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We sequenced and analyzed the complete mitogenome of a Norwegian isolate of the octocoral Alcyonium digitatum using the Ion Torrent sequencing technology. The 18,790 bp circular mitochondrial genome was found to harbor the same set of 17 genes, which encode 14 protein subunits, two structural ribosomal RNAs and one tRNA, as reported in other octocorals. In addition, we detected a new tRNAPro-like gene sequence nested within the MutS protein coding region. This putative tRNA gene feature appears to be conserved among the octocorals but has not been reported previously. The A. digitatum mitogenome was also shown to harbor an optional gene (ORFA) that encodes a putative protein of 191 amino acids with unknown function. A mitogenome-based phylogenetic analysis, presented as a maximum likelihood tree, showed that A. digitatum clustered with high statistical confidence with two other Alcyonium species endemic to the Mediterranean Sea and the Southeast Pacific Ocean.

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Molecular networking strategy-based prioritization of the isolation of the rarely studied soft coral Sinularia tumulosa yielded 14 sesquiterpenes. These isolated constituents consisted of nine different types of carbon frameworks, namely asteriscane, humulane, capillosane, seco-asteriscane, guaiane, dumortane, cadinane, farnesane, and benzofarnesane. Among them, situmulosaols A-C (1, 3 and 4) were previously undescribed ones, whose structures with absolute configurations were established by the combination of extensive spectral data analyses, quantum mechanical-nuclear magnetic resonance and time-dependent density functional theory electronic circular dichroism calculations, the Snatzke's method, and the modified Mosher's method. Notably, situmulosaol C (4) was the second member of capillosane-type sesquiterpenes. The plausible biogenetic relationships of these skeletally different sesquiterpenes were proposed. All sesquiterpenoids were evaluated for their antibacterial, cytotoxic and anti-inflammatory effects. The bioassay results showed compound 14 exhibited significant antibacterial activities against a variety of fish and human pathogenic bacteria with MIC90 values ranging from 3.6 to 33.8 µg/mL. Moreover, moderate cytotoxic effects against HEL cells for components 13 and 14 and moderate inhibitory effect on lipopolysaccharide-induced inflammatory responses in RAW264.7 cells for substance 13 were also observed.

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The mitogenome of a soft coral, Eleutherobia rubra (Brundin, 1896), was completely sequenced for the first time. The total mitogenome length of E. rubra is 18,724 bp with 14 protein-coding genes, two ribosomal RNA genes, one transfer RNA gene (tRNA-Met), and one non-coding region (NCR). The gene order is also consistent with other Alcyoniidae species. The base composition is 30.1% A, 16.7% C, 19.5% G, and 33.7% T, with a G-C content of 36.2%. This is the first record of the complete mitogenome sequence of the genus Eleutherobia.

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The soft-bodied corals of the genera Sarcophyton and Sinularia (Alcyoniidae) are known as a warehouse of casbane and cembranoid diterpenoids with remarkable antitumor effects. Two casbane-type diterpenoids (1, 2) along with four cembrane-type diterpenoids (3-6) were isolated from the diethyl ether soluble fraction of the organic extracts of the Red Sea soft corals Sinularia leptoclados and Sarcophyton glaucum, respectively. The antiproliferative activity of all isolated compounds (1-6) against three hepatocellular carcinoma cells, namely, Huh-7, SNU 499, and HepG2, along with the normal cells EA.hy 926, was evaluated. Sinueracabanone D (1) displayed a remarkable antiproliferative effect against the examined cancer cell lines, especially HepG2 cells with IC50 of 4.0 ± 0.37 µM. Cell cycle analysis indicated compound 1 caused the accumulation of HepG2 cells in the G2/M-phase. Further, compound 1 exhibited significant pro-apoptotic activities in HepG2 cells as evidenced by annexin V staining, enhanced mRNA expression of Bax, cytochrome C, and caspase 3, as well as inhibition of Bcl2 expression. Also, challenging HepG2 cells with sinueracabanone D (1) enhanced the active oxygen species generation and decreased mitochondrial membrane potential. In conclusion, compound 1 possesses potent antiproliferative activities against HepG2 cells. These antiproliferative activities are mediated, at least partly, by their ability to induce apoptosis, mitochondrial dysfunction, and oxidative stress.

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Sinulatones A and B, presented as the unusual carbon skeleton with bicyclo[4.5.0] system, two undescribed sesquiterpenoids, namely sinulalides A and B, along with eight known terpenoids, were isolated from the South China Sea soft coral Sinularia scabra. The structures and stereochemistry of these compounds were determined based on extensive spectroscopic data analyses, and computer-assisted methods, including the quantum mechanical-nuclear magnetic resonance (QM-NMR) and TDDFT-ECD calculations. In bioassay, sinulatones A and B showed inhibitory activity against osteoclast precursor cells, with IC50 values of 16.8 and 5.8 µM, respectively.

