Marine Natural Products Research Articles

Immunomodulatory and anti-angiogenesis effects of excavatolide B and its derivatives in alleviating atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin condition primarily driven by T helper 2 (Th2) cytokines, resulting in skin barrier defects, angiogenesis, and inflammatory responses. The marine natural product excavatolide B (EXCB), isolated from the Formosan Gorgonian coral Briareum stechei, exhibits anti-inflammatory and analgesic properties. To enhance solubility, EXCB is chemically modified into the derivatives EXCB-61 salt and EXCB-79. The study aims to investigate the therapeutic effects of these compounds on dinitrochlorbenzene (DNCB)-induced skin damage and to elucidate the underlying anti-inflammatory and anti-angiogenesis mechanism. In vitro, using lipopolysaccharide (LPS)-induced RAW 264.7 cells, all compounds at 10 μM significantly inhibited expression of inflammatory proteins (inducible nitric oxide synthase and cyclooxygenase-2), vascular endothelial growth factor (VEGF), and cytokines (interleukin (IL)−1β, IL-6, and IL-17A). In vivo, topical application of these compounds on DNCB-induced AD mice alleviated skin symptoms, reduced serum levels of IgE, IL-4, IL-13, IL-17, and interferon-γ, and moderated histological phenomena such as hyperplasia, inflammatory cell infiltration, and angiogenesis. The three compounds restored the expression of skin barrier-related proteins (loricrin, filaggrin, and claudin-1) and reduced the expression of angiogenesis-related proteins (VEGF and platelet endothelial cell adhesion molecule-CD31) in the tissues. This is the first study to indicate that EXCB, EXCB-61 salt, and EXCB-79 can treat AD disease by reducing inflammation and angiogenesis. Hence, they may be considered potential candidates for the development of new drugs for AD.

Computational assessment of marine natural products as LasR inhibitors for attenuating quorum sensing in Pseudomonas aeruginosa

The Quorum Sensing (QS) system in bacteria has become a focal point for researchers aiming to develop novel antimicrobials to combat multidrug-resistant bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterium, has developed resistance against a variety of antimicrobial agents, making it a formidable pathogen responsible for nosocomial infections. QS system mainly controls the expression of genes responsible for biofilm formation and virulence of bacteria. Within the QS system of P. aeruginosa, the transcription activator LasR plays a pivotal role and is an appealing target for the development of antimicrobial agents. In this study, we employed molecular docking and molecular dynamics simulations to identify potential inhibitors of LasR by screening marine natural products (MNPs) from the CMNPD database. We identified ten MNPs with excellent docking scores (less than −11.7 kcal/mol) against LasR, surpassing the binding energy of the co-crystal 3-oxo-C12-HSL (−8.594 kcal/mol) and the reference compound cladodionen (−6.71 kcal/mol). Furthermore, we selected five of these MNPs with the highest MM/GBSA binding energies for extensive 100 ns molecular simulations to assess their stability. The molecular dynamics simulations indicated three MNPs, namely CMNPD10886, CMNPD20987, and CMNPD20960, maintained high stability throughout the 100 ns simulation period, as evidenced by their root mean square deviation, root mean square fluctuation, radius of gyration, and hydrogen bond interactions within the ligand-protein complex analysis. Furthermore, essential dynamics (PCA and DCCM) were performed to analyse the correlated motion of amino acids. These findings suggest that these compounds hold potential as inhibitors of LasR, offering promising prospects for the development of treatments against infections. Communicated by Ramaswamy H. Sarma

Structural modification of natural axinelline A: Achieving reduced colitis side effects through balanced COX inhibition

