Four New 7,8-Epoxycembranoids from a Chinese Soft Coral <i>Lobophytum</i> sp.

Abstract

-trien-15,16-diol (4) were isolated from a Chinese soft coral Lobophytum sp., together with eleven known analogues 5-15. The structures of the new compounds were determined by extensive spectroscopic data analysis. All compounds were tested for the inhibitory effect on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in mouse peritoneal macrophages (PEMΦ).Key words soft coral; Lobophytum; 7,8-epoxycembranoid; nitric oxide (NO) inhibition Cembranoids, containing a 14-membered carbocyclic skeleton with varying degrees of oxygenation, comprise the largest group of diterpenoids derived from soft corals including the genera Lobophytum, Sinularia, and Sarcophyton.

Cembranoids from a Chinese Collection of the Soft Coral Lobophytum crassum

“…The other two olefinic carbons at δ C 138.9 (CH, C-11) and 124.4 (CH, C-10) and two olefinic proton signals at δ H 5.53 (m, H-10) and 5.52 (d, J = 18.6 Hz, H-11) were attributed to a 1,2-disubstituted double bond. These NMR data were similar to those of the known cembranoid (2 S *,7 S *,8 S *,12 R *,1 Z ,3 E ,10 E )-7,8:2,16-diepoxycembra-1(15),3,10-trien-12-ol [ 27 ]. The difference arose from the absence of a trisubstituted epoxy in 7 .…”

“…However, the soft coral L. crassum in the South China Sea has been rarely examined chemically [ 22 , 23 , 24 ]. In the course of our investigation of bioactive substances produced by marine invertebrates from the South China Sea [ 25 , 26 , 27 ], a specimen of L. crassum was collected. Chemical examination of this specimen led to the isolation of 18 cembrane-based diterpenes, including nine new cembranoids ( 1 , 2 , and 4 – 10 ), an unprecedented diterpene possessing a tetradecahydrobenzo[3,4]cyclobuta[1,2][8]annulene ring system ( 3 ), and eight known analogues ( 11 – 18 ) ( Figure 1 ).…”

Marine natural products

“…781 Two separate collections of Lobophytum sp. yielded epoxycembranes 876-880 (Ximao Is., Sanya Bay, Hainan, China) 782 and a-methylene-g-lactones 881-883 (Sanya Bay, Hainan, China). 783 This is the rst report 880 as an NP.…”

Structurally Diverse Metabolites from the Soft Coral Sinularia verruca Collected in the South China Sea

“…In the past several decades, more than 50 Sinularia species have been chemically investigated, resulting in the discovery of hundreds of secondary metabolites including sesquiterpenoids, diterpenoids, polyhydroxylated steroids, cyclopentenones, and butenolides . Many of these metabolites are structurally novel and display a wide range of significant ecological and pharmacological activities, such as antifouling, antifeedant, allelopathy, cytotoxic, antimicrobial, and anti-inflammatory properties. − In the course of our ongoing research on bioactive natural products from marine invertebrates of the South China Sea, − a previously unstudied soft coral, Sinularia verruca van Ofwegen, 2008, was collected. Detailed chemical examination of this specimen led to the isolation of 19 compounds with diverse structural scaffolds, including a rare pyrroloindoline alkaloid ( 1 ), a novel benzosesquiterpenoid ( 2 ), a new asteriscane-type sesquiterpenoid ( 3 ), and two new cyclopentenone derivatives ( 4 and 5 ).…”