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Five undescribed biscembranoids, bistrochelides H-L, along with four known biscembranoids, glaucumolides A-B and bistrochelides A-B, were isolated from the soft coral Sarcophyton serenei collected off the Xisha Island in the South China Sea. The structures of these compounds were elucidated by HRESIMS (high-resolution electrospray ionization mass spectroscopy) spectrometry, NMR (nuclear magnetic resonance) spectroscopy, X-ray diffraction analysis, electronic circular dichroism (ECD), and the comparison of their spectroscopic data with those reported in the literature. In bioassay, some compounds showed a strong inhibitory effect on osteoclast precursor cells at the concentration of 10 µM. Additionally, all compounds exhibited weakly antimicrobial activity against Vibrio harveyi.

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The octocoral family Alcyoniidae represents a rich source of bioactive substances with intriguing and unique structural features. This review aims to provide an updated overview of the compounds isolated from Alcyoniidae and displaying potential cytotoxic activity. In order to allow a better comparison among the bioactive compounds, we focused on molecules evaluated in vitro by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, by far the most widely used method to analyze cell proliferation and viability. Specifically, we surveyed the last thirty years of research, finding 153 papers reporting on 344 compounds with proven cytotoxicity. The data were organized in tables to provide a ranking of the most active compounds, to be exploited for the selection of the most promising candidates for further screening and pre-clinical evaluation as anti-cancer agents. Specifically, we found that (22S,24S)-24-methyl-22,25-epoxyfurost-5-ene-3ß,20ß-diol (16), 3ß,11-dihydroxy-24-methylene-9,11-secocholestan-5-en-9-one (23), (24S)-ergostane-3ß,5α,6ß,25 tetraol (146), sinulerectadione (227), sinulerectol C (229), and cladieunicellin I (277) exhibited stronger cytotoxicity than their respective positive control and that their mechanism of action has not yet been further investigated.

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Using various chromatographic separations, two new cembranoids, ehrenbergols F and G (1 and 2), along with three known analogs ehrenbergol D (3), (+)-isosarcophine (4) and sinulariol Z2 (5) were isolated from the soft coral Sarcophyton ehrenbergi. The structural elucidation was done by extensive analysis of the 1 D and 2 D NMR, HR-ESI-QTOF-MS as well as CD experiments. In addition, compounds 1 (IC50 of 38.38 ± 2.89 µM), 3 (IC50 of 37.14 ± 3.22 µM) and 4 (IC50 of 45.01 ± 2.49 µM) revealed moderate inhibitory activity on LPS-induced NO production in RAW264.7 cells, whereas 2 (IC50 of 73.32 ± 1.95 µM) and 5 (IC50 of 64.48 ± 4.93 µM) exhibited weak effect.

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Alcyonium corals are benthic animals, which live in different climatic areas, including temperate, Antarctic and sub-Antarctic waters. They were found to produce different chemical substances with molecular diversity and unique architectures. These metabolites embrace several terpenoidal classes with different functionalities. This wide array of structures supports the productivity of genus Alcyonium. Yet, majority of the reported compounds are still biologically unscreened and require substantial efforts to explore their importance. This review is an entryway to push forward the bio-investigation of this genus. It covers the era from the beginning of reporting metabolites from Alcyonium up to March 2019. Ninety-two metabolites are presented; forty-two sesquiterpenes, twenty-five diterpenes and twenty-five steroids have been reported from sixteen species.

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BACKGROUND AND AIM: The soft coral genus Sarcophyton is a source of cembraneterpen. Sarcophyton is reported to have anti-inflammatory properties, with the ability to reduce the expression of inducible nitric oxide synthase (iNOS) and inhibit nuclear factor-kappa B (NF-κB) activation. This study aimed to investigate the efficacy of dichloromethane (DCM) extracts of soft coral Sarcophyton spp. to inhibit the expression of NF-κB and iNOS induced by lipopolysaccharide (LPS). MATERIALS AND METHODS: Crude extracts of Sarcophyton spp. were macerated with DCM (1:3 v/v) for 24 h. Thirty-six Balb/c mice were divided into six treatment groups, namely, normal control (without LPS induction), negative control (LPS induction 4 mg/mL), comparative control (LPS+Dexamethasone 6 mg/kg), and 3 concentration groups extract (LPS+50, 125, and 250 mg/kg). The expression of NF-κB and iNOS was measured in each treatment group. RESULTS: Flow cytometry analysis showed that the relative number of NF-κB+ cells increased (18.38±1.24%) in LPS-induced mice compared with normal mice (13.24±1.15%). The Sarcophyton spp. DCM extracts decreased the relative number of NF-κB+ cells (125 mg/kg: 13.96±0.84%). Immunohistochemical analysis with ImmunoMembrane showed that LPS induction in mice increased iNOS expression when compared to normal mice. The Sarcophyton spp. DCM extracts reduced iNOS expression (especially at 125 mg/kg). CONCLUSION: DCM extracts of Sarcophyton spp. inhibited the activation of NF-κB, resulting in suppressed iNOS expression, which directly inhibits NO production.