Marine natural products continue to hold great promise as potential candidates for the discovery of anti-inflammatory drug. In our previous investigation, we successfully synthesized axinelline A, a naturally occurring cyclooxygenase-2 (COX-2) inhibitor, as a promising anti-inflammatory lead compound. This study was to discover novel COX inhibitors with balanced inhibition, aiming to mitigate the severe adverse effects through further structural modification of axinelline A. Of the synthetic derivatives, compound 5e showed highest COX-2 inhibitory activity and balanced COX inhibition (IC50 = 1.74 µM; selectivity ((IC50 (COX-1)/IC50(COX-2) = 16.32). The in vitro anti-inflammatory results indicated that 5e effectively suppressed the expression of pro-inflammatory mediators via the NF-κB signaling pathway rather than the MAPK signaling pathway. The in vivo ulcerative colitis assay demonstrated 5e significantly ameliorated the histological damages and showed strong protection against DSS-induced acute colitis. Therefore, our findings suggest that compound 5e exhibits potential as a promising anti-inflammatory agent with attenuated colitis-related adverse effects.

Unraveling the Red Sea soft coral Sarcophyton convolutum potentials against oxidative and inflammatory stresses in zebrafish

The Red Sea is one of the world's hotspots for biodiversity, and for marine natural products (MNPs) as well. These MNPs attract special interest for their capabilities to combat inflammatory and oxidative stress-related diseases, being some of the most serious health problems worldwide nowadays. The current study aimed to identify the bioactive ingredients of the Red Sea soft coral Sarcophyton convolutum, and to assess its protective potentials against oxidative and inflammatory stresses. Coral extract (CE) was analyzed using GC-MS and HPLC. In a protection trial, adult zebrafish were intraperitoneally injected with two doses of crab extract, i.e. 50 and 500 μg/fish in 1 % DMSO as a vehicle, then challenged with 30 μg L−1 of CuSO4 for 48 h. All groups, but the negative control one, were challenged with 30 μg L−1 of CuSO4. Total antioxidant activity, as well as mRNA levels of proinflammatory markers and antioxidant enzyme genes were measured. The results showed richness of S. convolutum extract with various bioactive ingredients, including phenolic compounds, flavonoids, alkanes, fatty acids, sesquiterpenes, and pheromone-like substances. CuSO4 significantly induced the expected signals of inflammatory and oxidative stress, reducing both the antioxidant activity and increasing proinflammatory marker genes. However, CE, especially the low dose, showed significant capability to reduce proinflammatory markers and elevating the total antioxidant activity. Therefore, we concluded that S. convolutum can be a promising source for future efforts of drug discovery and a wide spectrum of pharmaceutical products.

Applications of Quantum Chemistry in Biomimetic Syntheses of Polycyclic Furanocembrane Derivatives

AbstractThis account summarizes the guidance provided by quantum chemical calculations towards the biomimetic syntheses of polycyclic marine furanocembrane derivatives. Polycyclic furanocembrane derivatives are a group of structurally complex and biologically important marine natural products isolated from marine corals. Their syntheses are challenging due to their structural complexity. Biomimetic synthetic proposals are made and some are verified via chemical synthesis. Computational chemistry can support these biomimetic syntheses. Hence, we describe herein the synthetic and computational attempts that we have made on the biomimetic syntheses of polycyclic furanocembrane derivatives, including intricarene, bielschowskysin, providencin and plumarellide.1 Introduction2 Computational Methodology3 Introduction to Polycyclic Furanocembrane Derivatives4 Biomimetic Syntheses of Intricarene, Bielschowskysin and Providencin5 Computational Studies on the Biomimetic Synthesis of Intricarene6 Computational Studies on the Biomimetic Synthesis of Bielschowskysin7 Computational Studies on the Biomimetic Synthesis of Providencin8 Computational Studies on the Biomimetic Synthesis of Plumarellide9 Conclusion

First Description of Marinoquinoline Derivatives' Activity against Toxoplasma gondii.

