Antiplasmodial constituents from the stem bark of Polyalthia longifolia var pendula

Along with two known compounds (1 and 2), four new clerodane diterpenes were isolated and identified from the stem bark of Polyalthia longifolia: cleroda-3-ene pyrrole-15,16-dione (3), cleroda-3-ene, pyrrolidine-15,16-dione (4), cleroda-3,13(14)E-diene-15,16-diamide (5), and cleroda-3-ene-15,16-diamide (6). Their structures were elucidated by combinations of NMR, MS and IR. Using the WHO Mark III Microtest assay, the isolated compounds were evaluated for their antiplasmodial effects. They showed antiplasmodial effects, with IC50s ranging from 4.5 to 213.8 μM.