Isolation and Bioactivity Evaluation of Sesquiterpenes from an Alcyonarian of the Genus Lemnalia from the Saudi Arabian Red Sea

Over the last decades, soft corals have been proven a rich source of biologically active compounds, featuring a wide range of chemical structures. Herein, we investigated the chemistry of an alcyonarian of the genus Lemnalia (Neptheidae), specimens of which were collected from the coral reefs near Al Lith, on the south-west coast of Saudi Arabia. A series of chromatographic separations led to the isolation of 31 sesquiterpenes, featuring mainly the nardosinane and neolemnane carbon skeletons, among which three (13, 14 and 28) are new natural products. The metabolites isolated in sufficient amounts were evaluated in vitro in human tumor and non-cancerous cell lines for a number of biological activities, including their cytotoxic, anti-inflammatory, anti-angiogenic, and neuroprotective activities, as well as for their effect on androgen receptor (AR)-regulated transcription. Among the tested metabolites, compound 12 showed comparable neuroprotective activity to the positive control N-acetylcysteine, albeit at a 10-fold lower concentration.

New Diterpenes and Diterpene Glycosides with Antibacterial Activity from Soft Coral Lemnalia bournei

Five new biflorane-type diterpenoids, biofloranates E-I (1-5), and two new bicyclic diterpene glycosides, lemnaboursides H-I (6-7), along with the known lemnabourside, were isolated from the South China Sea soft coral Lemnalia bournei. Their chemical structures and stereochemistry were determined based on extensive spectroscopic methods, including time-dependent density functional theory (TDDFT) ECD calculations, as well as a comparison of them with the reported values. The antibacterial activities of the isolated compounds were evaluated against five pathogenic bacteria, and all of these diterpenes and diterpene glycosides showed antibacterial activities against Staphylococcus aureus and Bacillus subtilis, with MICs ranging from 4 to 64 µg/mL. In addition, these compounds did not exhibit noticeable cytotoxicities on A549, Hela, and HepG2 cancer cell lines, at 20 μM.

Lemneolemnanes A-D, Four Uncommon Sesquiterpenoids from the Soft Coral Lemnalia sp

Four undescribed sesquiterpenoids, lemneolemnanes A-D (1-4), have been isolated from the marine soft coral Lemnalia sp. The absolute configurations of the stereogenic carbons of 1-4 were determined by single-crystal X-ray crystallographic analysis. Compounds 1 and 2 are epimers at C-3 and have an unusual skeleton with a formyl group on C-6. Compound 3 possesses an uncommonly rearranged carbon skeleton, while 4 has a 6/5/5 tricyclic system. Compound 1 showed significant anti-Alzheimer's disease (AD) activity in a humanized Caenorhabditis elegans AD pathological model.

Nardosinane-related antimicrobial terpenoids from Lemnalia sp. soft coral

Ten nardosinane-related terpenoids, including five unreported nardosinane-type sesquiterpenoids, parathyrsoidins H-J and linardosinenes D-E, two unusual condensed nardosinanes, named nardosinoids A and B, together with three known related compounds, were isolated from the Xisha soft coral Lemnalia sp. Their structures were elucidated by extensive spectroscopic analysis and comparison of experimental and calculated electronic circular dichroism data. Nardosinoids A and B are the first condensates of two nardosinanes. All these compounds were evaluated for antimicrobial activity in vitro. Nardosinane-type sesquiterpenoids parathyrsoidin I and linardosinene E showed inhibitory effects against influenza A virus H1N1 (IC₅₀ 7.1 and 1.1 μM, respectively). In addition, nardosinoids A and B exhibited antibacterial activity against Bacillus subtilis (MIC 4-8 μg/mL).

Lemnalemnanes A-C, Three Rare Rearranged Sesquiterpenoids from the Soft Corals Paralemnalia thyrsoides and Lemnalia sp

Three novel sesquiterpenoids, lemnalemnanes A-C (1-3), were obtained from marine soft corals Paralemnalia thyrsoides and Lemnalia sp. Their structures were determined by 1D/2D NMR spectroscopy, HRESIMS, single-crystal X-ray diffraction analysis (Cu Kα), Mosher's method, and ECD quantum chemistry calculations. Lemnalemnane A (1) possessed an intriguing basket-like structure with a spiro[bicyclo[3.3.1]nonane-furan core, while lemnalemnanes B (2) and C (3) exhibited unusual 6/6/5 and 6/5/5 carbon skeletons, respectively. In the proposed biosynthesis pathway, 1-3 were suspected to originate from the same precursor, 4-O-deacetylparalemnolin D (4), a compound coisolated from both aforementioned species. Furthermore, lemnalemnane C (3) exhibited strong in vivo promoting-angiogenesis activity.

