Carpesabrolide A, a novel meroterpenoid with anti-inflammatory activity from Carpesium abrotanoides.

Carpesabrolide A (1), featuring an unprecedented fumaric acid-guaiane sesquiterpenoid hybrid, has been isolated from the folk medicinal plant Carpesium abrotanoides. The structure with absolute configuration has been established by spectroscopic methods and single crystal X-ray diffraction analysis. The plausible biosynthetic pathway for 1 is proposed. Compound 1 shows significant anti-inflammatory activity by inhibiting NO production with an IC50 value of 2.7 µM.

Two new quinoline alkaloid with neuroprotective activities from Xylaria longipes.

Two new quinoline alkaloids with an α, ß-unsaturated amide side chain, xylarinines A and B (1 and 2), were isolated from the ethyl acetate extracts of Xylaria longipes solid fermentation. The structures of these were primarily determined though NMR and HRESIMS data analysis. The absolute configuration of compound 1 was assigned using experimental and calculated ECD data. The neuroprotective effects of compounds 1 and 2 against glutamate-induced damage in PC12 cells were evaluated in vitro bioassay. The results demonstrated that both compounds significantly improved cell viability, inhibited apoptosis, decreased malondialdehyde (MDA) levels, increased superoxide dismutase (SOD) and glutathione (GSH) levels, and reduced intracellular reactive oxygen species (ROS) accumulation. These findings suggested that these mechanisms contribute to the neuroprotective effects of the compounds.

Chromones from the endophytic fungus Bipolaris eleusines.

Eight previously undescribed chromones eleusineketones A-H (1-8), as well as eight known compounds (9-16), were isolated from the endophytic fungus Bipolaris eleusines. These planar structures were created using an in-depth analysis of their spectral data, which included 1D, 2D, and HRESIMS data. Furthermore, the absolute configurations of compounds 1, 2, and 6 were determined by spectroscopic analysis and quantum chemical computational approaches, and compound 5 was determined by single-crystal X-ray diffraction analysis. The cytotoxic activity assay revealed that compounds 1 and 5 both inhibited MDA-MB-231 cells with IC50 values of 14.48 µM and 17.99 µM, respectively.

Penisimplicins A and B: Novel Polyketide-Peptide Hybrid Alkaloids from the Fungus Penicillium simplicissimum JXCC5.

In this study, two previously undescribed nitrogen-containing compounds, penisimplicins A (1) and B (2), were isolated from Penicillium simplicissimum JXCC5. The structures of 1 and 2 were elucidated on the basis of comprehensive spectroscopic data analysis, including 1D and 2D NMR and HRESIMS data. The absolute configuration of 2 was determined by Marfey's method, ECD calculation, and DP4+ analysis. Both structures of 1 and 2 feature an unprecedented manner of amino acid-derivatives attaching to a polyketide moiety by C-C bond. The postulated biosynthetic pathways for 1 and 2 were discussed. Additionally, compound 1 exhibited significant acetylcholinesterase inhibitory activity, with IC50 values of 6.35 µM.

Cascade hydroarylation/Diels-Alder cycloaddition of alkynylindoles with electron-deficient alkynes and alkenes.

Herein, a novel cascade gold(I)-catalyzed hydroarylation of alkynylindoles and subsequent Diels-Alder cycloaddition with electron-deficient alkynes and alkenes is described. A variety of azepino-fused hydrocarbazoles and carbazoles were obtained in moderate to excellent yields. Key features of this methodology are low catalyst loadings, high regioselectivity, broad functional group tolerances, access to important heterocycles, and 100% atom economy.

A pair of new chromone enantiomers from Xylaria nigripes.

A pair of new chromone derivative enantiomers, (+)-xylarichromone A (1a) and (-)-xylarichromone A (1b), were isolated from the solid fermentation of Xylaria nigripes. The planar structure of 1 was determined by extensive NMR spectroscopic data, and its absolute configuration was assigned by comparison the ECD spectra with the known chromone derivatives. Compound 1 was the first chromone derivative reported from this medicinal fungus. The neuroprotective effects of 1 against oxygen and glucose deprivation (OGD) induced pheochromocytoma-12 cells (PC12) injury was investigated.

Two highly conjugated ergosterols from the fungus Psathyrella rogueiana and their anti-inflammatory activity.

Two previously undescribed ergosterols containing a highly conjugated ring system, psathrosterols A and B (1 and 2), have been isolated from the fungus Psathyrella rogueiana. Their structures with absolute configurations were established by extensive spectroscopic methods, as well as single crystal X-ray diffraction. Compounds 1 and 2 showed inhibitory activity against NO production with IC50 values of 22.3 and 16.4 µM, respectively.

