Two new alkaloids from the tubers of Corydalis ambigua subsp. amurensis and their anti-proliferative activity.

Two new alkaloids, including one benzophenanthridine type, dehydroambiguanine A (1) and one isoquinoline type, ambiguanine J (2) together with four (3-6) known alkaloids were isolated from the n-butanol fraction of Corydalis ambigua subsp. amurensis. Their structures were elucidated by comprehensive spectroscopic methods including HR-ESIMS and NMR, and the absolute configuration of compound 1 was further confirmed by the quantum ECD calculations. In addition, all isolated alkaloids (1-6) were determined their anti-proliferative effects of on A549 and HCT 116 cell by colorimetric MTT assay. Among them, Compounds 1 and 4 exhibited anti-proliferative activity on HCT 116 cell line with the IC50 value at 49.8 ± 4.79, and 89.2 ± 1.86 μM, respectively. Compounds 2 and 5 showed mild anti-proliferative activity against A549 cell with IC50 values at 60.2 ± 10.7, and 89.2 ± 12.9 μM, respectively. Their preliminary structure-activity relationship was also discussed.