Indoloquinazoline Alkaloids from Araliopsis tabouensis

Three new indoloquinazolidine‐type alkaloids, 8,13‐dihydro‐2‐methoxyindolo[2′,3′: 3,4]pyrido[2,1‐ b ]quinazolin‐5(7 H )‐one ( 1 ), 8,13‐dihydro‐2‐methoxy‐13‐methylindolo[2′,3′: 3,4]pyrido[2,1‐ b ]quinazolin‐5(7 H )‐one ( 2 ), and 5,8,13,14‐tetrahydro‐2‐methoxy‐14‐methyl‐5‐oxo‐7 H ‐indolo[2′,3′: 3,4]pyrido[2,1‐ b ]quinazolim‐6‐iun chloride ( 3 ) were isolated from Araliopsis tabouensis , together with three known compounds. The structures of the new compounds were determined primarily from 1D‐ and 2D‐NMR analysis. The antimalarial activities of compounds 1 – 5 were evaluated against Plasmodium falciparum D6 and W2 clones. The IC 50 values in antimalarial bioassay for compounds 2 – 5 varied from 1.8 to 4.7 μg/ml.