Stachybotrysin, an Osteoclast Differentiation Inhibitor from the Marine-Derived Fungus Stachybotrys sp. KCB13F013

Discovery of novel natural cardiomyocyte protectants from a toxigenic fungus Stachybotrys chartarum

Stachybatranones A-F (1a/1b and 2-6) and three known analogues, namely methylatranones A and B (7 and 8) and atranone B (9), were isolated and identified from a toxigenic fungus Stachybotrys chartarum. Their structures and absolute configurations were elucidated via the extensive spectroscopic data, comparison of the experimental electronic circular dichroism (ECD) data, and single-crystal X-ray diffraction analyses. Structurally, compounds 2-6 belonged to a rare class of C-alkylated dolabellanes, featuring a unique five-membered hemiketal ring and a γ-butyrolactone moiety both fused to an 11-membered carbocyclic system, while compound 1 (1a/1b) represented the first example of a 5-11-6-fused atranone possessing a 2,3-butanediol moiety. The cardiomyocyte protective activity assay revealed that compounds 1-9 ameliorated cold ischemic injury at 24 h post cold ischemia (CI), with compounds 1 and 4 acting in a dose-dependent manner. Moreover, compound 1 prevented cold ischemia induced dephosphorylation of PI3K and AKT acting in a dose-dependent manner. In this study, a new class of natural products were found to protect cardiomyocytes against cold ischemic injury, providing a potential option for the development of novel cardioprotectants in heart transplant medicine.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Natural sesquiterpene quinone/quinols: chemistry, biological activity, and synthesis

Covering: 2010 to 2021Sesquiterpene quinone/quinols (SQs) are characterized by a C15-sesquiterpenoid unit incorporating a C6-benzoquinone/quinol moiety. Numerous unprecedented carbon skeletons have been constructed with various connection patterns between the two parts. The potent anti-cancer, anti-inflammatory, anti-microbial, anti-viral, and fibrinolytic activities of SQs are associated with their diverse structures. The representative avarol has even entered the stage of clinical phase II research as an anti-HIV agent, and was developed as paramedic medicine against psoriasis. This review provides an overall summary of 558 new natural SQs discovered between 2010 and 2021, including seven groups and sixteen structure-type subgroups, which comprehensively recapitulates their chemical structures, spectral characteristics, source organisms, biological activities, synthesis, and biosynthesis, aiming to expand the application scope of this unique natural product resource.

New Phenylspirodrimanes from the Sponge-Associated Fungus Stachybotrys chartarum MUT 3308

Two phenylspirodrimanes, never isolated before, stachybotrin J (1) and new stachybocin G (epi-stachybocin A) (2), along with the already reported stachybotrin I (3), stachybotrin H (4), stachybotrylactam (5), stachybotrylactam acetate (6), 2α-acetoxystachybotrylactam acetate (7), stachybotramide (8), chartarlactam B (9), and F1839-J (10) were isolated from the sponge-associated fungus Stachybotrys chartarum MUT 3308. Their structures were established based on extensive spectrometric (HRMS) and spectroscopic (1D and 2D NMR) analyses. Absolute configurations of the stereogenic centers of stachybotrin J (1), stachybocin G (2), and stachybotrin I (3), were determined by comparison of their experimental circular dichroism (CD) spectra with their time-dependent density functional theory (TD-DFT) circular dichroism (ECD) spectra. The putative structures of seventeen additional phenylspirodrimanes were proposed by analysis of their respective MS/MS spectra through a Feature-Based Molecular Networking approach. All the isolated compounds were evaluated for their cytotoxicity against five aggressive cancer cell lines (MP41, 786, 786R, CAL33, and CAL33RR), notably including two resistant human cancer cell lines (786R, CAL33RR), and compounds 5, 6, and 7 exhibited cytotoxicity with IC50 values in the range of 0.3−2.2 µM.

Marine natural products that inhibit osteoclastogenesis and promote osteoblast differentiation

Osteoporosis is a disease that affects the quality of life of elderly people. The balance between bone formation mediated by osteoblasts and bone resorption by osteoclasts is important to maintain the normal bone condition. Therefore, the promotion of osteoblast differentiation and the suppression of osteoclastogenesis are effective strategies for osteoporosis treatment. Marine organisms are a promising source of biologically active and structurally diverse secondary metabolites, and have been providing drug leads for the treatment of numerous diseases. We describe the marine-derived secondary metabolites that can inhibit receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and promote osteoblast differentiation.

Marine dissolved organic matter: a vast and unexplored molecular space

Abstract

Marine dissolved organic matter (DOM) comprises a vast and unexplored molecular space. Most of it resided in the oceans for thousands of years. It is among the most diverse molecular mixtures known, consisting of millions of individual compounds. More than 1 Eg of this material exists on the planet. As such, it comprises a formidable source of natural products promising significant potential for new biotechnological purposes. Great emphasis has been placed on understanding the role of DOM in biogeochemical cycles and climate attenuation, its lifespan, interaction with microorganisms, as well as its molecular composition. Yet, probing DOM bioactivities is in its infancy, largely because it is technically challenging due to the chemical complexity of the material. It is of considerable interest to develop technologies capable to better discern DOM bioactivities. Modern screening technologies are opening new avenues allowing accelerated identification of bioactivities for small molecules from natural products. These methods diminish a priori the need for laborious chemical fractionation. We examine here the application of untargeted metabolomics and multiplexed high-throughput molecular-phenotypic screening techniques that are providing first insights on previously undetectable DOM bioactivities.

