Differential antifungal activity of isomeric forms of nystatin

Reviving the interest in the versatile drug nystatin: A multitude of strategies to increase its potential as an effective and safe antifungal agent

Nystatin is an antifungal molecule with a remarkable yet squandered versatility. In this review, its mechanism of action is explored, along with its extensive action spectrum and toxicity. A multitude of methodologies to tackle the drug's physical and chemical hurdles are outlined along with some proven-effective strategies to increase its activity and/or decrease its toxicity. A separate detailed section focused on micro and nanotechnology solutions addresses new drug delivery systems made of polymeric, metallic or lipid materials. Although the topical route depicts greater representativeness amongst these formulations, the intravenous, dental, oral, vaginal and inhalation routes are also mentioned. The unsuccessful previous attempts at developing parenteral formulations of nystatin or even the withdrawal of a nystatin-loaded multilamellar liposome should not divert research away from this drug. In fact, the interest in nystatin ought to be reawakened with the ongoing clinical trials on the promising nystatin-like genetically engineered derivate BSG005.

Water-Soluble Nystatin and Derivative

Fungal infections are increasingly causing more morbidity and mortality, especially for immunocompromised people. In recent years, there is growing evidence that new medicine-resistant fungal strains are posing added challenges in the clinic. Nystatin is a known antifungal from the polyene family. Due to Nystatin limited solubility and high toxicity, it is used mainly to treat oral and dermal fungal infections. In search for new Nystatin derivatives and formulations, we obtained amide derivatives and a deoxycholate formulation that were not described previously for this compound. Furthermore, we tested the potency of the derivatives and formulation by the USP(81) method and minimum inhibitory concentration of Candida albicans and Aspergillus niger. Additionally, the in vitro toxicity and stability were tested, and it was found that the ethanol amide derivative of Nystatin was fully water-soluble (up to 100 mg/mL) with the same potency of Nystatin but with 13.5 times lower toxicity. The ethanol amide derivative of Nystatin is a promising candidate for future drug development.

Comparative Genomic and Metabolic Analysis of Streptomyces sp. RB110 Morphotypes Illuminates Genomic Rearrangements and Formation of a New 46-Membered Antimicrobial Macrolide

Morphotype switches frequently occur in Actinobacteria and are often associated with disparate natural product production. Here, we report on differences in the secondary metabolomes of two morphotypes of a Streptomyces species, including the discovery of a novel antimicrobial glycosylated macrolide, which we named termidomycin A. While exhibiting an unusual 46-member polyene backbone, termidomycin A (1) shares structural features with the clinically important antifungal agents amphotericin B and nystatin A1. Genomic analyses revealed a biosynthetic gene cluster encoding for a putative giant type I polyketide synthase (PKS), whose domain structure allowed us to propose the relative configuration of the 46-member macrolide. The architecture of the biosynthetic gene cluster was different in both morphotypes, thus leading to diversification of the product spectrum. Given the high frequency of genomic rearrangements in Streptomycetes, the metabolic analysis of distinct morphotypes as exemplified in this study is a promising approach for the discovery of bioactive natural products and pathways of diversification.

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.

A Novel High Performance Liquid Chromatographic Method for Determination of Nystatin in Pharmaceutical Formulations by Box-Behnken Statistical Experiment Design

In this study a novel High Performance Liquid Chromatography for the assay of nystatin in oral and vaginal tablets were optimized and validated using Box-Behnken experimental design. The method was performed in the isocratic mode on a RP-18 column (30 °C) using a mobile phase consisting of ammonium acetate 0.05 M buffer/ Methanol mixture (30:70) and a flow-rate of 1.0 mL/min. The specificity, linearity, precision, accuracy, LOD and LOQ of the method were validated. The method was linear over the range of 5-500 µg/mL with an acceptable correlation coefficient (r(2) = 0.9996). The method's limit of detection (LOD) and quantification (LOQ) were 0.01 and 0.025 µg/mL respectively. The results indicate that this validated method can be used as an alternative method for assay of nystatin.

Development and validation of an HPLC method for stability evaluation of nystatin

A liquid chromatography method for evaluating the stability of Nystatin (Nys) in an ointment was developed and validated, since the traditional pharmacopeial microbiological methods are unable to indicate stability. The stress experiments showed that Nys was found to significantly degrade in alkaline and acidic conditions and also under oxidative stress. Lower levels of degradation were detected under heat and with the sample exposed to Xenon light. Resolutions higher than 2 for Nys and degradation products (DP) chromatographic peaks were achieved by using an Inerstil ODS-3 column, isocratic elution with methanol:water and UV detection at 305 nm. The system was found to be linear over a range of 102 to 310 IU mL-1 and proved precise, since the RSD(%) was 0.24% for the six replicates tested. The method also exhibited good levels of recovery (from 98.24% to 100.74%). Therefore, the validation fulfilled pharmacopeial requirements and the procedure was found to be reliable, precise, accurate and selective for determination of Nys and its degradation products.

