An unusual proaporphine alkaloid bearing an isopropanenitrile group at isoquinoline nitrogen, named epiganine A ( 1 ) and a new aporphine alkaloid, epiganine B ( 2 ), together with eight known alkaloids, pronuciferine ( 3 ), dehydrodicentrine ( 4 ), romerine ( 5 ), romeline ( 6 ), N -methylcalycinine ( 7 ), phanostenine ( 8 ), dicentrine ( 9 ), and N -methyllaurotetanine ( 10 ), were isolated from the roots of Stephania epigaea . The absolute configuration of 1 was determined by calculating electronic circular dichroism (ECD) and comparing with experimental data. Compounds 2 and 4 showed strong acetylcholinesterase (AChE) inhibitory effects with the IC 50 values of 4.36 and 2.98 μM, respectively. Compounds 5 – 9 also exhibited potent AChE inhibitory activities. [ABSTRACT FROM AUTHOR]