Rumbrin, a new cytoprotective substance produced by Auxarthron umbrinum. I. Taxonomy, production, isolation and biological activities.

Higashi T., Yoshida C., Hachiro Y., Nakata C., Takechi A., Yagi T., Miyashita K., Kitada N., Obata R., Hirano T., Hara T., Maki S.A.

To develop novel drugs for treating T-cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML) which are highly malignant hematological tumors, a series of analogs having a polyenylpyrrole structure of natural compounds (rumbrin and auxarconjugatin B) were synthesized and investigated their structure-activity relationships (SAR) of in vitro anti-T-ALL and anti-AML activities. We obtained three findings: (1) introduction of a methyl group at the conjugated polyene terminus enhanced anti-T-ALL activity, (2) analogs with a 3-chloropyrrole moiety had even higher selectivity for T-ALL cells, and (3) some analogs were effective against AML-derived cells. Among the studied compounds, 3-chloro-2-(8-ethoxycarbonylnona-1,3,5,7-tetraenyl) pyrrole 4e was the most promising candidate of T-ALL- and AML-treating drug. This study provides useful structural information for designing novel drugs treating T-ALL and AML.

Miyashita K., Yagi T., Kagaya N., Takechi A., Nakata C., Kanda R., Nuriya H., Tanegashima K., Hoyano S., Seki F., Yoshida C., Hachiro Y., Higashi T., Kitada N., Toya T., et. al.

AbstractT‐cell acute lymphoblastic leukemia (T‐ALL) is one of the most frequently occurring cancers in children and is associated with a poor prognosis. Here, we performed large‐scale screening of natural compound libraries to identify potential drugs against T‐ALL. We identified three low‐molecular‐weight compounds (auxarconjugatin‐B, rumbrin, and lavendamycin) that inhibited the proliferation of the T‐ALL cell line CCRF‐CEM, but not that of the B lymphoma cell line Raji in a low concentration range. Among them, auxarconjugatin‐B and rumbrin commonly contained a polyenyl 3‐chloropyrrol in their chemical structure, therefore we chose auxarconjugatin‐B for further analyses. Auxarconjugatin‐B suppressed the in vitro growth of five human T‐ALL cell lines and two T‐ALL patient‐derived cells, but not that of adult T‐cell leukemia patient‐derived cells. Cultured normal T cells were several‐fold resistant to auxarconjugatin‐B. Auxarconjugatin‐B and its synthetic analogue Ra#37 depolarized the mitochondrial membrane potential of CCRF‐CEM cells within 3 h of treatment. These compounds are promising seeds for developing novel anti‐T‐ALL drugs.

Zhong B., Wan J., Shang C., Wen J., Wang Y., Bai J., Cen S., Hu Y.

Investigation on how nature produces natural compounds with chemical and biological diversity at the genetic level offers inspiration for the discovery of new natural products and even their biological targets. The polyketide rumbrin (1) is a lipid peroxide production and calcium accumulation inhibitor, which contains a chlorinated pyrrole moiety that is a rare chemical feature in fungal natural products. Here, we identify the biosynthetic gene cluster (BGC) rum of 1 and its isomer 12E-rumbrin (2) from Auxarthron umbrinum DSM3193, and elucidate their biosynthetic pathway based on heterologous expression, chemical complementation, and isotopic labeling. We show that rumbrins are assembled by a highly reducing polyketide synthase (HRPKS) that uniquely incorporates a proline-derived pyrrolyl-CoA starer unit, and followed by methylation and chlorination. Sequent precursor-directed biosynthesis was able to yield a group of rumbrin analogues. Remarkably, inspired by the presence of a human immunodeficiency virus (HIV)-Nef-associated gene in the rum cluster, we predicted and pharmacologically demonstrated rumbrins as potent inhibitors of HIV at the nanomolar level. This work enriches the recognition of unconventional starter units of fungal PKSs and provides a new strategy for genome mining-guided drug discovery.

Ji Ram V., Goel A., Pratap R.

2 H -pyran-2-one is six-membered oxygen heterocycle having one oxygen in the ring and oxo group at position 2 of the ring and is also known as cyclic unsaturated ester. Two double bonds present are in the conjugation of the ring oxygen. 2-Pyranone-based compounds are well known for more than a century, but the chemistry of these compounds was unexplored and recognized after 1960. Various plants, animals, marine organisms, insects, and bacteria contain pyranone-based compounds in their biological system and participate in various biological processes such as defense mechanism, biosynthetic intermediates, etc. They are reported as HIV protease inhibitors, antifungals, anticonvulsants, cardiotonics, pheromones, antimicrobials, natural pigments, antitumor, and plant growth regulators. In addition, they are synthetically very important precursors for the generation of large class of molecules, for example, use of triacetic acid lactone ( I) and tetraacetic acid lactone ( II) involved for the assembly of α-chymotrypsin, solanopyrones, elastase, pheromones, and coumarins. 6-Aryl-4-methylsulfanyl/ sec .amino-2 H -pyran-2-one-3-carbonitriles are used for the assembly of larger class of carbocycles and heterocycles.

