Reengineering an azaphilone biosynthesis pathway in Aspergillus nidulans to create lipoxygenase inhibitors

Sclerotiorin, an azaphilone polyketide, is a bioactive natural product known to inhibit 15-lipoxygenase and many other biological targets. To readily access sclerotiorin and analogs, we developed a 2-3 step semisynthetic route to produce a variety of azaphilones starting from an advanced, putative azaphilone intermediate (5) overproduced by an engineered strain of Aspergillus nidulans. The inhibitory activities of the semisynthetic azaphilones against 15-lipoxygenase were evaluated with several compounds displaying low micromolar potency.     

Xylariphilone: a new azaphilone derivative from the seagrass-derived fungus Xylariales sp. PSU-ES163

One new azaphilone derivative, named xylariphilone (1), along with 10 known compounds was isolated from the seagrass-derived fungus Xylariales sp. PSU-ES163. Their structures were elucidated on the basis of extensive spectroscopic analysis. The absolute and relative configurations of 1 were determined by circular dichroism spectroscopy and NOEDIFF data. The antimicrobial and cytotoxic activities of the isolated compounds were evaluated.     

Metabolites from fungi 15. New isocoumarins from an endophytic fungus isolated from the Canadian thistle Cirsium arvense

One known (1) and five new polyketide metabolites (2-6) were isolated from the culture extract of an endophytic fungus, Mycelia sterila, from the Canadian thistle Cirsium arvense. Compounds 1-4 are members of the isocoumarin family, whereas metabolite 5 is a dihydrobenzofuran and 6 has an open chain structure. All compounds have an unusual methyl group at the aromatic ring that does not fit into the usual polyketide pattern.     

Constituents of the Endophytic Fungus Annulohypoxylon boveri var. microspora BCRC 34012

A new azaphilone metabolite with a new substitution pattern, named annulohypoxylin ( 1 ), together with twelve known compounds, were isolated from the BuOH‐soluble fraction of the 95% EtOH extract of long‐grain rice (Oryza sativa) fermented with the endophytic fungus Annulohypoxylon boveri var. microspora (BCRC 34012). Annulohypoxylin ( 1 ) contains a dihydrobenzofuran‐2,4‐dione backbone, 1‐hydroxyoctyl side chain, and one γ‐lactone ring. Its structure was determined on the basis of extensive 1D‐ and 2D‐NMR analyses in combination with HR‐ESI‐MS. The relative configuration of 1 was confirmed by NOESY experiment. Other known compounds were identified by comparing their spectral data with those in the literature. All known compounds were isolated from this species for the first time.     

Citrinal A,a novel tricyclic derivative of citrinin,from an algicolous fungus Penicillium sp.i-1-1

Citrinal A(1),a novel tricyclic compound with a rare tetrahydro-2H-benzofuro[7-b][1,4]dioxin-9(3H)-one skeleton,along with two known related compounds,citrinin(2) and 2,3,4-trimethyl-5,7-dihydroxy-2,3-dihydrobenzofuran(3) were isolated from an algicolous fungus Penicillium sp.i-1-1.The structure and stereochemistry of 1 were determined by comprehensive spectral and biogenic analysis.Its cytotoxic effects on the A-549 and HL-60 cell lines were evaluated.     

Trichodermatides A-D, novel polyketides from the marine-derived fungus Trichoderma reesei

Four new polyketide derivatives, Trichodermatides A-D (1-4) were isolated from the marine-derived fungus Trichoderma reesei. Trichodermatide A (1) is an unprecedented example of a polyketide with a ketal-containing pentacyclic skeleton. The chemical structures and absolute configurations of compounds 1-4 were elucidated by extensive spectroscopic methods, especially 2D NMR and CD spectral analysis, and supported by their proposed biosynthesis pathway. The cytotoxicity of 1-4 was evaluated against A375-S2 human melanoma cell line.     

A new polyketide,penicillolide from the marine-derived fungus Penicillium sacculum

A new polyketide, penicillolide (1) was isolated from the fermentation broth of the marine-derived fungus Penicillium sacculum GT-308. Compound 1 is a polyketide with a unique carbon skeleton. The structure of this compound was established via extensive spectroscopic analyses including 1D-, 2D-NMR, and HRESI-MS.     