The antifungal properties of terpenoids from the endophytic fungus Bipolaris eleusines.

A series of terpenoids (1-17), comprising six new compounds designated bipolariterpenes A-F (1-6) and eleven recognized compounds (7-17), were isolated from the wheat culture of the potato endophytic fungus Bipolaris eleusines. Their structures and stereochemistry were clarified by HRESIMS, NMR, DP4 + probability analyses, and computations for electronic circular dichroism (ECD). All compounds are made up of six meroterpenoids, four sesterterpenes and seven sesquiterpenes. Among them, four sesterterpenes (4, 5, 10, 11) were investigated for their antifungal, antibacterial and cytotoxic properties, and six meroterpenoids (1-3, 7-9) were evaluated for their antifungal properties. The compounds 7, 9, and 10 had substantial antifungal activity against Epidermophyton floccosum at a concentration of 100 µM. No antibacterial and cytotoxic activities were observed.

Rhodium(III)-catalyzed intermolecular [3+3] annulation of benzoxazines with quinone compounds: access to spiro-heterocyclic scaffolds.

A rhodium(III)-catalyzed redox-neutral spiroannulation approach to access the spiro[benzo[b][1,4]oxazine-benzo[c]chromene skeleton is described in this contribution. A variety of spiro[5.5]-heterocyclic scaffolds were obtained in moderate to excellent yields under mild conditions. Key features of this protocol are good substrate scope, silver-free conditions, low catalyst loadings, easy handling under air and 100% atom economy. Furthermore, scale-up reactions and late-stage derivatizations highlight the potential synthetic utility of this methodology.

Boerelasins A-D, Four Unprecedented Cytochalasins from the Endophytic Fungus Boeremia Exigua.

Four undescribed cytochalasins (1-4) were isolated from the endophytic fungus Boeremia exigua. Structurally, boerelasin A (1) represents the first example of a cytochalasin with a rare 5/5 bicyclic carbon core. Boerelasin B (2) possesses an unprecedented 5/6/5/6/8 pentacyclic ring system. Boerelasin C (3), a derivative from the common biosynthetic intermediate to 1, is a macrocyclic ring-opening cytochalasin, and boerelasin D (4) contains an uncommon six-carbon alkyl acid side chain. The structures were elucidated based on spectroscopic methods, electronic circular dichroism, spin-spin coupling constants, and calculated nuclear magnetic resonance with DP4+ analysis. These compounds exhibited significant cytotoxicity against the tumor cells.

Boerechalasins A-G, cytochalasans from the fungus Boeremia exigua with anti-inflammatory and cytotoxic activities.

Seven previously undescribed cytochalasans, namely, boerechalasins A-G, together with one analogue, were characterized from the solid culture of the fungus Boeremia exigua. Their structures and absolute configurations were elucidated on the basis of extensive spectroscopic analysis as well as electronic circular dichroism calculations. Remarkably, boerechalasin F possessed an unusual sulfoxide moiety that might be derived from methionine, while boerechalasin G had an unusual 5-methylcyclohexane-1,2,3-triol substituent at N-2 position. Boerechalasins A and E exhibited inhibitory activities against nitric oxide production in LPS-induced RAW264.7 macrophages with IC50 values of 21.9 and 5.7 µM, respectively. Boerechalasin F displayed cytotoxicity against human MCF‒7 cells with an IC50 value of 22.8 µM.

Steccherins A-D, chamigrane-type sesquiterpenes from the fungus Steccherinum ochraceum with selective inhibition on B lymphocyte proliferation.

Four previously undescribed chamigrane sesquiterpenes, namely steccherins A-D, have been isolated from the fungus Steccherinum ochraceum. Their structures were elucidated by extensive spectroscopic analysis, as well as computational methods and single crystal X-ray diffraction. Steccherins A and B possess previously undescribed backbones which might be derived from normal chamigrane sesquiterpenes, especially that steccherin A possesses a spiro[5.6]dodecane carbon skeleton via a ring-rearrangement. Steccherins A, C, and D showed immunosuppressive activity with IC50 values ranging from 6.2 to 37.8 µM. The data suggested that these chamigrane sesquiterpenes have potential selective inhibition on LPS-induced B lymphocyte proliferation.

Lanostane triterpenoids with anti-proliferative and anti-inflammatory activities from medicinal mushroom Ganoderma lingzhi.