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A novel valerenane sesquiterpenoid sinulaspirolactam A (1), together with five known compounds, was isolated from the soft coral Sinularia sp. Their structures were determined by spectroscopic analyses. The absolute configuration of 1 was established by ECD calculation. Compound 1 was the first example of valerenane sesquiterpenoid bearing an aza-spiro[4.5] ring moiety, the plausible biogenetic pathway of which was proposed. Cytotoxic activities of these compounds were also evaluated.

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Using various chromatographic separations, four sesquiterpenes (1-4), including two new compounds, nanolobatols A and B (1 and 2), were isolated from the Vietnamese soft coral Sinularia nanolobata. Their structures were determined on the basis of spectroscopic data (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, NOESY and FT-ICR-MS) and by comparison with the literature values. The cytotoxic activity of isolated compounds against a panel of eight human cancer cell lines was also evaluated.

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Fifteen steroids, including two new compounds, leptosteroid (1) and 5,6ß-epoxygorgosterol (2), were isolated and structurally elucidated from the Vietnamese soft coral Sinularia leptoclados. Their cytotoxic effect against a panel of eight human cancer cell lines was evaluated using sulforhodamine B (SRB) method. Significant cytotoxicity against hepatoma cancer (HepG2, IC50=21.13±0.70 µM) and colon adenocarcinoma (SW480, IC50=28.65±1.53 µM) cell lines were observed for 1 and against acute leukemia (HL-60, IC50=20.53±2.26 µM) and SW480 (IC50=26.61±1.59 µM) for ergost-5-en-3ß,7ß-diol (8). In addition, 3ß,7ß-dihydroxyergosta-5,24(28)-diene (13) showed significant cytotoxic activity on all tested cell lines with IC50 values ranging from 13.45±1.81 to 29.01±3.21 µM.

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Four new bicyclogermacrenes, capgermacrenes D (1) E (2) F (3) and G (4) were isolated from a population of Bornean soft coral Capnella imbricata. The structures of these metabolites were elucidated based on their nuclear magnetic resonance and high-resolution electrospray ionisation mass spectrometry spectral data. These compounds showed bacteriastatic and bacteriacidal activities against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

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A methanol extract of the soft coral Sinularia microspiculata revealed five sterols, including two new compounds. Using combined chromatographic and spectroscopic experiments, the new compounds were found to be 7-oxogorgosterol (1) and 16α-hydroxysarcosterol (2). Their structures were determined on the basis of spectroscopic data ((1)H and (13)C NMR, HSQC, HMBC, (1)H-(1)H COSY, NOESY, and FT-ICR-MS) and by comparing obtained results to the values indicated in previous studies. Among the isolated compounds, 3 showed weak cytotoxic effects against HL-60 (IC50  =  89.02  ±  9.93 µM) cell line, whereas 5 was weakly active against HL-60 (IC50  =  82.80  ±  13.65 µM) and SK-Mel2 (IC50  =  72.32  ±  1.30 µM) cell lines.

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The soft coral genus Sinularia is a rich source of bioactive metabolites containing a diverse array of chemical structures. A solvent extract of Sinularia polydactyla resulted in the isolation of three new casbane diterpenes: sinularcasbane M (1), sinularcasbane N (2) and sinularcasbane O (3); in addition, known metabolites (4-5) were isolated. Compounds were elucidated on the basis of spectroscopic analyses; the absolute configuration was confirmed by X-ray analysis.

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The methanol extract of a Sinularia sp., collected from Bowden Reef, Queensland, Australia, yielded ten natural products. These included the new nitrogenous diterpene (4R*,5R*,9S*,10R*,11Z)-4-methoxy-9-((dimethylamino)-methyl)-12,15-epoxy-11(13)-en-decahydronaphthalen-16-ol (1), and the new lobane, (1R*,2R*,4S*,15E)-loba-8,10,13(14),15(16)-tetraen-17,18-diol-17-acetate (2). Also isolated were two known cembranes, sarcophytol-B and (1E,3E,7E)-11,12-epoxycembratrien-15-ol, and six known lobanes, loba-8,10,13(15)-triene-16,17,18-triol, 14,18-epoxyloba-8,10,13(15)-trien-17-ol, lobatrientriol, lobatrienolide, 14,17-epoxyloba-8,10,13(15)-trien-18-ol-18-acetate and (17R)-loba-8,10,13(15)-trien-17,18-diol. Structures of the new compounds were elucidated through interpretation of spectra obtained after extensive NMR and MS investigations and comparison with literature values. The tumour cell growth inhibition potential of 1 and 2 along with loba-8,10,13(15)-triene-16,17,18-triol, 14,17-epoxyloba-8,10,13(15)-trien-18-ol-18-acetate, lobatrienolide, (1E,3E,7E)-11,12-epoxycembratrien-15-ol and sarcophytol-B were assessed against three human tumour cell lines (SF-268, MCF-7 and H460). The lobanes and cembranes tested demonstrated 50% growth inhibition in the range 6.8-18.5 µM, with no selectivity, whilst 1 was less active (GI50 70-175 µM).

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