Macrolide Antifungal Antibiotic Research Articles

Antibiotic-sterol interactions provide insight into the selectivity of natural aromatic analogues of amphotericin B and their photoisomers

Aromatic heptaene macrolides (AHMs) belong to the group of polyene macrolide antifungal antibiotics. Members of this group were the first to be used in the treatment of systemic fungal infections. Amphotericin B (AmB), a non-aromatic representative of heptaene macrolides, is of significant clinical importance in the treatment of internal mycoses. It includes the all-trans heptaene chromophore, whereas the native AHMs contain two cis-type (Z) double bonds within the chromophore system. Lately we have proven that it is possible to obtain AHMs’ stable derivatives in the form of all-trans (AmB-type) isomers by photochemical isomerization. Our further studies have shown that such alteration leads to the improvement of their selective toxicity in vitro. Computational experiments carried out so far were only an initial contribution in the investigation of the molecular basis of the mechanism of action of AHMs and did not provide explanation to observed differences in biological activity between the native (cis-trans) and isomeric (all-trans) AHMs. Herein, we presented the results of two-dimensional metadynamics studies upon AmB and its aromatic analogues (AHMs), regarding preferable binary antibiotic/sterol complexes orientation, as well as more detailed research on the behaviour of AHMs’ alkyl-aromatic side chain in cholesterol- or ergosterol-enriched lipid bilayers.

Quest for the Molecular Basis of Improved Selective Toxicity of All-Trans Isomers of Aromatic Heptaene Macrolide Antifungal Antibiotics.

Three aromatic heptaene macrolide antifungal antibiotics, Candicidin D, Partricin A (Gedamycin) and Partricin B (Vacidin) were subjected to controlled cis-trans → all trans photochemical isomerization. The obtained all-trans isomers demonstrated substantially improved in vitro selective toxicity in the Candida albicans cells: human erythrocytes model. This effect was mainly due to the diminished hemotoxicity. The molecular modeling studies on interactions between original antibiotics and their photoisomers with ergosterol and cholesterol revealed some difference in free energy profiles of formation of binary antibiotic/sterol complexes in respective membrane environments. Moreover, different geometries of heptaene: sterol complexes and variations in polyene macrolide molecule alignment in cholesterol-and ergosterol-containing membranes were found. None of these effects are of the crucial importance for the observed improvement of selective toxicity of aromatic heptaene antifungals but each seems to provide a partial contribution.

The effects of Eushearilide, a novel macrolide antifungal antibiotic, on rat mitochondrial respiratory function

The effects of Eushearilide, a novel macrolide antifungal antibiotic, on rat mitochondrial respiratory function

Light-Induced Transformation of the Aromatic Heptaene Antifungal Antibiotic Candicidin D into Its All-Trans Isomer.

Illumination of the aromatic heptaene macrolide antifungal antibiotic candicicin D with UV light results in an isomerization of the molecule. The product formed after irradiation of the candicidin complex with UV light (λ = 365 nm), namely, iso-candicidin D, was isolated and subjected to 2D NMR studies, consisting of DQF-COSY, ROESY, TOCSY, HSQC, and HMBC experiments. The obtained spectral data unambiguously evidenced that iso-candicidin D was the all-trans isomer of the native antibiotic, and straightening of the heptaenic chromophore was the only light-induced structural change that occurred. Hence, iso-candicidin D was proclaimed to be a prototype of a novel class of polyene macrolide antifungal antibiotics: the all-trans aromatic heptaenes, containing a macrolide ring similar to that of amphotericin B.