Toxoplasmosis is a globally prevalent zoonotic disease with significant clinical implications, including neurotoxoplasmosis, a leading cause of cerebral lesions in AIDS patients. The current pharmacological treatments for toxoplasmosis face clinical limitations, necessitating the urgent development of new therapeutics. Natural sources have yielded diverse bioactive compounds, serving as the foundation for clinically used derivatives. The exploration of marine bacteria-derived natural products has led to marinoquinolines, which feature a pyrroloquinoline core and demonstrate in vitro and in vivo anti-Plasmodium activity. This study investigates the in vitro anti-Toxoplasma gondii potential of six marinoquinoline derivatives. Additionally, it conducts absorption, distribution, metabolism, excretion, and toxicity (ADMET) predictions, and evaluates the in vivo efficacy of one selected compound. The compounds displayed half-maximal effective concentration (EC50) values between 1.31 and 3.78 µM and half-maximal cytotoxic concentration (CC50) values ranging from 4.16 to 30.51 µM, resulting in selectivity indices (SI) from 3.18 to 20.85. MQ-1 exhibiting the highest in vitro SI, significantly reduced tachyzoite numbers in the peritoneum of RH-infected Swiss mice when it was orally administered at 12.5 mg/kg/day for eight consecutive days. Also, MQ-1 significantly reduced the cerebral parasite burden in chronically ME49 infected C57BL/6 mice when it was orally administered at 25 mg/kg/day for 10 consecutive days. These findings underscore the promising anti-T. gondii activity of marinoquinolines and their potential as novel therapeutic agents against this disease.

Identification of PLK1-PBD Inhibitors from the Library of Marine Natural Products: 3D QSAR Pharmacophore, ADMET, Scaffold Hopping, Molecular Docking, and Molecular Dynamics Study.

PLK1 is found to be highly expressed in various types of cancers, but the development of inhibitors for it has been slow. Most inhibitors are still in clinical stages, and many lack the necessary selectivity and anti-tumor effects. This study aimed to create new inhibitors for the PLK1-PBD by focusing on the PBD binding domain, which has the potential for greater selectivity. A 3D QSAR model was developed using a dataset of 112 compounds to evaluate 500 molecules. ADMET prediction was then used to select three molecules with strong drug-like characteristics. Scaffold hopping was employed to reconstruct 98 new compounds with improved drug-like properties and increased activity. Molecular docking was used to compare the efficient compound abbapolin, confirming the high-activity status of [(14S)-14-hydroxy-14-(pyridin-2-yl)tetradecyl]ammonium,[(14S)-15-(2-furyl)-14-hydroxypentadecyl]ammonium and [(14S)-14-hydroxy-14-phenyltetradecyl]ammonium. Molecular dynamics simulations and MMPBSA were conducted to evaluate the stability of the compounds in the presence of proteins. An in-depth analysis of [(14S)-15-(2-furyl)-14-hydroxypentadecyl]ammonium and [(14S)-14-hydroxy-14-phenyltetradecyl]ammonium identified them as potential candidates for PLK1 inhibitors.

Total Synthesis of Incarnatapeptins A and B

AbstractThe first total synthesis of incarnatapeptins A and B, two novel marine natural products, was accomplished from readily available (S)‐1‐benzyloxycarbonylhexahydropyridazine‐3‐carboxylic acid. This route, whose longest linear sequence was 12 steps, provided the incarnatapeptins A and B in yields of 26.5 % and 19.7 %, respectively, and enabled the structure and stereochemistry of both natural products to be unambiguously confirmed. Highlights of our synthesis include the photoredox‐mediated decarboxylative 1,4‐addition reaction and a novel and practical N‐acylation paradigm promoted by silver carbonate. The unusual facile atropisomerism of some linear peptidic intermediates was also observed by TLC analysis in the course of this work.

Total Synthesis of Incarnatapeptins A and B.

