Novaxenicins A-D and xeniolides I-K, seven new diterpenes from the soft coral Xenia novaebrittanniae

Seven new diterpenes, novaxenicins A-D (1-4) and xeniolides I-K (5-7), have been isolated from the Kenyan soft coral Xenia novaebrittanniae. The structures and relative stereochemistry of the compounds were elucidated by interpretation of MS, COSY, HSQC, HMBC, and NOESY experiments. The structure of novaxenicin A (1) was secured by X-ray diffraction analysis. Compound 5 possesses anti-bacterial activity at a concentration of 1.25 μg/ml and compound 2 induces apoptosis in transformed mammalian cells at a concentration of 1.25 μg/ml.     

Marine natural products: Cytotoxic spermidine derivatives from the soft coral sinularia brongersmai

Two new cytotoxic spermidine derivatives isolated from the Pacific soft coral $\text{Sinularia brongersmai}$ have been identified as CH₃(CH₂₈-C(CH₃)=CH-CO-NH(CH₂)₃-N(CH₃)- (CH₂)₄-N(CH₃)₂ and its dihydro analog by spectral methods combined with chemical conversions. Acid hydrolysis of the saturated amide followed by esterification yielded methyl 3-methyldodecanoate.     

Novel cytotoxic nine-membered macrocyclic polysulfur cembranoid lactones from the soft coral Sinularia sp.

One novel nine-membered macrocyclic polysulfur cembranoid lactone, sinulariaoid A (1); three new multioxygenated cembranoids, sinulariaoid B (2), sinulariaoid C (3), sinulariaoid D (4); and four known cembranoids, capilloloid (5), dihydrosinularin (6), sinularin (7), and dihydrosinuflexolide (8) were isolated from the soft coral Sinularia sp. collected off of Sanya Bay in the South China Sea. Their stereochemical structures were determined on the basis of extensive spectroscopic methods, including single crystal X-ray diffraction analysis. Sinulariaoid A (1) is the first reported nine-membered macrocyclic polysulfur cembranoid from soft coral. The cytotoxic activities of compounds 1–8 were determined in four human cancer cell lines (HepG2, HepG2/ADM, MCF-7, and MCF-7/ADM). Of these, sinulariaoid A (1) exhibited the most potent anticancer activity in vitro, and its cytotoxicity in HepG2/ADM was more potent than in the other three cell lines. Furthermore, it was found that sinulariaoid A (1) induced apoptosis, and its selective toxicity toward HepG2/ADM cells was not related to P-glycoproteins.     

Pavidolides A-E, new cembranoids from the soft coral Sinularia pavida

Five new cembrane-based diterpenoids, namely pavidolides A-E (1-5) were isolated from the marine soft coral Sinularia pavida, together with sarcophytin and chatancin. The structures of new compounds were determined on the basis of extensive spectroscopic data analysis. Pavidolide B (2) possesses an unprecedented 6,5,7-tricarbocyclic nucleus, whereas pavidolide C (3) is characteristic of an unusual C-5 and C-9 conjuncted cembranoid. Pavidolides C and D showed moderate antifouling activity against the larval settlement of barnacle Balanus amphitrite, while pavidolides B and C exhibited inhibitory activity against the human leukemia cell line HL-60.     

Sinularectin, a new diterpenoid from the soft coral Sinularia erecta

A new norcembrane, designated sinularectin 3, was isolated from the Kenyan soft coral Sinularia erecta. Sinularectin is a chlorinated highly oxygenated norcembrane with an unprecedented functionalisation of the cembrane isopropyl group. The structure of sinularectin was elucidated by interpretation of the HRESMS results as well as 1D and 2D NMR spectra.     