Kumar J., Singh I., Kushwaha R.K.

Keratinophilic fungi colonize keratinous substrates and convert them to the constituent components of low molecular weight. These fungi can be distinguished from others in their characteristic that they are adapted to consumption of keratinous proteins as sources of carbon and nitrogen. These tend to utilize proteins, peptides, and amino acids as carbon sources even in the presence of sugars. They also exhibit a great diversity in their mode of nutrition and physiology. This chapter critically reviews not only the distribution of keratinophilic fungi but also their social and environmental implications. Recycling of keratin contributes to nutrients in soils, pollution control, and solid waste management.

Yoshida C., Higashi T., Hachiro Y., Fujita Y., Yagi T., Takechi A., Nakata C., Miyashita K., Kitada N., Saito R., Obata R., Hirano T., Hara T., Maki S.A.

T-cell acute lymphoblastic leukemia (T-ALL) is a hardly curable disease with a high relapse rate. 20 analogs were synthesized based on the structures of two kinds of fungi-derived polyenylpyrrole products (rumbrin (1) and auxarconjugatin-B (2)) to suppress the growth of T-ALL-derived cell line CCRF-CEM and tested for growth-inhibiting activity. The octatetraenylpyrrole analog gave an IC50 of 0.27 μM in CCRF-CEM cells, while it did not affect Burkitt lymphoma-derived cell line Raji and the cervical cancer cell line HeLa, or the oral cancer cell line HSC-3 (IC50 > 10 μM). This compound will be a promising compound for developing T-ALL-specific drugs.

Kim J.W., Son S., Kim G.S., Otaka J., Miura Y., Muranaka A., Uchiyama M., Lee J., Jang M., Ko S., Takahashi S., Osada H., Jang J., Ahn J.S.

LC/MS-based chemical screening of fungal extract fraction library led to identification of three 2,3-aryl substituted furanone metabolites (1–3), including one known butenolide glycoside (1) whose stereochemistry remained unsolved and two new compounds gotjawaside and gotjawalide (2 and 3), from Auxarthron sp. KCB15F070, a fungus isolated from a soil sample of the volcanic island Jeju, Korea. Their planar structures were elucidated by 1D- and 2D-NMR spectroscopic and HRESIMS spectrometric techniques, and the absolute configurations of three compounds were solved using a combination of chemical derivatizations and computational analysis of vibrational circular dichroism (VCD) spectra.

Libor B., Harms H., Kehraus S., Egereva E., Crüsemann M., König G.M.

Fungi are an important source of bioactive metabolites. The Fungal one-step IsolatioN Device (FIND) technology allows the isolation of rare fungi from terrestrial and marine samples. The FIND comprises a multi-chambered micro agar plate, where initially only one fungal part (e.g., hyphal cell, mycelial fragment or spore) is located in each chamber. After inoculation the device is placed back into the original natural environment of sample collection, to ensure favourable growth conditions. Experiments were carried out with terrestrial soil and marine sediment, as well as sea water samples to validate this method. This yielded axenic cultures of 12 different filamentous fungi, one of them being the marine-adapted fungal strain Heydenia cf. alpina. The latter produced two new terpenoids, which are the first secondary metabolites from this genus.

Verekar S.A., Deshmukh S.K.

This chapter discusses the occurrence of keratinophilic fungi in different habitats wherein the population of these fungi is expected to occur: air, soil from various environments like gardens, caves, cold and saline habitat. The ability to degrade the keratinic material and mechanism of action is discussed. Importance of these fungi in petroleum hydrocarbon degradation is discussed. Various metabolites with antibacterial, antifungal, antitumor and related compounds produced by this group of fungi are documented. Examples of synthesis of silver nanoparticlesSilver nanoparticles are also included. The need for an extensive survey of keratinophilic fungi from unexplored substrates and habitats and biochemical potentialities is highlighted. It is concluded that fungi other than dermatophytes can be opportunistic pathogens. The need for a culture collection of this group of fungi is also highlighted.

Sarrocco S., Diquattro S., Baroncelli R., Cimmino A., Evidente A., Vannacci G., Doveri F.

