Two new bicyclic cembranolides from a new Sarcophyton species and determination of the absolute configuration of sarcoglaucol-16-one

Guided Isolation of An Uncommon Cembranoid Orthoester, Sarcotortin A, and Three Skeletal Diverse Terpenoids from the Hainan Soft Coral Sarcophyton tortuosum Based on Molecular Networking Strategy

Applying the emerging molecular networking strategy, an uncommon cembranoid orthoester, sarcotortin A (1), featuring a 3/14/8/5-fused scaffold, an unusual eunicellane-type diterpenoid, sarcotorolide A (2), and two new biscembranoids, ximaolides M and N (7 and 8), along with nine known terpenoids 3-6 and 9-13 were isolated from the Hainan soft coral Sarcophyton tortuosum. The structure and absolute configuration of all new compounds were established by a combination of spectroscopic data, X-ray diffraction analysis, and/or quantum chemical computational approaches. The plausible biogenetic relationship among these skeletally different terpenoids was proposed and discussed. In in vitro bioassay, new compound 7 exhibited a remarkable inhibitory activity against protein tyrosine phosphatases 1B (PTP1B) with the IC₅₀ value of 8.06 μM. In addition, compounds 4 and 10 displayed significant inhibitory effects on lipopolysaccharide (LPS)-induced inflammatory responses in RAW264.7 macrophages cells with the IC₅₀ values of 19.13 and 16.45 μM, respectively. Compound 9 showed interesting cytotoxicity against H1975, MDA-MB231, A549, and H1299 cancer cell lines with IC₅₀ values of 31.59, 34.96, 43.87, and 27.93 μM, respectively.

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.

Diversity-oriented synthesis of cembranoid derivatives as potential anti-inflammatory agents

Eleven novel cembranoid derivatives were designed, synthesized, and evaluated for their inflammation related activities on the basis of our isolated and previously reported anti-inflammatory marine cembranoids. In bioassay, compound 11 displayed the most promising inhibitory effects with IC₅₀ value of 1.1 μM for the TNF-α inhibitory activity. The further mechanism study of 11 on the inflammatory signaling transduction of RAW264.7 cells was also performed. This research may give an insight for the discovery of marine cembranoid derived anti-inflammatory drug leads.

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-1β 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.

Chemical Diversity in Species Belonging to Soft Coral Genus Sacrophyton and Its Impact on Biological Activity: A Review

One of the most widely distributed soft coral species, found especially in shallow waters of the Indo-Pacific region, Red Sea, Mediterranean Sea, and also the Arctic, is genus Sacrophyton. The total number of species belonging to it was estimated to be 40. Sarcophyton species are considered to be a reservoir of bioactive natural metabolites. Secondary metabolites isolated from members belonging to this genus show great chemical diversity. They are rich in terpenoids, in particular, cembranoids diterpenes, tetratepenoids, triterpenoids, and ceramide, in addition to steroids, sesquiterpenes, and fatty acids. They showed a broad range of potent biological activities, such as antitumor, neuroprotective, antimicrobial, antiviral, antidiabetic, antifouling, and anti-inflammatory activity. This review presents all isolated secondary metabolites from species of genera Sacrophyton, as well as their reported biological activities covering a period of about two decades (1998-2019). It deals with 481 metabolites, including 323 diterpenes, 39 biscembranoids, 11 sesquiterpenes, 53 polyoxygenated sterols, and 55 miscellaneous and their pharmacological activities.

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

Phyllodesmium longicirrum is the largest aeolidoidean species known to date, and extremely rich in terpenoid chemistry. Herein we report the isolation of a total of 19 secondary metabolites from a single specimen of this species, i.e., steroids 1-4, cembranoid diterpenes 5-13, complex biscembranoids 14 and 15, and the chatancin-type diterpenes 16-19. These compounds resemble those from soft corals of the genus Sarcophyton, of which to date, however, only S. trocheliophorum is described as a food source for P. longicirrum. Fish feeding deterrent activity was determined using the tropical puffer fish Canthigaster solandri, and showed activity for (2S)-isosarcophytoxide (10), cembranoid bisepoxide 12 and 4-oxochatancin (16). Determining the metabolome of P. longicirrum and its bioactivity, makes it evident that this seemingly vulnerable soft bodied animal is well protected from fish by its chemical arsenal.

Bioactive cembranoids from the South China Sea soft coral Sarcophyton elegans

Four new cembranoids, sarcophelegans A–D (1–4) and six known analogues (5–10) were isolated from the South China Sea soft coral Sarcophyton elegans. Their structures were elucidated through detailed spectroscopic analysis, and the absolute configuration of 1 was confirmed by single-crystal X-ray diffraction. The antimigratory potential of compounds 1–10 were evaluated and compounds 2 and 6 were found to inhibit human breast tumor MDA-MB-231 cell migration at 10 μM.

