The Invasive Anemone Condylactis sp. of the Coral Reef as a Source of Sulfur- and Nitrogen-Containing Metabolites and Cytotoxic 5,8-Epidioxy Steroids.

The Condylactis-genus anemones were examined for their proteinaceous poisons over 50 years ago. On the other hand, the current research focuses on isolating and describing the non-proteinaceous secondary metabolites from the invasive Condylactis anemones, which help take advantage of their population outbreak as a new source of chemical candidates and potential drug leads. From an organic extract of Condylactis sp., a 1,2,4-thiadiazole-based alkaloid, identified as 3,5-bis(3-pyridinyl)-1,2,4-thiadiazole (1), was found to be a new natural alkaloid despite being previously synthesized. The full assignment of NMR data of compound 1, based on the analysis of 2D NMR correlations, is reported herein for the first time. The proposed biosynthetic precursor thionicotinamide (2) was also isolated for the first time from nature along with nicotinamide (3), uridine (5), hypoxanthine (6), and four 5,8-epidioxysteroids (7-10). A major secondary metabolite (-)-betonicine (4) was isolated from Condylactis sp. and found for the first time in marine invertebrates. The four 5,8-epidioxysteroids, among other metabolites, exhibited cytotoxicity (IC50 3.5-9.0 µg/mL) toward five cancer cell lines.

New Verticillene Diterpenoids, Eudesmane Sesquiterpenoids, and Hydroperoxysteroids from the Further Chemical Investigation of a Taiwanese Soft Coral Cespitularia sp.

An investigation of the chemical composition of a Formosan soft coral Cespitularia sp. led to the discovery of one new verticillene-type diterpenoid, cespitulactam M (1); one new eudesmane sesquiterpenoid, cespilamide F (2); and three new hydroperoxysteroids (3-5) along with twelve known analogous metabolites (6-17). In addition, one new derivative, cespitulactam M-6,2'-diacetate (1a), was prepared from compound 1. The structures were determined by detailed spectroscopic analyses, particularly HRESIMS and NMR techniques. Moreover, the in vitro cytotoxicity, anti-inflammatory, and antibacterial activity of 1-17 and 1a were evaluated.

Isosarcophytoxide Derivatives with a 2,5-Dihydrofuran Moiety from the Soft Coral Sarcophyton cinereum.

The present chemical investigation on the organic extract of the soft coral Sarcophyton cinereum has contributed to the isolation of four new cembranoids: 16ß- and 16α-hydroperoxyisosarcophytoxides (1 and 2), 16ß- and 16α-methoxyisosarcophytoxides (3 and 4), and a known cembranoid, lobocrasol (5). The structures of all isolates were elucidated by detailed spectroscopic analysis. Their structures were characterized by a 2,5-dihydrofuran moiety, of which the relative configuration was determined by DU8-based calculation for long-range coupling constants (4JH,H). The cytotoxicity and immunosuppressive activities of all isolates were evaluated in this study.

Computationally Assisted Structural Elucidation of Cembranoids from the Soft Coral Sarcophyton tortuosum.

A persistent study on soft coral Sarcophyton tortuosum resulted in the characterization of two new cembranolides, tortuolides A and B (1 and 2), and a new related diterpene, epi-sarcophytonolide Q. Their structures were determined not only by extensive spectroscopic analysis but also by DFT calculations of ECD and NMR data, the latter of which was combined with statistical analysis methods, e.g., DP4+ and J-DP4 approaches. Anti-inflammatory and cytotoxicity activities were evaluated in this study.

A new species of anthothelid octocoral (Cnidaria, Alcyonacea) discovered on an algal reef of Taiwan.

A molecular phylogenetic analysis of 132 octocoral species reveals a close relationship between specimens collected from the intertidal pools of the Datan Algal Reef, Taoyuan, Taiwan, and Erythropodiumcaribaeorum (Duchassaing & Michelotti, 1860), but the two species have distinct morphological features. On the basis of morphological differences in polyps and sclerites, we identify and describe a new Erythropodium species: E.taoyuanensis sp. nov. The distinct identifying features of E.taoyuanensis sp. nov. include the upright contractile polyps from thin encrusting membranes and abundant 6-radiate sclerites. Using an integrative approach, we present the findings of morphological comparisons and molecular phylogenetic analyses to demonstrate that E.taoyuanensis sp. nov. is distinct from other Erythropodium species. Our study contributes to the knowledge of octocoral biodiversity in marginal habitats.

Cembranolides and Related Constituents from the Soft Coral Sarcophyton cinereum.

