Bioassay-guided fractionation of an EtOAc-soluble extract of Casearia membranacea has resulted in the isolation of six new clerodane diterpenes, caseamembrins A-F (1-6), and a known compound, rel-(2S,5R,6R,8S,9S,10R,18S,19R)-diacetoxy-18,19-epoxy-6-hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (7). The structures of 1-6 were established on the basis of extensive 1D and 2D NMR spectroscopic analysis. In addition, the new derivatives, 8 and 9, were prepared by acylation of 7 and 3, respectively. The isolated diterpenoids and their derivatives were tested against human prostate (PC-3) and hepatoma (Hep3B) cancer cells. Compounds 1, 3-5, and 7 exhibited cytotoxicity against both tumor cells, with IC(50) values below 3 micromicro, while compounds 2, 6, 8, and 9 were less effective.

Fractionation of the chloroform extract from the aerial part of Argemone mexicana led to the isolation of two benzophenanthridine-type alkaloids, N-demethyloxysanguinarine and pancorine; three benzylisoquinoline-type alkaloids, (+)-1,2,3,4-tetrahydro-1-(2-hydroxymethyl- 3,4-dimethoxyphenylmethyl)-6,7-methylenedioxyisoquinoline, (+)-higenamine and (+)-reticuline. Among them, N-demethyloxysanguinarine is a new compound, and (+)-1,2,3,4- tetrahydro-1-(2-hydroxymethyl-3,4-dimethoxyphenylmethyl)-6,7-methylenedioxy-isoquinoline was isolated form a natural source for the first time, to which was assigned a trivial name, (+)-argenaxine. In addition, six known non-alkaloidal compounds were also isolated and identified. All compounds were characterized on the basis of their spectral data and chemical evidences. Some isolated alkaloids from this species were evaluated for their cytotoxicity to human nasopharyngeal carcinoma (HONE-1) and human gastric cancer (NUGC) cell lines. Chelerythrine was found to exhibit significant activity against NUGC cell line, while angoline inhibited both types. (+)-Argenaxine showed moderate activity against the NUGC cell line.

Investigation of an EtOAc-soluble extract of the soft coral Sarcophyton stolidotum resulted in the isolation of seven new 14-membered carbocyclic cembranes, sarcostolides A-G (1-7), together with two known cembrane diterpenes, isosarcophytoxide and isosarcophine. The structural elucidation of these metabolites was determined on the basis of spectroscopic analyses, particularly 2D NMR techniques. Sarcostolide E (5) exhibited weak to moderate cytotoxic activity against human WiDr and Daoy tumor cell lines. A biogenetic pathway and relationship for compounds 1-7 was also proposed.