Polyoxygenated cembrane diterpenoids from the soft coral Sarcophyton ehrenbergi

Five new polyoxygenated cembranoids, named (+)-1,15-epoxy-2-methoxy-12-methoxycarbonyl-11E-sarcophytoxide (1), (+)-2-epi-12-methoxycarbonyl-11E-sarcophine (2), 3,4-epoxyehrenberoxide A (3), ehrenbergol D (4) and ehrenbergol E (5), were obtained from the soft coral Sarcophyton ehrenbergi. The structures of 1–5 were established on the basis of comprehensive NMR and HR-ESI-MS analyses and by comparison with reported data in the literature. Compounds 4 and 5 showed moderate cytotoxicity against P-388 (mouse lymphocytic leukemia) cancer cell line with EC₅₀ values of 2.0 and 3.0 μM, respectively. Compound 2 exhibited slight antiviral activity against HCMV (human cytomegalovirus) with IC₅₀ values of 25.0 μg/mL.

Terpenes from the soft corals of the genus Sarcophyton: chemistry and biological activities

This review covers structural diversity and biological activities of terpenes from soft corals of the genus of Sarcophyton, reported from 1995 to July, 2011. During this period, besides undefined species, 16 species of the genus Sarcophyton, from different geographical areas, had been chemically examined. Two hundred and five terpenes had been isolated from this genus, including eleven sesquiterpenes, 165 diterpenes, 29 biscembranoids, some of which had novel skeletons. They exhibited various biological features, such as antifeedant, anti-inflammatory, antiviral, and antifouling activities.

New diterpenoids from soft coral Sarcophyton ehrenbergi

Continuing chemical investigation on the acetone extracts of the soft coral Sarcophyton ehrenbergi collected off the coast of San-hsian-tai, Taitong County, Taiwan led to the isolation of two new diterpenoids, ehrenbergol C and acetyl ehrenberoxide B (1 and 2). The structures of these isolated metabolites were elucidated through extensive spectroscopic analyses. Moreover, in vitro tests show that compounds 1 and 2 displayed antiviral activity towards human cytomegalovirus, with EC₅₀ of 20 and 8.0 µg/mL, respectively.

Three new cembranoids from the Taiwanese soft coral Sarcophyton ehrenbergi

In order to search for new bioactive substances from marine organisms, we have investigated the acetone extracts of the soft coral Sarcophyton ehrenbergi collected at San-Hsian-Tai, Taitong County, Taiwan. Chromatographic fractionation of the extracts of the octocoral S. ehrenbergi led to the isolation of three new cembranoids, (+)-12-ethoxycarbonyl-11Z-sarcophine (1), ehrenbergol A and B (2 and 3). The structures of these isolated metabolites were elucidated through extensive spectroscopic analyses. Moreover, metabolites 1-3 were evaluated in vitro for their cytotoxicity towards selected cancer cell lines and antiviral activity against human cytomegalovirus (HCMV).

Bioactive hydroperoxyl cembranoids from the Red Sea soft coral Sarcophyton glaucum

A chemical investigation of an ethyl acetate extract of the Red Sea soft coral Sarcophyton glaucum has led to the isolation of two peroxide diterpenes, 11(S) hydroperoxylsarcoph-12(20)-ene (1), and 12(S)-hydroperoxylsarcoph-10-ene (2), as well as 8-epi-sarcophinone (3). In addition to these three new compounds, two known structures were identified including: ent-sarcophine (4) and sarcophine (5). Structures were elucidated by spectroscopic analysis, with the relative configuration of 1 and 2 confirmed by X-ray diffraction. Isolated compounds were found to be inhibitors of cytochrome P₄₅₀ 1A activity as well as inducers of glutathione S-transferases (GST), quinone reductase (QR), and epoxide hydrolase (mEH) establishing chemo-preventive and tumor anti-initiating activity for these characterized metabolites.

Cytotoxic Cembranoids from the Red Sea Soft Coral Sarcophyton glaucum

One new cembrane diterpene, 2 R,7 R,8 R-dihydroxydeepoxysarcophine (1), together with three known compounds, 7α,8β-dihydroxy-deepoxysarcophine (2), 7β-acetoxy-8α-hydroxydeepoxysarcophine (3), and sarcophine (4), have been isolated from the Red Sea soft coral Sarcophyton glaucum. Their structures were determined using 1D and 2D NMR spectroscopy. 7β-Acetoxy-8α-hydroxydeepoxysarcophine (3) exhibits cytotoxic activity against HepG2, HCT-116, and HeLa cells with IC50 values of 3.6, 2.3, and 6.7 μg/mL, respectively.