Chemical and biological studies on the soft coral Nephthea sp

Soft corals belonging to the family Nephtheidae have been appreciated as marine sources of diverse metabolites with promising anticancer potential. In view of that, the current work investigates the anti-proliferative potential of the crude extract, different fractions, and green synthesized silver nanoparticles (AgNPs) of the Red Sea soft coral, Nephthea sp. against a panel of tumor cell lines. The metabolic pool of the soft coral under study was also explored via an LC-HR-ESI-MS metabolomics approach, followed by molecular docking analysis of the characterized metabolites against the target proteins, EGFR, VEGFR, and HER2 (erbB2) that are known to be involved in cancer cell proliferation, growth, and survival. Overall, the n-butanol fraction of Nephthea sp. exhibited the highest inhibitory activities against MCF7 (breast cancer) and A549 (lung cancer) cell lines, with interesting IC₅₀ values of 2.30 ± 0.07 and 3.12 ± 0.10 μg ml⁻¹, respectively, whereas the maximum growth inhibition of HL60 (leukemia) cells was recorded by the total extract (IC₅₀ = 2.78 ± 0.09 μg ml⁻¹). More interestingly, the anti-proliferative potential of the total soft coral extract was evidently improved when packaged in the form of biogenic AgNPs, particularly against A549 and MCF7 tumor cells, showing IC₅₀ values of 0.72 ± 0.06 and 9.32 ± 0.57 μg ml⁻¹, respectively. On the other hand, metabolic profiling of Nephthea sp. resulted in the annotation of structurally diverse terpenoids, some of which displayed considerable binding affinities and molecular interactions with the studied target proteins, suggesting their possible contribution to the anti-proliferative properties of Nephthea sp. via inhibition of tyrosine kinases, especially the EGFR type. Taken together, the present findings highlighted the relevance of Nephthea sp. to future anticancer drug discovery and provided a base for further work on the green synthesis of a range of bioactive NPs from marine soft corals.

The cytotoxic potential of the crude extract, different fractions, and green synthesized nanoparticles of the soft coral Nephthea sp. was studied, supported by LC-HR-ESI-MS metabolomics analysis and molecular docking of the dereplicated compounds.

Different Macrophage Type Triggering as Target of the Action of Biologically Active Substances from Marine Invertebrates

Macrophages play a fundamental role in the immune system. Depending on the microenvironment stimuli, macrophages can acquire distinct phenotypes characterized with different sets of the markers of their functional activities. Polarization of macrophages towards M1 type (classical activation) is involved in inflammation and the related progression of diseases, while, in contrast, alternatively activated M2 macrophages are associated with the anti-inflammatory mechanisms. Reprogramming macrophages to switch their phenotypes could provide a new therapeutic strategy, and targeting the M1/M2 macrophage balance is a promising current trend in pharmacology. Marine invertebrates are a vast source of the variety of structurally diverse compounds with potent pharmacological activities. For years, a large number of studies concerning the immunomodulatory properties of the marine substances have been run with using some intracellular markers of immune stimulation or suppression irrespective of the possible application of marine compounds in reprogramming of macrophage activation, and only few reports clearly demonstrated the macrophage-polarizing activities of some marine compounds during the last decade. In this review, the data on the immunomodulating effects of the extracts and pure compounds of a variety of chemical structure from species of different classes of marine invertebrates are described with focus on their potential in shifting M1/M2 macrophage balance towards M1 or M2 phenotype.

Uncommon Polyoxygenated Sesquiterpenoids from South China Sea Soft Coral Lemnalia flava

A detailed chemical investigation of the Chinese soft coral Lemnalia flava yielded four new nardosinane-type sesquiterpenoids (1-4), one new neolemnane-type sesquiterpenoid (5), and one new sesquiterpenoid with an uncommon 6/9 fused bicyclic skeleton (6), together with two known related compounds (7 and 8). The structures and absolute configurations of 1-8 were determined on the basis of extensive spectroscopic data analyses, X-ray diffraction analysis, chemical reactions, and computer-assisted structural elucidation including ¹³C NMR data calculation, residual dipolar coupling based NMR analysis, and time-dependent density functional theoryelectronic circular dichroism calculation. Plausible biogenetic pathways of two uncommon sesquiterpenoids (4 and 6) were proposed.

Terpenoids from Marine Soft Coral of the Genus Lemnalia: Chemistry and Biological Activities

Lemnalia is one of the most widely-distributed marine soft coral in tropical oceans and is known to produce novel terpenoids with a broad spectrum of biological activities. This review provides the first comprehensive overview of terpenoids produced by soft coral Lemnalia since their first discovery in 1974.

