Antiinsectan decaturin and oxalicine analogues from Penicillium thiersii

Regulation of secondary metabolites in the endophytic fungus Penicillium sp. KMU18029 by the chemical epigenetic modifier 5-azacitidine

The chemical epigenetic modifier 5-azacitidine (5-Aza C), a DNA methyltransferase inhibitor, was used to manipulate the endophytic fungus Penicillium sp. KMU18029. From its rice fermentation extract, a new polyketone compound (3S,4R)-3,4,8-trihydroxy-6-methyl-3,4-dihydronaphthalen-1(2H)-one (1), along with 13 known compounds, 3,4,8-trihydroxy-6-(hydroxymethyl)-3,4-dihydronaphthalen-1(2H)-one (2), decaturin B (3), 15-hydroxydecaturin A (4), oxalicine A (5), pileotin A (6), pyrandecarurin A (7), decaturenol A (8), decaturenoid (9), penisarins A (10), oxaline (11), (4E,8E)-N-D-2'-hydroxyocta-decanoyl-1-O-β-D-glycopy-ranosyl-9-methyl-4,8-sphingadienine (12), ergosterol (13) and stigma-5-en-3-O-β-glucoside (14), were separated. Among the known compounds, 2, 7, 12 and 14 were not found in our previous research on this strain. The structure of the new compound was identified by spectroscopic techniques such as HR-ESIMS, 1D NMR, 2D NMR and CD. Furthermore, all the isolated compounds were tested for their antimicrobial activities, and only compounds 1, 2 and 11 showed weak activities against S. aureus, with MICs of 128 μg/mL.

Anti-Insect Properties of Penicillium Secondary Metabolites

In connection with their widespread occurrence in diverse environments and ecosystems, fungi in the genus Penicillium are commonly found in association with insects. In addition to some cases possibly implying a mutualistic relationship, this symbiotic interaction has mainly been investigated to verify the entomopathogenic potential in light of its possible exploitation in ecofriendly strategies for pest control. This perspective relies on the assumption that entomopathogenicity is often mediated by fungal products and that Penicillium species are renowned producers of bioactive secondary metabolites. Indeed, a remarkable number of new compounds have been identified and characterized from these fungi in past decades, the properties and possible applications of which in insect pest management are reviewed in this paper.

Late-stage cascade of oxidation reactions during the biosynthesis of oxalicine B in Penicillium oxalicum

Oxalicine B (1) is an α-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum. The biosynthetic pathway of 15-deoxyoxalicine B (4) was preliminarily reported in Penicillium canescens, however, the genetic base and biochemical characterization of tailoring reactions for oxalicine B (1) has remained enigmatic. In this study, we characterized three oxygenases from the metabolic pathway of oxalicine B (1), including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/α-KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 OxaB. Intriguingly, OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity. OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A (3) to 1 with a spiro-lactone core skeleton through oxidative rearrangement. We also solved the mystery of OxaL that controls C-15 hydroxylation. Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds, and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC₅₀ values in the range of 4.0-19.9 μmol/L. Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B (1) and create downstream derivatizations of oxalicines by employing enzymatic strategies.

Hybrid Diterpenic Meroterpenoids from an Endophytic Penicillium sp. Induced by Chemical Epigenetic Manipulation

Cultivation of an endophytic fungus Penicillium sp. KMU18029 with suberanilohydroxamic acid (SAHA), a histone deacetylase inhibitor, led to the isolation of two pairs of diterpenic meroterpenoids with a unique natural product framework combining features of pyripyropenes and decaturins/oxalicines, pyrandecarurins A (1) and B (2), pileotin A (3) and B (4), along with their potential precursor decaturenoid (5). Compounds 1, 2, 4, and 5 were new. The structures of 1-5 were elucidated by extensive spectroscopic analyses. The absolute configurations of 1-4 were determined by single-crystal X-ray diffraction, NOESY spectra, ECD calculations, and biogenetic considerations. The absolute configuration of compound 3 was confirmed for the first time. Compound 5 showed moderate activity against AChE with an IC₅₀ value of 13.9 ± 1.1 μM.

