Tsaokoic Acid: A New Bicyclic Nonene from the Fruits of IAmomum tsao-ko/I with Acetylcholinesterase Inhibitory Activity

A new bicyclic nonene, tsaokoic acid (1), was isolated from the fruits of Amomum tsao-ko, together with three known compounds (2-4). The structure of 1 was elucidated by analyzing spectroscopic data including 1D and 2D NMR spectra and compounds 2-4 were identified as tsaokoin, vanillin, and tsaokoarylone, respectively, by comparing their NMR spectra with previously reported data. Compounds 1-4 showed possible inhibitory activity against acetylcholinesterase (AChE) in silico molecular docking simulations. They were submitted to in vitro assay system and exhibited moderate inhibitory activity with IC[sub.50] values of 32.78, 41.70, 39.25, and 31.13 μM, respectively.