Maximizing chemical diversity of fungal metabolites: biogenetically related Heptaketides of the endolichenic fungus Corynespora sp. (1)

Bifusicoumarins A-D: Cytotoxic 3S-dihydroisocoumarins from the entomopathogenic fungus Cordyceps bifusispora (NBRC 108997)

Cordyceps is a genus of ascomycete fungi with some of them being edible and/or having a long tradition in Chinese medicine. The chemical characterization of a solvent extract of the entomopathogenic fungus Cordyceps bifusispora afforded four undescribed coumarins, bifusicoumarin A-D (1-4), along with previously reported metabolites (5-8). Structural elucidation was performed via NMR, UV and HRMS analyses, X-ray single crystal diffraction and experimental ECD. The high throughput resazurin reduction assay, that measures cell viability, indicated that 5 has a IC₅₀ between 1 and 15 μM for several assayed tumor lines. Moreover, a protein-interaction network indicated that C. bifusispora is a promising source of additional antitumor metabolites based on SwissTargetPrediction software predictions.

Epigenetic Manipulation Induced Production of Immunosuppressive Chromones and Cytochalasins from the Mangrove Endophytic Fungus Phomopsis asparagi DHS-48

A mangrove endophytic fungus Phomopsis asparagi DHS-48 was found to be particularly productive with regard to the accumulation of substantial new compounds in our previous study. In order to explore its potential to produce more unobserved secondary metabolites, epigenetic manipulation was used on this fungus to activate cryptic or silent genes by using the histone deacetylase (HDAC) inhibitor sodium butyrate and the DNA methyltransferase (DNMT) inhibitor 5-azacytidine (5-Aza). Based on colony growth, dry biomass, HPLC, and ¹H NMR analyses, the fungal chemical diversity profile was significantly changed compared with the control. Two new compounds, named phaseolorin J (1) and phomoparagin D (5), along with three known chromones (2–4) and six known cytochalasins (6–11), were isolated from the culture treated with sodium butyrate. Their structures, including their absolute configurations, were elucidated using a combination of detailed HRESIMS, NMR, and ECD and ¹³C NMR calculations. The immunosuppressive and cytotoxic activities of all isolated compounds were evaluated. Compounds 1 and 8 moderately inhibited the proliferation of ConA (concanavalin A)-induced T and LPS (lipopolysaccharide)-induced B murine spleen lymphocytes. Compound 5 exhibited significant in vitro cytotoxicity against the tested human cancer cell lines Hela and HepG2, which was comparative to the positive control adriamycin and fluorouracil. Our finding demonstrated that epigenetic manipulation should be an efficient strategy for the induction of new metabolites from mangrove endophytic fungi.

An acetonic extract and secondary metabolites from the endolichenic fungus Nemania sp. EL006872 exhibit immune checkpoint inhibitory activity in lung cancer cell

Background: Endolichenic fungi (ELF), which live the inside the lichen thallus, contain many secondary metabolites that show various biological activities. Recent studies show that lichen and ELF secondary metabolites have antioxidant, antibacterial, antifungal, cytotoxic, and anticancer activities.

Purpose: Here, the effects of an ELF extract and its bioactive compounds were investigated on the H1975 cell line focusing on immune checkpoint marker inhibition.

Methods: An ELF was isolated from the host lichen Bryoria fuscescens (Gyelnik) Brodo and D. Hawksw and identified the species as Nemania sp. EL006872. The fungus was cultured on agar medium and acetonic extracts were obtained. Secondary metabolites radianspenes C and D, and dahliane D, were isolated from the crude extract. The biological effects of both the crude extract and the isolated secondary metabolites were evaluated in cell viability, qRT-PCR assays, flow cytometry analysis and western blotting.

Results: The cell viability assay revealed that extracts from Nemania sp. EL006872 and the isolated secondary compounds had low cytotoxicity. The crude extract, radianspenes C and D, and dahliane D, suppressed expression of mRNA encoding PD-L1 and aromatic hydrocarbon receptor (AhR), and surface expression of PD-L1 protein by cells exposed to benzo[a] pyrene. Radianspenes C and D, and dahliane D, reduced expression of AhR, PD-L1, ICOSL, and GITRL proteins by H1975 lung cancer cells, as well as exerting anti-proliferative effects.

