Ulleunganilines A-C, Trichostatin Analogues Bearing a Modified Side Chain from Streptomyces sp. 13F051.

Three new trichostatin analogues, ulleunganilines A-C (1-3), and seven known trichostatins (4-10) were isolated from cultures of Streptomyces sp. 13F051. NMR, UV, and MS data indicated that the planar structures of 1-3 consisted of modified side chains in the trichostatic acid moiety. The absolute configuration of the 2,4-dimethyl-branched carbon chains in 1 and 2 was determined by the PGME method, while the amino acid group in 3 was identified by advanced Marfey's method. Based on the structure of the modified side chains, the origin of 1-3 is proposed. Further experiments indicated that 1 and 3 displayed moderate histone deacetylase inhibitory activity, suggesting that not only the hydroxamate group but also the N,N-dimethyl group were essential for the inhibitory activity.

Novel South African Rare Actinomycete Kribbella speibonae Strain SK5: A Prolific Producer of Hydroxamate Siderophores Including New Dehydroxylated Congeners.

In this paper, we report on the chemistry of the rare South African Actinomycete Kribbella speibonae strain SK5, a prolific producer of hydroxamate siderophores and their congeners. Two new analogues, dehydroxylated desferrioxamines, speibonoxamine 1 and desoxy-desferrioxamine D1 2, have been isolated, together with four known hydroxamates, desferrioxamine D1 3, desferrioxamine B 4, desoxy-nocardamine 5 and nocardamine 6, and a diketopiperazine (DKP) 7. The structures of 1-7 were characterized by the analysis of HRESIMS and 1D and 2D NMR data, as well as by comparison with the relevant literature. Three new dehydroxy desferrioxamine derivatives 8-10 were tentatively identified in the molecular network of K. speibonae strain SK5 extracts, and structures were proposed based on their MS/MS fragmentation patterns. A plausible spb biosynthetic pathway was proposed. To the best of our knowledge, this is the first report of the isolation of desferrioxamines from the actinobacterial genus Kribbella.

Thalassosamide, a Siderophore Discovered from the Marine-Derived Bacterium Thalassospira profundimaris.

Here we describe the rapid identification and prioritization of novel active marine natural products using an improved dereplication strategy. During the course of our screening of marine natural product libraries, a new cyclic trihydroxamate compound, thalassosamide, was discovered from the α-proteobacterium Thalassospira profundimaris. Its structure was determined by 2D NMR and MS/MS experiments, and the absolute configuration of the lysine-derived units was established by Marfey's analysis, whereas that of C-9, 9', and 9″ was determined via the circular dichroism data of the [Rh2(OCOCF3)4] complex and DFT NMR calculations. Thalassosamide showed moderate in vivo efficacy against Pseudomonas aeruginosa.

Neuroprotective effects of dimerumic acid and deferricoprogen from Monascus purpureus NTU 568-fermented rice against 6-hydroxydopamine-induced oxidative stress and apoptosis in differentiated pheochromocytoma PC-12 cells.

Context Oxidative stress plays a key role in neurodegenerative disorders, including Parkinson's disease (PD). Rice fermented with Monascus purpureus Went (Monascaceae) NTU 568 (red mould rice) was found to contain antioxidants, including dimerumic acid (DMA) and deferricoprogen (DFC). Objective The effects of DMA and DFC on 6-hydroxydopamine (6-OHDA)-induced cytotoxicity and potential protective mechanisms in differentiated PC-12 pheochromocytoma cells were investigated. Materials and methods DMA (0-60 µM) or DFC (0-10 µM) was co-treated with 6-OHDA (200 µM, 24 h exposure) in differentiated PC-12 cells. Cell viability and intercellular reactive oxygen species (ROS) were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and 2',7'-dichlorofluorescein-diacetate (DCFH-DA) assays, respectively. Cell apoptosis was determined by DNA fragmentation analysis and propidium iodide staining by flow cytometry. Western blot analysis was used to measure the levels of cell protein expression. Results DMA and DFC significantly increased cell viability to 72% and 81% in 6-OHDA-induced differentiated PC-12 cell cultures, respectively. Furthermore, DMA and DFC reduced 6-OHDA-induced formation of extracellular and intercellular ROS by 25% and 20%, respectively, and decreased NADPH oxidase-2 expression in differentiated PC-12 cells. DMA and DFC inhibited 6-OHDA-induced apoptosis and decreased activation of caspase-3 via regulation of Bcl-2-associated X protein (Bax) and Bcl-2 protein expression in differentiated PC-12 cells. Conclusion DMA and DFC may protect against 6-OHDA toxicity by inhibiting ROS formation and apoptosis. These results showed that the metabolites from M. purpureus NTU 568 fermentation were potential therapeutic agents for PD induced by oxidative damage and should be encouraged for further research.

