Tyrosinase, Acetyl- and Butyryl-Cholinesterase Inhibitory Activity of Stachys lavandulifolia Vahl (Lamiaceae) and Its Major Constituents

The n-hexane (HE), dichloromethane (DC), methanol (ME), ethanol 70% (ET), and methanol with Soxlhet apparatus (MS) extracts of Stachys lavandulifolia aerial parts were screened for their potential tyrosinase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity. ET and MS inhibited tyrosinase with IC50 values of 33.4 and 42.8 μg/mL, respectively. The phytochemical investigation of these extracts resulted in the isolation of the known compounds monomelittoside (1), melittoside (2), 5allosyloxy-aucubin (3), acteoside (4) and arbutin (5). The HE extract, characterized by germacrene D, β-pinene, β-myrcene, and trans-caryophyllene as main constituents, showed the highest AChE inhibitory activity with an IC50 value of 13.7 μg/mL while DC extract was the most active against BChE (IC50 value of 143.9 μg/mL). The diterpene stachysolone (6) was isolated from this extract. The antioxidant properties were also investigated by four in vitro methods (DPPH, ABTS, FRAP and β-carotene bleaching tests).