Conclusion: Radianspenes C and D, and dahliane D, bioactive compounds isolated from Nemania sp. EL006872 ELF, have the potential for use as immunotherapy and immunoncology treatments.

Annulohypoxylon sp. strain MUS1, an endophytic fungus isolated from Taxus wallichiana Zucc., produces taxol and other bioactive metabolites

The current study focuses on the isolation and in vitro characterization of bioactive metabolites produced by endophytic fungi isolated from the Himalayan yew (Taxus wallichiana Zucc.). The endophytic fungi were isolated on artificial media from inner tissues of bark and needles. Antimicrobial and antioxidant activity, along with total phenolic- and flavonoid-content assays were used in the evaluation of bioactivity of the fermented crude extracts. The ability of the endophytes to produce the anticancer compound Taxol was also analyzed using thin-layer chromatography (TLC) and reverse-phase high-performance liquid chromatography (RP-HPLC). A total of 16 fungal morphotypes were obtained from asymptomatic inner tissues of the bark and needles of T. wallichiana. Among the 16 isolates, the ethyl acetate (EA) fraction of isolate MUS1, showed antibacterial and antifungal activity against all test-pathogens used (Streptococcus faecalis ATCC 19433, Staphylococcus aureus ATCC 12600, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25922, Salmonella enterica ATCC 13076, Pseudomonas aeruginosa ATCC 27853, and Candida albicans). MUS1 showed significant inhibition against Pseudomonas aeruginosa ATCC 27853 (minimum inhibitory concentration (MIC): 250 µg/ml) and the pathogenic yeast, Candida albicans (MIC: 125 µg/ml). Antioxidant activity, total phenolic, and total flavonoid content as well as in vitro Taxol production were evaluated for EA fraction of isolate MUS1. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. At a concentration of 100 µg/ml, the % DPPH radical scavenging activity was 83.15 ± 0.40, 81.62 ± 0.11, and 62.36 ± 0.29, for ascorbic acid, butylated hydroxytoluene (BHT), and the EA fraction of MUS1, respectively. The DPPH-Half maximal inhibitory concentration (DPPH-IC₅₀) value for the EA fraction was 81.52 ± 0.23 µg/ml, compared to BHT (62.87 ± 0.08 µg/ml) and ascorbic acid (56.15 ± 0.19 µg/ml). The total phenolic and flavonoid content in the EA fraction were 16.90 ± 0.075 µg gallic acid equivalent (GAE) and 11.59 ± 0.148 µg rutin equivalent (RE), per mg of dry crude extract, respectively. TLC and RP-HPLC analysis showed that the isolate MUS1 also produces Taxol (282.05 µg/l of fermentation broth). Isolate MUS1 was identified as Annulohypoxylon sp. by internal transcribed spacer (ITS) sequencing. Having the ability to produce antimicrobial and antioxidant metabolites, as well as the anticancer compound Taxol, makes Annulohypoxylon sp. strain MUS1, a promising candidate for further study of naturally occurring bioactive metabolites.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02693-z.

An epigenetic modifier induces production of 3-(4-oxopyrano)-chromen-2-ones in Aspergillus sp. AST0006, an endophytic fungus of Astragalus lentiginosus

Incorporation of the epigenetic modifier suberoylanilide hydroxamic acid (SAHA) into a potato dextrose broth culture of the endophytic fungus Aspergillus sp. AST0006 affected its polyketide biosynthetic pathway providing two new 3-(4-oxopyrano)-chromen-2-ones, aspyranochromenones A (1) and B (2), and the isocoumarin, (-)-6,7-dihydroxymellein (3). Eight additional metabolites (4-11) and two biotransformation products of SAHA (12-13) were also encountered. The planar structures and relative configurations of the new metabolites 1-2 were elucidated with the help of high-resolution mass, 1D and 2D NMR spectroscopic data and the absolute configurations of 1-3 were determined by comparison of experimental and calculated ECD data. Possible biosynthetic pathways to 1 and 2 are presented.