Antimicrobial Meroterpenoids and Erythritol Derivatives Isolated from the Marine-Algal-Derived Endophytic Fungus Penicillium chrysogenum XNM-12

One new meroterpenoid-type alkaloid, oxalicine C (1), and two new erythritol derivatives, penicierythritols A (6) and B (7), together with four known meroterpenoids (2-5), were isolated from the marine algal-derived endophytic fungus Penicillium chrysogenum XNM-12. Their planar structures were determined by means of spectroscopic analyses, including UV, 1D and 2D NMR, and HRESIMS spectra. Their stereochemical configurations were established by comparing the experimental and calculated electronic circular dichroism (ECD) spectra for compound 1, as well as by comparison of the optical rotations with literature data for compounds 6 and 7. Notably, oxalicine C (1) represents the first example of an oxalicine alkaloid with a cleaved α-pyrone ring, whereas penicierythritols A (6) and B (7) are the first reported from the Penicillium species. The antimicrobial activities of compounds 1-7 were evaluated. Compounds 1 and 6 exhibited moderate antibacterial effects against the plant pathogen Ralstonia solanacearum with minimum inhibitory concentration (MIC) values of 8 and 4 μg/mL, respectively. Compound 6 also possesses moderate antifungal properties against the plant pathogen Alternaria alternata with a MIC value of 8 μg/mL.

Chemistry of fungal meroterpenoid cyclases

Covering: up to July 2020Fungal meroterpenoid cyclases are a recently discovered emerging family of membrane-integrated, non-canonical terpene cyclases. They catalyze the conversion of hybrid isoprenic precursors towards complex scaffolds and are therefore of great importance in the structure diversification in meroterpenoid biosynthesis. The products of these pathways exhibit intriguing molecular scaffolds and highly potent bioactivities, making them privileged structures from Nature and attractive candidates for drug development or industrial applications. This review will provide a comprehensive and comparative view on fungal meroterpenoid cyclases, their intriguing chemistries and importance for the scaffold formation step towards polycyclic meroterpenoid natural products.

Decaturenol A and known oxalicine related meroterpenoids isolated from Penicillium decaturense RO050, and their new biological activities

Decaturenol A (1), a new oxalicine related meroterpenoid, has been isolated from Penicillium decaturense RO050 along with seven known compounds (2-8). The structure of 1 was elucidated by spectroscopic data. The effects of isolated compounds (1-8) on endoplasmic reticulum (ER) stress-induced cell death in HT22 hippocampal nerve cells and on the interleukin 10 (IL-10)-induced expression of CD163, a M2 phenotype marker, in human monocyte-derived macrophages were evaluated. While decaturenol A (1) exhibited a protective effect on ER stress-induced cell death in HT22 cells at 10 µM, on the other hand oxalicine A (7) showed cytotoxic activity (IC₅₀ = 5.9 µM). Additionally, decaturenol A (1), decaturins D (2), E (3), and B (4) inhibited the IL-10-induced expression of CD163 each at a concentration of 20 µg/mL.

Classification of Aspergillus, Penicillium, Talaromyces and related genera (Eurotiales): An overview of families, genera, subgenera, sections, series and species

