Pyridine Nucleosides Neopetrosides A and B from a Marine Neopetrosia sp. Sponge. Synthesis of Neopetroside A and Its β-Riboside Analogue

Neopetroside-B alleviates doxorubicin-induced cardiotoxicity via mitochondrial protection

Doxorubicin, a member of the anthracycline family, is a widely prescribed anticancer chemotherapy drug. Unfortunately, cumulative doses of doxorubicin can cause mitochondrial dysfunction, leading to acute or chronic cardiotoxicity. This study demonstrated that Neopetroside-B (NPS-B) protects cardiomyocytes in the presence of doxorubicin. NPS-B improved mitochondrial function in cardiomyocytes by increasing ATP production and oxygen consumption rates. On the other hand, NPS-B negatively influenced cancer cell lines by increasing reactive oxygen species. We analyzed NPS-B-influenced metabolites (VIP > 1.0; AUC>0.7; p < 0.05) and proteins (FC > 2.0) and constructed metabolite-protein enrichment, which showed that NPS-B affected uracil metabolism and NAD-binding proteins (e.g., aldehyde dehydrogenase and glutathione reductase) in cardiomyocytes. However, for the cancer cells, NPS-B decreased the NAD+/NADH balance, impairing cell viability. In a xenograft mouse model treated with doxorubicin, NPS-B reduced cardiac fibrosis and improved cardiac function. NPS-B may be a beneficial intervention to reducing doxorubicin-induced cardiotoxicity with anticancer effects.

Novel GSK-3β Inhibitor Neopetroside A Protects Against Murine Myocardial Ischemia/Reperfusion Injury

Recent trends suggest novel natural compounds as promising treatments for cardiovascular disease. The authors examined how neopetroside A, a natural pyridine nucleoside containing an α-glycoside bond, regulates mitochondrial metabolism and heart function and investigated its cardioprotective role against ischemia/reperfusion injury. Neopetroside A treatment maintained cardiac hemodynamic status and mitochondrial respiration capacity and significantly prevented cardiac fibrosis in murine models. These effects can be attributed to preserved cellular and mitochondrial function caused by the inhibition of glycogen synthase kinase-3 beta, which regulates the ratio of nicotinamide adenine dinucleotide to nicotinamide adenine dinucleotide, reduced, through activation of the nuclear factor erythroid 2-related factor 2/NAD(P)H quinone oxidoreductase 1 axis in a phosphorylation-independent manner.

Neopetrosins A-D and Haliclorensin D, Indole-C-Mannopyranosides and a Diamine Alkaloid Isolated from the South China Sea Marine Sponge Neopetrosia chaliniformis

Four new indole-C-mannopyranoside alkaloids, neopetrosins A-D (1-4), together with one new diamine alkaloid, haliclorensin D (6), were isolated from the marine sponge Neopetrosia chaliniformis collected off Xisha Island in the South China Sea. Their structures and absolute configurations were determined by spectroscopic analysis, single-crystal X-ray diffraction, calculated electronic circular dichroism (ECD), and DP4+ probability analyses. Compounds 1, 2, and 4 exhibited in vivo hepatoprotective activity in a zebrafish model at a concentration of 20 μM.

Marine Pyrrole Alkaloids

Nitrogen heterocycles are essential parts of the chemical machinery of life and often reveal intriguing structures. They are not only widespread in terrestrial habitats but can also frequently be found as natural products in the marine environment. This review highlights the important class of marine pyrrole alkaloids, well-known for their diverse biological activities. A broad overview of the marine pyrrole alkaloids with a focus on their isolation, biological activities, chemical synthesis, and derivatization covering the decade from 2010 to 2020 is provided. With relevant structural subclasses categorized, this review shall provide a clear and timely synopsis of this area.

Marine alkaloids as the chemical marker for the prey-predator relationship of the sponge Xestospongia sp. and the nudibranch Jorunna funebris

The dietary relationship study between marine sponge Xestospongia sp. and its nudibranch predators Jorunna funebris based on the discovery of isoquinolinequinones has long been studied. In this study, chemical investigation of the sponge Xestospongia sp. and nudibranch J. funebris from the South China Sea yielded a new marine alkaloid neopetroside C (1), together with nine known alkaloids (2-10). The chemical structures of all the compounds were elucidated by extensive spectroscopic analysis. Neopetroside C (1) featured a riboside of nicotinic acid with a rare α-N glycosildic linkage and an acyl residue of (Z)-2-methylbut-2-enoic acid attached to C-5'. The plausible chemical ecology relationship between sponge Xestospongia sp. and its nudibranch predator J. funebris was proposed based on the biogenetic relationship of the common marine alkaloids. The observation of two structural fragments, (Z)-2-methylbut-2-enoyloxy and trigonelline groups in both sponge and nudibranch, indicated that nudibranch might uptake chemicals from sponge and then modify and transform them into chemical weapons to defend against predators.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-021-00096-w.

