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.

Two new lanostane-type triterpenoids from the fungus Periconia sp. TJ403-rc01.

The endophytic fungus Periconia sp. TJ403-rc01 (Dematiaceae) isolated from the leaves of Rosa chinensis Jacq. (Rosaceae) was cultivated on rice medium and chemically investigated, affording two new lanostane-type triterpenoids, namely pericinones A and B (1 and 2). Their structures were determined mainly by 1 D and 2 D NMR and HRESIMS data. Notably, it is the first report of lanostane-type triterpenoids from species of Periconia. Compounds 1 and 2 showed moderate anti-inflammatory activity against the NO production with IC50 values of 24.12 ± 0.73 and 11.38 ± 1.56 µM, respectively.

A new pair of cytotoxic enantiomeric isoprenylated chromone derivatives from Pestalotiopsis sp.

A new pair of enantiomeric isoprenylated chromone derivatives, (±)-pestaloficiol X [(±)-1], along with a known compound pestaloficiol J (2), were isolated from the plant endophytic fungus Pestalotiopsis sp. The racemic mixture 1 was separated through chiral HPLC. The structures of new compounds (±)-1 were elucidated on the basis of extensive spectroscopic data and their absolute configurations were further configured through computational analysis of their electronic circular dichroism (ECD) spectra. Compound (+)-1 showed significant inhibitory potency against HL-60 and HEP-3B cell lines, with IC50 values of 1.35 ± 0.15 and 3.70 ± 0.33 µM, respectively, while compound (-)-1 showed significant inhibitory potency against HL-60 and HEP-3B cell lines, with IC50 values of 2.39 ± 0.26 and 2.99 ± 0.35 µM, respectively.

Asperanstinoids A-E: Undescribed 3,5-dimethylorsellinic acid-based meroterpenoids from Aspergillus calidoustus.

Large-scale culture is a complementary and practical method for genome mining and OSMAC approaches to discover novel natural products through accumulation and reprocessing effects. By employing a large-scale culture approach, twelve 3,5-dimethylorsellinic acid (DMOA)-based meroterpenoids, including five undescribed compounds, namely asperanstinoids A-E, were obtained from fungus Aspergillus calidoustus, which was isolated from the wetland soil collected at Dianchi Lake, Yunnan Province. The structures and absolute configurations of asperanstinoids A-E were determined by various spectroscopic analyses, including NMR spectroscopy, high-resolution electrospray ionization mass spectrometry (HRESIMS), single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations, and the absolute configurations of three known compounds, dehydroaustinol, austinol, and austin, were confirmed via single-crystal X-ray diffraction for the first time. Notably, asperanstinoid A represents the second example of a DMOA-based meroterpenoid featuring a unique 6/5/6/6/6/5-fused hexacyclic skeleton with a rare "1,13-epoxy" moiety. The cytotoxicity assay of all these isolates revealed that asperanstinoid D, dehydroaustinol, and austin displayed considerable cytotoxicity against the HL-60 and SU-DHL-4 tumor cell lines with IC50 values ranging from 15.7 to 27.8 µM.

Bioassay-Directed Isolation of Antibacterial Metabolites from an Arthropod-Derived Penicillium chrysogenum.

Bioassay-directed isolation of secondary metabolites from an extract of Penicillium chrysogenum TJ403-CA4 isolated from the medicinally valuable arthropod Cryptotympana atrata afforded five new and 10 known compounds (1-15). All the compounds (except 14) belong to a minor class of highly rigid 6-5-5-5-fused tetracyclic cyclopiane-type diterpenes known to be exclusively produced by members of the Penicillium genus. The structures and absolute configurations of the new compounds (1-5) were elucidated by extensive spectroscopic analyses, including HRESIMS and 1D and 2D NMR, single-crystal X-ray diffraction, and comparison of the experimental electronic circular dichroism data. Compounds 1 and 2 represent the first examples of cyclopianes bearing a C-20 carboxyl group; compound 3 represents the first example of a cyclopiane with a gem-hydroxymethyl group; compound 4 represents the second example of a cyclopiane bearing a hydroxy group at C-7; compound 5 represents the first example of a cyclopiane bearing a hydroxy group at C-8. Compounds 2 and 3 exhibited activity against MRSA, with MIC values of 4.0 and 2.0 µg/mL, respectively. In addition, the structure-antibacterial activity relationship (SAR) of compounds 1-15 is discussed.

Modified Fusicoccane-Type Diterpenoids from Alternaria brassicicola.

Seven new modified fusicoccane-type diterpenoids (1-7), together with two known congeners (8 and 9), were obtained from Alternaria brassicicola. Their structures were elucidated from a combination of NMR and HRESIMS data and 13C NMR calculation as well as DP4+ probability analyses, and the absolute configurations of 1-5 were determined by ECD calculation and single-crystal X-ray diffraction (Cu Kα). Compounds 1-3 belong to a rare class of 16-nor-dicyclopenta[a,d]cyclooctane diterpenoids, and compounds 2 and 4 represent the first examples of fusicoccane-type diterpenoids featuring two previously undescribed tetracyclic 5/6/6/5 ring systems, while compound 5 features a previously undescribed tetracyclic 5/8/5/3 ring system. Compound 7 was moderately anti-inflammatory, and compounds 2, 3, 5, and 7 were weakly cytotoxic.