Identification of trichostatin derivatives from Streptomyces sp. CPCC 203909.

Four new trichostatin analogues (1-4) and six known analogues have been isolated from the rice fermentation of the Streptomyces sp. CPCC 203909. The structures and absolute configurations of these compounds were determined by extensive spectroscopic analysis including 2D NMR and electronic circular dichroism (ECD) calculations based on the quantum-mechanical time-dependent density functional theory (TDDFT). Compounds 2, 5-7, 9, and 10 up-regulated the transcriptional activity of human high density lipoprotein receptor (CLA-1) with EC50 values of 0.38-78.83µM.

A new trichostatin analog from Streptomyces sp. CPCC 203909.

A new trichostatin analog (1) and two known analogs (2, 3) have been isolated from the rice fermentation of the Streptomyces sp. CPCC 203909. Their structures were determined by spectroscopic and chemical methods. The absolute configurations of 1 were assigned by Marfey's method, combined with comparing the NMR and circular dichroism spectroscopic data of 2 and 3. Compound 1 showed cytotoxicity against human embryonic kidney 293 cell line with IC50 value of 39.2 µM.

[A novel trichostatin analogue culture of Streptomyces sp. CPCC 203909].

By using a cell-based high throughput screening model for the CLA-1 up-regulator, Streptomyces 203909 was found to produce up-regulator of CLA-1. A novel trichostatin analogue was isolated from the rice fermentation of Streptomyces sp. CPCC 203909by a combination of various chromatographic techniques including column chromatography (CC) over silica gel, flash C18 CC, and reversed-phase HPLC. Its structure was identified as (-)-(R,2E,4Z)-7-[(4'-dimethylamino) phenyl]-4,6-dimethyl-7-oxohepta-2,4-dienoyl-L-glutamine (1) by the spectroscopic and chemical methods, and combination with the CD spectroscopy and Marfey's method. In the prelimi- nary assays, Compound 1 showed cytotoxicity against human embryonic kidney 293 cell line with IC50 value 35.3 [µmol · L(-1).

Structure and biosynthesis of scabichelin, a novel tris-hydroxamate siderophore produced by the plant pathogen Streptomyces scabies 87.22.

Scabichelin and turgichelin, novel tris-hydroxamate siderophores, were isolated from Streptomyces antibioticus NBRC 13838/Streptomyces scabies JCM 7914 and Streptomyces turgidiscabies JCM 10429, respectively. The planar structures of scabichelin and turgichelin were elucidated by mass spectrometry, and 1- and 2-D NMR spectroscopic analyses of their gallium(III) complexes. The relative and absolute stereochemistry of the metabolites was determined by the modified Marfey's method in conjunction with computational modelling and NOESY NMR analysis of Ga-scabichelin and Ga-turgichelin. Genome sequence analysis of the plant pathogen Streptomyces scabies 87.22 identified a gene cluster containing a gene encoding a nonribosomal peptide synthetase (NRPS) that was predicted to direct the production of a pentapeptide with structural similarities to scabichelin and turgichelin. Comparative LC-MS/MS analyses of iron-deficient culture supernatants from wild type S. scabies 87.22 and a mutant in which the NRPS gene had been disrupted, and scabichelin purified from S. antibioticus, showed that scabichelin is the metabolic product of the cryptic gene cluster, strongly suggesting that it functions as a siderophore.