Antibacterial and cytotoxic metabolites of termite-associated Streptomyces sp. BYF63

Four anthraquinone derivatives, termstrin A, B, C and D (1-4), were isolated and purified from termite-associated Streptomyces sp. BYF63. Their structures were elucidated on the basis of extensive spectroscopic analyses (HR-ESI-MS, 1D and 2D NMR). Compounds 1 and 4 were found to possess potent antibacterial activities against Staphylococcus aureus, with the zone of inhibition (ZOI) values of 12.85 and 11.17 mm, respectively, which were comparable to that of penicillin sodium with ZOI of 13.15 mm. Furthermore, metabolite 1 showed moderate cytotoxicities against melanoma cell line A375 and gastric cancer cell line MGC-803, with IC₅₀ values of 22.76 and 36.65 μM, respectively, which were less than those of referenced adriamycin.

An Isoform-Selective PTP1B Inhibitor Derived from Nitrogen-Atom Augmentation of Radicicol

A library of natural products and their derivatives was screened for inhibition of protein tyrosine phosphatase (PTP) 1B, which is a validated drug target for the treatment of obesity and type II diabetes. Of those active in the preliminary assay, the most promising was compound 2 containing a novel pyrrolopyrazoloisoquinolone scaffold derived by treating radicicol (1) with hydrazine. This nitrogen-atom augmented radicicol derivative was found to be PTP1B selective relative to other highly homologous nonreceptor PTPs. Biochemical evaluation, molecular docking, and mutagenesis revealed 2 to be an allosteric inhibitor of PTP1B with a submicromolar Ki. Cellular analyses using C2C12 myoblasts indicated that 2 restored insulin signaling and increased glucose uptake.

Wood-decaying fungi found in Ghana: A rich source of new anti-infective compounds

Background: Discovery of bioactive natural products are instrumental for development of novel antibiotics. The discovery and development of natural products such as penicillin represented a major milestone in the treatment of bacterial infections. Currently, many antibiotics have lost their relevance in clinics due to the emergence of drug-resistant microbial pathogens. Hence, there is the need for continuous search of new compounds endowed with potent antimicrobial activity. Methods: In this study, wood-decaying fungi (WDF) from Ghana were explored for their potential as sources of novel antimicrobial compounds with intent of expanding the effort into a drug discovery programme in the near future. Extracts from cultures of 54 morphologically distinct WDF isolates were analyzed for the presence of antimicrobial agents. Results: The extracts from 40 out of the 54 WDF isolates exhibited significant antimicrobial activity against either Staphylococcus aureus, Escherichia coli or Candida albicans. Fractionation of these bioactive extracts, followed by bioassay of the organic fractions obtained, indicate that extracts exhibiting antimicrobial activity against more than one of the three test organisms could be attributed to the presence of different bioactive compounds. Analysis of the composition of the extracts revealed that terpenes were predominant. Conclusions: This study suggests that a significant proportion of WDF in Ghana produce antimicrobial compounds which could be potential sources of novel anti-infective agents and support the plans of developing a drug discovery programme in Ghana based on the fermentation of WDF.

Modulation of polyketide biosynthetic pathway of the endophytic fungus, Anteaglonium sp. FL0768, by copper (II) and anacardic acid