The first total synthesis of incarnatapeptins A and B, two novel marine natural products, was accomplished from readily available (S)-1-benzyloxycarbonylhexahydropyridazine-3-carboxylic acid. This route, whose longest linear sequence was 12 steps, provided the incarnatapeptins A and B in yields of 26.5 % and 19.7 %, respectively, and enabled the structure and stereochemistry of both natural products to be unambiguously confirmed. Highlights of our synthesis include the photoredox-mediated decarboxylative 1,4-addition reaction and a novel and practical N-acylation paradigm promoted by silver carbonate. The unusual facile atropisomerism of some linear peptidic intermediates was also observed by TLC analysis in the course of this work.

Exploring the potential of marine natural products in drug development: A comprehensive review

The discovery of drugs from marine natural products has witnessed a significant resurgence in recent years. A diverse range of marine organisms, including cone snails, bacteria, cyanobacteria, fungi, and halophytes, have yielded valuable compounds for drug development. These organisms contribute over 90% of the oceanic biomass, offering unique chemical properties with great potential, particularly in the field of anticancer research. The review highlights the historical successes in marine natural product-based drug discovery, emphasizing their novel chemical structures and bioactive properties. It sheds light on critical factors contributing to these discoveries, such as interdisciplinary collaborations between marine biologists, chemists, and pharmacologists, advanced isolation and characterization techniques, and the understanding of marine ecological niches. Challenges include limited supply, environmental concerns, and the complexity of chemical synthesis. Translating marine-derived compounds into viable pharmaceuticals requires rigorous testing, preclinical studies, and clinical trials. Looking forward, advances in research and technology, such as metagenomics and synthetic biology, offer promising avenues for faster and more efficient discovery and development of marine-derived drugs. The potential for uncovering new therapeutic agents remains vast, and the continued exploration of marine natural products holds the promise of significant breakthroughs in drug development while considering sustainable practices and environmental concerns.

Exploring a Marine Zoanthid - Zoanthus sansibaricus – A Potential candidate for Drug Discovery

The oceans and all the marine life forms that they harbor remain a major source of treasure to mankind, covering 71% of the earth's surface and representing over 95% of the biosphere. Zoanthids, a subclass of the benthic Anthozoans, are found in almost all marine environments. Despite this fact, the order Zoantharia is still one of the most taxonomically neglected and least examined orders of the phylum Cnidaria. However, they are gaining importance in the pharmaceutical research field due to the significance of bioactive compounds secreted from their bodies. Zoanthus sansibaricus species collected from the Indian coast have been explored in the present study. The study aimed to isolate chemical constituents from the methanol and methanol: chloroform (1:1) extract of Zoanthus sp. by subjecting it to a series of chromatographic analysis. In total, eight compounds were purified from petroleum ether, chloroform, n-butanol, and methanol-soluble parts of aqueous fractions. The compounds were characterized using spectroscopic techniques such as Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR), 1H and 13C Nuclear Magnetic Resonance (NMR), and Mass spectrometry. Total phenolic content and total flavonoid content were estimated using the Folin-Ciocalteu method and Aluminum chloride method, respectively. The phenolic compound contents of the petroleum ether and methanol-soluble part of the aqueous fraction were 18.92mg/g GAE and 7.02mg/g GAE, respectively. Total flavonoid content in the petroleum ether fraction was 8.05mg/g QUE and 1.38mg/g QUE in the methanol-soluble part of the aqueous fraction. This study emphasizes the need for a more extensive compilation of such data to extend our pool of knowledge about marine natural products as potential candidates for drug discovery.

In Vitro Anti-Inflammatory and Skin Protective Effects of Codium fragile Extract on Macrophages and Human Keratinocytes in Atopic Dermatitis.

