Benzopyranones from the endophytic fungus Hyalodendriella sp. Ponipodef12 and their bioactivities

The endophytic fungus Hyalodendriella sp. Ponipodef12 was isolated from the hybrid 'Neva' of Populus deltoides Marsh × P. nigra L. In this study, four benzopyranones were isolated from the ethyl acetate extract of Hyalodendriella sp. Ponipodef12, and identified as palmariol B (1), 4-hydroxymellein (2), alternariol 9-methyl ether (3), and botrallin (4) by means of physicochemical and spectroscopic analysis. All the compounds were evaluated for their antibacterial, antifungal, antinematodal and acetylcholinesterase inhibitory activities. 4-Hydroxymellein (2) exhibited stronger antibacterial activity than the other compounds. Palmariol B (1) showed stronger antimicrobial, antinematodal and acetylcholinesterase inhibitory activities than alternariol 9-methyl ether (3) which indicated that the chlorine substitution at position 2 may contribute to its bioactivity. The results indicate the potential of this endophytic fungus as a source of bioactive benzopyranones.

[Group-I introns in 18S rDNA of Cenococcum geophilum Fr]

OBJECTIVE

To analyze the sequences and secondary structure of group-I introns in 18S rDNA of Cenococcum geophilum, and to study the factors effecting Cg genetic diversity.

METHOD

The 3' end region of 18S rDNA were amplified from twenty-three Cg isolates, and the PCR fragments from thirteen isolates were sequenced. The Neighbor-Joining phylogenetic analyses were performed using MAGE version 4.0, and the secondary structures of the Cg introns were predicted using Mfold.

RESULT

The results showed that fourteen out of nineteen Cg isolates originated in China had group-I introns in 18S rDNA. Their sequences, ranging in size from 488 to 590 nucleotides, were from 92.3% to 100% similar to each other from our data and GenBank data. The 5' end sequences of the introns were conserved, while the 3' end sequences were variable. The analysis of secondary structure indicated all the introns from forty-five Cg isolates contained ten pairing regions (P1-P10). The P5 region was composed of P5, P5a, P5b, P5c and P5d, and there were two extra pairing stems (P9. 1, P9. 2) besides the 3' end of P9.

CONCLUSION

It was suggested that Cg had rich genetic diversity, and we did not found the relationship between Cg genetic variation and its geographical and host origination.

[Study on the extraction of mycelium polysaccharides from selenium-rich Morchella esculenta with neutral proteinase method]

OBJECTIVE

To study the extraction conditions of mycelium polysaccharides from selenium-rich Morchella esculenta with neutral proteinase for increasing of yield.

METHODS

On the basis of single factor tests, orthogonal experiment design was applied to analyze the influence of factors including enzyme dosage, enzymolysis time, enzymolysis temperature and material/liquid ratio on the extraction rate of the polysaccharides.

RESULTS

The optimal extraction conditions of mycelium polysaccharides from selenium-rich Morchella esculenta was as follows: enzyme dosage was 1.5%, enzymolysis time was 2 h, enzymolysis temperature was 40 degrees C, and material/liquid ratio was 1:15. The extraction rate of polysaccharide was 11.26% under the extraction conditions.

CONCLUSION

The process is simple, stable and practicable, and can be used for the extraction of mycelium polysaccharides from selenium-rich Morchella esculenta.

Two new metabolites from a soil fungus Curvularia affinis strain HS-FG-196

Two new metabolites, pyrenocine J (1) and pyrenochaetic acid D (2), together with two known metabolites, pyrenocine A (3) and pyrenochaetic acid A (4), were isolated from a soil fungus, Curvularia affinis strain HS-FG-196. Their structures were established by extensive spectroscopic analysis. Compound 1 showed cytotoxic activity against the human hepatic cancer cell line HepG2 with an IC(50) value of 28.5 μg/ml.

