Isolation and antimalarial activity of alkaloids from Pseudoxandra cuspidata

A novel and very unusual azaanthracene alkaloid, 1-aza-7,8,9,10-tetramethoxy-4-methyl-2-oxo-1,2-dihydroanthracene ( 1) and a new diastereoisomer of the bis-benzylisoquinoline alkaloid rodiasine, 1 S,1' R-rodiasine ( 2), as well as the alkaloids O-methylpunjabine ( 3) and O-methylmoschatoline ( 4) have been isolated from Pseudoxandra cuspidata bark, used in French Guiana as an antimalarial. Their structures were elucidated by spectroscopic analyses, especially 2D-NMR techniques (ADEQUATE and NOESY). We found that the antimalarial activity of this bark was mostly due to bis-benzylisoquinoline 1 S,1' R-rodiasine ( 2) (IC (50)= 1 microM) also displaying a low cytotoxicity.