Linear fusigen as the major hydroxamate siderophore of the ectomycorrhizal Basidiomycota Laccaria laccata and Laccaria bicolor.

A screening for siderophores produced by the ectomycorrhizal fungi Laccaria laccata and Laccaria bicolor in synthetic low iron medium revealed the release of several different hydroxamate siderophores of which four major siderophores could be identified by high resolution mass spectrometry. While ferricrocin, coprogen and triacetylfusarinine C were assigned as well as other known fungal siderophores, a major peak of the siderophore mixture revealed an average molecular mass of 797 for the iron-loaded compound. High resolution mass spectrometry indicated an absolute mass of m/z = 798.30973 ([M + H](+)). With a relative error of Δ = 0.56 ppm this corresponds to linear fusigen (C33H52N6O13Fe; MW = 797.3). The production of large amounts of linear fusigen by these basidiomycetous mycorrhizal fungi may possibly explain the observed suppression of plant pathogenic Fusarium species. For comparative purposes Fusarium roseum was included in this study as a well known producer of cyclic and linear fusigen.

Isobutylhydroxyamides from the pericarp of Nepalese Zanthoxylum armatum inhibit NF1-defective tumor cell line growth.

A neurofibromatosis type 1 (NF1)-based bioassay-guided phytochemical investigation on Zanthoxylum armatum collected in Nepal led to the isolation of new timuramides A-D (1-4) and six known sanshools (5-10). The structures of all compounds were established by using modern spectroscopic techniques, including 1D and 2D NMR analysis and comparison with previously reported data. Most of the compounds inhibited growth of an Nf1- and p53-deficient mouse glioma cell line at noncytotoxic concentrations.

Structural requirements for the activity of the MirB ferrisiderophore transporter of Aspergillus fumigatus.

Siderophores have been identified as virulence factors in the opportunistic fungal pathogen Aspergillus fumigatus. The 14-pass transmembrane protein MirB is postulated to function as a siderophore transporter, responsible for uptake of the hydroxamate siderophore N,N',N″-triacetylfusarinine C (TAFC). Our aim was to identify amino acids of A. fumigatus MirB that are crucial for uptake of TAFC. Site-directed mutagenesis was used to create MirB mutants. Expression of wild-type and mutant proteins in the Saccharomyces cerevisiae strain PHY14, which lacks endogenous siderophore transporters, was confirmed by Western blotting. TAFC transport assays using (55)Fe-labeled TAFC and growth assays with Fe-TAFC as the sole iron source identified alanine 125, tyrosine 577, loop 3, and the second half of loop 7 (Loop7Del2) as crucial for function, since their substitution or deletion abrogated uptake completely. Wild-type MirB transported ferricrocin and coprogen as well as TAFC but not ferrichrysin. MirB was localized by fluorescence microscopy using antisera raised against a MirB extracellular loop peptide. Immunofluorescence microscopy showed that in yeast, wild-type MirB had a punctate distribution under the plasma membrane, as did the A125D and Y577A strains, indicating that the defect in transport of these mutants was unlikely to be due to mislocalization or degradation. MirB immunolocalization in A. fumigatus showed that the transporter was found in vesicles which cycled between the cytoplasm and the plasma membrane and was concentrated at the hyphal tips. The location of MirB was not influenced by the presence of the siderophore TAFC but was sensitive to internal iron stores.

Isolation, structure elucidation, and biosynthesis of an unusual hydroxamic acid ester-containing siderophore from Actinosynnema mirum.

