Four New Briarane Diterpenoids from the Gorgonian Coral Junceella fragilis

Chemical investigation of the gorgonian coral Junceella fragilis, collected by scuba diving in Taiwan, resulted in the isolation of four new briarane‐type diterpenoids, frajunolides A–D ( 1 – 4 ), along with three known briaranes. Their structures were elucidated on the basis of spectroscopic studies, especially 1‐ and 2D‐NMR as well as HR‐MS experiments. The inhibitory effect of all isolated metabolites towards superoxide‐anion generation and elastase release by human neutrophils in response to formylmethionyl‐leucyl‐phenylalanine/dihydrocytochalasin B (FMLP/CB) was evaluated.     

Juncenolides H – K,New Briarane Diterpenoids from Junceella juncea

Chemical investigation of the Taiwanese gorgonian coral Junceella juncea resulted in the isolation of four new briarane‐type diterpenoids, juncenolides H, I, J, and K ( 1 – 4 ). Their structures were determined on the basis of spectroscopic analysis, especially 1‐ and 2D‐NMR. The inhibitory effects of compounds 1 – 4 on superoxide‐anion generation and elastase release by human neutrophils were evaluated.     

Junceellonoids A and B,Two New Briarane Diterpenoids from the Chinese Gorgonian Junceella fragilis Ridley

Two new diterpenoids, junceellonoids A and B ( 1 and 2 , resp.), together with the seven known diterpenoids 3 – 9 , all possessing the briarane carbon skeleton, were isolated from the gorgonian Junceella fragilis Ridley , collected in the South Sea of China. The structures and relative configurations of the new metabolites were elucidated based on extensive spectral analysis and by comparison with known spectral data.     

New Briaranes from the South China Sea Gorgonian Junceella fragilis

Three new briarane diterpenes, junceellonoids C–E ( 1 – 3 ), along with six known briaranes, junceellin A ( 4 ), praelolide ( 5 ), and junceellolides A‐D ( 6 – 9 ), were isolated from the EtOH/CH₂Cl₂ extracts of the South China Sea gorgonian coral Junceella fragilis. The structures of 1 – 3 were established by extensive spectroscopic analysis, including 1D‐ and 2D‐NMR data. Compounds 1 and 2 exhibited mild cytotoxicity against human galactophore carcinoma (MDA‐mB‐231 and MCF‐7) cells at the concentration of 100 μM .     

Ten new antifouling briarane diterpenoids from the South China Sea gorgonian Junceella juncea

Ten new antifouling briarane diterpenoids, juncins R-ZI (1-10) were isolated from the South China Sea gorgonian coral Junceella juncea. The structures of these new compounds were established by extensive spectroscopic analysis, including 1D and 2D NMR data. Compounds 1-10 all showed potent antifouling activities against the larval settlement of barnacle Balanus amphitrite at nontoxic concentrations with EC₅₀ values of 0.004, 0.34, 2.65, 1.61, 3.77, 21.06, 0.004, 0.14, 1.47, and 0.51 μg mL⁻¹. The structure-activity relationship was discussed.     

New briaranes from the octocorals Briareum excavatum (Briareidae) and Junceella fragilis (Ellisellidae)

Six 12-hydroxybriaranes, including four new diterpenoids, briaexcavatins I-L (1-4), and two known metabolites, excavatolides C (5) and E (6), have been isolated from the cultured scleraxonia Briareum excavatum. In addition, the gorgonian coral Junceella fragilis yielded a new chlorinated briarane, fragilide C (10). The structures of above compounds were determined by spectroscopic methods and the structures of 5 and 6 were further confirmed by X-ray data analysis for the first time. The absolute configuration of 6 was elucidated by chemical conversion. Some of these briaranes have displayed inhibitory effects on superoxide anion generation by human neutrophils.     

Antifeedant and antifouling briaranes from the South China Sea gorgonian <Emphasis Type="Italic">Junceella juncea</Emphasis>

A new briarane diterpene, juncin ZII (1), along with three known briaranes (2–4), was isolated from the EtOH/CH₂Cl₂ extracts of the South China Sea gorgonian Junceella juncea. The structure of 1 was established by extensive spectroscopic analysis, including 1D and 2D NMR data. For compounds 1–4 and eight other briaranes (5–12) isolated from J. juncea previously, the antifeedant activity against second-instar larvae of Spodoptera litura and cytotoxicity against S. litura cells were investigated, and it was observed that they all exhibit medium antifeedant activity. Compounds 1, 8, 9, and 12 also showed potent antifouling activity against the larval settlement of barnacle Balanus amphitrite at nontoxic concentrations with EC₅₀ values of 0.004, 0.005, 2.82, and 0.447 μg/mL, respectively, while all compounds did not show obvious cytotoxicity against tumor cell lines K562, A549, Hela, and Hep-2. Their structure-activity relationship was discussed. Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 44–47, January–February, 2009.     

