Studies On The Chemical Constituents Of Two Marine Organisms

This dissertation describes studies on chemical constituents of two marine organisms, the soft coral Sinularia numerosa Tixier-Durivault and the marine alga Sargassum thunbergii (Mert.)O'Kuntze. Most obtained compounds were preliminarily screened for bioactivity eluciation .The soft coral S. numerosa were collected at Sanya waters, Hainan island of South China Sea in July 2004, and the freeze-dried soft coral sample (1.6 kg) was extracted with acetone and concentrated to yield 120 g crude extract. The alga S. thunbergii were collected along the coast of Qingdao, Shandong province, China, in May 2003, and the dried marine alga sample (8.3 kg) was extracted with EtOH for three times at room temperature (one week for each time) to yield 430 g crude extract, and then the concentrated extract was dissolved in water and partitioned with petroleum ether, ethyl acetate, and n-butanol, successively.The compounds were isolated by the combination of column chromatography on silica gel, RP-18, and Sephadex LH-20, as well as preparative thin layer chromatography (pTLC), re-crystallization, and semi-preparative HPLC. The structures of the obtained compounds were elucidated on the basis of spectroscopic methods including IR, UV, MS, HR-MS, 1D-NMR and 2D-NMR. 38 compounds were isolated and 27 of them were structurally elucidated. From S. numerosa, 30 compounds were isolated and 19 of them were structurally elucidated, including two new cembranoid derivatives, namely, Numerolides A–B (SN1–SN2), and a new sterol, namely, Gorgost-3β, 7β-diol (SN3), and fifteen compounds were isolated from S. numerosa for the first time. From S. thunbergii, eight compounds were isolated, including phytol, fucosterol, two monoterpenoids, a cyclopenten-1-one and three unsaturated aliphatic compounds, all of which were isolated from S. thunbergii for the first time.Most of the pure compounds were screened for their cytotoxic and antibacteria activities. None of the tested compounds showed remarkable activity in the in vitro cytotoxic assay against tumor cell line SMMC-7721. Compound SN15 showed moderate inhibitory activity against Staphylococcus aureus and Escherichia coli, while Compound SN19 showed growth promoting activity of S. aureus.