In an attempt to explore the biosynthetic potential of endosymbiotic fungi, the secondary metabolite profiles of the endophytic fungus, Anteaglonium sp. FL0768, cultured under a variety of conditions were investigated. In potato dextrose broth (PDB) medium, Anteaglonium sp. FL0768 produced the heptaketides, herbaridine A (1), herbarin (2), 1-hydroxydehydroherbarin (3), scorpinone (4), and the methylated hexaketide 9S,11R-(+)-ascosalitoxin (5). Incorporation of commonly used epigenetic modifiers, 5-azacytidine and suberoylanilide hydroxamic acid, into the PDB culture medium of this fungus had no effect on its secondary metabolite profile. However, the histone acetyl transferase inhibitor, anacardic acid, slightly affected the metabolite profile affording scorpinone (4) as the major metabolite together with 1-hydroxydehydroherbarin (3) and a different methylated hexaketide, ascochitine (6). Intriguingly, incorporaion of Cu2+ into the PDB medium enhanced production of metabolites and drastically affected the biosynthetic pathway resulting in the production of pentaketide dimers, palmarumycin CE4 (7), palmarumycin CP4 (8), and palmarumycin CP1 (9), in addition to ascochitine (6). The structure of the new metabolite 7 was established with the help of spectroscopic data and by MnO2 oxidation to the known pentaketide dimer, palmarumycin CP3 (10). Biosynthetic pathways to some metabolites in Anteaglonium sp. FL0768 are presented and possible effects of AA and Cu2+ on these pathways are discussed.

Phytotoxic Activity of Metabolites Isolated from Rutstroemia sp.n., the Causal Agent of Bleach Blonde Syndrome on Cheatgrass (Bromus tectorum)

A fungal pathogen soon to be described as Rutstroemia capillus-albis (Rutstroemiaceae, Helotiales, Leotiomycetes) has been identified as the causal agent of 'bleach blonde syndrome' on the invasive annual grass weed Bromus tectorum (cheatgrass) in western North America. This apparently common but previously undescribed disease causes premature senescence and sterility, but does not affect seed germination or seedling emergence and growth. This study investigated whether the new species produces phytotoxins that could be implicated in pathogenesis. The compounds 9-O-methylfusarubin, 9-O-methylbostrycoidin, 5-O-methylnectriafurone, trans-methyl-p-coumarate and terpestacin were isolated from the solid culture of this fungus. The undescribed absolute stereochemistry at C-3 of 9-O-methylfusarubin and at C-1' of 5-O-methylnectriafurone were assigned by applying electronic and vibrational circular dichroism (ECD and VCD) combined with computational methods and the advanced Mosher's method, respectively. The first three listed compounds are naphtoquinone pigments, while terpestacin is a sesterterpene, and trans-methyl-p-coumarate could be the product of an unusual fungal phenylpropanoid biosynthesis pathway. In a juvenile plant immersion bioassay, both 9-O-methylfusarubin and terpestacin proved to be highly toxic at 10^-4 M, causing wilting and plant death within 10 days. This finding suggests that these two compounds could play a role in pathogenesis on B. tectorum.

Fungal Diversity in Lichens: From Extremotolerance to Interactions with Algae

Lichen symbioses develop long-living thallus structures even in the harshest environments on Earth. These structures are also habitats for many other microscopic organisms, including other fungi, which vary in their specificity and interaction with the whole symbiotic system. This contribution reviews the recent progress regarding the understanding of the lichen-inhabiting fungi that are achieved by multiphasic approaches (culturing, microscopy, and sequencing). The lichen mycobiome comprises a more or less specific pool of species that can develop symptoms on their hosts, a generalist environmental pool, and a pool of transient species. Typically, the fungal classes Dothideomycetes, Eurotiomycetes, Leotiomycetes, Sordariomycetes, and Tremellomycetes predominate the associated fungal communities. While symptomatic lichenicolous fungi belong to lichen-forming lineages, many of the other fungi that are found have close relatives that are known from different ecological niches, including both plant and animal pathogens, and rock colonizers. A significant fraction of yet unnamed melanized (‘black’) fungi belong to the classes Chaethothyriomycetes and Dothideomycetes. These lineages tolerate the stressful conditions and harsh environments that affect their hosts, and therefore are interpreted as extremotolerant fungi. Some of these taxa can also form lichen-like associations with the algae of the lichen system when they are enforced to symbiosis by co-culturing assays.