Chemical and sensory effects of the freezing process on the aroma profile of black truffles (Tuber melanosporum)

The aim of this work was to evaluate the effect of freezing black truffles (Tuber melanosporum) on their aroma both in sensory and chemical terms. The truffles were frozen at temperatures of -20 to -80°C. Descriptive and discriminative sensory and chemical analyses, based on headspace solid phase microextraction followed by gas chromatography-mass spectrometry analysis (HS-SPME-GC-MS), were carried out after 1, 20, 40 and 60 days. Fifteen compounds with high aromatic potential in truffles were determined. Their selective ion peak areas were calculated, summed and expressed as percentage of active odour compound, in order to monitor changes in odour profile. The aroma of frozen truffles differed significantly from the aroma of fresh truffles. Volatile composition data revealed that T. melanosporum aromatic profile is deeply modified as a consequence of a freezing process. These aromatic changes could explain the loss of freshness observed in all frozen truffles. Methional and some phenols were suggested as markers of freezing time. Interestingly, 1-octen-3-one appeared as a general marker of freezing process.

A macrocyclic β-iodoallenolate intermediate is key: synthesis of the ABD core of phomactin A

An enantioselective strategy for the synthesis of phomactin natural products is described. The Lewis acid triggered cyclization of a β-iodoallenolate embedded in a 12-membered macrocycle was used to obtain a highly functionalized bicyclo[9.3.1]pentadecane in good yield and high diastereoselectivity. This iodoenone contains the substituents of the AD ring system of the phomactin family of natural products, appropriate for further functionalization. Synthesis of the oxadecalin core of phomactin A from the AD iodoenone intermediate was achieved. In this unusual strategy, rings A and B are both fashioned within a macrocyclic precursor.

Polyketide metabolites from the endophytic fungus Microdiplodia sp. KS 75-1

Through our screening for new natural compounds, four new polyketide metabolites, 7,8-dihydonivefuranone A (1), 6(7)-dehydro-8-hydroxyterrefuranone (2), 8-hydroxyterrefuranone (3), and 6-hydroxyterrefuranone (4) were isolated from the fermentation extract of Microdiplodia sp. KS 75-1, together with the known compounds nivefuranones A (5) and B (6); their structures were determined by spectroscopic (NMR, UV and IR) and MS analysis. Compounds 1, 2, 4 and 5 showed antimicrobial activity against Candida albicans and Staphylococcus aureus.

Case study of empirical and computational chemical shift analyses: reassignment of the relative configuration of phomopsichalasin to that of diaporthichalasin

Phomopsichalasin was isolated and assigned structure 1 over 15 years ago. Analysis of its proton NMR data led us to hypothesize that not all aspects of the relative configuration of this structure were correct. We have used both empirical and computational methods to propose an alternative structure. Diaporthichalasin was reported several years ago, and its structure was assigned as 7, a diastereomer of structure 1, and confirmed by a single-crystal X-ray study. We have shown that diaporthichalasin and phomopsichalasin are identical; that is, both have structure 7. Additional aspects of NMR interpretation that provide guidance for avoiding some of the pitfalls that can lead to incorrect structure assignments are discussed. These recommendations/reminders include (i) the use of complementary solvents for acquiring NMR data that break accidental chemical shift degeneracy, (ii) the importance of assigning coupling constants as extensively as possible, and (iii) exercising caution when interpreting correlations in 2D spectra where overlapping resonances are involved.

Morphology regulatory metabolites from Arthrobotrys oligospora

Novel autoregulatory metabolites, arthrosporols A-C (1-3), involved in regulating the morphological switch in fungi, were purified and characterized from the carnivorous fungus Arthrobotrys oligospora. These compounds possess a novel hybrid carbon skeleton consisting of an epoxy-cyclohexenol combined with a rare monocyclic sesquiterpenol substructure. This is the first report of a monocyclic sesquiterpenol of this type of fungal origin. Compounds 1-3 displayed significant inhibitory activities toward the formation of conidiophores, while compounds 1 and 3 showed the opposite effects on the formation of a two-dimensional network with increasing rates of 40-90% and inhibiting rates of 30-90%, respectively.

