Alkaloids from the roots and leaves of Stichoneuron halabalensis and their acetylcholinesterase inhibitory activities

A study of the hitherto unreported Stichoneuron halabalensis Inthachub led to the characterization of the known compounds (+)-α-tocopherol and (R)-(+)-

goniothalamin; four known Stemona alkaloids, bisdehydoxystemoninine A (1), stemoninine (2), sessilistemonamine C (3) and sessilistemonamine A (4); and

three new alkaloids, stichoneurine C (5), D (6) and E (7). The structures of these compounds were determined on the basis of their spectroscopic data. Alkaloid

7 showed significant inhibitory activity against electric eel acetylcholinesterase (AChE) (IC50 5.90+0.084 μM), while goniothalamin and compounds 1 and 2

showed significant inhibitory activities against human AChE (IC50 7.24+0.52, 5.52+0.13 and 3.74+0.09 μM, respectively).