In this study we report the isolation, structure elucidation, and biosynthesis of mirubactin (1), a siderophore containing an unprecedented chemical functionality in natural products, namely, an O-acyl hydroxamic acid ester. Mirubactin represents the first siderophore isolated from the genus Actinosynnema and the first natural product produced by Actinosynnema mirum whose biosynthetic gene cluster could be identified. Structure elucidation was accomplished through a combination of spectroscopic (NMR, IR, and UV/vis) and mass spectrometric methods and revealed the presence of an unusual ester bond between the δ-N-hydroxyl group of δ-N-formyl-δ-N-hydroxyornithine and a 2,3-dihydroxybenzoate moiety. Bioinformatic analysis of the A. mirum genome and subsequent biochemical characterization of the putative biosynthetic machinery identified the gene cluster responsible for mirubactin assembly. The proposed biosynthesis of mirubactin comprises the iterative use of a stand-alone carrier-protein-bound substrate, as well as an ester-bond-forming step catalyzed by a C-terminal condensation domain, thus revealing an interesting system for further biochemical studies to gain a deeper understanding of nonribosomal peptide synthetase-catalyzed siderophore biosynthesis.

Inhibitory effect of cyclic trihydroxamate siderophore, desferrioxamine E, on the biofilm formation of Mycobacterium species.

Formation of biofilm in pathogenic bacteria defends them from antibiotics and the immune system of a host's life. Hence, investigation of the molecular mechanisms of biofilm formation and search for new substances counteracting this formation are becoming an attractive research area. In the course of our search for new inhibitors of biofilm formation in Mycobacterium species, we rediscovered a cyclic trihydroxamate siderophore, desferrioxamine E, from the culture of the marine-derived Actinomycete MS67. Desferrioxamine E inhibited biofilm formation of Mycobacterium smegmatis and M. bovis BACILLE de CALMETTE et GUÉRIN (BCG) with minimum inhibitory concentration (MIC) value of 10 µM, while no anti-microbial activity was observed up to 160 µM. Desferrioxamine E was also able to restore the anti-microbial activity of isoniazid against M. smegmatis by inhibiting biofilm formation. Mechanistic analysis of desferrioxamine E suggested that such inhibition might come from the depletion of iron in the medium, which is essential for biofilm formation in Mycobacterium species.

Chemical and structural characterization of hydroxamate siderophore produced by marine Vibrio harveyi.

In the present study, 22 different bacteria were isolated from open ocean water from the Gulf of Mannar, India. Of the 22 isolates, 4 were identified as Vibrio spp. (VM1, VM2, VM3 and VM4) and found to produce siderophores (iron-binding chelators) under iron-limited conditions. Different media were found to have an influence on siderophore production. Maximum siderophore production was observed with VM1 isolate in MM9 salts medium at 48 h of incubation. The isolate was confirmed as Vibrio harveyi based on 16S rRNA gene sequencing and phylogenetic analysis. Fourier-transform infrared (FTIR) and (1)H nuclear magnetic resonance (NMR) spectra revealed the hydroxamate nature of the siderophore produced. Further characterization of the siderophore revealed it to be of dihydroxamate nature, forming hexadentate ligands with Fe(III) ions. A narrow shift in ultraviolet (UV)-Vis spectrum was observed on photolysis due to ligand oxidation. Growth-promotion bioassay with Aeromonas hydrophila, Staphylococcus aureus and E. coli confirmed the iron-scavenging property of the siderophore produced by Vibrio harveyi.

Isolation of nocobactin NAs as Notch signal inhibitors from Nocardia farcinica, a possibility of invasive evolution.

Notch signaling inhibitors with the potential of immune suppressor production by pathogenic bacteria for easy host infection were searched from extracts of Nocardia sp. Nocobactin NA-a (compound 1) and nocobactin NA-b (compound 2), which have been suggested as pathogenesis factors, were isolated from N. farcinica IFM 11523 isolated from the sputum of a Japanese patient with chronic bronchitis. Compounds 1 and 2 showed Notch inhibitory activities with IC50 values of 12.4 and 17.6 µM, respectively. Compound 1 and 2 decreased of Notch1 protein, Notch intracellular domain, and hairy and enhancer of split 1, which is a Notch signaling target protein. In addition, compounds 1 and 2 showed cytotoxicity against mouse macrophage-like cell line RAW264.7 with IC50 values of 18.9 and 21.1 µM, respectively. These results suggested that the Notch inhibitors production by pathogenic bacteria may increase pathogen infectivity.