Fungal communities associated with Evernia prunastri, Ramalina fastigiata and Pleurosticta acetabulum: Three epiphytic lichens potentially active against Candida biofilms

Fungal communities associated to three epiphytic lichens active against Candida, were investigated using culture-based methods We hypothetized that associated fungi would contribute to lichens activities. The ability of specific fungi to grow inside or outside lichens was investigated. To detect biogenesis pathways involved in the production of secondary metabolites, genes coding for nonribosomal peptide synthetase (NRPS) and polyketide synthase I (PKS I) were screened by PCR from fungal DNA extracts. Both endo and epilichenic communities were isolated from two fructicose (Evernia prunastri and Ramalina fastigiata) and one foliose (Pleurosticta acetabulum) lichens. A total of 86 endolichenic and 114 epilichenic isolates were obtained, corresponding to 18 and 24 phylogenetic groups respectively suggesting a wide diversity of fungi. The communities and the species richness were distinct between the three lichens which hosted potentially new fungal species. Additionally, the endo- and epilichenic communities differed in their composition: Sordariomycetes were particularly abundant among endolichenic fungi and Dothideomycetes among epilichenic fungi. Only a few fungi colonized both habitats, such as S. fimicola, Cladosporium sp1 and Botrytis cinerea. Interestingly, Nemania serpens (with several genotypes) was the most abundant endolichenic fungus (53% of isolates) and was shared by the three lichens. Finally, 12 out of 36 phylogenetic groups revealed the presence of genes coding for nonribosomal peptide synthetase (NRPs) and polyketide synthase I (PKS I). This study shows that common lichens are reservoirs of diverse fungal communities, which could potentially contribute to global activity of the lichen and, therefore, deserve to be isolated for further chemical studies.

Acetonic extracts of the endolichenic fungus EL002332 isolated from Endocarpon pusillum exhibits anticancer activity in human gastric cancer cells

BACKGROUND

Endolichenic fungi are microbes that inhabit the thalli of lichens and produce various unique chemicals that can be used for pharmaceutical purposes.

PURPOSE

This study screened a library of endolichenic fungal extracts to identify novel anticancer agents capable of suppressing the tumorigenicity of human cancer cells.

METHODS

Active compounds were isolated from extracts of endolichenic fungi by column chromatography and reverse-phase HPLC. The anticancer effects of the extracts on cell viability was assessed with the use of MTT assay, Western blotting, fluorescence labeling of apoptotic cell, and flow cytometric analysis; and cell motility with the use of migration, invasion and soft agar colony-formation assay in vitro; and on skin and intraperitoneal mouse xenograft tumors in vivo were investigated. The therapeutic effects of the extract alone or in combination with the conventional chemoreagent docetaxel were analyzed by sulforhodamine B assay.

RESULTS

Acetone extracts of EL002332, isolated from Endocarpon pusillum collected in the China desert in 2010, showed selective cytotoxicity against AGS human gastric cancer cells and CT26 mouse colon cancer cells. An active pure compound named myC was isolated from mycelium acetone extracts in a liquid culture system and showed more potent cytotoxicity than crude extracts in the AGS cell line. Especially, myC greatly increased the apoptotic cell population at the IC₅₀ concentration and activated apoptotic signaling by regulating Bcl2 family protein expression and caspase pathway activity. EL002332 crude extracts and myC decreased AGS cell motility at sub-lethal concentrations. In vivo skin and intraperitoneal xenograft tumor experiments showed that the size of tumors and the tumor score were significantly smaller in EL002332 crude extract-treated groups than in control groups. EL002332 crude extracts showed synergistic effects with docetaxel on the AGS and TMK1 cell lines.

CONCLUSION

The endolichenic fungus EL002332 has potential anticancer activity in gastric cancer and peritoneal carcinomatosis.

Effects of Growth Media on the Diversity of Culturable Fungi from Lichens

Microscopic and molecular studies suggest that lichen symbioses contain a plethora of associated fungi. These are potential producers of novel bioactive compounds, but strains isolated on standard media usually represent only a minor subset of these fungi. By using various in vitro growth conditions we are able to modulate and extend the fraction of culturable lichen-associated fungi. We observed that the presence of iron, glucose, magnesium and potassium in growth media is essential for the successful isolation of members from different taxonomic groups. According to sequence data, most isolates besides the lichen mycobionts belong to the classes Dothideomycetes and Eurotiomycetes. With our approach we can further explore the hidden fungal diversity in lichens to assist in the search of novel compounds.