Enhanced natamycin production by co-expression of Vitreoscilla hemoglobin and antibiotic positive regulators in Streptomyces gilvosporeus

ABSTRACTNatamycin, an important 26-member tetraene macrolide antifungal antibiotic, is widely used as antifungal agent in the food industry and medical fields. However, low yields of the currently used production strains limit its wider applications. To improve the productivity of natamycin-producing strains, we co-expressed the Vitreoscilla hemoglobin gene vgb in Streptomyces gilvosporeus with two genes that constitute part of the natamycin biosynthesis gene cluster: pimE (encoding a signalling protein) and pimM (encoding a positive regulator). Both genes were cloned and ligated into the shuttle vector pIMEP under the control of the strong, constitutive Perm promoter, and integrated into the chromosome of S. gilvosporeus via conjugation. Natamycin production was increased 40.3% upon overexpression of pimE and pimM. Furthermore, in order to alleviate oxygen limitation, we additionally expressed vgb in the pimE and pimM over-expressing strain, yielding S. gilvosporeus/pIMEP::pimE::pimM::vgb, which showed a further 55.7% improvement for natamycin production compared to that of the recipient strain. In conclusion, co-expression of pimE and pimM with vgb led to markedly increased natamycin production, thus pointing out a potential strategy for enhancing the microbial production of other antibiotics as well.

Intramolecular transformation of an antifungal antibiotic nystatin A1 into its isomer, iso-nystatin A1 - structural and molecular modeling studies.

Nystatin A1 , a polyene macrolide antifungal antibiotic, in a slightly basic or acidic solution undergoes an intramolecular transformation, yielding a structural isomer, the translactonization product, iso-nystatin A1 with lactone ring diminished by two carbon atoms. Structural evidence is provided by advanced NMR and Mass Spectrometry (MS) studies. Molecular dynamics simulations and quantum mechanics calculations gave the insight into the course and mechanism of the transformation and its effect on the conformation of the subject molecule. Copyright © 2016 John Wiley & Sons, Ltd.

Crucial factor for increasing the conjugation frequency in Streptomyces netropsis SD-07 and other strains.

Streptomyces netropsis SD-07, the producer of novel polyene macrolide antifungal antibiotics, was isolated from soil. For the investigation of the functions of its biosynthesis genes and regulation mechanisms, a genetic operating system is necessary. In this study, we successfully transferred the plasmid DNA of pSET152 from the methylation deficient donor, Escherichia coli ET12567/pSET152/pUZ8002, to S. netropsis SD-07 by conjugation and evaluated the crucial factors influencing the conjugation frequency. Ca(2+) ions in presence the conjugation media may increase the conjugation frequency by 1000-10 000 times than Ca(2+) ions absence in the same conjugation media, and 10-100 time higher than Mg(2+) ions. Similar results (increasing the conjugation frequency by 10-100 times when media containing 60 mM CaCl2 ) were also obtained from the conjugation between E. coli ET12567 and Streptomyces coelicolor, S. lavendulae, S. venezuelae, despite their conjugation media were different (MS, CM, GS). So, CaCl2 concentration is a crucial factor for increasing the conjugation frequency, and the suitable concentration may probably be 60 mM. In addition, synthetic medium containing a small amount of organic nitrogen source may benefit increasing the conjugation frequency. These findings could be valuable for the development of a practical method for achieving conjugation in other Streptomyces spp.

Characteristics and biotechnological applications of microbial cholesterol oxidases

Microbial cholesterol oxidase is an enzyme of great commercial value, widely employed by laboratories routinely devoted to the determination of cholesterol concentrations in serum, other clinical samples, and food. In addition, the enzyme has potential applications as a biocatalyst which can be used as an insecticide and for the bioconversion of a number of sterols and non-steroidal alcohols. The enzyme has several biological roles, which are implicated in the cholesterol metabolism, the bacterial pathogenesis, and the biosynthesis of macrolide antifungal antibiotics. Cholesterol oxidase has been reported from a variety of microorganisms, mostly from actinomycetes. We recently reported cholesterol oxidases from gram-negative bacteria such as Burkholderia and Chromobacterium. These enzymes possess thermal, detergent, and organic solvent tolerance. There are two forms of cholesterol oxidase, one containing a flavin adenine dinucleotide cofactor non-covalently bound to the enzyme (class I) and the other containing the cofactor covalently linked to the enzyme (class II). These two enzymes have no significant sequence homology. The phylogenetic tree analyses show that both class I and class II enzymes can be further divided into at least two groups.

