Three new cembranoids from the Taiwanese soft coral Sarcophyton ehrenbergi

Investigating the hepatoprotective potentiality of marine-derived steroids as promising inhibitors of liver fibrosis

It has been reported that organic extracts derived from soft corals belonging to the genus Sarcophyton have exhibited a wide range of therapeutic characteristics. Based on biochemical and histological techniques, we aimed to assess the hepatoprotective role of the organic extract and its principal steroidal contents derived from the Red Sea soft coral Sarcophyton glaucum on acetaminophen-induced liver fibrosis in rats. Serum liver function parameters (ALT, AST, ALP and total bilirubin) were quantified using a spectrophotometer, and both alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) levels were determined by using enzyme-linked immunosorbent assay (ELISA) kits while transformed growth factor beta (TGF-β) and tumor necrosis factor α (TNF-α) in liver tissue homogenate were determined using ELISA, and TGF-β and TNF-α gene expression in liver tissue was determined using real-time PCR following extraction and purification. Histopathological alterations in hepatic tissue were also examined under a microscope. In order to prioritize the isolation and characterization of the most promising marine steroids from the organic extract of the Red Sea soft coral Sarcophyton glaucum as hepatoprotective agents, a computational approach was employed. This approach involved molecular docking (MDock) and analysis of the structure-activity relationship (SAR) against glutathione-S-transferase (GST) and Cu-Zn human superoxide dismutase (Cu-ZnSOD) enzymes. Although the major role in the detoxification of foreign chemicals and toxic metabolites of GST and SOD enzymes is known, there is a lack of knowledge about the mode of action of the hepatoprotective process and those of the targets involved. The present study investigated the multiple interactions of a series of marine steroids with the GST and SOD enzymes, in order to reveal insights into the process of hepatoprotection.

Cembrane diterpenoids: Chemistry and pharmacological activities

Cembrane diterpenoids (cembranoids), characterized by a 14-membered carbon ring and wide variety of functional groups, found in marine and terrestrial organisms. Many studies have shown that cembrane diterpenoids have cytotoxic and anti-inflammatory activities and are widely used in the development of new drugs. This review covered publications from 2011 to 2022 and classified the cembrane-type diterpenoids into isopropyl (ene) type, γ-lactone or unsaturated five-membered ring, δ-lactone or unsaturated six-membered ring, ε-lactone or unsaturated seven-membered ring, and other cembrane diterpenes. In addition, the biological activity and structure-activity relationship were summarized. This will provide guidance for new cembrane-type diterpenes as lead compounds to explore their potential application for treating cancer and inflammatory diseases.

Isolation of moderately halotolerant bacterial strains, associated with coral Porites lutea from Gulf of Kachchh: Antibacterial activity and PHB production

The marine ecosystem contains a solution for food, shelter, pharmaceutical problems and has a key role in the economy of the country as tourism. The Gulf of Kachchh, known for its high tides and the coral reefs are less explored for its antibiotic activity due to the coral bleaching and diseases. The bacterial strains in the coral Porites lutea are determined to possess antibiotic activity against bacterial strains such as E.coli, P. aeruginosa, S. aureus and S. faecalis. Among thirty bacterial strains isolated from the tissue, skeleton and mucus, two bacterial strains resulted in the better antagonistic activity. The antibiotic compound extracted from both the bacteria elucidated to be 4-[(2E)-4-hydroxypent-2-en-1-yl]-5,6-dihydro-2H-pyran-2-one. Further, through ADMET prediction it was inferred that it is an effective drug lead as it reports less toxicity and better drug-likeliness. The study also includes the effect of Poly Hydroxy Butarate (PHB) production by the isolated bacterial strain.

Potential of Marine Terpenoids against SARS-CoV-2: An In Silico Drug Development Approach

