Phytochemical investigation of <i>Crinum asiaticum</i> L.: isolation and characterisation of a new dimeric alkaloid and evaluation of acetylcholinesterase inhibition with molecular docking

<i>Crinum asiaticum</i> L. (Amaryllidaceae) is a perennial bulbous plant commonly used for its various pharmacological benefits, such as anticancer, immune-boosting, pain-relieving, antiviral, antimalarial, antibacterial, and antifungal properties, while also being appreciated for its ornamental value. A phytochemical investigation of the bulbs of <i>C. asiaticum</i> resulted in the isolation of a new dimeric alkaloid, <i>bis</i>-(-)-8-demethylepimaritidine (<b>1</b>) together with five known compounds, lycorine (<b>2</b>), 3-<i>O</i>-acetyl-8-<i>O</i>-demethylmaritidine (<b>3</b>), (-)-siculine (<b>4</b>), (-)-8-demethylmaritidine (<b>5</b>), and (4a<i>α</i>,5<i>β</i>,10b<i>β</i>)-4,4a-dihydro-9-methoxy-3H,6H-5,10b-ethanophenanthridine-3,10-diol (<b>6</b>). Structural elucidation of all the compounds was performed by spectral methods such as 1D and 2D NMR as well as HR-ESI-MS analysis. The absolute configuration of <b>1</b> was determined by CD spectrum. All isolates were <i>in vitro</i> evaluated for their acetylcholinesterase (AChE) inhibitory activities. Additionally, molecular docking analyses were conducted to investigate the interactions between the active compound and AChE, and to evaluate its binding affinity, thereby revealing the underlying mechanisms of enzyme inhibition.