Antioxidant and anticholinesterase active constituents from Micromeria cilicica by radical-scavenging activity-guided fractionation

From the acetone extract of Micromeria cilicica, two new (1 and 2) and five known (3-7) compounds were obtained through radical-scavenging activity guided isolation. Structures of the compounds were identified as piperitone 7-O-β-d-glucoside (1), isothymonin 4′-methyl ether (2), sudachitin (3), isomucronulatol (4), rutin (5), ursolic acid (6) and saccharose (7), based on UV, 1D-and 2D-NMR and mass spectroscopic techniques. The antioxidant potentials of the extract and the isolated compounds were established by using three radical-scavenging assays, namely, DPPH scavenging, O2- scavenging and ABTS+ scavenging, besides β-carotene bleaching assay. Particularly, the acetone extract showed a strong inhibition of lipid peroxidation by β-carotene bleaching assay, with a result close to that of (+)-catechin. Among the pure compounds, rutin (5) showed the strongest lipid peroxidation inhibition and antiradical activity while both sudachitin (3) and isomucronulatol (4) exhibited noticeable ABTS+ scavenging activity. The anticholinesterase activity of the compounds (1-7) was also determined. Against acetylcholinesterase, they exhibited weak inhibition while compounds 3, 4 and 6 exhibited moderate inhibition against butyrylcholinesterase.