Eight new diterpenoids from soft coral Cespitularia hypotentaculata

Chemical investigation of the soft coral Cespitularia hypotentaculata resulted in the isolation of eight new diterpenes, cespihypotins E-L (1-8). The new metabolites comprise of six verticillene-type diterpenes, one cespitularane derivative, and one derivative with 14-membered lactone ring. The structures were determined through detailed spectroscopic analyses, especially high resolution ESIMS and 2D NMR techniques. The relative stereochemistry was deduced from NOESY spectrum and application of Mosher's ester technique. Immunomodulatory and antiviral activities of 1-8 were tested and evaluated. The biogenetic pathways for 1-8 were also proposed.     

New cembranoid diterpenes from the Vietnamese soft coral Sarcophyton mililatensis stimulate osteoblastic differentiation in MC3T3-E1 cells

Chemical investigation of the Vietnamese soft coral Sarcophyton mililatensis resulted in the isolation of four new cembranoid diterpenes, namely (-)-7beta-hydroxy-8alpha-methoxydeepoxysarcophytoxide (1), (+)-7beta,8beta-dihydroxydeepoxysarcophytoxide (2), (-)-17-hydroxysarcophytonin A (3) and sarcophytol V (4), along with two known compounds, (+)-sarcophine (5) and sarcophytoxide (6). The NMR spectral data of the new compounds were completely assigned by using a combination of 2D NMR experiments including (1)H-(1)H COSY, HSQC, HMBC, and ROESY. To investigate the bioactivities of compounds, which act on bone metabolism, we studied the effects of compounds on the function of osteoblastic MC3T3-E1 cells. Compound 1 caused a significant elevation of alkaline phosphatase activity, collagen content, and nodules mineralization compared to those of the control (p<0.05). These results suggest that newly isolated compound 1 has a direct stimulatory effect on bone formation in vitro and may contribute to the prevention for osteoporosis.     

A novel chlorinated norsesquiterpenoid and two related new metabolites from the soft coral Paralemnalia thyrsoides

A structurally unique chlorinated norsesquiterpenoid, paralemnolin A (1), along with two new metabolites, paralemnolin B (2) and C (3), have been isolated from the soft coral Paralemnalia thyrsoides. Their structures were determined by extensive spectroscopic analyses. Single-crystal X-ray diffraction analysis of 1 further establish the absolute stereochemistry of 1.     

Kitungolides A, B, and C, new diterpenes from a soft coral of a new genus

Three novel compounds, designated kitungolides A (1), B (2), and C (3), were isolated from a soft coral of a new genus collected at Kitungamwe, Kenya. The three new compounds are of a unique heterotricyclic skeleton. The structures and relative stereochemistry of the compounds were elucidated by interpretation of MS, COSY, HMQC, HMBC, and NOESY experiments. [structure: see text]     

Emblide,a new polyfunctional cembranolide from the soft coral sarcophyton glaucum

From a Pacific marine coelenterate we have isolated emblide, a cembrane diterpenoid which bears acetoxy, dienoic ester, and α,β-unsaturated ?-lactone functions. Its structure (1) was deduced from spectral and X-ray crystallographic data.     

New pyranosyl cembranoid diterpenes from Sarcophyton trocheliophorum

During our continual searching programme for novel bioactive metabolites from Sarcophyton trocheliophorum, collected from Red Sea, we describe herein the isolation and structural elucidation of further two new pyrane-based cembranoid diterpenes: 9-hydroxy-7,8-dehydro-sarcotrocheliol (1) and 8,9-expoy-sarcotrocheliol acetate (2), along with the well-known sarcotrocheliol acetate (3), (+)-sarcophine (4), (+)-sarcophytoxide (5) and (-)-sarcophytoxide (6). The chemical structures of compounds 1 and 2 were determined on the basis of 1D and 2D NMR (¹H, ¹³C, ¹H–¹H COSY, HMQC, HMBC and NOE), mass spectra (ESI and HR-ESIMS) and by comparison with related structures. The antimicrobial activities of the reported compounds 1–6 were investigated. According to the molecular docking study of compounds 1–6 using 3D structure of α,β tubulin in complex with taxol (PDB code 1JFF) and epothilone A (PDB code 1TVK), sarcophine (4) displayed the highest affinity towards both crystal structures, followed by 5 and 6, meanwhile pyrane-based cembranoid diterpenes (1–3) showed less affinity.     