p-Terphenyl Derivatives from the Endolichenic Fungus Floricola striata

Ten new p-terphenyl derivatives, floricolins A-J (1-10), together with six known compounds (11-16), were isolated from the extract of the endolichenic fungus Floricola striata. Chemical structures of these compounds were elucidated using spectroscopic data (HRESIMS and NMR). Among them, 9 and 10 were enantiomeric mixtures, and their configurations were established by single-crystal X-ray diffraction analysis using Cu Kα radiation. Evaluation of the isolated compounds against Candida albicans revealed that the most active compound, 3 (MIC 8 μg/mL), exerted fungicidal action by destruction of the cell membrane.

Myxochelins target human 5-lipoxygenase

Extracts of the predatory myxobacterium Pyxidicoccus fallax HKI 727 showed antiproliferative effects on leukemic K-562 cells. Bioactivity-guided fractionation led to the isolation of the bis-catechol myxochelin A and two new congeners. The biosynthetic origin of myxochelins C and D was confirmed by feeding studies with isotopically labeled precursors. Pharmacological testing revealed human 5-lipoxygenase (5-LO) as a molecular target of the myxochelins. In particular, myxochelin A efficiently inhibited 5-LO activity with an IC50 of 1.9 μM and reduced the proliferation of K-562 cells at similar concentrations.

Chromone derivatives from a sponge-derived strain of the fungus Corynespora cassiicola

Twelve new chromone derivatives, corynechromones A-L (1-12), were isolated from the sponge-derived fungus Corynespora cassiicola XS-200900I7. Among them, 1/2, 3/4, 5/6, and 7/8 were pairs of epimers. The planar structures were determined by extensive NMR spectroscopic data. The absolute configurations of 1-10 were assigned by the modified Mosher's method and TDDFT ECD calculations together with comparison of their CD spectra. These are the first chromone derivatives reported from the genus Corynespora. A possible rule to determine the absolute configurations at C-2 in chromone derivatives by CD was proposed.

One strain-many compounds (OSMAC) method for production of polyketides, azaphilones, and an isochromanone using the endophytic fungus Dothideomycete sp

Polyketides 1-6 were produced by a one strain-many compounds (OSMAC) approach using the endophytic fungus Dothideomycete sp. CRI7 as a producer. Metabolite production of the fungus Dothideomycete sp. CRI7 was sensitive to sources of potato and malt extract used for the preparation of PDB and Czapek malt media, respectively. Three hitherto unknown metabolites were obtained from the fungus CRI7 grown in PDB medium prepared from a commercial potato powder instead of fresh tubers of potato, while three others were obtained from the fungus cultivated in Czapek malt medium. Moreover, a source of malt extract used in the Czapek malt medium was found to influence metabolite production by the fungus CRI7. Structure elucidation of these compounds was achieved by analysis of spectroscopic data, as well as by single crystal X-ray analysis. Two of the compounds showed weak cytotoxic activity, while the remainders were inactive toward the cell lines tested. One compound exhibited radical scavenging activity with an IC50 value of 21.7 μM, and inhibited aromatase with an IC50 value of 12.3 μM.

Metabolites from Aspergillus versicolor, an endolichenic fungus from the lichen Lobaria retigera

Three new anthraquinone derivatives (1-3) and one new artifact (4) were isolated, along with six known anthraquinone derivatives (5-10) and three xanthones (11-13), from a culture of an endolichenic fungus, Aspergillus versicolor, that was isolated from the lichen Lobaria retigera. The structures of these substances were determined on the basis of 1D and 2D (COSY, HMQC, and HMBC) NMR and MS analyses. The substances 1-4 were also tested for their cytotoxic activity.

Functional chromatography reveals three natural products that target the same protein with distinct mechanisms of action

Access to lead compounds with defined molecular targets continues to be a barrier to the translation of natural product resources. As a solution, we developed a system that uses discrete, recombinant proteins as the vehicles for natural product isolation. Here, we describe the use of this functional chromatographic method to identify natural products that bind to the AAA+ chaperone, p97, a promising cancer target. Application of this method to a panel of fungal and plant extracts identified rheoemodin, 1-hydroxydehydroherbarin, and phomapyrrolidone A as distinct p97 modulators. Excitingly, each of these molecules displayed a unique mechanism of p97 modulation. This discovery provides strong support for the application of functional chromatography to the discovery of protein modulators that would likely escape traditional high-throughput or phenotypic screening platforms.

