Antioxidant and anticholinesterase activities of lupane triterpenoids and other constituents of Salvia trichoclada
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The methanol extract of the aerial parts of Salvia trichoclada Bentham (Lamiaceae) was studied for bioactive non-volatile secondary metabolites, and nine compounds were isolated. Structures of the isolated compounds were elucidated as lupeol (1), lupenone (2), glochidone (3), monogynol A (4), oleanolic acid (5), ursolic acid (6), beta-sitosterol (7), apigenin-7-O-rhamnoside (8), and rosmarinic acid (9) by using 1D and 2D-NMR spectroscopic techniques. A lupane triterpene glochidone was isolated from a Salvia species and Lamiaceae family for the first time in this study. The antioxidant potential of the extract and the isolated compounds were carried out by using lipid peroxidation inhibitory activity (beta-carotene bleaching method) and DPPH free radical scavenging activity test assays. Their anticholinesterase activity was investigated by the Ellman method against both acetylcholinesterase (AChE) and butyrylcholinesterase enzymes. Compounds 1, 3, 5, 6, 8 and 9 showed fairly high anticholinesterase activity almost at all concentrations. Among them, a flavone glycoside apigenin-7-O-rhamnoside exhibited the highest and selective AChE inhibitory activity. Glochidone (3) was found to be the most active one among the isolated lupanes, which exhibited a close activity to that of standard compound galanthamine. Among all the tested compounds, rosmarinic acid (9) exhibited highest antioxidant and good anticholinesterase activity.