Codium fragile has been traditionally used in oriental medicine to treat enterobiasis, dropsy, and dysuria, and it has been shown to possess many biological properties. Atopic dermatitis (AD) is one of the types of skin inflammation and barrier disruption, which leads to chronic inflammatory skin diseases. In the current investigation, the protective effects of C. fragile extract (CFE) on anti-inflammation and skin barrier improvement were investigated. In LPS-stimulated RAW 264.7 cells, nitric oxide generation and the expression levels of interleukin (IL)-1β, IL-4, IL-6, iNOS, COX-2, and tumor necrosis factor-alpha (TNF)-α were reduced by CFE. CFE also inhibited the phosphorylation of NF-κB-p65, ERK, p-38, and JNK. Additionally, CFE showed inhibitory activity on TSLP and IL-4 expression in HaCaT cells stimulated with TNF-α/interferon-gamma (IFN-γ). Enhanced expression of factors related to skin barrier function, FLG, IVL, and LOR, was confirmed. These findings implied that CFE may be used as a therapeutic agent against AD due to its skin barrier-strengthening and anti-inflammatory activities, which are derived from natural marine products.

Benzosceptrin C induces lysosomal degradation of PD-L1 and promotes antitumor immunity by targeting DHHC3

Programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blockade has become a mainstay of cancer immunotherapy. Targeting the PD-1/PD-L1 axis with small molecules is an attractive approach to enhance antitumor immunity. Here, we identified a natural marine product, benzosceptrin C (BC), that enhances the cytotoxicity of Tcells to cancer cells by reducing the abundance of PD-L1. Furthermore, BC exerts its antitumor effect in mice bearing MC38 tumors by activating tumor-infiltrating Tcell immunity. Mechanistic studies suggest that BC can prevent palmitoylation of PD-L1 by inhibiting DHHC3 enzymatic activity. Subsequently, PD-L1 is transferred from the membrane to the cytoplasm and cannot return to the membrane via recycling endosomes, triggering lysosome-mediated degradation of PD-L1. Moreover, the combination of BC and anti-CTLA4 effectively enhances antitumor Tcell immunity. Our findings reveal a previously unrecognized antitumor mechanism of BC and represent an alternative immune checkpoint blockade (ICB) therapeutic strategy to enhance the efficacy of cancer immunotherapy.

Mechanism of action of pseudopteroxazole and pseudopterosin G: Diterpenes from marine origin.

Pseudopteroxazole (Ptx) and the pseudopterosins are marine natural products with promising antibacterial potential. While Ptx has attracted interest for its antimycobacterial activity, pseudopterosins are active against several clinically relevant pathogens. Both compound classes exhibit low cytotoxicity and accessibility to targeted synthesis, yet their antibacterial mechanisms remain elusive. In this study, we investigated the modes of action of Ptx and pseudopterosinG (PsG) in Bacillus subtilis employing an unbiased approach that combines gel-based proteomics with a mathematical similarity analysis of response profiles. Proteomic responses to sublethal concentrations of Ptx and PsG were compared to a library of antibiotic stress response profiles revealing that both induce a stress response characteristic for agents targeting the bacterial cell envelope by interfering with membrane-bound steps of cell wall biosynthesis. Microscopy-based assays confirmed that both compounds compromise the integrity of the bacterial cell wall without disrupting the membrane potential. Furthermore, LC-MSE analysis showed that the greater potency of PsG against B.subtilis, reflected in a lower MIC and a more pronounced proteomic response, may be rooted in a more effective association with and penetration of B. subtilis cells. We conclude that Ptx and PsG target the integrity of the gram-positive cell wall.

Anti-herpes simplex virus activities and mechanisms of marine derived compounds.

Herpes simplex virus (HSV) is the most widely prevalent herpes virus worldwide, and the herpetic encephalitis and genital herpes caused by HSV infection have caused serious harm to human health all over the world. Although many anti-HSV drugs such as nucleoside analogues have been ap-proved for clinical use during the past few decades, important issues, such as drug resistance, toxicity, and high cost of drugs, remain unresolved. Recently, the studies on the anti-HSV activities of marine natural products, such as marine polysaccharides, marine peptides and microbial secondary metabolites are attracting more and more attention all over the world. This review discusses the recent progress in research on the anti-HSV activities of these natural compounds obtained from marine organisms, relating to their structural features and the structure-activity relationships. In addition, the recent findings on the different anti-HSV mechanisms and molecular targets of marine compounds and their potential for therapeutic application will also be summarized in detail.