Herbarone, a rearranged heptaketide derivative from the sea hare associated fungus Torula herbarum

Herbarone (1), a novel heptaketide with a tetrahydro-5,9-methanobenzo[8]annulen-10(5H)-one skeleton, together with the new ent-astropaquinones B (2) and C (3) and four known pyranonaphthoquinones (4-7), was isolated from the sea hare associated fungus Torula herbarum. The structures of the new compounds were elucidated by detailed spectroscopic analysis, and the absolute configurations were determined by solution TDDFT/ECD calculations. Absolute configurations of the known compounds were studied by ECD measurements and calculations. The isolation of heptaketide 1 suggests that an intramolecular aldol reaction takes place to form the tricyclic scaffold.

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.

Heptaketides with antiviral activity from three endolichenic fungal strains Nigrospora sp., Alternaria sp. and Phialophora sp

Two new heptaketides, (+)-(2S,3S,4aS)-altenuene (1a) and (-)-(2S,3S,4aR)-isoaltenuene (2a), together with six known compounds, (-)-(2R,3R,4aR)-altenuene (1b), (+)-(2R,3R,4aS)-isoaltenuene (2b), 5'-methoxy-6-methyl-biphenyl-3,4,3'-triol (3), alternariol (4), alternariol-9-methyl ether (5), and 4-hydroxyalternariol-9-methyl ether (6) were isolated from the EtOAc extract of an endolichenic fungal strain Nigrospora sphaerica (No.83-1-1-2). Compounds 1a and 1b were separated from enantiomers 1 by chiral HPLC, and so were 2a and 2b from enantiomers 2. Interestingly, 1-6 were also obtained from other two endolichenic fungal strains Alternaria alternata (No.58-8-4-1) and Phialophora sp. (No.96-1-8-1). The structures of 1-6 were elucidated by means of MS, HR-MS, NMR, and X-ray diffraction. Furthermore, the absolute configurations of 1a-2b were determined by CD experiments and CD calculation. Of these compounds, 4 and 5 showed antiviral activity against herpes simplex virus (HSV) in vitro, with IC(50) values of 13.5 and 21.3 μM, and with selective index (SI) values of 26.5 and 17.1, respectively.

Unusual withanolides from aeroponically grown Withania somnifera

In an attempt to maximize production and the structural diversity of plant metabolites, the effect of growing the medicinal plant Withania somnifera under soil-less aeroponic conditions on its ability to produce withaferin A and withanolides was investigated. It resulted in the isolation and characterization of two compounds, 3α-(uracil-1-yl)-2,3-dihydrowithaferin A (1) and 3β-(adenin-9-yl)-2,3-dihydrowithaferin A (2), in addition to 10 known withanolides including 2,3-dihydrowithaferin A-3β-O-sulfate. 3β-O-Butyl-2,3-dihydrowithaferin A (3), presumably an artifact formed from withaferin A during the isolation process was also encountered. Reaction of withaferin A with uracil afforded 1 and its epimer, 3β-(uracil-1-yl)-2,3-dihydrowithaferin A (4). The structures of these compounds were elucidated on the basis of their high resolution mass and NMR spectroscopic data.

The first naturally occurring thiepinols and thienol from an endolichenic fungus Coniochaeta sp

Coniothiepinols A (1) and B (2) and coniothienol A (3), the first naturally occurring thiepinols (1 and 2) and thienol (3), have been isolated from the crude extract of an endolichenic fungus Coniochaeta sp. 1 possesses a unique 8-oxa-2-thia-bicyclo[3.2.1]octane skeleton, and its structure was assigned by NMR spectroscopy and X-ray crystallography. 1 showed significant activity against the gram-positive bacteria, Enterococcus faecium and Enterococcus faecalis.