In an attempt to explore the bioactive metabolites of the soft coral Sarcophyton cinereum, three new cembranolides, cinerenolides A-C (1-3), and 16 known compounds were isolated and identified from the EtOAc extract. The structures of the new cembranolides were elucidated on the basis of spectroscopic analysis, and the NOE analysis of cinerenolide A (1) was performed with the assistance of the calculated lowest-energy molecular model. The relative configuration of cinerenolide C (3) was determined by the quantum chemical NMR calculation, followed by applying DP4+ analysis. In addition, the cytotoxic assays disclosed that some compounds exhibited moderate to potent activities in the proliferation of P388, DLD-1, HuCCT-1, and CCD966SK cell lines.

Using 3D photogrammetry to quantify the subtle differences of coral reefs under the impacts of marine activities.

Marine activities may cause the degradation of coral reefs. The composition of benthic communities and seawater quality have been commonly used as the proxies to assess the impacts of marine activities. However, these proxies may not be able to detect the subtle differences within homogeneous environment. We used photogrammetry to quantify the subtle differences of structural complexity between heavily and lightly trafficked sites at Wanlitong, southern Taiwan. Our study demonstrated that the impacts of marine activities can be detected within tens of meters through quantifying structural complexity of coral reefs. Vector ruggedness measure (VRM) is a more suitable metric than conventional linear rugosity to detect such impacts. The correlations between structural complexity and coral cover have variances while comparing with previous studies. The results show that using photogrammetry to quantify the structure of coral reefs can provide a novel aspect to evaluate the subtle differences caused by marine activities.

Polyoxygenated Klysimplexane- and Eunicellin-Based Diterpenoids from the Gorgonian Briareum violaceum.

Three new polyoxygenated diterpenoids with a rare 4-isopropyl-1,5,8a-trimethylperhydrophenanthrane structure of the klysimplexane skeleton, briarols A‒C (1‒3), and one eunicellin-based diterpenoid, briarol D (4), were isolated from Briareum violaceum, a gorgonian inhabiting Taiwanese waters. The chemical structures of these compounds were determined by employing extensive analyses of NMR and high-resolution electrospray ionization mass spectrometry (HRESIMS) data. Metabolites 1‒3 were found to possess the rarely found skeleton of the diterpenoid klysimplexin T. All isolated compounds showed very weak cytotoxic activity against the growth of three cancer cell lines. A plausible biosynthetic pathway for briarols A‒C from the coexisting eunicellin diterpenoid briarol D (4) was postulated.

New secondary metabolite with cytotoxicity from spawning soft coral Asterospicularia laurae in Taiwan.

We have conducted a long-term research on the Taiwanese soft coral Asterospicularia laurae, which resulted in many xenicane-type diterpenoids such as asterolaurins A-M from A. laurae coral tissues during the non-spawning period were isolated. Here, we report a new xenicane diterpenoid, asterolaurin N (1), along with three known xenicane-type monocarbocyclic diterpenes [13-epi-9-desacetylxenicin (2), xeniolide-B 9-acetate (3) and asterolaurin I (4)] from A. laurae during the spawning period. The structures of the new secondary metabolite were established with an extensive spectroscopic analysis. The 1D and 2D nuclear magnetic resonance (NMR) data of the compounds were discussed. We discovered that the C-15 of 1 contains two methyl groups on a carbon bearing an acetyl group, which has not been reported previously. In addition, Compounds 1, 3, and 4 showed selective cytotoxic activity against Molt 4, while 2 exhibited significant cytotoxicity against Molt 4, K562, Sup-T1 and U937 cell lines.

New Biscembranoids Sardigitolides A-D and Known Cembranoid-Related Compounds from Sarcophyton digitatum: Isolation, Structure Elucidation, and Bioactivities.

Chemical examination from the cultured soft coral Sarcophyton digitatum resulted in the isolation and structural identification of four new biscembranoidal metabolites, sardigitolides A-D (1-4), along with three previously isolated biscembranoids, sarcophytolide L (5), glaucumolide A (6), glaucumolide B (7), and two known cembranoids (8 and 9). The chemical structures of all isolates were elucidated on the basis of 1D and 2D NMR spectroscopic analyses. Additionally, in order to discover bioactivity of marine natural products, 1-8 were examined in terms of their inhibitory potential against the upregulation of inflammatory factor production in lipopolysaccharide (LPS)-stimulated murine macrophage J774A.1 cells and their cytotoxicities against a limited panel of cancer cells. The anti-inflammatory results showed that at a concentration of 10 µg/mL, 6 and 8 inhibited the production of IL-1ß to 68 ± 1 and 56 ± 1%, respectively, in LPS-stimulated murine macrophages J774A.1. Furthermore, sardigitolide B (2) displayed cytotoxicities toward MCF-7 and MDA-MB-231 cancer cell lines with the IC50 values of 9.6 ± 3.0 and 14.8 ± 4.0 µg/mL, respectively.

Bioactive Capnosanes and Cembranes from the Soft Coral Klyxum flaccidum.

