Structurally diverse isoquinoline alkaloids from the bulbs of Corydalis decumbens and their anti-inflammatory activity.

Phytochemical investigation of the bulbs of Corydalis decumbens led to the discovery of thirty structurally diverse isoquinoline alkaloids, including twelve phthalideisoquinolines (1-12), two morphines (13-14), one benzylisoquinoline (15), two aporphines (16-17), five protoberberines (18-22), four protopines (23-26), and four simple isoquinolines (27-30). Among them, compounds 1 and 2 were two novel phthalideisoquinoline hemiacetal alkaloids with a rare 2-pyrrolidinone moiety at C-7'. Compound 3 was an undescribed naturally occurring phthalideisoquinoline alkaloid and the NMR data were assigned for the first time. Their structures and absolute configurations were elucidated by extensive spectroscopic analysis, electronic circular dichroism analysis, and X-ray crystallographic data. Furthermore, the isolated compounds were evaluated for cytotoxicity in RAW264.7 cells, and their anti-inflammatory effects were determined by the rate of nitric oxide (NO) production in LPS-induced RAW264.7 cells. Compounds 7, 12, and 23 exhibited potential anti-inflammatory effects.