Citrofulvicin, an Antiosteoporotic Polyketide from Penicillium velutinum

New piperazine derivatives helvamides B-C from the marine-derived fungus Penicillium velutinum ZK-14 uncovered by OSMAC (One Strain Many Compounds) strategy

Four extracts of the marine-derived fungus Penicillium velutinum J.F.H. Beyma were obtained via metal ions stress conditions based on the OSMAC (One Strain Many Compounds) strategy. Using a combination of modern approaches such as LC/UV, LC/MS and bioactivity data analysis, as well as in silico calculations, influence metal stress factors to change metabolite profiles Penicillium velutinum were analyzed. From the ethyl acetate extract of the P. velutinum were isolated two new piperazine derivatives helvamides B (1) and C (2) together with known saroclazin A (3) (4S,5R,7S)-4,11-dihydroxy-guaia-1(2),9(10)-dien (4). Their structures were established based on spectroscopic methods. The absolute configuration of helvamide B (1) as 2R,5R was determined by a combination of the X-ray analysis and by time-dependent density functional theory (TD-DFT) calculations of electronic circular dichroism (ECD) spectra. The cytotoxic activity of the isolated compounds against human prostate cancer PC-3 and human embryonic kidney HEK-293 cells and growth inhibition activity against yeast-like fungi Candida albicans were assayed.

Discovery of antifungal secondary metabolites from an intestinal fungus Fusarium sp

Intestinal fungi, which are important parts of the gut microbiota, have the ability to produce specialized metabolites that significantly contribute to maintaining the balance of the gut microbiota and promoting the health of the host organism. In the present study, two new glycosides, including fusintespyrone A (1) and cerevisterolside A (4), as well as ten known compounds were isolated from the intestinal fungus Fusarium sp. LE06. The structures of the new compounds were elucidated by a combination of spectroscopic methods, such as mass spectrometry (MS) and nuclear magnetic resonance (NMR), along with chemical reactions and calculations of NMR and ECD spectra. Compounds 1-3 showed significant growth inhibition against Aspergillus fumigatus, Fusarium oxysporum, and Verticillium dahliae with MIC values in the range of 1.56-6.25 μg ml-1.

Citrisorbicillinol, an undescribed hybrid sorbicillinoid with osteogenic activity from Penicillium citrinum ZY-2

Citrisorbicillinol (1), along with six other known compounds (2-7), was isolated from an endphyte Penicillium citrinum ZY-2 of Plantago asiatica L. Citrisorbicillinol (1) was characterized as a skeletally unprecedented hybrid sorbicillinoid, and its unique framework is likely formed by intermolecular [4 + 2] cycloaddition between intermediates derived from citrinin and sorbicillinoid biosynthetic gene clusters. Compounds 1 and 2 demonstrated to promote osteoblastic differentiation in MC3T3-E1 cells, and to be osteogenic in the prednisolone induced osteoporotic zebrafish. Compounds 3-7 exhibited moderate cytotoxicity against four human cancer cell lines.

Structurally various p-terphenyls with neuraminidase inhibitory from a sponge derived fungus Aspergillus sp. SCSIO41315

Guided by Global Natural Products Social molecular networking, 14 new p-terphenyl derivatives, asperterphenyls A-N (1-14), together with 20 known p-terphenyl derivatives (15-34), were obtained from a sponge derived fungus Aspergillus sp. SCSIO41315. Among them, new compounds 2-8 and 15-17 were ten pairs of enantiomers. Comprehensive methods such as chiral-phase HPLC analysis, ECD calculations and X-ray diffraction analysis were applied to determine the absolute configurations. Asperterphenyls B (2) and C (3) represented the first reported natural p-terphenyl derivatives possessing a dicarboxylic acid system. Asperterphenyl A (1) displayed neuraminidase inhibitory activity with an IC₅₀ value of 1.77 ± 0.53 µM and could efficiently inhibit infection of multiple strains of H1N1 with IC₅₀ values from 0.67 ± 0.28 to 1.48 ± 0.60 µM through decreasing viral plaque formation in a dose-dependent manner, which suggested that asperterphenyl A (1) might be exploited as a potential antiviral compound in the pharmaceutical fields.