Two new capnosane-based diterpenoids, flaccidenol A (1) and 7-epi-pavidolide D (2), two new cembranoids, flaccidodioxide (3) and flaccidodiol (4), and three known compounds 5 to 7 were characterized from the marine soft coral Klyxum flaccidum, collected off the coast of the island of Pratas. The structures of the new compounds were determined by extensive spectroscopic analyses, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and spectroscopic data comparison with related structures. The rare capnosane diterpenoids were isolated herein from the genus Klyxum for the first time. The cytotoxicity of compounds 1 to 7 against the proliferation of a limited panel of cancer cell lines was assayed. The isolated diterpenoids also exhibited anti-inflammatory activity through suppression of superoxide anion generation and elastase release in the N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLF/CB)-stimulated human neutrophils. Furthermore, 1 and 7 also exhibited cytotoxicity toward the tested cancer cells, and 7 could effectively inhibit elastase release. It is worth noting that the biological activities of 7 are reported for the first time in this paper.

Briarenones A‒C, New Briarellin Diterpenoids from the Gorgonian Briareum violaceum.

Three new eunicellin-derived diterpenoids of briarellin type, briarenones A‒C (1‒3), were isolated from a Formosan gorgonian Briareum violaceum. The chemical structures of the compounds were elucidated on the basis of extensive spectroscopic analyses, including two-dimensional (2D) NMR. The absolute configuration of 1 was further confirmed by a single crystal X-ray diffraction analysis. The in vitro cytotoxic and anti-inflammatory potentialities of the isolated metabolites were tested against the growth of a limited panel of cancer cell lines and against the production of superoxide anions and elastase release in N-formyl-methionyl-leucyl-phenyl-alanine and cytochalasin B (fMLF/CB)-stimulated human neutrophils, respectively.

Cembranoid-Related Metabolites and Biological Activities from the Soft Coral Sinularia flexibilis.

Five new cembranoid-related diterpenoids, namely, flexibilisins D and E (1 and 2), secoflexibilisolides A and B (3 and 4), and flexibilisolide H (5), along with nine known compounds (6⁻14), were isolated from the soft coral Sinularia flexibilis. Their structures were established by extensive spectral analysis. Compound 3 possesses an unusual skeleton that could be biogenetically derived from cembranoids. The cytotoxicity and anti-inflammatory activities of the isolates were investigated, and the results showed that dehydrosinulariolide (7) and 11-epi-sinulariolide acetate (8) exhibited cytotoxicity toward a limited panel of cancer cell lines and 14-deoxycrassin (9) displayed anti-inflammatory activity by inhibition of superoxide anion generation and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLF/CB)-induced human neutrophils.

New Cembranoids and a Biscembranoid Peroxide from the Soft Coral Sarcophyton cherbonnieri.

Six new cembranoids, cherbonolides A-E (1⁻5) and bischerbolide peroxide (6), along with one known cembranoid, isosarcophine (7), were isolated from the Formosan soft coral Sarcophyton cherbonnieri. The structures of these compounds were elucidated by detailed spectroscopic analysis and chemical methods. Compound 6 was discovered to be the first example of a molecular skeleton formed from two cembranoids connected by a peroxide group. Compounds 1⁻7 were shown to have the ability of inhibiting the production of superoxide anions and elastase release in N-formyl-methionyl-leucyl-phenyl-alanine/cytochalasin B (fMLF/CB)-induced human neutrophils.

Isolation and Structure Elucidation of Cembranoids from a Dongsha Atoll Soft Coral Sarcophyton stellatum.

Six new polyoxygenated cembrane-based diterpenoids, stellatumolides A⁻C (1⁻3), stellatumonins A and B (4 and 5), and stellatumonone (6), were isolated together with ten known related compounds (7⁻16) from the ethyl acetate (EtOAc) extract of soft coral Sarcophyton stellatum. The structures of the new compounds were established by extensive spectroscopic analyses, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and data comparison with related structures. Compounds 8 and 14 were isolated from a natural source for the first time. The isolated metabolites were shown to be not cytotoxic against a limited panel of cancer cells. Compound 9 showed anti-inflammatory activity by reducing the expression of proinflammatory cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proteins in lipopolysaccharide (LPS)-stimulated mouse leukaemic monocyte macrophage (RAW 264.7) cells.

Anti-Inflammatory Polyoxygenated Steroids from the Soft Coral Lobophytum michaelae.

