Mucroniferanines A–G, Isoquinoline Alkaloids from Corydalis mucronifera

Five pairs of isoquinoline alkaloid enantiomers, mucroniferanines A–E ( 1 – 5 ), two inseparable epimeric pairs, mucroniferanines F and G ( 6, 7 ), and 10 known isoquinoline alkaloids ( 8 – 17 ) were obtained from Corydalis mucronifera . The structures were characterized using spectroscopic data analysis, and the absolute configurations were established by ECD and X-ray data analysis. The new compounds except for 3 possess a rare 9-methyl group in the isoquinoline alkaloids, and compounds 2 and 3 possess rare benzo[1,2- d:3,4- d ]bis[1,3]dioxole moieties. It is the first report of stereoisomerism involving the 9-methyl phthalideisoquinoline alkaloids. Compounds (−)- 4, 6, and 7 exhibited acetylcholinesterase inhibitory activities with IC 50 values of 28.3, 12.2, and 11.3 μM, respectively.