Suberoretisteroids A–E,Five New Uncommon Polyoxygenated Steroid 24‐Ketals from the Hainan Gorgonian Suberogorgia reticulata

Five new uncommon polyoxygenated steroids, namely suberoretisteroids A–E ( 1 – 5 ), were isolated from the gorgonian Suberogorgia reticulata, never studied so far. The structures and relative configurations of these new compounds were elucidated on the basis of extensive spectral analysis. This work led to the structural revision of some steroids previously found in the Indian gorgonian Gorgonella umbraculum.     

New Steroids and a New Alkaloid from the Gorgonian Isis minorbrachyblasta: Structures,Cytotoxicity, and Antilarval Activity

Two new polyoxygenated steroids, (1α,3β,7α,11α,12β)‐gorgost‐5‐ene‐1,3,7,11,12‐pentol 12‐acetate ( 1 ) and 11‐O‐acetyl‐22‐epihippuristanol ( 2 ), and a new alkaloid, 2,3,5,6,11,11b‐hexahydro‐2‐hydroxy‐1H‐indolizino[8,7‐b]indole‐2‐carboxylic acid ( 3 ), together with three known compounds, 22‐epihippuristanol ( 4 ), hippuristanol ( 5 ), and tryptamine ( 6 ), were isolated from the EtOH/CH₂Cl₂ extracts of the South China Sea gorgonian Isis minorbrachyblasta. The structures of the new compounds were determined by spectroscopic methods. Compound 1 showed weak cytotoxicity against A549, HONE1, and HeLa cancer cell lines and strong antilarval activity towards Bugula neritina larvae with an EC₅₀ value of 5.8 μg/ml. Compound 5 showed moderate cytotoxicity against A549, HONE1, and HeLa cell lines, and the epimer mixture 4 / 5 (weight ratio 3 : 2) exhibited potent cytotoxicity against A549 and HONE1 cell lines with IC₅₀ values of 4.2 and 4.8 μg/ml, which indicated that epimers 4 and 5 might have a synergistic effect on their cytotoxicity against A549 and HONE1 cell lines.     

Briaexcavatins A and B, novel briaranes from the octocoral Briareum excavatum

Two novel briaranoidal derivatives, designated as briaexcavatins A (1) and B (2), along with two known metabolites, excavatolides B and C (3 and 4), were isolated from the octocoral Briareum excavatum. Both compounds 1 and 2 possess unprecedented 5,6-epoxy moiety in the 10-membered ring. Diterpenoid 1 possesses a novel pentacyclic skeleton with a ε-lactone. The structures of diterpenoids 1 and 2 were elucidated by interpretation of spectral data and the absolute stereochemistry was established by application of modified Mosher’s method on 3.     

New 8-hydroxybriarane diterpenoids from the gorgonians Junceella juncea and Junceella fragilis (Ellisellidae)

Four new 8-hydroxybriarane diterpenoids, including junceols A-C (1-3) and fragilide D (4), have been isolated from the gorgonian corals Junceella juncea and Junceella fragilis, respectively. The structures of briaranes 1-4 were elucidated by the interpretations of spectral data analysis. Briaranes 1-3 have displayed inhibitory effects on superoxide anion generation by human neutrophils.     

Menverins H–L,New Highly Oxygenated Guaiane Lactones from the Gorgonian Coral Menella kanisa

By further chemical investigation of South China Sea gorgonian Menella kanisa, five new highly oxygenated guaiane lactones, menverins H–L ( 1 – 5 , resp.), were obtained. Their structures were established by employing spectroscopic methods, computer modeling, and comparison of their data with those of related metabolites.     

New Eunicellin Diterpenes and 9,10‐Secosteroids from the Gorgonian Muricella sibogae

Bioactivity‐guided isolation of the rare gorgonian Muricella sibogae (Nutting ) yielded the two new eunicellin diterpenes sibogin A and B ( 1 and 2 ), the three new 9,10‐secosteroids sibogol A–C ( 6 – 8 ), together with the three known eunicellin diterpenes 3 – 5 and the five known 9,10‐secosteroids 9 – 13 . Their structures were established by extensive spectral analysis (1D‐ and 2D‐NMR, IR, and MS). The cytotoxicity of the isolates 1 – 13 was evaluated in vitro against the selected tumor cell lines P388 and BEL‐7402. All the compounds showed only weak activity against P388 cell lines, with an inhibition rate ranging from 10 to 60% at a concentration of 50 μg/ml, whereas the were inactive against BEL‐7402 cell lines.     