Three new polyoxygenated steroids, michosterols A-C (1-3), and four known compounds (4-7) were isolated from the ethyl acetate (EtOAc) extract of the soft coral Lobophytum michaelae, collected off the coast of Taitung. The structures of the new compounds were elucidated on the basis of spectroscopic analyses and comparison of the nuclear magnetic resonance (NMR) data with related steroids. The cytotoxicity of compounds 1-3 against the proliferation of a limited panel of cancer cell lines was assayed. Compound 1 was found to display moderate cytotoxicity against adenocarcinomic human alveolar basal epithelial (A549) cancer cells. It also exhibited potent anti-inflammatory activity by suppressing superoxide anion generation and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-stimulated human neutrophils. Furthermore, 3 could effectively inhibit elastase release, as well.

The Octocorals of Dongsha Atoll (South China Sea): An Iterative Approach to Species Identification Using Classical Taxonomy and Molecular Barcodes.

Yehuda Benayahu, Leendert Pieter van Ofwegen, Chang-feng Dai, Ming-Shiou Jeng, Keryea Soong, Alex Shlagman, Samuel W. Du, Prudence Hong, Nimrah H. Imam, Alice Chung, Tiana Wu, and Catherine S. McFadden (2018) Surveys of octocorals from Dongsha Atoll, Taiwan were conducted during 2011, 2013 and 2015 by SCUBA at a depth range of 6-25 m. The collections yielded ~540 specimens, encompassing the variety of taxa occurring in the explored sites; estimates of their abundances were also recorded. Dongsha features a highly diverse octocoral fauna, and octocorals are the dominant benthic organisms in the surveyed reef sites, often covering the majority of the hard substratum. Specimens were identified to the genus and species levels based on an iterative approach that integrates classical taxonomy with character-based molecular barcodes. A total of 51 nominal species representing 20 genera belonging to seven families were recorded, plus ~30 colonies that could only be assigned to a genus. Members of the family Alcyoniidae were the most abundant and diverse taxa, with 27 nominal species plus at least one potentially new, undescribed species of Sinularia, and 5-7 species each of Cladiella, Lobophytum and Sarcophyton. Problems with the taxonomic identification and phylogenetic relationships of species in these genera are discussed. The peculiarity of the Dongsha octocoral species composition is noted, and the composition is also compared to the other Taiwanese reef systems.

Anti-Inflammatory Lobane and Prenyleudesmane Diterpenoids from the Soft Coral Lobophytum varium.

New lobane-based diterpenoids lobovarols A-D (1-4) and a prenyleudesmane-type diterpenoid lobovarol E (5) along with seven known related diterpenoids (6-12) were isolated from the ethyl acetate extract of a Taiwanese soft coral Lobophytum varium. Their structures were identified on the basis of multiple spectroscopic analyses and spectral comparison. The absolute configuration at C-16 of the known compound 11 is reported herein for the first time. The anti-inflammatory activities of compounds 1-12 were assessed by measuring their inhibitory effect on N-formyl-methionyl-leucyl-phenyl-alanine/cytochalasin B (fMLP/CB)-induced superoxide anion generation and elastase release in human neutrophils. Metabolites 2, 5, and 11 were found to show moderate inhibitory activity on the generation of superoxide anion, while compounds 5, 8, 11, and 12 could effectively suppress elastase release in fMLP/CB-stimulated human neutrophil cells at 10 µM. All of the isolated diterpenoids did not exhibit cytotoxic activity (IC50 > 50 µM) towards a limited panel of cancer cell lines.

Bioactive Steroids with Methyl Ester Group in the Side Chain from a Reef Soft Coral Sinularia brassica Cultured in a Tank.

A continuing chemical investigation of the ethyl acetate (EtOAc) extract of a reef soft coral Sinularia brassica, which was cultured in a tank, afforded four new steroids with methyl ester groups, sinubrasones A-D (1-4) for the first time. In particular, 1 possesses a ß-D-xylopyranose. The structures of the new compounds were elucidated on the basis of spectroscopic analyses. The cytotoxicities of compounds 1-4 against the proliferation of a limited panel of cancer cell lines were assayed. The anti-inflammatory activities of these new compounds 1-4 were also evaluated by measuring their ability to suppress superoxide anion generation and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-induced human neutrophils. Compounds 2 and 3 were shown to exhibit significant cytotoxicity, and compounds 3 and 4 were also found to display attracting anti-inflammatory activities.

Isoprenoids from the Soft Coral Sarcophyton glaucum.

Five new isoprenoids, 3,4,8,16-tetra-epi-lobocrasol (1), 1,15ß-epoxy-deoxysarcophine (2), 3,4-dihydro-4α,7ß,8α-trihydroxy-Δ²-sarcophine (3), ent-sarcophyolide E (4), and 16-deacetyl- halicrasterol B (5) and ten known compounds 6‒15, were characterized from the marine soft coral Sarcophyton glaucum, collected off Taitung coastline. Their structures were defined by analyzing spectra data, especially 2D NMR and electronic circular dichroism (ECD). The structure of the known compound lobocrasol (7) was revised. Cytotoxicity potential of the isolated compounds was reported, too.