Structurally diverse isoquinoline and amide alkaloids with dopamine D2 receptor antagonism from Corydalis bungeana.

Four new isoquinoline alkaloids including a benzophenanthridine alkaloid (1), a morphine derivative (2), a narceine-type alkaloid (3) and a simple isoquinoline alkaloid (4), a new amide alkaloid (5) and a new phthalic acid derivative (6), together with eleven known alkaloids (7-17) were obtained from the whole herbs extract of Corydalis bungeana Turcz. Their structures and absolute configurations were elucidated by extensive spectroscopic data analysis including HRESIMS, NMR and electronic circular dichroism (ECD) and ECD calculation. Compounds 1-17 were evaluated for dopamine D2 receptor activity in CHO-D2 cells. Among them, 16 showed the highest antagonistic activity on the D2 receptor with an IC value of 2.04 ± 0.01 μM. Compounds 14 and 15 exhibited moderate antagonism with IC values of 13.66 ± 2.28 and 31.72 ± 2.52 μM, respectively.