A novel symmetric sulfur-containing biscembranoid from the Formosan soft coral Sinularia flexibilis
Graphical abstract
Introduction
Soft corals have been well recognized to be a rich source of secondary metabolites possessing variety of skeletons and biological activities.1 Previously, we have discovered series of structurally novel and bioactive sesquiterpenoids,2, 3 norcembranoids,4, 5 cembranoids,6, 7, 8 and steroids9, 10, 11 from Taiwanese soft corals of the genus Sinularia. In our continuing search for bioactive metabolites from soft corals of Taiwanese waters, we investigated the chemical constituents of Sinularia flexibilis. This study has led to the discovery of a novel sulfur-containing biscembranolide, thioflexibilolide A (1), from the CH2Cl2 extract of this marine organism. The structure of 1 was determined on the basis of extensive spectroscopic analysis, including 2D NMR (1H–1H COSY, HMQC, HMBC, and NOESY) spectroscopy. Compound 1 demonstrated anti-inflammatory activity to inhibit the accumulation of the pro-inflammatory protein, inducible nitric oxide synthase (iNOS), in lipopolysaccharide (LPS)-stimulated microglial cells. Furthermore, the interesting neuroprotective activity of 1 against the damage of 6-OHDA (6-hydroxydopamine)-induced cytotoxic effect on SH-SY5Y cells was also observed.
Section snippets
Results and discussion
The soft coral S. flexibilis (2.1 kg) was collected by hand using scuba off the coast of Taitung County, located in the southeastern part of Taiwan. The acetone extract of the organism was partitioned between CH2Cl2 and H2O. The CH2Cl2-soluble portion (15.3 g) was subjected to column chromatography on silica gel using n-hexane/EtOAc mixture of increasing polarity as eluent. A fraction eluted with n-hexane/EtOAc (1:1) was further purified by reverse-phase HPLC (MeOH/H2O, 2.3:1) to afford 1 (15.2
Acknowledgments
The financial support of this work was provided by the National Science Council (NSC-98-2113-M-110-002-MY3) and Ministry of Education (98C031702) of Taiwan awarded to J.-H.S.
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