Anticancer activity of sclerotiorin, isolated from an endophytic fungus Cephalotheca faveolata Yaguchi, Nishim. & Udagawa

Biodiversity provides critical support for drug discovery. A significant proportion of drugs are derived, directly or indirectly, from biological sources. Through high throughput screening (HTS) and bioassay-guided isolation, bioactive compound sclerotiorin has been isolated from an endophytic fungus Cephalotheca faveolata. Sclerotiorin was found to be potent anti-proliferative against different cancer cells. In this study sclerotiorin has been found to induce apoptosis in colon cancer (HCT-116) cells through the activation of BAX, and down-regulation of BCL-2, those further activated cleaved caspase-3 causing apoptosis of cancer cells.

Agropyrenol and agropyrenal, phytotoxins from Ascochyta agropyrina var. nana, a fungal pathogen of Elitrigia repens

A strain of Ascochyta agropyrina var. nana, a fungal pathogen of the perennial weed Elytrigia repens, produced several toxins in a liquid medium, and its primary toxin, named agropyrenol, was characterized as a substituted salicylaldehyde on the basis of its chemical and spectroscopic properties. Its absolute stereochemistry was determined by Mosher's method. Two other minor metabolites were isolated from the same culture and named agropyrenal and agropyrenone, respectively. They were characterized as a trisubstituted naphthalene carbaldehyde and a pentasubstituted 3H-benzofuranone, respectively, using the same techniques. When assayed on leaves of several weed plants, i.e., Mercurialis annua, Chenopodium album and Setaria viridis, agropyrenol proved to be phytotoxic, causing the appearance of necrotic lesions, agropyrenal was less active, while agropyrenone was inactive. None of the compounds showed antibiotic, fungicidal or zootoxic activity.

Isolation and structural elucidation of cyclic tetrapeptides from Onychocola sclerotica

Three new cyclic tetrapeptides (1-3) have been isolated from the crude fermentation extract of Onychocola sclerotica. The planar structures of 1-3 were elucidated by detailed spectroscopic analyses using one- and two-dimensional NMR experiments and high-resolution mass spectrometry. The absolute configuration of the amino acid residues in each cyclotetrapeptide was established by Marfey's method. Compounds 1-3 displayed activity as cardiac calcium channel blockers (Cav1.2) but did not inhibit the hERG potassium channel and were not cytotoxic. These peptides are the first secondary metabolites ever reported from fungi of the order Arachnomycetales.

Phomentrioloxin: A phytotoxic pentasubstituted geranylcyclohexentriol produced by Phomopsis sp., a potential mycoherbicide for Carthamus lanatus Biocontrol

A new phytotoxic geranylcyclohexenetriol, named phomentrioloxin, was isolated from the liquid culture of Phomopsis sp., a fungal pathogen proposed for the biological control of Carthamus lanatus, a widespread and troublesome thistle weed belonging to the Asteraceae family causing severe crop and pastures losses in Australia. The structure of phomentrioloxin was established by spectroscopic, X-ray, and chemical methods as (1S,2S,3S,4S)-3-methoxy-6-(7-methyl-3-methylene-oct-6-en-1-ynyl)cyclohex-5-ene-1,2,4-triol. At a concentration of 6.85 mM, the toxin causes the appearance of necrotic spots when applied to leaves of both host and nonhost plants. It also causes growth and chlorophyll content reduction of fronds of Lemna minor and inhibition of tomato rootlet elongation. Finally, in preliminary bioassays, phomentrioloxin did not show any antibacterial, fungicidal, or zootoxic activities.