Development of a validated LC method for enantiomeric separation and determination of adrafinil and its related substances on a Chiralcel OJ-H column connected to PDA and polarimetric detectors in series.

A rapid and reliable high-performance liquid chromatographic method for resolution of enantiomers of adrafinil [(±)-ADL], a novel vigilance promoting agent, and its synthetic intermediates was developed. The separation was carried out on a Chiralcel OJ-H using n-hexane-ethanol (62:38 v/v) as a mobile phase. The detection was carried out at 225 nm using a photodiode array (PDA) detector. The optical rotation and order of elution of enantiomers were assigned. The method is suitable not only for process development of ADL but also for quality assurance of bulk drugs and pharmaceuticals.

Clonocoprogens A, B and C, new antimalarial coprogens from the Okinawan fungus Clonostachys compactiuscula FKR-0021.

Three new antimalarial compounds, clonocoprogens A, B, and C, were isolated from the static culture of an Okinawan fungus, Clonostachys compactiuscula FKR-0021. These compounds were new analogs of N14-palmitoylcoprogen, reported as a siderophore. They showed moderate antimalarial activity against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum strains, with IC50 values ranging from 1.7 to 9.9 µM.

Hydroxamate siderophores of Scedosporium apiospermum.

Scedosporium apiospermum is an emerging pathogen colonizing the airways of patients with cystic fibrosis and causing severe infections in immunocompromised hosts. In order to improve our knowledge on the pathogenic mechanisms of this fungus, we investigated the production of siderophores. Cultivation on CAS medium and specific assays for different classes of siderophores suggested the secretion of hydroxamates. A maximal production was obtained by cultivation of the fungus at alkaline pH in an iron-restricted liquid culture medium. Siderophores were then extracted from the culture filtrate by liquid/liquid extraction, and separated by reverse phase high performance liquid chromatography. Two siderophores, dimerumic acid and Nα-methyl coprogen B, were identified by electrospray ionization-mass spectrometry and MS-MS fragmentation. Finally, comparison of various strains suggested a higher production of Na-methyl coprogen B by clinical isolates of respiratory origin. Studies are initiated in order to determine the potential usefulness of these siderophores as diagnostic markers of scedosporiosis.

Analysis of Microbial Siderophores by Mass Spectrometry.

Siderophores represent important microbial virulence factors and infection biomarkers. Their monitoring in fermentation broths, bodily fluids, and tissues should be reproducible. Similar isolation, characterization, and quantitation studies can often have conflicting results, and without proper documentation of sample collection, data processing, and analysis methods, it is difficult to reexamine the data and reconcile these differences. In this Springer Nature Protocol, we present the procedure optimized for ferricrocin/triacetylfusarinine C extraction from biological material as well as for tissue fixation and cryosectioning for optical microscopy and for both elemental and molecular mass spectrometry imaging. Special attention is paid to siderophore data mining from conventional and product ion mass spectra, liquid chromatography, and mass spectrometry imaging datasets, performed here by our free software called CycloBranch.

Talarolide A, a Cyclic Heptapeptide Hydroxamate from an Australian Marine Tunicate-Associated Fungus, Talaromyces sp. (CMB-TU011).

A miniaturized 24-well plate microbioreactor approach was used to explore secondary metabolite media dependence in an Australian marine tunicate-associated fungus, Talaromyces sp. (CMB TU011). Detailed chemical investigations of an antifungal M1-saline cultivation yielded talarolide A (1), only the second reported natural cyclic peptide hydroxamate, and the first from a fungus. The antifungal properties of the M1-saline extract were attributed to the known diterpene glycoside sordarin (2). Structure elucidation of 1 and 2 was achieved by detailed spectroscopic analysis, with amino acid configurations in 1 assigned by the C3 and C18 Marfey's methods, and l-Ala and d-Ala regiochemistry by the recently reported 2D C3 Marfey's method.