The Eurotiales is a relatively large order of Ascomycetes with members frequently having positive and negative impact on human activities. Species within this order gain attention from various research fields such as food, indoor and medical mycology and biotechnology. In this article we give an overview of families and genera present in the Eurotiales and introduce an updated subgeneric, sectional and series classification for Aspergillus and Penicillium. Finally, a comprehensive list of accepted species in the Eurotiales is given. The classification of the Eurotiales at family and genus level is traditionally based on phenotypic characters, and this classification has since been challenged using sequence-based approaches. Here, we re-evaluated the relationships between families and genera of the Eurotiales using a nine-gene sequence dataset. Based on this analysis, the new family Penicillaginaceae is introduced and four known families are accepted: Aspergillaceae, Elaphomycetaceae, Thermoascaceae and Trichocomaceae. The Eurotiales includes 28 genera: 15 genera are accommodated in the Aspergillaceae (Aspergillago, Aspergillus, Evansstolkia, Hamigera, Leiothecium, Monascus, Penicilliopsis, Penicillium, Phialomyces, Pseudohamigera, Pseudopenicillium, Sclerocleista, Warcupiella, Xerochrysium and Xeromyces), eight in the Trichocomaceae (Acidotalaromyces, Ascospirella, Dendrosphaera, Rasamsonia, Sagenomella, Talaromyces, Thermomyces, Trichocoma), two in the Thermoascaceae (Paecilomyces, Thermoascus) and one in the Penicillaginaceae (Penicillago). The classification of the Elaphomycetaceae was not part of this study, but according to literature two genera are present in this family (Elaphomyces and Pseudotulostoma). The use of an infrageneric classification system has a long tradition in Aspergillus and Penicillium. Most recent taxonomic studies focused on the sectional level, resulting in a well-established sectional classification in these genera. In contrast, a series classification in Aspergillus and Penicillium is often outdated or lacking, but is still relevant, e.g., the allocation of a species to a series can be highly predictive in what functional characters the species might have and might be useful when using a phenotype-based identification. The majority of the series in Aspergillus and Penicillium are invalidly described and here we introduce a new series classification. Using a phylogenetic approach, often supported by phenotypic, physiologic and/or extrolite data, Aspergillus is subdivided in six subgenera, 27 sections (five new) and 75 series (73 new, one new combination), and Penicillium in two subgenera, 32 sections (seven new) and 89 series (57 new, six new combinations). Correct identification of species belonging to the Eurotiales is difficult, but crucial, as the species name is the linking pin to information. Lists of accepted species are a helpful aid for researchers to obtain a correct identification using the current taxonomic schemes. In the most recent list from 2014, 339 Aspergillus, 354 Penicillium and 88 Talaromyces species were accepted. These numbers increased significantly, and the current list includes 446 Aspergillus (32 % increase), 483 Penicillium (36 % increase) and 171 Talaromyces (94 % increase) species, showing the large diversity and high interest in these genera. We expanded this list with all genera and species belonging to the Eurotiales (except those belonging to Elaphomycetaceae). The list includes 1 187 species, distributed over 27 genera, and contains MycoBank numbers, collection numbers of type and ex-type cultures, subgenus, section and series classification data, information on the mode of reproduction, and GenBank accession numbers of ITS, beta-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) gene sequences.

Onydecalins, Fungal Polyketides with Anti- Histoplasma and Anti-TRP Activity

We report an unusual 3-substituted pyridine polyketide, onydecalin A (1), which was obtained along with 2 as a major constituent from the fungus Aioliomyces pyridodomos (order: Onygenales) following a two-month fermentation. Feeding studies demonstrated that the pyridine subunit originates via an unprecedented biosynthetic process in comparison to other polyketide-linked pyridines or derivatives such as pyridones. The slow growth of the fungus led us to perform a one-year fermentation, leading to production of compounds 2-4 as the major constituents. These compounds showed modest but selective inhibition against a variety of transient receptor potential channels, as well as against the human pathogenic fungus Histoplasma capsulatum.

A new phenolic enamide and a new meroterpenoid from marine alga-derived endophytic fungus Penicillium oxalicum EN-290

Ten secondary metabolites (1-10) including a new phenolic enamide, methyl (Z)-3-(3,4-dihydroxyphenyl)-2-formamidoacrylate (1), and a new meroterpenoid, 15-hydroxydecaturin A (2), were characterized from the EtOAc extracts of the marine alga-derived endophytic fungus Penicillium oxalicum EN-290. The structures of these compounds were elucidated on the basis of 1D and 2D NMR experiments and the absolute configuration of compound 2 was confirmed by electronic circular dichroism quantum calculations. Compound 1 showed potent activity against Staphylococcus aureus with an MIC value of 2.0 μg/ml, which is stronger than that of the positive control (chloromycetin, with an MIC 4.0 μg/ml). This compound also showed activity against harmful algal bloom causative species Nitzschia closterium with inhibition zones of 20, 16, and 10 mm at 20, 10, and 5 mg/ml, respectively. Interestingly, so far, this type of anti-HAB metabolites has only been found in the algal-derived isolate of P. oxalicum. It could probably be a defense of this fungus against environmental stress and threat of survival.