Key points

• Marine DOM is a vast, unexplored biotechnological resource.

• Untargeted bioscreening approaches are emerging for natural product screening.

• Perspectives for developing bioscreening platforms for marine DOM are discussed.

The chemistry and biology of fungal meroterpenoids (2009-2019)

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

Antibacterial phenylspirodrimanes from the marine-derived fungus Stachybotrys sp. SCSIO 40434

Five new phenylspirodrimanes, stachybomycins A - E (1-5), together with four known compounds (6-9), were isolated from the marine-derived fungus Stachybotrys sp. SCSIO 40434. Their structures were elucidated by comprehensive spectroscopic analyses of NMR and HRESIMS. The absolute configuration of 1 was confirmed by single crystal X-ray diffraction analysis. Compounds 5 and 7 showed moderate antibacterial activities against Micrococcus luteus, Staphylococcus aureus and methicillin resistant Staphylococcus aureus with minimal inhibition concentration (MIC) values of 8, 16 and 16 μg mL^-1, respectively.

Metabolites of Marine Sediment-Derived Fungi: Actual Trends of Biological Activity Studies

Marine sediments are characterized by intense degradation of sedimenting organic matter in the water column and near surface sediments, combined with characteristically low temperatures and elevated pressures. Fungi are less represented in the microbial communities of sediments than bacteria and archaea and their relationships are competitive. This results in wide variety of secondary metabolites produced by marine sediment-derived fungi both for environmental adaptation and for interspecies interactions. Earlier marine fungal metabolites were investigated mainly for their antibacterial and antifungal activities, but now also as anticancer and cytoprotective drug candidates. This review aims to describe low-molecular-weight secondary metabolites of marine sediment-derived fungi in the context of their biological activity and covers research articles published between January 2016 and November 2020.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Four new steroids from the marine soft coral-derived fungus Penicillium sp. SCSIO41201

Penicildiones A-D (1-4), four new steroids derivatives together with three known compounds including 16α-methylpregna-17α,19-dihydroxy-(9,11)-epoxy-4-ene-3,18-dione-20-acetoxy (5), stachybotrylactone B (6) and stachybotrin (7) were isolated from the soft coral-derived fungus Penicillium sp. SCSIO41201, cultured in the 1% NaCl PDB substrate. Their structures were determined through spectroscopic methods and X-ray crystallography. Biological evaluation results revealed that 6 exhibited significant cytotoxic activity against HL-60, K562, MOLT-4, ACHN, 786-O, and OS-RC-2 cell lines with IC₅₀ values of 5.23, 4.12, 4.31, 23.55, 7.65 and 10.81 μmol·L^-1, respectively, while other compounds showed weak or no cytotoxicity at 50 μmol·L^-1.

Bistachybotrysins L–V, bioactive phenylspirodrimane dimers from the fungus Stachybotrys chartarum

Bistachybotrysins L–V (1–11), eleven novel dimeric phenylspirodrimanes, were isolated from the fungus Stachybotrys chartarum CGMCC 3.5365.

Phenylspirodrimane Derivatives From Cultures of the Fungus Stachybotrys chartarum YIM DT 10079

A new phenylspirodrimane derivative, stachartin F (1), and 2 known secondary metabolites stachybonoid E (2) and stachybonoid F (3) were isolated from cultures of the tin mine tailings-associated fungus Stachybotrys chartarum YIM DT 10079. Their structures were determined with the help of extensive spectroscopic analyses and absolute configuration of compound 1 was rationalized by quantum chemical calculations of the electronic circular dichroism spectra.

A Systematic Review of Recently Reported Marine Derived Natural Product Kinase Inhibitors

Protein kinases are validated drug targets for a number of therapeutic areas, as kinase deregulation is known to play an essential role in many disease states. Many investigated protein kinase inhibitors are natural product small molecules or their derivatives. Many marine-derived natural products from various marine sources, such as bacteria and cyanobacteria, fungi, animals, algae, soft corals, sponges, etc. have been found to have potent kinase inhibitory activity, or desirable pharmacophores for further development. This review covers the new compounds reported from the beginning of 2014 through the middle of 2019 as having been isolated from marine organisms and having potential therapeutic applications due to kinase inhibitory and associated bioactivities. Moreover, some existing clinical drugs based on marine-derived natural product scaffolds are also discussed.