Seven drimane-type sesquiterpenoids from an earwig-associated Aspergillus sp

Drimane-type sesquiterpenoids are widely distributed in fungi. From the ethyl acetate extract of the earwig-derived Aspergillus sp. NF2396, seven new drimane-type sesquiterpenoids, named drimanenoids A-G (1-7), were isolated. Their structures were elucidated by diverse spectroscopic analysis including high-resolution ESI-MS, one- and two-dimensional NMR spectroscopy. Drimanenoids A-F (1-6) are new members of drimane-type sesquiterpenoid esterified with unsaturated fatty acid side chain at C-6. Drimanenoids C (3), D (4) and F (6) showed antibacterial activity against five types of bacteria with different inhibition diameters. Drimanenoid D (4) exhibited moderate cytotoxicity against human myelogenous leukemia cell line K562 with an IC₅₀ value of 12.88 ± 0.11 μmol·L^-1.

The First Comprehensive Biodiversity Study of Culturable Fungal Communities Inhabiting Cryoconite Holes in the Werenskiold Glacier on Spitsbergen (Svalbard Archipelago, Arctic)

Cryoconite holes on glacier surfaces are a source of cold-adapted microorganisms, but little is known about their fungal inhabitants. Here, we provide the first report of distinctive fungal communities in cryoconite holes in the Werenskiold Glacier on Spitsbergen (Svalbard Archipelago, Arctic). Due to a combination of two incubation temperatures (7 °C and 24 ± 0.5 °C) and two media during isolation (PDA, YPG), as well as classical and molecular identification approaches, we were able to identify 23 different fungi (21 species and 2 unassigned species). Most of the fungi cultured from cryoconite sediment were ascomycetous filamentous micromycetes. However, four representatives of macromycetes were also identified (Bjerkandera adusta, Holwaya mucida, Orbiliaceae sp., and Trametes versicolor). Some of the described fungi possess biotechnological potential (Aspergillus pseudoglaucus, A. sydowii, Penicillium expansum, P. velutinum, B. adusta, and T. versicolor), thus, we propose the Arctic region as a source of new strains for industrial applications. In addition, two phytopathogenic representatives were present (P. sumatraense, Botrytis cinerea), as well as one potentially harmful to humans (Cladosporium cladosporioides). To the best of our knowledge, we are the first to report the occurrence of A. pseudoglaucus, C. allicinum, C. ramotenellum, P. sumatraense, P. velutinum, P. cumulodentata, B. adusta, and T. versicolor in polar regions. In all likelihood, two unassigned fungus species (Orbiliaceae and Dothideomycetes spp.) might also be newly described in such environments. Additionally, due to experimenting with 10 sampling sites located at different latitudes, we were able to conclude that the number of fungal spores decreases as one moves down the glacier. Considering the prevalence and endangerment of glacial environments worldwide, such findings suggest their potential as reservoirs of fungal diversity, which should not be overlooked.

Three new polyketide derivatives of the endophytic fungus Aspergillus cristatus 2H1

Three new polyketide derivatives, 2-ethoxycarbonyl-endocrocin (1), 6-methoxy-2-ethoxycarbonyl-endocrocin (2) and pannorin C (3), along with sixteen known compounds (4-19) were isolated from a plant endophytic fungus Aspergillus cristatus 2H1. Their structures were elucidated by 1D/2D NMR and HR-ESI-MS data analysis. Compound 3 showed weak antibacterial activity against Staphylococcus aureus (MIC 20 μg/ml). Compounds 14 and 15 showed effective cytotoxicity on human melanoma A375 cells (IC₅₀ 4.13 μM for 14, 3.39 μM for 15).

A new bioactive isocoumarin from the mangrove-derived fungus Penicillium sp. TGM112

A new isocoumarin, penicimarin N (1), along with five known compounds (2-6), were isolated from the mangrove-derived fungus Penicillium sp. TGM112. The structure of 1 was elucidated on the basis of extensive spectroscopic data analysis, and the absolute configuration of 1 was determined by comparison of their circular dichroism (CD) spectra with the literature. The structures of known compounds were determined by comparison with the literature data. All the isolated compounds were examined for their antioxidant and α-glucosidase activities. Compound 1 showed strong antioxidant activity with the IC₅₀ value of 1.0 mM, and 1 also exhibited moderate inhibitory activity against α-glucosidase with the IC₅₀ value of 620 μM.