Secondary metabolites from fungus Nigrospora sp

Six compounds were purified from the extracts of fungus Z18-17 (Nigrospora sp.) isolated from Scyphiphora hydrophyllacea, a tree from the intertidal zone of Shankou, Guangxi Province of China, which was reported to have cytotoxic activity. Systematic study on the chemical constituents of Nigrospora sp. resulted in the isolation of one new 6-phenylhexanoic acid derivative, one new derivative of uridine, and four known compounds. Their structures were characterized, respectively, as methyl 5-acetamido-6-(4-hydroxyphenyl)-4-oxohexanoate (1), uridine-5'α-hydroxypropanoate (2), 4-hydroxyphenethyl 2-hydroxypropanoate (3), methyl pyroglutamate (4), cyclo (Pro-Val) (5), and cyclo (Phe-Hyp) (6). The cytotoxic activities of the two new compounds against HL-60 cell line were tested and the IC(50) values of the two new compounds were all over 100 μM.

Pinolide, a new nonenolide produced by Didymella pinodes , the causal agent of ascochyta blight on Pisum sativum

An aggressive isolate of Didymella pinodes isolated from pea ( Pisum sativum ) produced four different metabolites in vitro. The metabolites isolated from the culture filtrates were characterized by spectroscopic and optical methods. A new nonenolide, named pinolide, was isolated and characterized as (2S*,7R*,8S*,5E,9R*)-2,7,8-trihydroxy-9-propyl-5-nonen-9-olide. Pinolidoxin, the main toxin produced by D. pinodes, was also isolated together with two other closely related nonenolides, identified as herbarumin II and 2-epi-herbarumin II. Herbarumin II and 2-epi-herbarumin II have been previously isolated from the fungi Phoma herbarum and Paraphaeosphaeria recurvifoliae , respectively, but described here to be isolated for the first time from D. pinodes. When tested on leaves of the host plant and other legumes and weeds, pinolidoxin was phytotoxic in all of the plant species, whereas the other three nonenolides did not produce any symptoms. The importance of the stereochemistry of the hydroxy group at C-7 on phytotoxicity also is discussed.

Antibacterial anthraquinone derivatives from a sea anemone-derived fungus Nigrospora sp

Chemical investigation of a marine-derived fungus Nigrospora sp., isolated from an unidentified sea anemone, yielded two new hydroanthraquinone analogues, 4a-epi-9α-methoxydihydrodeoxybostrycin (1) and 10-deoxybostrycin (2), together with seven known anthraquinone derivatives (3-9). The structures of the two new compounds were established through extensive NMR spectroscopy as well as a single-crystal X-ray diffraction analysis using Cu Kα radiation. The antibacterial activities of compounds 1-9 and 10 acetyl derivatives (6a, 7a, 8a-8g, 9a) were evaluated in vitro. Compound 6a, the acetylated derivative of 6, exhibited promising activity against Bacillus cereus with an MIC value of 48.8 nM, which was stronger than that of the positive control ciprofloxacin (MIC = 1250 nM). Analysis of the antibacterial screening data for the metabolites and their acetyl derivatives revealed the key structural features required for this activity.

Antiprotozoal and antimicrobial compounds from the plant pathogen Septoria pistaciarum

Four new 1,4-dihydroxy-5-phenyl-2-pyridinone alkaloids, 17-hydroxy-N-(O-methyl)septoriamycin A (1), 17-acetoxy-N-(O-methyl)septoriamycin A (2), 13-(S)-hydroxy-N-(O-methyl)septoriamycin A (3), and 13-(R)-hydroxy-N-(O-methyl)septoriamycin A (4), together with the known compounds (+)-cercosporin (5), (+)-14-O-acetylcercosporin (6), (+)-di-O-acetylcercosporin (7), lumichrome, and brassicasterol, were isolated from an ethyl acetate extract of a culture medium of Septoria pistaciarum. Methylation of septoriamycin A (8) with diazomethane yielded three di-O-methyl analogues, two of which existed as mixtures of rotamers. We previously reported antimalarial activity of septoriamycin A. This compound also exhibited significant activity against Leishmania donovani promastigotes. Compounds 5-7 showed moderate in vitro activity against L. donovani promastigotes and chloroquine-sensitive (D6) and -resistant (W2) strains of Plasmodium falciparum, whereas compound 5 was fairly active against methicillin-sensitive and methicillin-resistant strains of Staphylococcus aureus. Compounds 5-7 also displayed moderate phytotoxic activity against both a dicot (lettuce, Lactuca sativa) and a monocot (bentgrass, Agrostis stolonifera) and cytotoxicity against a panel of cell lines.

