Marine Streptomyces sp. derived antimycin analogues suppress HeLa cells via depletion HPV E6/E7 mediated by ROS-dependent ubiquitin-proteasome system.

Four new antimycin alkaloids (1-4) and six related known analogs (5-10) were isolated from the culture of a marine derived Streptomyces sp. THS-55, and their structures were elucidated by extensive spectroscopic analysis. All of the compounds exhibited potent cytotoxicity in vitro against HPV-transformed HeLa cell line. Among them, compounds 6-7 were derived as natural products for the first time, and compound 5 (NADA) showed the highest potency. NADA inhibited the proliferation, arrested cell cycle distribution, and triggered apoptosis in HeLa cancer cells. Our molecular mechanic studies revealed NADA degraded the levels of E6/E7 oncoproteins through ROS-mediated ubiquitin-dependent proteasome system activation. This is the first report that demonstrates antimycin alkaloids analogue induces the degradation of high-risk HPV E6/E7 oncoproteins and finally induces apoptosis in cervical cancer cells. The present work suggested that these analogues could serve as lead compounds for the development of HPV-infected cervical cancer therapeutic agents, as well as research tools for the study of E6/E7 functions.

Antimycin-type depsipeptides: discovery, biosynthesis, chemical synthesis, and bioactivities.

Covering: up to 2016Antimycin-type depsipeptides are a family of natural products with great structural diversity and outstanding biological activities. These compounds have typically been isolated from actinomycetes and are generated from hybrid nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) assembly lines. This review covers the literature on the four classes of antimycin-type depsipeptides, which differ by macrolactone ring size, and it discusses the discovery, biosynthesis, chemical synthesis, and biological activities of this family of compounds.

Anti-Candida properties of urauchimycins from actinobacteria associated with trachymyrmex ants.

After decades of intensive searching for antimicrobial compounds derived from actinobacteria, the frequency of isolation of new molecules has decreased. To cope with this concern, studies have focused on the exploitation of actinobacteria from unexplored environments and actinobacteria symbionts of plants and animals. In this study, twenty-four actinobacteria strains isolated from workers of Trachymyrmex ants were evaluated for antifungal activity towards a variety of Candida species. Results revealed that seven strains inhibited the tested Candida species. Streptomyces sp. TD025 presented potent and broad spectrum of inhibition of Candida and was selected for the isolation of bioactive molecules. From liquid shake culture of this bacterium, we isolated the rare antimycin urauchimycins A and B. For the first time, these molecules were evaluated for antifungal activity against medically important Candida species. Both antimycins showed antifungal activity, especially urauchimycin B. This compound inhibited the growth of all Candida species tested, with minimum inhibitory concentration values equivalent to the antifungal nystatin. Our results concur with the predictions that the attine ant-microbe symbiosis may be a source of bioactive metabolites for biotechnology and medical applications.

Isolating antifungals from fungus-growing ant symbionts using a genome-guided chemistry approach.

We describe methods used to isolate and identify antifungal compounds from actinomycete strains associated with the leaf-cutter ant Acromyrmex octospinosus. These ants use antibiotics produced by symbiotic actinomycete bacteria to protect themselves and their fungal cultivar against bacterial and fungal infections. The fungal cultivar serves as the sole food source for the ant colony, which can number up to tens of thousands of individuals. We describe how we isolate bacteria from leaf-cutter ants collected in Trinidad and analyze the antifungal compounds made by two of these strains (Pseudonocardia and Streptomyces spp.), using a combination of genome analysis, mutagenesis, and chemical isolation. These methods should be generalizable to a wide variety of insect-symbiont situations. Although more time consuming than traditional activity-guided fractionation methods, this approach provides a powerful technique for unlocking the complete biosynthetic potential of individual strains and for avoiding the problems of rediscovery of known compounds. We describe the discovery of a novel nystatin compound, named nystatin P1, and identification of the biosynthetic pathway for antimycins, compounds that were first described more than 60 years ago. We also report that disruption of two known antifungal pathways in a single Streptomyces strain has revealed a third, and likely novel, antifungal plus four more pathways with unknown products. This validates our approach, which clearly has the potential to identify numerous new compounds, even from well-characterized actinomycete strains.

Preparative separation of six antimycin A components from antimycin fermentation broth by high-speed counter-current chromatography.

A method of using high-speed counter-current chromatography (HSCCC) was established for preparative isolation and purification of antimycin A components from antimycin fermentation broth. Six antimycin A components were successfully purified for the first time by HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (5:2:4:1, by volume). Total of 20mg antimycin A(4)(a or b), 25mg antimycin A(3)(a or b), 21mg antimycin A(8)(a or b), 34mg antimycin A(2)(a or b), 26mg antimycin A(1)(a or b) and 34mg antimycin A(1)(a or b) with the purities of 93.2, 98.6, 96.2, 94.1, 94.9 and 96.7%, respectively, determined by high-performance liquid chromatography (HPLC), were yielded from 200mg crude sample only in one HSCCC run.