(+)-Pathylactone A, a New Natural Nor-sesquiterpenoid from the Octocoral Paralemnalia thyrsoides

A new natural marine nor-sesquiterpenoid, (+)-pathylactone A (1), along with a know nor-sesquiterpenoid, napalilactoe (2), were isolated from the octocoral Paralemnalia thyrsoides. The structure of 1 was established on the basis of spectroscopic methods and by comparison of the spectral data with those of synthetic analogues. Nor-sesquiterpenoid 1 was found to inhibit the protein experssion of pro-inflammatory inducible nitric oxide synthase (iNOS) in a murine macrophage-like cell line.

New Cytotoxic Terpenoids from Soft Corals Nephthea chabroli and Paralemnalia thyrsoides

A novel cytotoxic diterpenoid, chabrolin A (1) (possessing an unprecedented terpenoid skeleton), as well as three new cytotoxic sesquiterpenoids, parathyrsoidins E-G (2-4), were isolated by cytotoxicity-guided fractionation from soft corals Nephtheachabroli and Paralemnalia thyrsoides. The structures of the new compounds were determined by extensive analysis of spectroscopic data.

Anti-inflammatory activities of natural products isolated from soft corals of Taiwan between 2008 and 2012

This review reports details on the natural products isolated from Taiwan soft corals during the period 2008–2012 focusing on their in vitro and/or in vivo anti-inflammatory activities. Chemical structures, names, and literature references are also reported. This review provides useful and specific information on potent anti-inflammatory marine metabolites for future development of immune-modulatory therapeutics.

Oxygenated ylangene-derived sesquiterpenoids from the soft coral Lemnalia philippinensis

Chemical examination of a Taiwanese soft coral Lemnalia philippinensis led to the isolation of three oxygenated ylangene-derived sesquiterpenoids 1-3, including two new metabolites, philippinlins A and B (1 and 2). The structures of these compounds were elucidated on the basis of detailed spectroscopic data. Compound 1 was shown to exhibit cytotoxicity against HepG2, MDA-MB231 and A549 cancer cell lines.

Antitumour effect of sesquiterpene (+)-chabranol on four human cancer cell lines by inducing apoptosis and autophagy

OBJECTIVE

To investigate the effects and mechanisms of sesquiterpene (+)-chabranol on proliferation of a panel of four human tumour cell lines (BGC-823, SGC-7901, SSMC-7721 and HepG2).

METHODS

Cell viability was assessed using a standard methyltetrazolium assay; cell-cycle analysis of BGC-823 cells was performed by flow cytometry. Transmission electron microscopy (TEM) was used to examine the ultrastructure of BGC-823 cells exposed to (+)-chabranol. Apoptosis was investigated by evaluating DNA laddering, using gel electrophoresis.

RESULTS

(+)-Chabranol had a marked time- and concentration-dependent inhibitory effect on BGC-823 cell proliferation. The effect was less marked in SGC-7901, SSMC-7721 and HepG2 cells. Exposure of BGC-823 cells to (+)-chabranol arrested the cell cycle at G(1). Evidence of apoptosis and autophagy was observed by TEM; DNA laddering in BGC-823 cells supported the presence of apoptosis.

CONCLUSIONS

This study suggested that (+)-chabranol has antitumour activity against BGC-823 cells, and may exert its action by inhibition of proliferation and induction of apoptosis and autophagy. With further development, (+)-chabranol may represent a potential novel treatment for poorly differentiated gastric cancer.

Parathyrsoidins A-D, four new sesquiterpenoids from the soft coral Paralemnalia thyrsoides

Four new nardosinane-type sesquiterpenoids, parathyrsoidins A–D (1–4) were isolated from the soft coral Paralemnalia thyrsoides. The structures of parathyrsoidins A–D (1–4) were determined by extensive spectral analysis and their cytotoxicity against selected cancer cell lines as well as antiviral activity against human cytomegalovirus (HCMV) were evaluated in vitro.

Marine natural products

Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) 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 (1003 for 2010), 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.

Nardosinane sesquiterpenoids from the Formosan soft coral Lemnalia flava

Four new nardosinane-type sesquiterpenoids, flavalins A-D (1-4), have been isolated from the Formosan soft coral Lemnalia flava. The structures of the new metabolites were determined by extensive spectroscopic analysis, and the structure of 2 was confirmed by X-ray diffraction analysis. A plausible biosynthetic pathway to 1 and 2 is proposed. Compound 1 was found to display dose-dependent inhibition of iNOS protein expression, and 1 and 2 were shown to possess significant neuroprotective activity.