Genome mining and molecular characterization of the biosynthetic gene cluster of a diterpenic meroterpenoid, 15-deoxyoxalicine B, in Penicillium canescens

Meroterpenoids are a class of secondary metabolites that are produced from polyketide and terpenoid precursors. 15-Deoxyoxalicine B (1) belongs to one structural group consisting of a unique pyridinyl-α-pyrone polyketide subunit and a diterpenoid subunit connected through a characteristic asymmetric spiro carbon atom. An understanding of the genes involved in the biosynthesis of this class of compounds should provide a means to facilitate engineering of second-generation molecules and increasing production of first-generation compounds. We found that the filamentous fungus Penicillium canescens produces 15-deoxyoxalicine B (1). Using targeted gene deletions, we have identified a cluster of 12 responsible contiguous genes. This gene cluster includes one polyketide synthase gene which we have designated olcA. Chemical analysis of wild-type and gene deletion mutant extracts enabled us to isolate and characterize 7 additional metabolites that are either intermediates or shunt products of the biosynthetic pathway. Two of the compounds identified have not been reported previously. Our data have allowed us to propose a biosynthetic pathway for 15-deoxyoxalicine B (1).

A taxonomic and phylogenetic revision of Penicillium section Aspergilloides

Species belonging to Penicillium section Aspergilloides have a world-wide distribution with P. glabrum, P. spinulosum and P. thomii the most well-known species of this section. These species occur commonly and can be isolated from many substrates including soil, food, bark and indoor environments. The taxonomy of these species has been investigated several times using various techniques, but species delimitation remains difficult. In the present study, 349 strains belonging to section Aspergilloides were subjected to multilocus molecular phylogenetic analyses using partial β-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) sequences. Section Aspergilloides is subdivided into 12 clades and 51 species. Twenty-five species are described here as new and P. yezoense, a species originally described without a Latin diagnosis, is validated. Species belonging to section Aspergilloides are phenotypically similar and most have monoverticillate conidiophores and grow moderately or quickly on agar media. The most important characters to distinguish these species were colony sizes on agar media, growth at 30 °C, ornamentation and shape of conidia, sclerotium production and stipe roughness.

Novel Decaturin Alkaloids from the Marine-Derived Fungus Penicillium Oxalicum

From the mycelia of Penicillium oxalicum two new compounds, decaturins E (1) and F (2), have been isolated, along with four known analogues, decaturin A (3), decaturin C (4), decaturin D (5), and oxalicine B (6). The structures were determined by HR-ESI-MS and 1D and 2D NMR analysis.

Aspergillus sect. Aeni sect. nov., a new section of the genus for A.karnatakaensis sp. nov. and some allied fungi

The new species Aspergilluskarnatakaensis sp. nov. is described and illustrated. All three isolates of this species were isolated from Indian soil; two from soil under a coconut palm in a coffee plantation in Karnataka, and one from soil in the Machrar river bed in Bansa district. This species is closely related to, but clearly distinct, from A. aeneus based on β-tubulin or calmodulin sequence data. Sequences of the ITS region of these two species are identical. Aspergillus karnatakaensis produced terrein, gregatins, asteltoxin, karnatakafurans A and B and the unknown metabolite, provisionally named NIDU. Aspergillus karnatakaensis belongs to a well-defined clade within Aspergillus subgenus Nidulantes together with eight other species including A. aeneus, A. crustosus, A. eburneocremeus, A. heyangensis, and the teleomorph producing-species Emericella bicolor, E. discophora, E. spectabilis, and E. foeniculicola. This clade is placed in a new section, Aspergillus sect. Aenei sect. nov. All teleomorph species assigned to this section are able to produce sterigmatocystin.