Dissociation of nystatin and amphotericin analogues: characterisation of minor anti-fungal macrolides

Tandem mass spectrometry combined with Fourier transform ion cyclotron resonance (FT-ICR) has been the basis for rationalizing the fragmentation mechanisms of anti-fungal macrolides nystatin A(1), amphotericin B and pimaricin. The positive ion mass spectra were not informative, however, the dissociation of deprotonated molecules led to structurally significant ring-opened fragments. Using this approach of tandem FT-ICR mass spectrometry and electrospray ionisation coupled with high-performance liquid -chromatography (HPLC), 11 macrolide natural analogues or degradation products were characterised in the nystatin mixture.

Interaction between nystatin and natural membrane lipids in Langmuir monolayers--the role of a phospholipid in the mechanism of polyenes mode of action

Nystatin (NYS), a polyene antifungal antibiotic, has been investigated in Langmuir monolayers alone and in mixtures with mammalian and fungi membrane sterols (cholesterol and ergosterol, respectively) as well as with a model phospholipid (DPPC). The interactions between film molecules have been examined both in a qualitative and quantitative way with the excess area per molecule (AExc), excess free energy of mixing (DeltaGExc) and the interaction parameter (alpha). The obtained results have been compared with those previously reported for another polyene antimycotic: amphotericin B (AmB) mixed with lipids. Higher affinity of NYS has been observed for ergosterol vs. cholesterol, however, the strongest attractions were found for its mixtures with DPPC. The obtained results have been verified with biological studies reported previously for both antibiotics (NYS and AmB). A thorough analysis of the Langmuir experiment results performed for both polyenes enabled us to conclude that the presence of DPPC can be considered as a key factor affecting their antifungal activity as well as their toxicity towards host cells.

Nystatin in Langmuir monolayers at the air/water interface

The paper presents a thorough characteristics of Langmuir monolayers formed at the air/water interface by a polyene macrolide antibiotic-nystatin. The investigations are based on the analysis of pi/A isotherms recorded for monolayers formed by this antibiotic at different experimental conditions. A significant part of this work is devoted to the stability and relaxation phenomena. It has been found that nystatin forms at the air/water interface monolayers of the LE state. A plateau region, observed during the course of the isotherm compression, is suggested to be due to the orientational change of nystatin molecules from horizontal to vertical position. Quantitative analysis of the desorption of the monolayer material into bulk water indicates that the solubility of nystatin monolayers increases with surface pressure. At low surface pressures, the desorption of nystatin from a monolayer is controlled both by dissolution and by diffusion. However, at the plateau and in the post-plateau region, the desorption does not achieve a steady state and the monolayer is less stable than in the pre-plateau region. However, the presence of membrane lipids, even at a low mole fraction, considerably increases the stability of nystatin monolayers. This enables the application of the Langmuir monolayer technique to study nystatin in mixture with cellular membrane components, aiming at verifying its mode of action and the mechanism of toxicity.

Chemical diversity of polyene macrolides produced by Streptomyces noursei ATCC 11455 and recombinant strain ERD44 with genetically altered polyketide synthase NysC

The gram-positive bacterium Streptomyces noursei ATCC 11455 produces a complex mixture of polyene macrolides generally termed nystatins. Although the structures for nystatins A(1) and A(3) have been reported, the identities of other components of the nystatin complex remain obscure. Analyses of the culture extract from the S. noursei wild type revealed the presence of several nystatin-related compounds for which chemical structures could be suggested on the basis of their molecular weights, their UV spectra, and knowledge of the nystatin biosynthetic pathway. Nuclear magnetic resonance (NMR) studies with one of these polyene macrolides identified it as a nystatin analogue containing a mycarose moiety at C-35. A similar investigation was performed with the culture extract of the ERD44 mutant, which has a genetically altered polyketide synthase (PKS) NysC and which was previously shown to produce a heptaene nystatin analogue. The latter compound, tentatively named S44HP, and its derivative, which contains two deoxysugar moieties, were purified; and their structures were confirmed by NMR analysis. Nystatin analogues with an expanded macrolactone ring were also observed in the extract of the ERD44 mutant, suggesting that the altered PKS can "stutter" during the polyketide chain assembly. These data provide new insights into the biosynthesis of polyene macrolide antibiotics and the functionalities of PKSs and post-PKS modification enzymes.