Peganumine A, a β-Carboline Dimer with a New Octacyclic Scaffold from Peganum harmala

Peganumine A (1), a new dimeric beta-carboline alkaloid characterized by a unique 3,9-diazatetracyclo-[6.5.2.0(1,9).0(3,8)]pentadec-2-one scaffold, was isolated from the seeds of Peganum harmala. The structure including the absolute configuration was determined by spectroscopic data, X-ray crystallography, ECD calculation, and CD exciton chirality approaches. Compound 1 showed moderate cytotoxic activity against MCF-7, PC-3, and HepG2 cells and selective effects on HL-60 cells with an IC50 value of 5.8 mu M.