Secondary metabolites from selected marine organisms

Marine organisms are known to produce secondary metabolites which have novel structures and are often biologically active. Chemical studies of biologically active metabolites from three different marine organisms led to the discovery of six new compounds and six previously known compounds. The brown alga Dictyota binghamiae is fairly abundant in British Columbia coastal waters. A chemical study of this alga yielded ten diterpenoids of which four are new compounds. All the new compounds, dictyoxide A (66), dictyol G acetate (68), dictyotriol A diacetate (69), and epidictyol B acetate (70) contain a perhydroazulene carbon skeleton first encountered in the algal metabolite pachydictyol A (29). Dictyoxide A (66) appears to be an artifact of isolation. The acetates 68, 69, 70 were found to be antibacterial and antifungal. Six previously known compounds pachydictyol A (29), dictyol C (32), dictyoxide (35), acetyldictyolal (49) and the acetals 61a and 61b were also isolated from this alga. Chemical studies on an Agelas sp. of sponge collected in Sri Lanka yielded the antimicrobial metabolite desbromooroidin (79). An interesting interaction between the starfish Dermasterias imbricata and the sea anemone Stompia coccinea was observed a long time ago. When contacted by the starfish, the anemone displays an unusual "swimming" response which was, according to other subsequent studies, caused by a single chemical substance in the starfish. A study conducted to elucidate the structure of this starfish metabolite led to the isolation of imbricatine (91), a unique benzyltetrahydroisoquinoline alkaloid. Imbricatine (91) induced S. coccinea swimming response at a very low concentration and also exhibited antitumor activity. Structures of all the new metabolites were determined by spectral analysis, and chemical degradations and chemical interconversions.Science, Faculty ofChemistry, Department ofGraduat