Eight previously undescribed lanostane triterpenoids and nine known ones were identified from the fruiting bodies of Ganoderma lingzhi S.H. Wu, Y. Cao & Y.C. Dai. Their structures were determined based on spectroscopic data and quantum chemical calculations. Structurally, ganoderane GL-1, featuring a hydrogenated tetramethyls-phenanthraquinone, represents the first example in lanostane nor-triterpenoid group. Biologically, ganoderanes GL-2 and GL-3, distinguished by the presence of a rare "1,11-epoxy" moiety, exhibited significant inhibition against nitric oxide production induced by lipopolysaccharide in RAW264.7 macrophage cells, while ganoderanes GL-4 and GL-8 exhibited bifunctional activities of anti-proliferation and anti-inflammation.

Biochemical and Genetic Basis of Guanacastane Diterpene Biosynthesis in Basidiomycete Fungi.

Guanacastane diterpenoids with an unusual 5/7/6 tricyclic skeleton mainly produced by basidiomycete fungi represent a structurally intriguing class of natural products. While the chemical synthesis of several members has been achieved, the biochemical and genetic basis of their biosynthesis remain unknown. Herein, we present the identification and characterization of two crucial enzymes in the biosynthesis of guanacastane diterpenoids in Psathyrella candolleana. Heterologous expression reveals that PsaD, a typical class I diterpene synthase, catalyzes the cyclization of geranylgeranyl diphosphate to form a new guanacastane-type diterpene, guanacasta-1,3-diene (7). Moreover, we demonstrate that PsaA, a cytochrome P450 monooxygenase, can catalyze multiple oxidations of 7 to yield guanacastepene U (8). These results provide new opportunities for genome mining and metabolic engineering of guanacastane diterpenoids.

Triquinane Sesquiterpene Glycosides from the Basidiomycete Antrodiella zonata.

In our ongoing study of fungal bioactive natural products, 12 previously undescribed triquinane sesquiterpene glycosides, namely, antrodizonatins A-L (1-12), and four known compounds (13-16) have been obtained from the fermentation of the basidiomycete Antrodiella zonata. The structures were established unambiguously via extensive spectroscopic analysis and theoretical calculations of electronic circular dichroism spectra. This is the first report of triquinane sesquiterpene glycosides. Compounds 1, 5, and 12 displayed antibacterial activity against Staphylococcus aureus with MIC50 values of 35, 34, and 69 µM, respectively.

Polyketides from the fungus Pochonia chlamydosporia and their bioactivities.

Three previously undescribed griseofulvin derivatives, namely pochonichlamydins A-C, one small polyketide, namely pochonichlamydin D, together with nine known compounds, have been isolated from cultures of the fungus Pochonia chlamydosporia. Their structures with absolute configurations were elucidated on the basis of extensive spectrometric methods and single-crystal X-ray diffraction. Dechlorogriseofulvin and griseofulvin exhibited inhibitory activities against Candida albicans at the concentration of 100 µM, with inhibition rates of 69.1% and 56.3%, respectively. Meanwhile, pochonichlamydin C showed mild cytotoxicity against the human cancer MCF-7 cell line with an IC50 value of 33.1 µM.

Palladium(II)-Catalyzed Intramolecular [2 + 2 + 2] Annulation of Indolyl 1,3-Diynes: Construction of Azepino-Fused Carbazoles.

A novel palladium(II)-catalyzed intramolecular [2 + 2 + 2] annulation of indolyl 1,3-diynes is described in this contribution. A variety of azepino-fused carbazoles are obtained in moderate to excellent yields. The key to the success of this transformation is the use of a carboxylic acid as an additive. This protocol features broad functional group tolerances, easy handling in air, and 100% atom economy. Furthermore, scale-up reactions, late-stage derivatizations, and photophysical property investigations highlight the potential synthetic utility of this methodology.

A flavin-monooxygenase catalyzing oxepinone formation and the complete biosynthesis of vibralactone.

Oxepinone rings represent one of structurally unusual motifs of natural products and the biosynthesis of oxepinones is not fully understood. 1,5-Seco-vibralactone (3) features an oxepinone motif and is a stable metabolite isolated from mycelial cultures of the mushroom Boreostereum vibrans. Cyclization of 3 forms vibralactone (1) whose ß-lactone-fused bicyclic core originates from 4-hydroxybenzoate, yet it remains elusive how 4-hydroxybenzoate is converted to 3 especially for the oxepinone ring construction in the biosynthesis of 1. In this work, using activity-guided fractionation together with proteomic analyses, we identify an NADPH/FAD-dependent monooxygenase VibO as the key enzyme performing a crucial ring-expansive oxygenation on the phenol ring to generate the oxepin-2-one structure of 3. The crystal structure of VibO reveals that it forms a dimeric phenol hydroxylase-like architecture featured with a unique substrate-binding pocket adjacent to the bound FAD. Computational modeling and solution studies provide insight into the likely VibO active site geometry, and suggest possible involvement of a flavin-C4a-OO(H) intermediate.