A novel hexahydrobenzophenanthridine alkaloid, corygaline A (1), was isolated from Corydalis bungeana Turcz. Its structure and absolute configuration were elucidated by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Corygaline A (1) is the first example of an alkaloid which features a 6/6/6/6/6-fused pentacyclic skeleton in nature. It exhibited significant NO production inhibitory activity in LPS-activated RAW264.7 macrophages with an IC50 value of 2.9 muM. A plausible biosynthetic pathway for 1 is also discussed.