Two novel isoquinoline alkaloids from the seedling of Corydalis decumbens

Two new isoquinoline alkaloids, decumbensine (1) and decumbendine (2), together with nine known compounds including tetrahydropalmatine (3), bicuculline (4), allocryptopine (5), bulbocapine (6), protopine (7), kikemanine (8), decumbenine B (9), decumbenine C (10), and muramine (11) were isolated from the seedling of Corydalis decumbens (Thunb.) Pers. (Papaveraceae). Their structures were decisively elucidated by spectroscopic analysis including 1D and 2D NMR techniques. Furthermore, the biogenetic pathways of two new compounds were proposed, which would provide valuable information for further understanding of the isoquinoline alkaloids of C. decumbens.