Sinugrandisterols A-D, trihydroxysteroids from the soft coral Sinularia grandilobata

Four new trihydroxysteroids, sinugrandisterols A-D (1-4), have been isolated from the CH₂Cl₂-soluble fraction of the EtOH extract of Sinularia grandilobata. The structures of these metabolites were determined on the basis of spectroscopic (IR, MS, and 1D and 2D NMR) analysis. The cytotoxicity of 1-4 toward a limited panel of cancer cell lines is also reported.     

Oxygenated Cembrane Diterpenes from the South China Sea Soft Coral Sinularia tumulosa**

The chemical investigation of the rarely studied soft coral Sinularia tumulosa resulted in the discovery of five oxygenated cembrane diterpenes 1 – 5 , including two new compounds situmulins A ( 1 ) and B ( 2 ). The structures of 1 and 2 were established through the extensive analyses of 1D and 2D NMR spectral data together with the comparisons with the known compounds. Furthermore, the absolute configuration of 1 was determined by the time-dependent density functional theory (TDDFT) ECD approach, while the relative configuration of 2 was assigned via the quantum mechanical-NMR (QM-NMR) calculations. It might be worth to point out it is the first time to disclose the presence of cembrane diterpenes in the title species. In the bioassays, compound 2 not only showed strong antibacterial activities against fish pathogenic bacteria Streptococcus parauberis FP KSP28 and Phoyobacterium damselae FP2244 with both minimum inhibitory concentration for 90 % (MIC₉₀) values of 25 μM, but also demonstrated substantial inhibitory efficacy against vancomycin-resistant Enterococcus faecium bacteria G1, G4, G7, G8 and G13 from several individuals, with MIC₉₀ values of 25, 50, 100, 50 and 25 μM, respectively.     

软珊瑚(Sinularia flexibilis)和柳珊瑚(Plexaura homomalla)化学防御物质研究进展

软珊瑚(Sinularia flexibilis)和柳珊瑚(Plexaura homomalla)属于海洋低等无脊椎动物,虽然这些动物自身缺乏有效的物理防御手段,却能在竞争激烈的海洋环境中生存与繁衍,这主要是依靠其次级代谢产物的化学防御作用.这些次级代谢产物聚积在体内或释放到环境中,作用主要体现在抵御捕食者、抗病原微生物、克生与防附着等方面.珊瑚化学防御物质的研究有助于探讨珊瑚与其环境中其它生物的化学生态关系,属于海洋化学生态学研究的重要内容之一,其研究方法和思路对海洋活性天然产物乃至海洋新药先导化合物的发现,具有重要的启迪作用.综述了软珊瑚和柳珊瑚化学防御物质的研究进展,并阐释了软珊瑚和柳珊瑚中具有拒捕食、克生、防生物附着等生物活性的次级代谢产物的结构及其化学防御作用.     

A diffusion chamber for assessing efficacy of natural anti-fouling defenses in marine organisms

A slow-release diffusion chamber is here described for use in assessing the effectiveness of potentially bioactive compounds as anti-fouling agents. Its settlement surface is a porous 15 mm thick slab of Portites lobata skeleton, through which an aqueous extract of a given marine organism is permitted to diffuse. The chamber is placed at an underwater site for 30 days at a time, and settlement of sessile, benthic organisms, particularly algae, is permitted to occur. Comparative settlement levels were compared between chambers containing an extract and a seawater control. An extract of Sinularia flexibilis (Octocorallia, Alcyonacea) was assessed using such chambers and found to be an effective natural anti-fouling agent or defense mechanism against Ectocarpus sp. and pennate diatoms, reducing their cover by ∼ 50% when compared to experimental conditions using seawater as a control. Intra-chamber variability in extract concentration was found to be minimal. No significant differences were found in extract concentrations between replicate chambers through time. The chamber is a highly cost-effective and efficient tool by which such assessments can be made and easily replicated. It is recommended that coral which has recently died be collected and used as a source of substratum for this purpose.     

栎壮短指软珊瑚的化学成分研究

从南中国海采集的栎壮短指软珊瑚Sinularia robusta macfadyen中分离到神经酰胺苷(4E,8E)-N-D-2'-hydroxydocosanoyl-1-O-β-D-glycopyranosyl-9-methyl-4,8-sphingadienine(1)和开环甾醇3β,11-dihydroxy-9,11-secogorgost-5-en-9-one(2).首次利用X-单晶衍射技术研究了化合物2的晶体结构.     

1alpha,3beta,5beta-trihydroxy-24-methylenecholestan-6-one: a novel steroid from a soft coral Sinularia gibberosa

A novel steroid, 1alpha,3beta,5beta-trihydroxy-24-methylenecholestan-6-one (gibberoketosterol) (1), along with four known steroids, was isolated from the lipophilic extracts of a Taiwanese soft coral Sinularia gibberosa. The structure of the new metabolite was determined on the basis of extensive spectral analyses and chemical reaction. The relative stereochemistry of gibberoketosterol was established by the NOESY experiments and analysis of the pyridine-induced deshielding effect of the axial hydroxy groups. Gibberoketosterol is the first example of 1alpha,3beta,5beta-trihydroxy-6-oxosteroids isolated from natural sources and was found to exhibit a moderate cytotoxicity against the growth of Hepa59T/VGH cancer cells.