Fusicoccane-derived diterpenoids with bridgehead double-bond-containing tricyclo[9.2.1.03,7]tetradecane ring systems from Alternaria brassicicola.

Fusicoccane-derived diterpenoids bearing a unique bridgehead double-bond-containing tricyclo[9.2.1.03,7]tetradecane (5-9-5 ring system) core skeleton represent a rarely reported class of rearranged terpenoids, which traced back to fusicoccanes with a classical dicyclopenta[a,d]cyclooctane (5-8-5 ring system) core skeleton via a crucial Wagner-Meerwein rearrangement reaction. In this research, alterbrassicenes B-D (1-3), three new rearranged fusicoccane diterpenoids bearing a rare bridgehead double-bond-containing tricyclo[9.2.1.03,7]tetradecane core skeleton, together with two known congeners, brassicicenes O and K (4 and 5), were isolated from the modified cultures of fungus Alternaria brassicicola. Their structures were elucidated by comprehensive analyses of the NMR and HRESIMS data, and the absolute configurations of 1 and 4 were further confirmed via a combination of 13C NMR and ECD calculations and single-crystal X-ray diffraction analysis (Cu Kα). Interestingly, alterbrassicene B (1) represented the second case of bridgehead C-10-C-11 double-bond-containing natural products with a bicyclo[6.2.1]undecane core skeleton, and also featured an undescribed oxygen bridge between C-6 and C-14 to construct an unprecedentedly caged tetracyclic system. Alterbrassicenes B-D showed moderate cytotoxic activity against certain human tumor cell lines with IC50 values in the range of 15.87-36.85 µM.

Structurally diverse and bioactive alkaloids from an insect-derived fungus Neosartorya fischeri.

Seven undescribed alkaloids, namely fischeramides A and B, 5,6-dimethoxycircumdatin C, 6-hydroxyacetylaszonalenin, 3-methoxyglyantrypine, 9-methoxyfumitremorgin C, and spirotryprostatin M, one undescribed natural product, namely 11-deacetyl pyripyropene A, together with nine known congeners, were isolated from the solid cultures of fungus Neosartorya fischeri, which was separated from a medicinal insect Cryptotympana atrata. Their structures were elucidated by extensive spectroscopic data, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction analyses. Structurally, fischeramides A and B represented a pair of rare geometric isomers of the benzodiazepinedione derivatives with a highly conjugated feature. Fischeramide A showed potential immunosuppressive activity in LPS and anti-CD3/anti-CD28 mAbs activated murine splenocytes proliferation with IC50 values of 7.08 and 6.31 µM, respectively, and also showed anti-inflammatory activity against the lipopolysaccharide-induced nitric oxide production with an IC50 value of 25 ± 1 µM. In addition, 5,6-dimethoxycircumdatin C showed remarkable antibacterial activity against ESBL-producing E. coli with an MIC value of 2.0 µg/mL.

Reisolation and Configurational Reinvestigation of Cottoquinazolines E-G from an Arthropod-Derived Strain of the Fungus Neosartorya fischeri.

The reported fumiquinazoline-related alkaloids cottoquinazolines E-G (1-3) were reisolated from solid cultures of the fungus Neosartorya fischeri, which was isolated from the medicinal arthropod Cryptotympana atrata. The unresolved issues regarding the absolute configurations (for cottoquinazolines E and F) prompted a reinvestigation of the configurations for all three compounds, as enabled by extensive spectroscopic methods, comparisons of experimental electronic circular dichroism data, and X-ray crystallography. In addition, cottoquinazoline F (2) showed significant antibacterial activity against ESBL-producing Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterococcus faecalis with MIC values of 8, 32, 32, and 16 µg/mL, respectively.

Alterbrassinoids A-D: Fusicoccane-Derived Diterpenoid Dimers Featuring Different Carbon Skeletons from Alternaria brassicicola.

Alterbrassinoids A-D (1-4), the first examples of fusicoccane-derived diterpenoid dimers furnished by forming an undescribed C-12-C-18' linkage, were isolated from modified cultures of Alternaria brassicicola. Compounds 1 and 2 represent unprecedented heterodimers, whereas 3 and 4 represent unprecedented homodimers, and 4 also features an undescribed anhydride motif. Their structures were assigned via spectroscopic methods, electronic circular dichroism calculations, and single-crystal X-ray diffraction. Putative biosynthetic pathways and a bioactivity evaluation for 1-4 were discussed.