Spirocitromycetin, a Fungal Polyketide with an Antiosteoporotic Pharmacophore

Spirocitromycetin, an antiosteoporotic polyketide bearing a unique spirocycle, was characterized from a human mucus sputum-derived Penicillium velutinum. Its structure and absolute configuration were elucidated spectrally, with its biosynthetic pathway likely mediated via polivione, a reported heptaketide. Spirocitromycetin was shown to be antiosteoporotic at 0.1 μM in the prednisolone-induced osteoporotic zebrafish model. A combination of spirocitromycetin variant synthesis and bioassay has identified 5'-methyl-3'H-spiro[chromane-3,2'-furan]-3',4-dione as an unreported antiosteroporotic pharmacophore. Collectively, this work offers new starting (sub)structures that may be of significance for antiosteoporotic drug discovery.

Metabolites isolated from the human intestinal fungus Penicillium oxalicum SL2 and their agonistic effects on PXR and FXR

Intestinal commensal fungi are vital to human health, and their metabolites play a key role in the reciprocal relationship. In the present work, eighteen alkaloids and seven monoterpenoids were isolated from the fermentation of the human intestinal fungus Penicillium oxalicum SL2, including seven undescribed alkaloids (penicilloxalines A-G), three undescribed monoterpenoids (penicilloxalines H-J), and fifteen reported compounds. The structures of the isolated compounds were identified by HRESIMS, 1D and 2D NMR, electronic circular dichroism spectra and quantum chemical calculations. Some metabolites displayed moderate agonistic effects against the pregnane X receptor (PXR), whereas (6R)3,7-dimethyl-6,7-dihydroxy-2(Z)-octenoic acid displayed a significant agonistic effect against the farnesoid X receptor (FXR) with an EC₅₀ value of 0.43 μM, which was verified by investigating FXR downstream target genes and proteins, such as small heterodimer partner 1 (SHP1), fibroblast growth factor (FGF), and bile salt export pump (BSEP).

Zebrafish Models for Human Skeletal Disorders

In 2019, the Nosology Committee of the International Skeletal Dysplasia Society provided an updated version of the Nosology and Classification of Genetic Skeletal Disorders. This is a reference list of recognized diseases in humans and their causal genes published to help clinician diagnosis and scientific research advances. Complementary to mammalian models, zebrafish has emerged as an interesting species to evaluate chemical treatments against these human skeletal disorders. Due to its versatility and the low cost of experiments, more than 80 models are currently available. In this article, we review the state-of-art of this “aquarium to bedside” approach describing the models according to the list provided by the Nosology Committee. With this, we intend to stimulate research in the appropriate direction to efficiently meet the actual needs of clinicians under the scope of the Nosology Committee.

Synthesis of the Core Ring System of the Antiosteoporotic Citrofulvicin

Synthesis of the octacyclic ring system of citrofulvicin is described in nine steps from readily available starting materials. Blocking undesired intramolecular cyclization of a reactive β-diketone intermediate by transient incorporation of a dithiolane ring led to the formation of the requisite 1-hydroxy-2,4,6-trioxaadamantane ring system of citrofulvicin.

Fish Models of Induced Osteoporosis

Osteopenia and osteoporosis are bone disorders characterized by reduced bone mineral density (BMD), altered bone microarchitecture and increased bone fragility. Because of global aging, their incidence is rapidly increasing worldwide and novel treatments that would be more efficient at preventing disease progression and at reducing the risk of bone fractures are needed. Preclinical studies are today a major bottleneck to the collection of new data and the discovery of new drugs, since they are commonly based on rodent in vivo systems that are time consuming and expensive, or in vitro systems that do not exactly recapitulate the complexity of low BMD disorders. In this regard, teleost fish, in particular zebrafish and medaka, have recently emerged as suitable alternatives to study bone formation and mineralization and to model human bone disorders. In addition to the many technical advantages that allow faster and larger studies, the availability of several fish models that efficiently mimic human osteopenia and osteoporosis phenotypes has stimulated the interest of the academia and industry toward a better understanding of the mechanisms of pathogenesis but also toward the discovery of new bone anabolic or antiresorptive compounds. This mini review recapitulates the in vivo teleost fish systems available to study low BMD disorders and highlights their applications and the recent advances in the field.

