Isolation, characterization and antimicrobial assay of some components from the chloroform extract of Lobophyton crassum

The chloroform extract of the soft coral Lobophyton crassum was found to contain two isolates with potent antimicrobial properties. The first isolate, Isolate I was partially elucidated based on the spectral evidences (IR, 1H nmr, 13C nmr). Comparison of its 13C nmr chemical shifts with that of 3 beta-hydroxylated steroids, and of its 1H nmr with that of a gorgosterol, the major components of Isolate 1 is either an isomer or derivative of gorgosterol. The exact structure of its side chain could not be determined due to presence of impurity. The second isolate, Isolate 2 was structurally elucidated based on the spectral evidences (IR, 1H nmr, 13C nmr) and comparison of its 13C nmr chemical shift with a known diterpene. The isolate has a molecular formula of C20H30O2 and it is systematically named as 2-[(E,E,E,)-7\u27,8\u27,12\u27-trimethylcyclotetradeca-1\u27,3\u27,11\u27-trienyl]propan-2-ol.Both isolates exhibited antimicrobial activity against six of seven test organisms. Of the six text organisms, Isolates 1 and 2 were most active against M. aevium exhibiting a complete zone of inhibition measuring 24.0 mm and 20.6 mm, respectively