Isoquinoline alkaloids from Corydalis edulis Maxim. Exhibiting insulinotropic action

Eleven undescribed isoquinoline analogues, namely edulisines A–K, along with sixteen known alkaloids, were isolated from the whole plants of Corydalis edulis. The structures of the isolated alkaloids were established on the basis of extensive spectroscopic data (1D and 2D NMR, UV, IR, and HRESIMS). Their absolute configurations were determined by single-crystal X-ray crystallographic analysis and ECD. Compounds (+)-1 and (−)-1 are a pair of undescribed isoquinoline alkaloids bearing a unique coupled pattern of coptisine and ferulic acid via Diels-Alder [4 + 2] cycloaddition, while compounds (+)-2 and (−)-2 feature benzo [1,2-d:3,4-d]bis [1,3]dioxole moiety. Compounds (+)-2, (−)-2, (−)-5, 10, 13, 15, 20, 22, and 23 significantly triggered the secretion of insulin in the HIT-T15 cells at a concentration of 40 μM.