In an emergency, drug repurposing is the best alternative option against newly emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. However, several bioactive natural products have shown potential against SARS-CoV-2 in recent studies. The present study selected sixty-eight broad-spectrum antiviral marine terpenoids and performed molecular docking against two novel SARS-CoV-2 enzymes (main protease or M^pro or 3CL^pro) and RNA-dependent RNA polymerase (RdRp). In addition, the present study analysed the physiochemical-toxicity-pharmacokinetic profile, structural activity relationship, and phylogenetic tree with various computational tools to select the 'lead' candidate. The genomic diversity study with multiple sequence analyses and phylogenetic tree confirmed that the newly emerged SARS-CoV-2 strain was up to 96% structurally similar to existing CoV-strains. Furthermore, the anti-SARS-CoV-2 potency based on a protein-ligand docking score (kcal/mol) exposed that the marine terpenoid brevione F (-8.4) and stachyflin (-8.4) exhibited similar activity with the reference antiviral drugs lopinavir (-8.4) and darunavir (-7.5) against the target SARS-CoV-M^pro. Similarly, marine terpenoids such as xiamycin (-9.3), thyrsiferol (-9.2), liouvilloside B (-8.9), liouvilloside A (-8.8), and stachyflin (-8.7) exhibited comparatively higher docking scores than the referral drug remdesivir (-7.4), and favipiravir (-5.7) against the target SARS-CoV-2-RdRp. The above in silico investigations concluded that stachyflin is the most 'lead' candidate with the most potential against SARS-CoV-2. Previously, stachyflin also exhibited potential activity against HSV-1 and CoV-A59 within IC₅₀, 0.16-0.82 µM. Therefore, some additional pharmacological studies are needed to develop 'stachyflin' as a drug against SARS-CoV-2.

New Hydroquinone Monoterpenoid and Cembranoid-Related Metabolites from the Soft Coral Sarcophyton tenuispiculatum

Chemical investigation of the marine soft coral Sarcophyton tenuispiculatum resulted in the isolation of a 1,4-dihydrobenzoquinone, sarcotenuhydroquinone (1), three new cembranoids, sarcotenusenes A‒C (2‒4), and ten previously reported metabolites 5–14. The chemical structures of all isolated metabolites were determined by detailed spectroscopic analyses. In biological assays, anti-inflammatory, cytotoxic, and peroxisome proliferator-activated receptor γ (PPAR-γ) transcription factor assays of all compounds were performed. None of the isolated compounds were found to exhibit activity in the PPAR-γ transcription factor assay. The anti-inflammatory assays showed that (+)-7α,8β-dihydroxydeepoxysarcophine (13) inhibited the production of IL-1β to 56 ± 1% at a concentration of 30 µM in lipopolysaccharide (LPS)-stimulated J774A.1 macrophage cells. In addition, 1 and 2 were found to exhibit cytotoxicity towards a panel of cancer cell lines.

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.

Coral and Coral-Associated Microorganisms: A Prolific Source of Potential Bioactive Natural Products

Marine invertebrates and their associated microorganisms are rich sources of bioactive compounds. Among them, coral and its associated microorganisms are promising providers of marine bioactive compounds. The present review provides an overview of bioactive compounds that are produced by corals and coral-associated microorganisms, covering the literature from 2010 to March 2019. Accordingly, 245 natural products that possess a wide range of potent bioactivities, such as anti-inflammatory, cytotoxic, antimicrobial, antivirus, and antifouling activities, among others, are described in this review.

Coral and Coral-Associated Microorganisms: A Prolific Source of Potential Bioactive Natural Products

Marine invertebrates and their associated microorganisms are rich sources of bioactive compounds. Among them, coral and its associated microorganisms are promising providers of marine bioactive compounds. The present review provides an overview of bioactive compounds that are produced by corals and coral-associated microorganisms, covering the literature from 2010 to March 2019. Accordingly, 245 natural products that possess a wide range of potent bioactivities, such as anti-inflammatory, cytotoxic, antimicrobial, antivirus, and antifouling activities, among others, are described in this review.

Sarcoehrenbergilides D–F: cytotoxic cembrene diterpenoids from the soft coral Sarcophyton ehrenbergi

A solvent extract of the soft coral Sarcophyton ehrenbergi afforded cembrene diterpenoids, sarcoehrenbergilid D–F (1–3). Chemical structures were established by modern spectroscopic techniques with absolute stereochemistries determined by circular dichroism (CD) and time-dependent density functional theory electronic CD calculations (TDDFT-ECD). Cytotoxicity activities for 1–3 were evaluated against three human cancer cell lines: lung (A549), colon (Caco-2) and liver (HepG2).

A solvent extract of the soft coral Sarcophyton ehrenbergi afforded cembrene diterpenoids, sarcoehrenbergilid D–F (1–3).

Antimicrobials from Cnidarians. A New Perspective for Anti-Infective Therapy?