A novel antimycin-like compound, JBIR-06, from Streptomyces sp. ML55.

A novel compound of antimycin family, JBIR-06 (1), was isolated from Streptomyces sp. ML55. The structure of 1 was established as a twelve-membered macrocyclic skeleton with a 3-(formylamino)-2-hydroxybenzamide based on the spectroscopic data. Compound 1 inhibited the expression of GRP78 induced by 2-deoxyglucose at the IC50 value of 250 nM.

A new fungicide produced by a Streptomyces sp. GAAS7310.

Directed bioassay guided fraction led to a new macrodiolide antimycin A(17) (1), isolated from a Streptomyces sp. GAAS7310, which showed significant antimicrobial activity against eleven fungal species, including Curvularia lunata (Wakker) Boed, Rhizopus nigrtcans Ehrb and Colletotrichum nigrum EL. et Halst. The structure was unambiguously established by interpretation of 1D and 2D NMR data and comparison with the known antimycin A(1a).

A new antibiotic, antimycin Ag, produced by Streptomyces sp. K01-0031.

A new antimycin group antibiotic, antimycin A9, was isolated from a cultured broth of Streptomyces sp. K01-0031 together with antimycins A3a, A3b, A4, and A7, and flazin methyl ester. Antimycin A9 is the first antimycin having an aromatic 8-acyl residue. It showed potent nematocidal and insecticidal activities against Caenorhabditis elegans and Artemia salina, respectively. It inhibited bovine heart NADH oxidase at nanomolar level like other known antimycins.

Novel antimycin antibiotics, urauchimycins A and B, produced by marine actinomycete.

Two novel antimycin antibiotics, urauchimycins A and B, were isolated from a fermentation broth of a Streptomyces sp. Ni-80. The strain was isolated from an unidentified sponge. Their chemical structures were determined by 2D NMR analysis. They are the first antimycin antibiotics which possess a branched side chain moiety. They exhibited inhibitory activity against morphological differentiation of Candida albicans.

High-performance liquid chromatographic separation of subcomponents of antimycin A.

Using a reversed-phase high-performance liquid chromatographic (HPLC) technique, a mixture of antimycins A was separated into eight hitherto unreported subcomponents, A1a, A1b, A2a, A2b, A3a, A3b, A4a, and A4b. Although a base-line resolution of the known four major antimycins A1, A2, A3, and A4 was readily achieved with mobile phases containing acetate buffers, the separation of the new antibiotic subcomponents was highly sensitive to variation in mobile phase conditions. The type and composition of organic modifers, the nature of buffer salts, and the concentration of added electrolytes had profound effects on capacity factors, separation factors, and peak resolution values. Of the numerous chromatographic systems examined, a mobile phase consisting of methanol-water (70:30) and 0.005 M tetrabutylammonium phosphate at pH 3.0 yielded the most satisfactory results for the separation of the subcomponents. Reversed-phase gradient HPLC separation of the dansylated or methylated antibiotic compounds produced superior chromatographic characteristics and the presence of added electrolytes was not a critical factor for achieving separation. Differences in the chromatographic outcome between homologous and structural isomers were interpreted based on a differential solvophobic interaction rationale. Preparative reversed-phase HPLC under optimal conditions enabled isolation of pure samples of the methylated antimycin subcomponents for use in structural studies.

High-performance liquid chromatographic resolution and quantification of a dilactonic antibiotic mixture (antimycin A).

High-performance liquid chromatographic (HPLC) conditions are presented for the separation and quantitative determination of a homologous antibiotic complex (antimycin A). Combined HPLC and chemical ionization mass spectrometry proved to be exceptionally useful for the structural identification of chromatographic components. Using electrochemical, fluorescence, and ultraviolet detectors, the minimum detectable amounts of the antibiotics were found to be in the ranges 0.10-1.12, 0.31-1.69, and 4.10-28.2 ng, respectively. Advantages of the preparation of Dns derivatives for use in fluorescence detection are discussed. Application of the HPLC technique to the analysis of the antibiotic mixture in organic tissues is demonstrated.

Simple isolation of antimycin A1 and some of its toxicological properties.

An unidentified actinomycete, RTI 246, was found to produce antimycin A(1) in high yield on a high protein cereal medium. The antibiotic compound was extracted from the cells and isolated in pure form by crystallization. It was identified by ultraviolet, infrared, nuclear magnetic resonance, and mass spectroscopy and by alkaline hydrolysis to antimycic acid and a neutral lactone. The intravenous LD(50) was 1.0 mg/kg in white mice, whereas the intraperitoneal LD(50) was 1.50 +/- 0.19 mg/kg. Animals receiving an intraperitoneal injection displayed an incoordination of the hind limbs and impaired reflexes before showing signs of respiratory distress. These findings indicated that antimycin A(1) possesses a neurotoxic property separate from its well-documented property as a respiratory poison.