Alkaloids with cholinesterase inhibitory activities from the bulbs of Crinum × amabile Donn ex Ker Gawl.

Seven previously undescribed alkaloids, crinamabilines A-G, two non-alkaloidal compounds, crinamabidiene and 6-phenylpiperonyl alcohol, two first naturally occurring alkaloids, 3-epibuphanisine and (+)-1β,2β-epoxy-epicrinine, together with nineteen known alkaloids, were isolated from the bulbs of Crinum × amabile Donn ex Ker Gawl. Their structures and absolute configurations were elucidated by NMR, MS and ECD spectroscopic techniques. Ungeremine displayed the most potent inhibitory activity against acetylcholinesterase (IC50 0.21 μM), which was about 6-fold more active than the reference drug, galanthamine (IC50 1.23 μM). Ungeremine also exhibited the strongest inhibitory activity against butyrylcholinesterase (IC50 3.57 μM), which was comparable to galanthamine (IC50 3.11 μM). The molecular docking studies were performed and were well in agreement with the experimental results.