Hymenopsins A and B and a macrophorin analogue from a fungicolous Hymenopsis sp

Hymenopsin A (1), hymenopsin B (2), and a new macrophorin analogue, 2',3'-epoxy-13-hydroxy-4'-oxomacrophorin A (3), have been isolated from a fungicolous isolate of Hymenopsis sp. (MYC-1703; NRRL 37638). The structures and relative configurations of these compounds were assigned on the basis of 2D NMR and MS data, and the identity of 1 was confirmed by X-ray crystallographic analysis. The absolute configuration of 2 was proposed on the basis of CD analysis using both empirical and computational methods. Compounds 2 and 3 showed antibacterial activity against Staphylococcus aureus and Bacillus subtilis. Compound 3 was also active against Aspergillus flavus and Fusarium verticillioides.

Breviane spiroditerpenoids from an extreme-tolerant Penicillium sp. isolated from a deep sea sediment sample

Breviones F-H (1-3), three new bioactive breviane spiroditerpenoids, have been isolated from the crude extract of an extreme-tolerant Penicillium sp. obtained from a deep sea sediment sample that was collected at a depth of 5115 m. The structures of these compounds were elucidated primarily by NMR spectroscopy. The absolute configurations of 1 and 3 were assigned by application of the modified Mosher method, and 3 is further confirmed by X-ray crystallographic analysis of its S-MTPA ester. Compound 2 could be the precursor for 3, which features a previously undescribed skeleton of mixed biogenesis.

The Janus-faced atracotoxins are specific blockers of invertebrate K(Ca) channels

The Janus-faced atracotoxins are a unique family of excitatory peptide toxins that contain a rare vicinal disulfide bridge. Although lethal to a wide range of invertebrates, their molecular target has remained enigmatic for almost a decade. We demonstrate here that these toxins are selective, high-affinity blockers of invertebrate Ca(2+)-activated K(+) (K(Ca)) channels. Janus-faced atracotoxin (J-ACTX)-Hv1c, the prototypic member of this toxin family, selectively blocked K(Ca) channels in cockroach unpaired dorsal median neurons with an IC(50) of 2 nm, but it did not significantly affect a wide range of other voltage-activated K(+), Ca(2+) or Na(+) channel subtypes. J-ACTX-Hv1c blocked heterologously expressed cockroach large-conductance Ca(2+)-activated K(+) (pSlo) channels without a significant shift in the voltage dependence of activation. However, the block was voltage-dependent, indicating that the toxin probably acts as a pore blocker rather than a gating modifier. The molecular basis of the insect selectivity of J-ACTX-Hv1c was established by its failure to significantly inhibit mouse mSlo currents (IC(50) approximately 10 mum) and its lack of activity on rat dorsal root ganglion neuron K(Ca) channel currents. This study establishes the Janus-faced atracotoxins as valuable tools for the study of invertebrate K(Ca) channels and suggests that K(Ca) channels might be potential insecticide targets.

Diterpenoids

This review covers the isolation and structures of diterpenoids, including labdanes, clerodanes,pimaranes, abietanes, kauranes, cembranolides, taxanes and marine diterpenoids. The literature from January to December 2005 is reviewed, and 195 references are cited.

Phenotypic taxonomy and metabolite profiling in microbial drug discovery

Microorganisms and in particular actinomycetes and microfungi are known to produce a vast number of bioactive secondary metabolites. For industrially important fungal genera such as Penicillium and Aspergillus the production of these compounds has been demonstrated to be very consistent at the species level. This means that direct metabolite profiling techniques such as direct injection mass spectrometry or NMR can easily be used for chemotyping/metabolomics of strains from both culture collections and natural samples using modern informatics tools. In this review we discuss chemotyping/metabolomics as part of intelligent screening and highlight how it can be used for identification and classification of filamentous fungi and for the discovery of novel compounds when used in combination with modern methods for dereplication. In our opinion such approaches will be important for future effective drug discovery strategies, especially for dereplication of culture collections in order to avoid redundancy in the selection of species. This will maximize the chemical diversity of the microbial natural product libraries that can be generated from fungal collections.