Aromatic polyketide glycosides from an entomopathogenic fungus,Cordyceps indigotica

A new aromatic polyketide glycoside, indigotide A (1), was isolated from the culture broth of the entomopathogenic fungus, Cordyceps indigotica, along with known cyclic depsipeptides, destruxins A, A₂, B, B₂ and E (3–7), and a polyketide, NG-393 (8). Repeated treatment of the C. indigotica culture broth with 5-azacytidine, a DNA methyltransferase inhibitor, led to the isolation of another new aromatic polyketide glycoside, indigotide B (2).     

Pleosporalone A,the first azaphilone characterized with aromatic A-ring from a marine-derived Pleosporales sp. fungus

A fungal strain, Pleosporales sp. CF09-1, was isolated from marine sediment collected from the Bohai Sea. A novel azaphilone derivative, named pleosporalone A (1), along with two known analogues, cohaerins A and B (2 and 3), were obtained and identified from the culture extract of Pleosporales sp. CF09-1. Their planar structures were elucidated by detailed analysis of spectroscopic data and by comparison with related known compounds. Pleosporalone A (1) represents the first azaphilone derivative characterised with A-ring aromatisation. Compound 1 showed strong antifungal activity against three plant pathogenic fungi Botrytis cinerea, Rhizopus oryzae and Phytophthora capsici with the MIC values of 0.39, 0.78 and 0.78 μM, respectively.     

Chemistry and cytotoxic activities of polyketides produced by the mangrove endophytic fungus <Emphasis Type="Italic">Phomopsis</Emphasis> SP. ZSU-H76

A new polyketide, 2-(7′-hydroxyoxooctyl)-3-hydroxy-5-methoxybenzeneacetic acid ethyl ester (1), together with three known compounds dothiorelone A (2), B (3), and C (4) were isolated from the mangrove endophytic fungus Phomopsis sp. ZSU-H76 obtained from the South China Sea. Their structures were elucidated by spectroscopic methods, mainly 1D and 2D NMR spectroscopic techniques. Primary bioassays showed that 1 exhibited cytotoxicity against HEp-2 and HepG2 cells with IC₅₀ values of 25 and 30 μg/mL, respectively.     

(+)- and (−)-Eurotone A: A pair of enantiomeric polyketide dimers from a marine-derived fungus Eurotium sp. SCSIO F452

(±)-Eurotone A [(±)-1], a pair of new enantiomeric polyketide dimers, as well as six known biogenetically related polyketides (2–7) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by comprehensive spectroscopic methods, X-ray diffraction and quantum chemical calculations. Compound 1 represented the first pair of spirodihydrobenzanthracene enantiomers isolated from marine fungi with their absolute configurations assigned. A plausible biosynthetic pathway involving a key acid-mediated dimerization was proposed for 1. The antioxidative activities of the new enantiomers were evaluated.     

New Cytotoxic Metabolites from the Marine‐Derived Fungus Penicillium sp. ZLN29

One new penicillide derivative, prenpenicillide ( 1 ), and one new xanthone derivative, prenxanthone ( 2 ), were isolated from the culture extract of the marine‐derived fungus Penicillium sp. ZLN29, together with six known polyketide compounds, 3 – 8 . Their structures were elucidated on the basis of spectroscopic and spectrometric analyses. The cytotoxicities of these eight compounds were evaluated on four tumor‐cell lines by SRB (=sulforhodamine B) or MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) methods. Compounds 1 and 3 exhibited weak cytotoxicities against HepG2 cell line with IC₅₀ values of 9.9 and 9.7 μM , respectively.     

Pafuranones A and B,two dimeric polyketides from a rare marine algae-derived fungus Paraconiothyrium sp.

A pair of dimeric polyketide epimers formed through conjugate addition and intramolecular lactonization were identified from the culture of a rare marine algae-derived fungus, Paraconiothyrium sp. OUCMDZ-3316.     