Cytotoxic metabolites from the antarctic psychrophilic fungus Oidiodendron truncatum

Two new epipolythiodioxopiperazines, named chetracins B and C (1 and 2), and five new diketopiperazines, named chetracin D (4) and oidioperazines A-D (5, 10, 12, and 13), were isolated from the fungus Oidiodendron truncatum GW3-13, along with six known compounds (3, 6, 7, 8, 9, and 11). Their structures were elucidated by extensive NMR, MS, and CD analyses, as well as chemical transformation. An in vitro MTT cytotoxicity assay revealed potent biological activity for 1 in the nanomolar range against a panel of five human cancer lines.

Induction of apoptosis against cancer cell lines by four ascomycetes (endophytes) from Malaysian rainforest

Endophytic fungi have been shown to be a promising source of biologically active natural products. In the present study, extracts of four endophytic fungi isolated from plants of the National Park, Pahang were evaluated for their cytotoxic activity and the nature of their active compounds determined. Those extracts exhibiting activity with IC(50) values less than 17 μg/ml against HCT116, MCF-7 and K562 cell lines were shown to induce apoptosis in these cell lines. Molecular analysis, based on sequences of the rDNA internal transcribed spacers ITS1 and ITS4, revealed all four endophytic fungi to be ascomycetes: three sordariomycetes and a dothideomycete. Six known compounds, cytochalasin J, dechlorogriseofulvin, demethylharzianic-acid, griseofulvin, harzianic acid and 2-hexylidene-3-methyl-succinic acid were identified from a rapid dereplication technique for fungal metabolites using an in-house UV library. The results from the present study suggest the potential of endophytic fungi as cytotoxic agents, and there is an indication that the isolates contain bioactive compounds that mainly kill cancer cells by apoptosis.

Afritoxinones A and B, dihydrofuropyran-2-ones produced by Diplodia africana the causal agent of branch dieback on Juniperus phoenicea

Two phytotoxic dihydrofuropyran-2-ones, named afritoxinones A and B, were isolated from liquid culture of Diplodia africana, a fungal pathogen responsible for branch dieback of Phoenicean juniper in Italy. Additionally, six others known metabolites were isolated and characterized: oxysporone, sphaeropsidin A, epi-sphaeropsidone, R-(-)-mellein, (3R,4R)-4-hydroxymellein and (3R,4S)-4-hydroxymellein. The structures of afritoxinones A and B were established by spectroscopic and optical methods and determined to be as (3aS(*),6R(*),7aS)-6-methoxy-3a,7a-dihydro-3H,6H-furo[2,3-b]pyran-2-one and (3aR(*),6R(*),7aS)-6-methoxy-3a,7a-dihydro-3H,6H-furo[2,3-b]pyran-2-one, respectively. The phytotoxic activity of afritoxinones A and B and oxysporone was evaluated on host (Phoenicean juniper) and non-host plant (holm oak, cork oak and tomato) by cutting and leaf puncture assay. Oxysporone proved to be the most phytotoxic compound. This study represents the first report of secondary metabolites produced by D. africana. In addition, the taxonomic implications of secondary metabolites in Botryosphaeriaceae family studies are discussed.