Marine Natural Products as Novel Treatments for Parasitic Diseases.

Parasitic diseases including malaria, leishmaniasis, and trypanosomiasis have received significant attention due to their severe health implications, especially in developing countries. Marine natural products from a vast and diverse range of marine organisms such as sponges, corals, molluscs, and algae have been found to produce unique bioactive compounds that exhibit promising potent properties, including antiparasitic, anti-Plasmodial, anti-Leishmanial, and anti-Trypanosomal activities, providing hope for the development of effective treatments. Furthermore, various techniques and methodologies have been used to investigate the mechanisms of these antiparasitic compounds. Continued efforts in the discovery and development of marine natural products hold significant promise for the future of novel treatments against parasitic diseases.

Marine natural products.

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of NP structure class diversity in relation to biota source and biome is discussed.

Synthesis of N-heterocyclic carbene gold(I) complexes from the marine betaine 1,3-dimethylimidazolium-4-carboxylate.

The marine natural product norzooanemonin (1,3-dimethylimidazolium-4-carboxylate) has been used to prepare a series of carboxyl- or carboxylate-functionalized N-heterocyclic carbene (NHC) gold(I) complexes from [(Me2S)AuCl] in the presence of potassium carbonate. The potential of the resulting mono- and dicarbene complexes to act as cytotoxic or antibacterial drugs was investigated.

Assessments of anti-breast cancer activity and profiling of active compounds using LC-MS/MS from the Indonesian Agelas nakamurai

Breast cancer is now one of the leading causes of death in women worldwide. Finding a cure is, therefore, critical for women’s health. Marine sponge-derived drugs have gained interest in breast cancer treatment. The development of marine natural products into cancer therapy includes several stages. It starts with the screening using the cytotoxic test method, a preclinical trial using the animal mode, and clinical trial phases I and II. In this study, we focus on the basic cytotoxic test to find the new source of anti-breast cancer compounds derived from Agelas nakamurai to know the potential for further investigation to become lead compounds. However, the anti-breast cancer potential of the Indonesian marine sponge A. nakamurai has never been studied. This study aimed to evaluate the anti-breast cancer potential of extract and fraction of A. nakamurai against epithelial human breast cancer cells (MDA-MB-231 and MCF-7 cells line) and to preliminary profile the known active compounds. The maceration using methanol was used for extraction and followed by partitioning with varied solvents [ethyl acetate (EtOAc), butanol, and water]. Fractionation was done using normal phase open column chromatography, and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) was used for analyzing compounds. MDA-MB-231, MCF-7, and HEK-293 cell lines were used for biological activities. The chromatographic separation of the EtOAc fraction led to the F7 subfraction which strongly inhibits proliferation against the MDA-MD-231 (IC50: 10.677 μg/mL), MCF-7 (IC50: 15.154 μg/mL), and HEK-293 cells line. The LC-MS/MS data of active fraction F7 contained gelatin-D and ageloxime-D. This study reported that fraction 7 of A. nakamurai showed strong activity against MDA-MB-231, MCF-7, and HEK-293 cell lines. Further analysis will be carried out to know the mechanisms of action of active compounds.

Total synthesis of jamaicamide B.

Jamaicamide B was isolated from the cyanobacterium Moorea producens in Jamaica and shows neurotoxicity. This unique mixed peptide-polyketide structure contains a pyrrolinone ring, a β-methoxy enone, an (E)-olefin, an undetermined stereocenter at C9, an (E)-chloroolefin, and a terminal alkyne. We report herein the first total synthesis and structural confirmation of the marine natural product (9R)-jamaicamide B.