In the search for acetylcholinesterase (AChE) inhibitors from Indian medicinal plants, via bioassay-guided isolation, a carbazole alkaloid, mahanimbine [3, 5-dimethyl-3-(4- methylpent-3-enyl)-11H-pyrano [5, 6-a] carbazole], was isolated from the petroleum ether extract of the leaves of Murraya koenigii. Inhibition of AChE was evaluated based on Ellman's method using 96-well microplate readers. Mahanimbine inhibited AChE activity in a dose-dependent manner with an IC(50) value of 0.03 +/- 0.09 mg/mL, while galantamine was used as a standard. The AChE inhibitory activity of this carbazole alkaloid has not been reported so far, and this study is the first to reveal this activity in carbazole alkaloid mahanimbine, isolated from Murraya koenigii.
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