(+)- and (-)-Corydecumbenines A and B, two pairs of novel quaternary protoberberine alkaloid cycloadduct enantiomers with anti-neuroinflammatory and neuroprotective activities from the rhizomes of Corydalis decumbens

Two novel Diels-Alder [4 + 2] cycloadducts of quaternary protoberberine alkaloids and fumaric acid monoanion, corydecumbenines A and B (1 and 2), and six known isoquinoline analogues (3-8) were isolated from the rhizomes of Corydalis decumbens. The planar structures of 1 and 2 were elucidated by extensive spectroscopic analysis including UV, IR, HRESIMS, 1D and 2D NMR. Chiral chromatography of 1 and 2 afforded two pairs of enantiomers (+)-corydecumbenine A (1a), (-)-corydecumbenine A (1b), (+)-corydecumbenine B (2a), and (-)-corydecumbenine B (2b), respectively, and their absolute configurations were determined by single-crystal X-ray crystallography and comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1b and 2b exhibited significant nitric oxide (NO) inhibitory activities in lipopolysaccharide (LPS)-stimulated BV-2 cells with IC₅₀ values of 11.6 and 16.2 μM, respectively, comparable to the positive control indomethacin (IC₅₀ = 10.3 μM), and they could also decrease the level of interleukin (IL)-1β in BV-2 cells in a dose-dependent manner. Most of the isolates showed neuroprotective effects against the injury of OGD/R-induced PC12 cells at 20 μM.

Survey of natural products reported by Asian research groups in 2018

The new natural products reported in 2018 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2018 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Two new secondary metabolites from a mangrove-derived fungus Cladosporium sp. JS1-2

One new pentenoic acid derivative, named 1,1'-dioxine-2,2'-dipropionic acid (1) and a new natural product, named 2-methylacetate-3,5,6-trimethylpyrazine (2), along with six known compounds (3-8), were obtained from the Cladosporium sp. JS1-2, an endophytic fungus isolated from the mangrove Ceriops tagal collected in South China Sea. Their structures were elucidated by detailed analysis of comprehensive spectroscopic data, and the structure of 1 was further determined by X-ray diffraction analyses. ¹³C NMR chemical shifts of structure 2 was further determined by GIAO based ¹³C NMR chemical shifts calculations. Compounds 1-4 and 6 showed growth inhibition activities against newly hatched larvae of Helicoverpa armigera Hubner with the IC₅₀ values ranging from 100 to 150 μg ml^-1. Compounds 1, 2, 4, 6 and 7 showed moderate antibacterial activities against Staphylococcus aureus with the MIC values of 25.0, 12.5, 6.25, 1.25, and 6.25 μg ml^-1, respectively.

Bioactive Meroterpenoids and Isocoumarins from the Mangrove-Derived Fungus Penicillium sp. TGM112

Two new meroterpenoids, penicianstinoids A and B (1 and 2), and eight new isocoumarins, peniciisocoumarins A-H (3-10), together with 10 known analogues (11-20) were obtained from the mangrove-derived fungus Penicillium sp. TGM112. The structures and absolute configurations of 1-10 were determined by interpretation of detailed NMR, MS spectroscopic data, X-ray diffraction analyses, modified Mosher's method, and calculated electronic circular dichroism data. Compounds 1-4, 7, 8, 10, 12, 13, and 16 showed growth inhibition activity against newly hatched larvae of Helicoverpa armigera Hubner with IC₅₀ values ranging from 50 to 200 μg/mL, respectively. Compounds 1, 2, and 11-15 displayed activity against Caenorhabditis elegans with EC₅₀ values ranging from 9.4 (± 1.0) to 38.2 (± 0.6) μg/mL, respectively. Compound 1 represents an austinoid-like meroterpenoid that is reported here for the second time, in which a carbon-carbon double bond was oxidized to a carbonyl group at C-1'-C-2'.

Canescones A–E: aromatic polyketide dimers with PTP1B inhibitory activity from Penicillium canescens

Canescones A–E (1–5), aromatic polyketide dimers bearing unprecedented 5/6/6/6/5 heteropentacyclic ring skeletons with novel scaffolds, were isolated from Penicillium canescens.

Phloroglucinol heterodimers and bis-indolyl alkaloids from the sponge-derived fungus Aspergillus sp. SCSIO 41018

Gilluones A–C (1–3), three new phloroglucinol heterodimers, asterriquinones I–K (4–6), three new bis-indolylquinones, and asterriquinols G–I (7–9), three new bis-indolylbenzenoids, were isolated from the sponge-derived fungus Aspergillus sp. SCSIO 41018.

Hot off the Press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as huperphlegmine A from Huperzia phlegmaria.