Tenuipyrone, a novel skeletal polyketide from the entomopathogenic fungus, Isaria tenuipes, cultivated in the presence of epigenetic modifiers

The concomitant addition of the histone deacetylase inhibitor and the DNA methyltransferase inhibitor to the culture medium of an entomopathogenic fungus, Isaria tenuipes, greatly enhanced its secondary metabolite production and led to the isolation of tenuipyrone (1), a novel polyketide with an unprecedented tetracyclic ring system bearing a spiroketal structural component, along with two known C(10)-polyketides, cephalosporolide B (2), which is a plausible biosynthetic precursor of 1, and cephalosporolide F (3).     

A new polyketide synthase nonribosomal peptide synthetase hybrid metabolite from plant endophytic fungus Periconia sp.

A new polyketide synthase–nonribosomal peptide synthetase(PKS–NRPS) hybrid metabolite, named pericoannosin B(1), was isolated from endophytic fungus Periconia sp. F-31 of the medicinal plant Annona muricata. The structure and absolute configuration were elucidated by means of extensive spectroscopic analyses(HRMS, NMR, IR, and CD).     

Cytosporacin,a highly unsaturated polyketide: application of the ACCORD-ADEQUATE experiment to the structural determination of natural products

Cytosporacin (1), a novel antibacterial polyketide containing naphthopyranone and isochromandione moieties, was isolated from the fermentation broth of the fungus Cytospora rhizophorae. A (1)H-detected ACCORD-ADEQUATE pulse sequence that distinguished (2)J(CH) from (3)J(CH) correlations provided critical information for structural determination. NOE studies established the relative configuration and revealed the presence of two rotamers. A biosynthetic (13)C-labeling experiment indicated that cytosporacin was derived from acetate origin.     

Synthetic studies towards the phomactins. Concise syntheses of the tricyclic furanochroman and the oxygenated bicyclo[9.3.1]pentadecane ring systems in phomactin A

A concise synthesis of the tricyclic furanochroman unit 3 found in the PAF antagonist phomactin A (1) isolated from the marine fungus Phoma sp., is described. In complementary studies, a variety of synthetic routes towards the bicyclo[9.3.1]pentadecane ring system 4 in phomactin A were explored. These studies culminated in a synthesis of the substituted ring system 79 containing all the carbon atoms and all the necessary oxygen centres for elaboration to phomactin A itself.     

Epicocconone,a novel fluorescent compound from the fungus epicoccumnigrum

Epicocconone represents a new class of natural fluorescent probes based on a polyketide skeleton isolated from the fungus Epicoccum nigrum. Epicocconone is a small, cell permeable natural product with a high molar absorbtivity and a long Stokes' shift that will be useful in biotechnological applications.     

Sesterterpenes and 2H‐Pyran‐2‐ones (=α‐Pyrones) from the Mangrove‐Derived Endophytic Fungus Fusarium proliferatum MA‐84

Two new tricyclic sesterterpenes, fusaprolifins A and B ( 1 and 2 ), and three new 2H‐pyran‐2‐one derivatives, prolipyrones A – C ( 3 – 5 ), were isolated and characterized from Fusarium proliferatum MA‐84, an endophytic fungus obtained from the fresh tissue of the marine mangrove plant Bruguiera sexangula. In addition, two known sesterterpenes, terpestacin ( 6 ) and fusaproliferin ( 7 ), and one known 2H‐pyran‐2‐one derivative, gibepyrone D ( 8 ), were also identified. The structures of these compounds were elucidated by detailed spectroscopic analyses. Fusaprolifin A ( 1 ) showed moderate activity against brine shrimp (Artemia salina), with a lethality rate of 49.5% at 100 μg/ml, while fusaprolifin B ( 2 ) showed weak activity.     

A new azaphilone from the entomopathogenic fungus Hypocrella sp.

This report describes the isolation of a new azaphilone, designated hypocrellone A (2), together with five known compounds (1, 3–6) from a submerged culture of the entomopathogenic fungus Hypocrella sp. (isolate WYTY-21). The absolute stereostructures of the two compounds (1 and 2) were elucidated based on 1D and 2D NMR spectroscopic and mass spectrometric data combined with the data from various chemical transformations. Hypocrellone A (2) and three (3–6) of the five known compounds were cytotoxic to hepatoma cells (cell line BEL-7404); IC₅₀ values ranged from 6.2 to 17.4 μM. At 200 μM, none of the six compounds was toxic to normal human liver cells (cell line HL-7702) or to normal human kidney epithelial cells (cell line HEK-293T).