Seven new cytotoxic phenylspirodrimane derivatives from the endophytic fungus Stachybotrys chartarum

Seven undescribed phenylspirodrimane derivatives, stachybochartins A–G (1–7), and four known analogues (8–11) were isolated from the endophytic fungus Stachybotrys chartarum obtained from Pinellia ternata. Stachybochartins A–D are four rare C–C-coupled dimeric derivatives and stachybochartin G features a seco-bisabosqual skeleton. Their structures and configurations were elucidated via spectroscopic analysis, electronic circular dichroism (ECD) calculations, the ECD exciton chirality method and the modified Mosher's method. Stachybochartins A–D and G displayed cytotoxic activities against MDA-MB-231 breast cancer cells and U-2OS osteosarcoma cells, with IC₅₀ values ranging from 4.5 to 21.7 μM. Stachybochartins C and G exerted strong anti-proliferative activities against U-2OS cells in concentration- and time-dependent manners and induced apoptosis.

The diverse structures and anticancer activities of phenylspirodrimane derivatives are investigated.

Highly oxygenated isoprenoid lipids derived from fungi and fungal endophytes: Origin and biological activities

This mini review is devoted to highly oxygenated isoprenoid lipids (HOIL) that are produced by fungi and fungal endophytes from various ecological niches, both terrestrial and aquatic. Steroids were distributed as from edible cultivated fungi, as well as fungi collected in forests. Fungal endophytes were generally isolated from plants and cultured to obtain sufficient biomass. Marine fungi were obtained from marine brown and red algae and marine invertebrates such as sponges, corals, worms, crustacea or from marine sediments. HOIL isolated from the terrestrial ecosystem have the pharmacological potential on anti-hypercholesterolemic, anti-neoplastic, anti-eczematic and anti-inflammatory activity estimated with a confidence of 84-90%. HOIL that produced by marine fungal species are predicted as having anti-inflammatory and anti-hypercholesterolemic activity with a confidence of 82-91%. In addition, they may have potential acetylcholinesterase and cell adhesion molecule inhibitors estimated with a confidence of 86-88%.

Pestynol, an Antifungal Compound Discovered Using a Saccharomyces cerevisiae 12geneΔ0HSR-iERG6-Based Assay

The multidrug-sensitive budding yeast, Saccharomyces cerevisiae 12geneΔ0HSR-iERG6, is very useful in antifungal screens. A novel compound, named pestynol (1), was discovered from a culture of the fungus Pestalotiopsis humus FKI-7473 using the multidrug-sensitive yeast. The structure of 1 was elucidated by NMR studies and modified Mosher's method as (1 R,2 R,3 R,4 R)-( E)-5-(7,11-dimethyl-3-methylenedodeca-6,10-dien-1-yn-1-yl)cyclohex-5-ene-1,2,3,4-tetraol. Compound 1 showed antimicrobial activity against the Gram-positive bacteria, Klebsiella pneumoniae, and S. cerevisiae 12geneΔ0HSR-iERG6 and Mucor racemosus, but displayed only weak cytotoxicity against various human cancer cell lines. Compound 1 displayed antifungal activities against S. cerevisiae 12geneΔ0HSR-iERG6 and Mucor racemosus at 10 μg/disc.

Marine natural products

Covering: 2016. Previous review: Nat. Prod. Rep., 2017, 34, 235-294This review covers the literature published in 2016 for marine natural products (MNPs), with 757 citations (643 for the period January to December 2016) 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 (1277 in 432 papers for 2016), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included.

Regioselective 1,2-Diol Rearrangement by Controlling the Loading of BF3·Et2O and Its Application to the Synthesis of Related Nor-Sesquiterene- and Sesquiterene-Type Marine Natural Products

The regiocontrolled rearrangement of 1,2-diols has been achieved by controlling the loading of BF₃·Et₂O. Its applicability is showcased by the divergent synthesis of austrodoral, austrodoric acid, and 8-epi-11-nordriman-9-one, as well as a formal synthesis of siphonodictyal B and liphagal. A new light is shed on piancol-type rearrangements that will be useful in diversity-oriented synthesis of related natural products.

Stachybotrysins A-G, Phenylspirodrimane Derivatives from the Fungus Stachybotrys chartarum

Seven new phenylspirodrimane derivatives named stachybotrysins A-G (2-8), together with five known compounds (1, 9-12), were isolated from Stachybotrys chartarum CGMCC 3.5365. Stachybotrysin D (5) is the first reported example of a naturally occurring alcoholic O-sulfation of a phenylspirodrimane, and stachybotrysins F and G (7 and 8) are the first examples possessing an isobenzotetrahydrofuran ring with an acetonyl moiety attached. The structures of these compounds were elucidated on the basis of extensive spectroscopic data analysis and by comparison with reported data. The absolute configurations of 1-8 were determined by X-ray single-crystal diffraction, electronic circular dichroism (ECD), and calculated ECD. Compounds 1 and 8 displayed anti-HIV activity with IC₅₀ values of 15.6 and 18.1 μM, respectively, and 2, 7, 9, and 11 showed inhibitory effect on influenza A virus with IC₅₀ values ranging from 12.4 to 18.9 μM.

Antiviral and anti-inflammatory meroterpenoids: stachybonoids A–F from the crinoid-derived fungus Stachybotrys chartarum 952

Six new meroterpenoids, which have been named as stachybonoids A–F (1–3 and 5–7), and three known phenylspirodrimanes (4, 8 and 9) were isolated from the crinoid-derived fungus Stachybotrys chartarum 952.