Fragilolides A-Q,norditerpenoid and briarane diterpenoids from the gorgonian coral Junceella fragilis

Chemical investigation of the gorgonian coral Junceella fragilis resulted in the isolation of a new norditerpenoid fragilolide A (1), sixteen new briarane diterpenoids fragilolides B-Q (2–17), together with frajunolides H and N, and three known norcembranoids scabrolide D, sinuleptolide and 5-epi-sinuleptolide. The structures of new compounds were determined on the basis of extensive spectroscopic analysis, including the experimental and calculated ECD data and single-crystal X-ray diffraction for the configurational assignments. The structure of fragilolide A featured an unprecedented 4,13- and 7,11-fused tetracyclic norcembranoid, while the biogenetic relationships of the briarane analogues were postulated. Frajunolide H exerted significant inhibition against a panel of tumor cell lines, and six briarane diterpenoids (3, 6, 8, 12, 16, and frajunolide N) exhibited the inhibitory effects against the HBeAg express of hepatitis B virus in HepAD38 cells. In addition, sinuleptolide and 5-epi-sinuleptolide exerted the effects to inhibit NO production in RAW264.7 macrophage cells, in addition to the activation of ARE and the inhibition of NF-κB expression.     

New metabolites with antibacterial activity from the marine angiosperm Cymodocea nodosa

Four new metabolites (1-4) have been isolated from the organic extract of the seagrass Cymodocea nodosa, collected at the coastal area of Porto Germeno, in Attica Greece. Compounds 1 and 2 belong to the structural class of diarylheptanoids, which have been found only once before in marine organisms [Kontiza, I.; Vagias, C.; Jakupovic, J.; Moreau, D.; Roussakis, C.; Roussis, V. Tetrahedron Lett.2005, 46, 2845-2847]. Compound 3 is a new meroterpenoid, while compound 4, to the best of our knowledge, is the first briarane diterpene isolated from seaweeds, and only the second analog of this class with a tricyclic skeleton. Furthermore metabolite 4 is the first brominated briarane diterpene. The structures and the relative stereochemistry of the new natural products were established by spectral data analyses. The new metabolites were submitted for evaluation of their antibacterial activity against multidrug-resistant (MDR) pathogens including methicillin-resistant (MRSA) strains of Staphylococcus aureus, as well as the rapidly growing mycobacteria, Mycobacterium phlei, Mycobacterium smegmatis, and Mycobacterium fortuitum.     

Briarenolide J,the first 12-chlorobriarane diterpenoid from an octocoral Briareum sp. (Briareidae)

A novel 6,12-dichlorobriarane diterpenoid, briarenolide J (1), was isolated from an octocoral identified as Briareum sp. The structure of briarane 1 was elucidated by spectroscopic methods. Briarenolide J (1) is the first metabolite of a briarane-related natural product found to possess a chlorine atom at C-12 and this compound was found to display inhibitory effects on the generation of superoxide anions and the release of elastase by human neutrophils with IC₅₀ values of 14.98 and 9.96 μM, respectively.     

New Cembrane Diterpenes from Taiwanese Soft Coral Sinularia flexibilis

A chemical investigation of the Taiwanese soft coral Sinularia flexibilis has resulted in the isolation of three new cembrane diterpenes designated sinuladiterpenes G–I ( 1 – 3 , resp.). The structures of 1 – 3 were determined on the basis of spectroscopic analyses, especially 2D‐NMR and HR‐ESI‐MS.     

New Meroditerpenoids from a Taiwanese Marine Sponge Strongylophora Durissima

In addition to strongylophorines 1 (3), 2 (4), 3 (5) and 8 (6), two new meroditerpenoids named strongylophorines 9(1) and 11 (2) were isolated from a Taiwanese marine sponge Strongylophora durissima. The structures of the new compounds were established by spectral methods and chemical derivatizations.     

A new briarane-type diterpenoid from the South China Sea Gorgonian Dichotella gemmacea

One new briarane-type diterpenoid, dichotellide V (1), along with four known analogues, gemmacolide N (2), dichotellide J (3), junceelin A (4) and junceellolide A (5), was isolated from the South China Sea gorgonian Dichotella gemmacea. All of the isolated compounds (1–5) were established by comprehensive analysis of the spectral data, especially 1D and 2D NMR (HMQC and HMBC) spectra. The cytotoxic activities of these compounds were evaluated.