Neopetrothiazide: An Intriguing Pentacyclic Thiazide Alkaloid from the Sponge Neopetrosia sp

Neopetrothiazide (1), a pentacyclic isoquinoline quinone, was isolated from a Neopetrosia sp. sponge. The structure elucidation was facilitated by utilizing long-range heteronuclear single quantum multiple bond correlation (LR-HSQMBC) and heteronuclear multiple bond correlation (HMBC) nuclear magnetic resonance (NMR) pulse sequences optimized to detect four- and five-bond 1H-13C heteronuclear correlations. These NMR experiments can help assign proton-deficient structural motifs like neopetrothiazide (1), which has 14 contiguous nonprotonated centers (C, N, and S). Neopetrothiazide (1), with an unprecedented thiazide-fused structural scaffold, is the first natural product containing a thiazide moiety.

Xidaosterols A and B, two new steroids with unusual α-keto-enol functionality from the South China Sea sponge Neopetrosia chaliniformis

Two new C29 steroids, xidaosterols A (1) and B (2), characterised by a common unusual α-keto-enol functionality bearing A-ring, together with three related known ones (3-5), were isolated from the South China Sea sponge Neopetrosia chaliniformis. Their structures were elucidated by extensive spectroscopic analyses and comparison with the spectral data reported in the literature, Xidaosterol B is an A-nor derivative of 1.

Terreuspyridine: An Unexpected Pyridine-Fused Meroterpenoid Alkaloid with a Tetracyclic 6/6/6/6 Skeleton from Aspergillus terreus

Terreuspyridine (1), the first 3,5-demethylorsellinic acid (DMOA) derived meroterpenoid alkaloid, was isolated from the fungus Aspergillus terreus, which represents a new type of meroterpenoid possessing an unexpected tetracyclic 6/6/6/6 architecture. The structure of 1 with absolute configuration was determined by X-ray diffraction analysis. Biogenetically, it was proposed to be derived from the fusion of a DMOA-meroterpenoid and a glutamate. Terreuspyridine (1) exhibited moderate inhibitory activity against the BChE with an IC₅₀ value of 16.4 μM.

Kinase-Inhibitory Nucleoside Derivatives from the Pacific Bryozoan Nelliella nelliiformis

Marine organisms are a valuable source of bioactive natural products, yet bryozoan invertebrates have been relatively understudied. Herein, we report nelliellosides A and B, new secondary metabolites of the Pacific bryozoan Nelliella nelliiformis, found using NMR-guided isolation. Their structures, including absolute configurations, were elucidated using spectroscopic and chromatographic techniques. Total synthesis of the natural products and four analogues was also achieved, in addition to an assessment of their biological activity, especially kinase inhibition.

Marine Pharmacology in 2014-2015: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, Antiviral, and Anthelmintic Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The systematic review of the marine pharmacology literature from 2014 to 2015 was completed in a manner consistent with the 1998-2013 reviews of this series. Research in marine pharmacology during 2014-2015, which was reported by investigators in 43 countries, described novel findings on the preclinical pharmacology of 301 marine compounds. These observations included antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral, and anthelmintic pharmacological activities for 133 marine natural products, 85 marine compounds with antidiabetic, and anti-inflammatory activities, as well as those that affected the immune and nervous system, and 83 marine compounds that displayed miscellaneous mechanisms of action, and may probably contribute to novel pharmacological classes upon further research. Thus, in 2014-2015, the preclinical marine natural product pharmacology pipeline provided novel pharmacology as well as new lead compounds for the clinical marine pharmaceutical pipeline, and thus continued to contribute to ongoing global research for alternative therapeutic approaches to many disease categories.

Alkynylation of Pentose Derivatives with Stereochemical Fidelity: Implications for the Regioselectivity of Alkynyl Diol Cycloisomerizations to Cyclic Enol Ethers

This work characterizes a previously undetected epimerization in the preparation of alkynyl diols from pentose precursors utilizing the Ohira-Bestmann reagent. Lithium trimethylsilyldiazomethane (Colvin reagent) additions to the d-ribose and d-lyxose-derived benzylidene acetals provide the respective alkynyl diol stereoisomers, without epimerization. Regioselective tungsten-catalyzed cycloisomerizations of the d-ribose- and d-lyxose-derived alkynyl diols yield rigid bicyclic pyranose glycals, confirming the stereochemical fidelity of the Colvin alkynylation process.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) 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 (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Gramine-derived Bromo-alkaloids Activating NF-κB-dependent Transcription from the Marine Hydroid Abietinaria abietina

Two new natural products, 6-bromogramine (1) and bis-6-bromogramine (2) were isolated from the marine hydroid Abietinaria abietina and their structures were established using NMR and MS analysis. Compounds 1 and 2 activate NF-κB-dependent transcriptional activity in JB6 Cl 41 NF-κB cells at 1.6 μM concentrations.

Absolute Configuration and Body Part Distribution of the Alkaloid 6-epi-Monanchorin from the Marine Polychaete Chaetopterus variopedatus

As a result of the first study on secondary metabolites from the cosmopolitan bioluminescent marine tube polychaete Chaetopterus variopedatus, a new bicyclic guanidine alkaloid, 6- epi-monanchorin (1), along with the previously known monanchorin (2) were isolated. The structure of 1 was elucidated by spectroscopic and chemical methods, including a cleavage of the C1–O7 bond to obtain a secondary alcohol (3), which was used to determine the absolute configurations by Mosher's method. It was found that 1 and 2 were mainly accumulated in a secreted mucus special organ of the worm (food net), where green and blue-green microalgae were detected. A biosynthetic pathway to 6- epi-monanchorin and monanchorin from dietary polyenic fatty acid precursors was proposed.