Molecular modelling of membrane activity of amphotericin B, a polyene macrolide antifungal antibiotic.

Amphotericin B (AmB) is a well known polyene macrolide antibiotic used to treat systemic fungal infections. Despite its toxicity AmB is still regarded as a life-saving drug. The lack of adequate knowledge of the AmB mechanism of action is a serious obstacle to efficient development of new less toxic derivatives. Complementary to various experimental approaches, computational chemistry methods were used to study AmB mechanism of action. A programme lasting for a decade, that was run by our group covered studies of: i) molecular properties of AmB and its membrane targets, ii) structure and properties of AmB membrane channels, and iii) interaction of AmB with the membrane.

TMC-34, a new macrolide antifungal antibiotic.

TMC-34, a new macrolide antifungal antibiotic.

Structure of malolactomycins A and B, novel 40-membered macrolide antibiotics

Malolactomycins A and B are novel 40-membered polyol macrolide antifungal antibiotics which have hemiacetal, malonate and dimethylguanidyl groups. Malolactomycins A and B are positional isomers of malonate and interconvertible each other by transesterification. The structures of malolactomycins A and B have been determined by spectroscopic analyses, especially NMR for the parent antibiotics and MS for the oxidative product.

Hydrazides-a novel type of derivatives of polyene macrolide antifungal antibiotics.

Hydrazides-a novel type of derivatives of polyene macrolide antifungal antibiotics.

A screening method for antifungal substances using Saccharomyces cerevisiae strains resistant to polyene macrolides.

Strains of Saccharomyces cerevisiae FL200 capable of growing on a solid medium containing a mixture of polyene macrolide antibiotics (nystatin, 40 micrograms/ml, amphotericin B, 40 micrograms/ml, pimaricin, 150 micrograms/ml and RP9971 antibiotic, 10 micrograms/ml) have been isolated after successive selection steps. The mutant strains, PR13 and PRC24, are 10 to 100 times more resistant than the polyene macrolide antibiotics. When 4% Tween 80 is added to the medium, resistance to these antifungal drugs is further increased. In addition, strain PRC24, derived from strain PR13, is resistant to a non-polyene macrolide antifungal antibiotic, cycloheximide. In contrast, PR13 and PRC24 are both highly susceptible to a large range of compounds, including non-polyenic antifungal, antitumor and antibacterial agents. These particular characteristics make these strains useful for the rapid detection of antifungal compounds of the polyene macrolide and cycloheximide types, as well as for the recognition of antimitotic substances.

Relationship between ionophoric and haemolytic activities of perimycin A and vacidin A, two polyene macrolide antifungal antibiotics

The ionophoric and hemolytic activities of two antifungal aromatic heptaenes: vacidin A and perimycin A, were studied on human red blood cells. Measurements of hemolysis, K + influx and efflux, H + movement and potential difference across the cell membrane, show that the hemolytic activity, being related to the K + permeability induced by the polyene, is strongly dependent on the ability of this polyene to induce H + movement. It was shown that: (1) both antibiotics have approximately the same efficiency in inducing K + permeability, but a 100-fold difference in their hemolytic activity; (2) their hemolytic activity is related to their ability to induce H + movement; (3) the protonophoric activity requires the existence of a free carboxyl group in the macrolide ring, as in vacidin A. The hemolytic activity is determined by the intrinsic efficiency of a K +/H + exchange induced by this polyene. With perimycin A, which lacks the free carboxyl group, the hemolytic activity is dependent on the Cl + conductive flux which slows down the K + flux.

Tetrafungin, a new polyene macrolide antibiotic. I. Fermentation, isolation, characterization, and biological properties.