Intraspecific genotypic variability determines concentrations of key truffle volatiles

• Aroma variability in truffles has been attributed to maturation (Tuber borchii), linked to environmental factors (Tuber magnatum), but the involvement of genetic factors has been ignored. We investigated aroma variability in Tuber uncinatum, a species with wide distribution. Our aim was to assess aroma variability at different spatial scales (i.e. trees, countries) and to quantify how aroma was affected by genotype, fruiting body maturity, and geographical origin. • A volatile fingerprinting method was used to analyze the aroma of 223 T. uncinatum fruiting bodies from seven European countries. Maturity was estimated from spore melanization. Genotypic fingerprinting was performed by amplified fragment length polymorphism (AFLP). • Discriminant analysis revealed that, regardless of the geographical origin of the truffles, most of the aroma variability was caused by eight-carbon-containing volatiles (C8-VOCs). In an orchard of T. uncinatum, truffles producing different concentrations of C8-VOCs clustered around distinct host trees. This clustering was not associated with maturity, but was associated with fungal genotype. • These results indicate that the variation in C8-VOCs in truffles is most likely under genetic control. They exemplify that understanding the factors behind aroma variability requires a holistic approach. Furthermore, they also raise new questions regarding the ecological role of 1-octen-3-ol in truffles.

Geopyxins A-E, ent-kaurane diterpenoids from endolichenic fungal strains Geopyxis aff. majalis and Geopyxis sp. AZ0066: structure-activity relationships of geopyxins and their analogues

Four new ent-kaurane diterpenoids, geopyxins A-D (1-4), were isolated from Geopyxis aff. majalis, a fungus occurring in the lichen Pseudevernia intensa, whereas Geopyxis sp. AZ0066 inhabiting the same host afforded two new ent-kaurane diterpenoids, geopyxins E and F (5 and 6), together with 1 and 3. The structures of 1-6 were established on the basis of their spectroscopic data, while the absolute configurations were assigned using modified Mosher's ester method. Methylation of 1-3, 5, and 6 gave their corresponding methyl esters 7-11. On acetylation, 1 and 7 yielded their corresponding monoacetates 12 and 14 and diacetates 13 and 15. All compounds were evaluated for their cytotoxic and heat-shock induction activities. Compounds 2, 7-10, 12, 14, and 15 showed cytotoxic activity in the low micromolar range against all five cancer cell lines tested, but only compounds 7-9, 14, and 15 were found to activate the heat-shock response at similar concentrations. From a preliminary structure-activity perspective, the electrophilic α,β-unsaturated ketone carbonyl motif present in all compounds except 6 and 11 was found to be necessary but not sufficient for both cytotoxicity and heat-shock activation.

Isolation, structure elucidation, and antibacterial activity of methiosetin, a tetramic acid from a tropical sooty mold (Capnodium sp.)

Drug-resistant bacteria continue to make many existing antibiotic classes ineffective. In order to avoid a future epidemic from drug-resistant bacterial infections, new antibiotics with new modes of action are needed. In an antibiotic screening program for new drug leads with new modes of action using antisense Staphylococcus aureus Fitness Test screening, we discovered a new tetramic acid, methiosetin, from a tropical sooty mold, Capnodium sp. The fungus also produced epicorazine A, a known antibiotic. The structure and relative configuration of methiosetin was elucidated by 2D NMR and ESIMS techniques. Methiosetin and epicorazine A showed weak to modest antibacterial activity against S. aureus and Haemophilus influenzae. The isolation, structure elucidation, and antibacterial activity of both compounds are described.

A thiopyranchromenone and other chromone derivatives from an Endolichenic fungus, Preussia africana

The first example of a naturally occurring thiopyranchromenone, preussochromone A (1), and five other new chromone derivatives, preussochromones B-F (2-6), were isolated from solid cultures of an endolichenic fungus, Preussia africana. The structures of 1-6 were established primarily by NMR experiments, and 2 and 4 were further confirmed by X-ray crystallography. The absolute configurations of 1 and 2 were determined by the application of electronic circular dichroism (ECD), whereas those of C-5 in 3, C-6 in 4, and the 6,7-diol in 5 were deduced via the CD data of the in situ formed [Rh₂(OCOCF₃)₄] complex, the modified Mosher method, and Snatzke's method, respectively. Compounds 1 and 3 showed significant cytotoxicity against A549 cells.