The ability of microbes to counter the scientific and therapeutic advancements achieved during the second half of the twentieth century to provide effective disease treatments is currently a significant challenge for researchers in biology and medicine. The discovery of antibiotics, and the subsequent development of synthetic antimicrobial compounds, altered our therapeutic approach towards infectious diseases, and improved the quality and length of life for humans and other organisms. The current alarming rise in cases of antibiotic-resistance has forced biomedical researchers to explore new ways to recognize and/or produce new antimicrobials or to find other approaches for existing therapeutics. Aquatic organisms are known to be a source of compounds having the potential to play a role in fighting the battle against pathogenic microbes. In this connection, cnidarians occupy a pre-eminent role. Over the past few decades several studies have explored the antimicrobial/antibiotic properties of cnidarian extracts with the aim of isolating compounds possessing useful therapeutic features. This paper aims to review the existing data on this subject, taking into account the possible utilization of identified compounds.

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.

Isolation, structural assignment and synthesis of (SE)-2-methyloctyl 3-(4-methoxyphenyl) propenoate from the marine soft coral Sarcophyton ehrenbergi

A new metabolite 1 has been isolated from the marine soft coral Sarcophyton ehrenbergi along with two known diterpenoids 2 and 3 and cholesterol 4. The structure of 1 was determined by means of detailed spectroscopic analysis and unambiguously confirmed to have the S configuration by the synthesis of both enantiomers using 4-benzyl-2-oxazolidinone auxiliaries. (S)- and (R)-1, 3 and some of the synthetic intermediates were evaluated for cytotoxic activity against human lung cancer (A549), prostate cancer (DU145), cervical cancer (HeLa) and breast cancer (MCF-7) cell lines in an in vitro bioassay.

New cytotoxic isoprenoid derivatives from the Red Sea soft coral Sarcophyton glaucum

Chemical investigation of the soft coral Sarcophyton glaucum collected from the Red Sea led to isolation of 11 isoprenoidal metabolites (1-11). A new sesquiterpenoid, 6-oxo-germacra-4(15),8,11-triene (1), a new natural cembranoid, sarcophinediol, along with two known sesquiterpenoids (2 and 3) and seven known cembranoids (5-11) was obtained. The structures of the compounds were established based on their NMR, MS, IR and UV spectral data. All compounds were evaluated for their cytotoxicity employing three cancer cell lines (HepG2, MCF-7 and HCT116). Compounds 4 and 6 showed significant cytotoxicity towards HepG2 with IC50 values of 18.8 ± 0.07 and 19.9 ± 0.02 μM; respectively. Compounds 5-7 exhibited potent cytotoxicity against MCF-7 cells with IC50 values of 9.9 ± 0.03, 2.4 ± 0.04 and 3.2 ± 0.02 μM, respectively. Compounds 1, 4 and 5 showed significant activities towards HCT116 cells with IC50 values of 29.4 ± 0.03, 19.4 ± 0.02 and 25.8 ± 0.03 μM, respectively.

New terpenes from the Egyptian soft coral Sarcophyton ehrenbergi

Chemical investigations of the Egyptian soft coral Sarcophyton ehrenbergi have led to the isolation of compounds 1-3 as well as the previously reported marine cembranoid diterpene sarcophine (4). Structures were elucidated by comprehensive NMR and HRMS experimentation. Isolated compounds were in vitro assayed for cytotoxic activity against human hepatocarcinoma (HepG2) and breast adenocarcinoma (MCF-7) cell lines.

Marine natural products

This review covers the literature published in 2012 for marine natural products, with 1035 citations (673 for the period January to December 2012) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1241 for 2012), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Tortuosenes A and B, new diterpenoid metabolites from the Formosan soft coral Sarcophyton tortuosum

Tortuosenes A and B (1 and 2), possessing new diterpenoid molecular structures, were isolated from the Formosan soft coral Sarcophyton tortuosum along with a known cembrane, emblide (3). The structures of 1 and 2 were established by extensive spectroscopic analysis, and the absolute configuration of 1 was determined by TDDFT ECD calculations. Tortuosene A was found to display significant inhibitory effects on the generation of the superoxide anion in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-induced neutrophils.

Bioactive cembranoids, sarcocrassocolides P-R, from the Dongsha Atoll soft coral Sarcophyton crassocaule

New cembranoids, sarcocrassocolides P–R (1–3) and four known compounds (4–7) were isolated from the soft coral Sarcophyton crassocaule. The structures of the metabolites were determined by extensive spectroscopic analysis. Compounds 3–5 and 7 were shown to exhibit cytotoxicity toward a limited panel of cancer cell lines and all compounds 1–7 displayed potent in vitro anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells by inhibiting the expression of inducible nitric oxide synthase (iNOS) protein. Compound 7 also showed significant activity in reducing the accumulation of cyclooxygenase-2 (COX-2) protein in the same macrophage cells.

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.