation, anti-ageing and antiwrinkle agents as well as in the treatment of other dermatological disorders [45].

**Figure 1.** The inhibitory effect of *S. perfoliata* on mushroom tyrosinase at different treatment concentrations. Data is represented as are means ± SD (n = 3).

Compounds previously isolated from *S. perfoliata* that have been reported for their tyrosinase and/or melanin production inhibitory activity were acteoside, ajugoside, caffeic acid, leucoceptoside A, lavandulifolioside and martynoside [9,46–51]. A study conducted by Song and Sim. in 2009 concluded that acteoside inhibited both melanogenesis and the tyrosinase protein activity in B16F10 melanoma cells, but the effects were dose-dependent [49]. The same effects of the inhibition of tyrosinase and melanogenesis were confirmed by Son et al. [50]. Furthermore, acteoside lowered cyclic AMP levels in cells that were stimulated by α-melanocyte stimulating hormone [49]. Acteoside inhibited melanogenesis on a post-translational level by reducing the levels of microphthalmia associated transcription factor (MITF) proteins, tyrosinase-related protein-1 (TRP-1) and tyrosinase [50]. It was reported that acteoside resulted in a 25.78% reduction in tyrosinase activity at a concentration of 53 μM [48], however a more recent study reported a 50% reduction in enzyme activity at a concentration of 20.67 μM [51]. Other compounds potentialy responsible for the tyrosinase inhibitory activity, exhibited by the ethanol extract of *S. perfoliata*, were caffeic acid, leucosceptoside A, lavandulifolioside and martynoside exhibiting 27.00%, 21.65%, 12.00% and 20.55% enzyme inhibition at 90 μM, 51 μM, 44 μM and 52 μM, respectively [47,48].