Lobozoanthamine, a new zoanthamine-type alkaloid from the Indonesian soft coral Lobophytum sp.

A new member of the family of zoanthamine-type alkaloids, lobozoanthamine (1), has been isolated from the Indonesian soft coral Lobophytum sp. This represents the first report of a zoanthamine-type alkaloid from a marine invertebrate different from zoanthids. The densely functionalized heptacyclic stereostructure of lobozoanthamine (1) has been established through the interpretation of 2D NMR data and application of the modified Mosher method.     

Sinugibberosides A-E, new terpenoids with cyclic peroxyhemiketal from the soft coral Sinularia gibberosa

The organic extract of the soft coral Sinularia gibberosa, collected from the northern Taiwan, has been investigated and resulted in the isolation of five new xeniaphyllane-type diterpenoids with a rare cyclic peroxyhemiketal (3,6-dihydro-1,2-dioxin-3-ol) moiety, sinugibberosides A-E (1-5). The structures of the new terpenoids, including their stereochemistries, were established on the basis of extensive spectroscopic analysis, including 1D and 2D NMR (¹H-¹H COSY, HMQC, HMBC, and NOESY), and by comparison of their NMR data with those of related compounds. Metabolites 1-5 represent the first example of marine terpenoids possessing a cyclic peroxyhemiketal moiety.     

Pukalide,a furanocembranolide from the soft coral Sinularia abrupta

We have assigned structure 1a to pukalide, which is a constituent of an alcyonarian, on the basis of spectral data. Pukalide is diterpenoid with a cembrane skeleton, bearing butenolide, epoxide, isopropenyl, and an unprecedented α,α-disubstituted furan-β-carboxylate function.     

Novel steroids from the soft coral Nephthea chabrolii

Three new metabolites including two new steroids, chabrolosteroids A and B (1 and 2), and a novel spirosteroid chabrolosteroid C (3), were isolated from the organic extract of a Taiwanese soft coral Nephthea chabrolii. The structures of these metabolites were elucidated by extensive spectroscopic analysis and by comparison of the spectral data with those of related steroids. This is the first report of a steroid with a spiro-ring A, B system in natural products.     

Two new abietane diterpenes from Cordia latifolia

Two new abietane diterpenes cordioic acid and cordifolic acid were isolated from the methanolic extract of Cordia latifolia stem bark. The structures of these diterpenes were elucidated using spectroscopic techniques. To the best of our knowledge, this is the first instance of isolation of diterpenoids from this source. Furthermore, cordifolic acid is a rare 2,3-seco-abietane suggestive of its biogenesis from 3-keto-analogue.     

Cytotoxic cembranoids from the Red Sea soft coral, Sarcophyton auritum

Chemical investigation of the Red Sea soft coral Sarcophyton auritum led to the isolation and structure elucidation of two new diterpene cembranoids; 2-epi-sarcophine (2) and (1R,2E,4S,6E,8R,11R,12R)-2,6-cembradiene-4,8,11,12-tetrol (4), as well as two known diterpene cembranoids, reported for the first time from this species, namely sarcophine (1) and (+)-7α,8β-dihydroxydeepoxysarcophine (3). Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The isolated cembranoids were found to display high cytotoxicity against HepG2 (liver cancer cell line) and MCF-7 (breast cancer cell line).     

Novel sesquiterpenoids from the Formosan soft coral Paralemnalia thyrsoides

Three sesquiterpenoids with unprecedented skeletons, paralemnanone (1), isoparalemnanone (2), and paralemnanol (3), were isolated from the Formosan soft coral Paralemnalia thyrsoides. Their structures were elucidated by extensive spectroscopic analysis, and the structure of 1 was further confirmed by X-ray crystallographic analysis. The absolute stereochemistries of 1-3 were established by application of the Mosher’s method on 2.