A novel aporphine alkaloid was isolated from the leaves of Epimedium koreanum Nakai during activity-guided fractionation in search of compounds with an anticholinesterase activity. The structure of the new compound was assigned as 1,10-methoxy-7-hydroxy-aporphine (1), which we have named epimediphine. Unambiguous (1)H-NMR and (13)C-NMR data for epimediphine are described. Epimediphine inhibited an acetylcholinesterase (AchE) activity in a dose-dependent manner with an IC50 value of 3.1 µM. Meanwhile, tacrine, dehydroevodiamine and physostigmine, which are therapeutic drugs or candidates for AD, exhibited an anti-AchE activity with IC50 values of 0.4, 37.9 and 0.12 µM, respectively.