A new polyene macrolide antifungal antibiotic, named tetrafungin, was isolated from the cultured mycelium of a Streptomyces strain. Fermentation, isolation, physico-chemical and biological properties of the antibiotic are described. Its UV absorption spectrum and its physico-chemical characteristics place this antibiotic in the group 2.2.2.3 of the Berdy classification.

The structure of roflamycoin, a new polyene macrolide antifungal antibiotic.

The structure of roflamycoin, a new polyene macrolide antifungal antibiotic.

Hydroheptin: a water-soluble polyene macrolide. II. Chemical and biological properties.

Hydroheptin, a new polyene macrolide antifungal antibiotic, is co-produced with the antibiotic, chartreusin, by a strain of Streptomyces chartreusis designated as IMRU 3962 isolated in our laboratory. The unique water-solubility of this antibiotic at neutrality, revealing in aqueous solution molecular dispersion and an ultraviolet-visible absorption spectrum characteristic of an all-trans heptaene chromophore, clearly distinguishes it from all previously-described and naturally-occurring heptaene macrolides. The isolation and identification of the amino sugar, mycosamine (3-amino-3,6-dideoxy-D-mannose), in acid hydrolysates of hydroheptin and the absence of an aromatic amine upon retrograde alkaline dealdolization of the molecule certainly characterize the antibiotic as a member of the non-aromatic heptaene macrolide group. Chromatographic and countercurrent distribution studies likewise support its novelty. With little or no demonstrable activity against bacteria, hydroheptin as compared to other non-aromatic heptaene macrolides exhibits excellent but somewhat less activity against a wide variety of yeasts and fungi. Likewise, its parenteral toxicity appears to be less than that of other heptaene macrolides.

Hydroheptin: a water-soluble polyene macrolide. I. Taxonomy, fermentation and isolation.

A soil isolate of Streptomyces, which has been deposited in the culture collection of the Waksman Institute of Microbiology, Rutgers University as IMRU 3962, produces a new heptaene macrolide antifungal antibiotic, hydroheptin. The producing microorganism, which co-produces the antibiotic, chartreusin, has been identified as a strain of Streptomyces chartreusis. Fermentation and bioassay procedures were developed for the production and analysis of hydroheptin and chartreusin. Isolation and purification procedures based on solvent extraction and precipitation of an organic acid yielded a relatively pure product of hydroheptin.

The Antihypercholesterolemic Activity of Candicidin as a Function of Dietary Cholesterol in Cockerels

In the first of two experiments using White Leghorn cockerels, a multifactorial analysis of variance was employed to characterize the antihypercholesterolemic responses (AHC) to candicidin (a heptaene macrolide antifungal antibiotic)-containing diets and the manner in which hypercholesterolemic challenges of different magnitudes modify these responses. In hypercholesterolemic diets, oral candicidin reduced plasma cholesterol concentration in a dose-dependent manner. The relative AHC effects of the diet were dependent on and varied directly with the presence and magnitude of the hypercholesterolemic challenge. The AHC effects of oral candicidin appeared to be additive to the homeostatic mechanisms limiting the rise in plasma cholesterol concentration induced by hypercholesterolemic diets. In the second experiment the absorption of oral 14C-candicidin was studied. Radioactivity above background levels was not found in any of the sampled tissues 4 days after administration of the 14C-candicidin pulse. The total cumulative recovery of radioactivity in the excreta was approximately 95% of the administered dose after 4 days. Within the limits of detection, oral candicidin did not appear to be absorbed from the intestine and appeared to be rapidly and quantitatively eliminated from the body in the feces. Chronic provision of candicidin appeared to increase transit time through the gastrointestinal tract.

The structure of mycoheptin, a polyene macrolide antifungal antibiotic.

The complete structure of mycoheptin, a heptaene macrolide antifungal antibiotic, has been established as I by chemical degradation methods and MS and 1H NMR analysis of the products.