(±)-Corysaxicolaine A: a pair of antitumor enantiomeric alkaloid dimers from Corydalis saxicola .

(±)-Corysaxicolaine A (1), isolated from the aerial parts of Corydalis saxicola for the first time, is a pair of novel dimeric alkaloids, each of which is directly coupled by the rare 6, 12' C-C σ-bond between benzophenanthridine and protoberberine. The enantiomeric separation was achieved using chiral chromatography. Their structures, including stereochemistry, were clarified by carrying out extensive spectroscopic techniques and an electronic circular dichroism (ECD) calculation. (-)-Corysaxicolaine A was observed to exhibit an apparent cytotoxic effect against T24 cells with an IC 50 value of 9.45 μM.