In a survey of coprophilous fungi in Italy, two interesting ascomycetes were recovered from hedgehog dung. These fungi showed a sexual morph characterized by gymnothecia, globose reticulate ascospores, a Malbranchea asexual state, and a keratinolytic ability, and were identified morphologically and molecularly as Auxarthron umbrinum and A. concentricum of the Onygenaceae. The history, ecology, and morphology of the genus Auxarthron as a whole, and of A. umbrinum and A. concentricum in particular, are revised. A preliminary evaluation of the antagonistic properties of A. umbrinum and A. concentricum against phytopathogenic fungi has been performed in dual cultures. Growth inhibition of some plant pathogenic fungi was recorded, and the effects were growth medium dependent. When solid-state fermentation (SSF) substrate of both Auxarthron isolates has been submitted to extraction, both the organic extract residues (n-hexane and CH2Cl2) and the lyophilized aqueous phases were used for the antibiotic test against plant pathogenic fungi. Significant antifungal activity was obtained by organic fractions and aqueous residue of A. concentricum against Alternaria brassicicola and Botrytis cinerea, whereas A. umbrinum appeared to be less effective. The analysis of ITS nrDNA sequences suggests that an extensive phylogenetic revision of the genus Auxarthron is necessary.

Mal D., Shome B., Dinda B.K.

Clark B.R., O'Connor S., Fox D., Leroy J., Murphy C.D.

The biosynthesis of the pyrrolyl moiety of the fungal metabolite rumbrin originates from pyrrole-2-carboxylic acid. In an effort to produce novel derivatives with enhanced biological activity a series of substituted pyrrole-2-carboxylates were synthesised and incubated with the producing organism, Auxarthron umbrinum. Several 4-halo-pyrrole-2-carboxylic acids were incorporated into the metabolite yielding three new derivatives: 3-fluoro-, 3-chloro- and 3-bromo-isorumbrin, which were generated in milligram quantities enabling cytotoxicity assays to be conducted. The 3-chloro- and 3-bromo-isorumbrins had improved activity against HeLa cells compared with rumbrin; 3-bromoisorumbrin also showed dramatically improved activity towards a lung cancer cell line (A549).

Fang Z., Liao P., Yang Y., Yang F., Chen Y., Lam Y., Hua K., Wu S.

A class of polyenylpyrroles and their analogues were designed from a hit compound identified in a fungus. The compounds synthesized were evaluated for their cell cytotoxicity against human non-small-cell lung carcinoma cell lines A549. Two compounds were found to exhibit high cytotoxicity against A549 cells with IC(50) of 0.6 and 0.01 μM, respectively. The underlying mechanisms for the anticancer activity were demonstrated as caspases activation dependent apoptosis induction through loss of mitochondrial membrane potential, release of cytochrome c, increase in B-cell lymphoma-2-associated X protein (Bax) level, and decrease in B-cell lymphoma-2 (Bcl-2) level. The two compounds were nontoxic to normal human lung Beas-2b cells (IC(50) > 80 μM), indicating that they are highly selective in their cytotoxicity activities. Furthermore, one compound showed in vivo anticancer activity in human-lung-cancer-cell-bearing mice. These results open promising insights on how these conjugated polyenes mediate cytotoxicity and may provide a molecular rationale for future therapeutic interventions in carcinogenesis.

Murphy B., Anderson K., Borissow C., Caffrey P., Griffith G., Hearn J., Ibrahim O., Khan N., Lamburn N., Lee M., Pugh K., Rawlings B.

Amphotericin B is a powerful but toxic drug used against fungal infections and leishmaniases. These diseases would be treated more effectively if non-toxic amphotericin derivatives could be produced on a large scale at low cost. Genetic manipulation of the amphotericin B producer, Streptomyces nodosus, has previously led to the detection and partial characterisation of 8-deoxyamphotericin B, 16-descarboxyl-16-methyl-amphotericin B, 15-deoxy-16-descarboxyl-16-methyl-15-oxo-amphotericin B, 7-oxo-amphotericin B and pentaene analogues. Here we report improved production and purification protocols that have allowed detailed chemical analyses of these compounds. The polyketide synthase product 8-deoxy-16-descarboxyl-16-methyl-amphoteronolide B was identified for the first time. In addition, the ketoreductase 10 domain of the polyketide synthase was specifically inactivated by targeted gene replacement. The resulting mutants produced truncated polyketide intermediates as linear polyenyl-pyrones.

Goel A., Ram V.J.

An overview of the natural presence and development of the chemistry of the 2 H -pyran-2-one ring system is delineated. The report contains 363 references. Figure options Download full-size image Download as PowerPoint slide