Identification and evaluation of soft coral diterpenes as inhibitors of HIF-2α induced gene expression

Kidney cancer was the cause of almost 13,000 deaths in the United States in 2009. Loss of function of the VHL tumor suppressor gene (von Hippel-Lindau disease) dramatically increases the risk of developing clear cell kidney cancer. The VHL protein is best understood for its regulation of hypoxia inducible factor (HIF). HIF responds to changes in oxygen levels in the cell and is responsible for mediating the transcriptional response to hypoxia. Of the three known HIFα gene products, HIF-2α appears to play a fundamental role in renal carcinoma. A high throughput screen was developed to identify small molecule inhibitors of HIF-2 gene expression. The screen was performed and yielded 153 confirmed active natural product extracts. Three of the active extracts were from marine soft corals of the order Alcyonacea: Sarcophyton sp., Lobophytum sarcophytoides and Asterospicularia laurae. Bioassay-guided fractionation led to the isolation of two new cembrane diterpenes, (4Z,8S*,9R*,12E,14E)-9-hydroxy-1-(prop-1-en-2-yl)-8,12-dimethyl-oxabicyclo[9.3.2]-hexadeca-4,12,14-trien-18-one (1), and (1E,3E,7R*,8R*,11E)-1-(2-methoxypropan-2-yl)-4,8,12-trimethyloxabicyclo[12.1.0]-pentadeca-1,3,11-triene (7), as well as eight known compounds, 2-6 and 8-10.

Cembranoids from the octocoral Sarcophyton ehrenbergi

Chemical investigation of the octocoral Sarcophyton ehrenbergi led to the isolation of six new cembranoids, (+)-12-carboxy-11Z-sarcophytoxide (1), (+)-12-methoxycarbonyl-11Z-sarcophine (3), ehrenberoxides A-C (4-6), and lobophynin C (2), along with two known compounds, (+)-sarcophytoxide (7) and (+)-sarcophine (8). The structures of these isolated metabolites were elucidated through extensive spectroscopic analyses, while the relative configuration of 1 was confirmed by X-ray diffraction analyses. The chemical evidence combined with spectroscopic and physical data suggested that the locations of the epoxide and the methyl carboxylate for lobophynin C should be exchanged. Moreover, metabolites 1-6 were evaluated in vitro for their cytotoxicity against selected cancer and normal cells lines, antiviral activity against human cytomegalovirus, and antibacterial activity against Salmonella enteritidis.

Cembrane diterpenoids from the taiwanese soft coral Sarcophyton stolidotum

Investigation of an EtOAc-soluble extract of the soft coral Sarcophyton stolidotum resulted in the isolation of seven new 14-membered carbocyclic cembranes, sarcostolides A-G (1-7), together with two known cembrane diterpenes, isosarcophytoxide and isosarcophine. The structural elucidation of these metabolites was determined on the basis of spectroscopic analyses, particularly 2D NMR techniques. Sarcostolide E (5) exhibited weak to moderate cytotoxic activity against human WiDr and Daoy tumor cell lines. A biogenetic pathway and relationship for compounds 1-7 was also proposed.

Biocatalytic and antimetastatic studies of the marine cembranoids sarcophine and 2-epi-16-deoxysarcophine

The soft coral Sarcophyton glaucum is a rich resource of several bioactive cembranoids. Sarcophytol A (1) and sarcophine (2) are cembranoid diterpenes reported from this soft coral and extensively investigated for their cancer chemopreventive properties. This study aimed at investigating the antimetastatic potential of the major cembranoids, sarcophine (2) and 2-epi-16-deoxysarcophine (3), from the Red Sea soft coral S. glaucum. Biocatalytic transformation of 3 using Rhizopus stolonifer ATCC 6227a and Absidia spinosa ATCC 6648 afforded four new metabolites, 5-7 and 9, along with the known 9alpha-hydroxysarcophine (8). Sarcophine, 2-epi-16-deoxysarcophine, and metabolites 5-9 revealed significant antimetastatic activity against the highly metastatic mouse melanoma cell line (B16B15b). Cembranoids demonstrate a great potential for further development as antimetastatic agents.

Marine natural products

This review covers the literature published in 2004 for marine natural products, with 693 citations (491 for the period January to December 2004) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (716 for 2004), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies (8), and syntheses (80), including those that lead to the revision of structures or stereochemistries, have been included.

Bioactive rearranged and halogenated semisynthetic derivatives of the marine natural product sarcophine

Cembranoids are natural diterpenes with 14-membered macrocyclic rings. The simplest natural cembranoid, (+)-cembrene, was isolated from pine oleoresin. Sarcophytols A and B are known cembranoids that inhibit tumor promotion. Sarcophine is a related cembranoid isolated from the Red Sea soft coral Sarcophyton glaucum. Sarcophine and its bioconversion products and semisynthetic derivatives are reported to possess cancer chemopreventive activity. Oxymercuration-demercuration of sarcophine using Hg(OAc)2 and NaBH4 afforded four new rearranged and hydroxylated products. Bromination of sarcophine with N-bromosuccinimide (NBS) furnished two new brominated and rearranged products. Reaction with iodine gave the known iso-sarcophinone and (+)-sarcophytoxin B. Structure elucidation was based on a combination of transition state modeling, molecular dynamics, mechanistic considerations, and 2D NMR data. The antiproliferative activity of the new products is also reported.