HPLC-DAD-Directed Isolation of Linearly Fused Prenylated Indole Alkaloids from a Soil-Derived Aspergillus versicolor.

An HPLC-DAD-directed chemical investigation of the soil-derived fungus Aspergillus versicolor QC812 resulted in the isolation and identification of eight new linearly fused prenylated indole alkaloids, asperversiamides I-P (1-8), along with a congener, asperversiamide H (9). Their structures and absolute configurations were determined by spectroscopic analysis including HRESIMS and 1D and 2D NMR, electronic circular dichroism analysis, and single-crystal X-ray diffraction. Asperversiamide I (1), the first diketopiperazine derived from d-proline and l-tryptophan, possesses an unprecedented C-11-spiro-fused 6/6/5/5/6/5 hexacyclic ring system. Asperversiamide J (2) is the first linearly fused 6/6/5 tricyclic prenylated indole alkaloid to be reported. 1 and 2 showed moderate inhibitory activities against HeLa cells with IC50 values of 7.3 and 6.4 µM, respectively.

Antimicrobial Dolabellanes and Atranones from a Marine-Derived Strain of the Toxigenic Fungus Stachybotrys chartarum.

Three new dolabellane-type diterpenoids (1-3) and three new atranones (4-6) were isolated and identified from a marine-derived strain of the toxigenic fungus Stachybotrys chartarum. The planar and relative structures of 1-6 were elucidated using extensive spectroscopic methods, and their absolute configurations were fully confirmed via single-crystal X-ray diffraction analysis. Structurally, compounds 2 and 3 have a 1,14-seco dolabellane-type diterpenoid skeleton; compound 4 is the first C23 atranone featuring a propan-2-one motif linked to a dolabellane-type diterpenoid by a carbon-carbon bond; compound 5 represents the first example of a C24 atranone with a 2-methyltetrahydrofuran-3-carboxylate motif fused to a dolabellane-type diterpenoid at C-5-C-6. In an in vitro antimicrobial activity assay, compound 2 was active against Acinetobacter baumannii and Enterococcus faecalis with MIC values of 16 and 32 µg/mL, respectively, while compound 4 exhibited significant inhibitory activities against Candida albicans, Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 8, 16, and 32 µg/mL, respectively.

Mycophenolic Acid Derivatives with Immunosuppressive Activity from the Coral-Derived Fungus Penicillium bialowiezense.

Mycophenolic acid (MPA) is a potent inosine-5′-monophosphate dehydrogenase (IMPDH) inhibitor for immunosuppressive chemotherapy. Most importantly, as the 2-morpholinoethyl ester prodrug of MPA, mycophenolate mofetil (MMF) is a well-known immunosuppressant used to prevent rejection in organ transplantations. Nevertheless, due to its frequently occurred side effects, searching for new therapeutic agents is ongoing. In our current work, by virtue of efficient bioassay-guided fractionation and purification, eleven mycophenolic acid derivatives, including five previously unreported metabolites (3⁻7) and six known compounds (1, 2, and 8⁻11), were obtained from the coral-derived fungus Penicillium bialowiezense. Their structures were elucidated by means of extensive spectroscopic analyses (including 1D and 2D NMR and HRESIMS data) and comparison of the NMR and other physical data with those reported in the literature in the case of the known compounds. All the isolates 1⁻11 were evaluated for the immunosuppressive activity, and 1⁻3 showed potent IMPDH2 inhibitory potency with IC50 values of 0.84⁻0.95 μM, which were comparable to that of MPA (the positive control), while 4⁻10 showed significant inhibitory potency with IC50 values of 3.27⁻24.68 μM. All the MPA derivatives showed promising immunosuppressive activity, endowing them as potential drug leads for organ transplantations and autoimmune related diseases.

A New Breviane Spiroditerpenoid from the Marine-Derived Fungus Penicillium sp. TJ403-1.

Marine-derived fungi are a promising and untapped reservoir for discovering structurally interesting and pharmacologically active natural products. In our efforts to identify novel bioactive compounds from marine-derived fungi, four breviane spiroditerpenoids, including a new compound, brevione O (1), and three known compounds breviones I (2), J (3), and H (4), together with a known diketopiperazine alkaloid brevicompanine G (5), were isolated and identified from an ethyl acetate extract of the fermented rice substrate of the coral-derived fungus Penicillium sp. TJ403-1. The absolute structure of 1 was elucidated by HRESIMS, one- and two-dimensional NMR spectroscopic data, and a comparison of its electronic circular dichroism (ECD) spectrum with the literature. Moreover, we confirmed the absolute configuration of 5 by single-crystal X-ray crystallography. All the isolated compounds were evaluated for isocitrate dehydrogenase 1 (IDH1) inhibitory activity and cytotoxicity, and compound 2 showed significant inhibitory activities against HL-60, A-549, and HEP3B tumor cell lines with IC50 values of 4.92 ± 0.65, 8.60 ± 1.36, and 5.50 ± 0.67 µM, respectively.