Himalaquinones A-G, Angucyclinone-Derived Metabolites Produced by the Himalayan Isolate Streptomyces sp. PU-MM59.

Himalaquinones A-G, seven new anthraquinone-derived metabolites, were obtained from the Himalayan-based Streptomyces sp. PU-MM59. The chemical structures of the new compounds were identified based on cumulative analyses of HRESIMS and NMR spectra. Himalaquinones A-F were determined to be unique anthraquinones that contained unusual C-4a 3-methylbut-3-enoic acid aromatic substitutions, while himalaquinone G was identified as a new 5,6-dihydrodiol-bearing angucyclinone. Comparative bioactivity assessment (antimicrobial, cancer cell line cytotoxicity, impact on 4E-BP1 phosphorylation, and effect on axolotl embryo tail regeneration) revealed cytotoxic landomycin and saquayamycin analogues to inhibit 4E-BP1p and inhibit regeneration. In contrast, himalaquinone G, while also cytotoxic and a regeneration inhibitor, did not affect 4E-BP1p status at the doses tested. As such, this work implicates a unique mechanism for himalaquinone G and possibly other 5,6-dihydrodiol-bearing angucyclinones.

Design of green coating material of combining rigid and flexible properties for the extraction of aminoglycosides residues.

Bio-based and low-cost hybrid polyvinyl alcohol (PVA) and gelatin (Gel) hydrophilic macromolecular complex coated microspheres were prepared based on one-pot process, characterized, and applied as novel sorbent materials for the purification of trace aminoglycosides from complex matrices. PVA acts as a "rigid" component in the hybrid complex to enhance its mechanical properties, while Gel's "flexible" role is to improve the swelling properties of the hybrid complex in water. It is shown that hybrid PVA/Gel-functionalized sorbents are more efficient than the respective PVA or Gel sorbents since the presence of Gel increases the material selectivity for aminoglycosides, which is due to the specific interactions occurring between the targets and amino acid residues in the hybrid materials. Under the optimum conditions, material preparation and pretreatment processes were entirely carried out in single water system without toxic organic solvent. The detection limit (LOD) of spectinomycin, kanamycin, streptomycin and dihydrostreptomycin in honey were 0.811, 0.303, 0.168, 0.045 µg⋅kg-1 respectively. Linearity was obtained in the range of 20 to 2000 ug⋅kg-1, relative recovery yield up to 84.1-111.7% were obtained and matrix effect of all four aminoglycosides was within 100.8-107.6%. Intra-day and inter-day precision under four spiking levels (5, 200, 500 and 1000 ug⋅kg-1) were less than 10.9% (n=6) and 13.6% (n=3) respectively. In addition, the sorbents exhibited excellent reusability even after six recycles. This work demonstrates the potential of bio-based and low-cost hybrid polymer extraction platforms as promising bonded phase alternatives, in which eco-friendly and natural-based polymers can be used to improve the material selectivity and are conducive to the realization of "green chemistry".

Comprehensive study of antimicrobial susceptibility pattern and extended spectrum beta-lactamase (ESBL) prevalence in bacteria isolated from urine samples.

Nowadays, increasing extended-spectrum ß-lactamase (ESBL)-producing bacteria have become a global concern because of inducing resistance toward most of the antimicrobial classes and making the treatment difficult. In order to achieve an appropriate treatment option, identification of the prevalent species which generate ESBL as well as their antibiotic susceptibility pattern is essential worldwide. Hence, this study aimed to investigate the prevalence of ESBL-producing bacteria and assess their drug susceptibility in Fardis Town, Iran. A total of 21,604 urine samples collected from patients suspected to have urinary tract infection (UTI) were processed in the current study. The antimicrobial susceptibility of the isolates was tested by the disk diffusion method. The ESBL producing bacteria were determined by Double Disc Synergy Test (DDST) procedure. Bacterial growth was detected in 1408 (6.52%) cases. The most common bacterial strains causing UTI were found E. coli (72.16%), followed by K. pneumoniae (10.3%) and S. agalactiae (5.7%). Overall, 398 (28.26%) were ESBL producer. The highest ESBL production was observed in E. coli, followed by Klebsiella species. ESBL producers revealed a higher level of antibiotic resistance compared with non-ESBLs. In conclusion, ESBL production in uropathogens was relatively high. Carbapenems and Aminoglycosides were confirmed as the most effective treatment options for these bacteria.

Poly(N-acryloyl-glucosamine-co-methylenebisacrylamide)-based hydrophilic magnetic nanoparticles for the extraction of aminoglycosides in meat samples.

Poly(N-acryloyl-glucosamine-co-methylenebisacrylamide) (poly(AGA-co-MBA))-modified Fe3O4 nanoparticles were prepared via simple aqueous surface polymerization. The resultant Fe3O4@poly(AGA-co-MBA) nanoparticles were used as hydrophilic magnetic solid phase extraction sorbents. Ten aminoglycosides were selected as model analytes to evaluate the extraction performance and mechanism of the sorbents. The prepared magnetic nanoparticles were characterized by Fourier transformed infrared spectroscopy, elemental analysis, a vibrating sample magnetometer, and so on. The sorbents exhibited efficient extraction towards model analytes in hydrophilic interaction chromatography. Only 10.0 mg of sorbent was needed to adsorb analytes from 10.0 mL of a sample solution within a short time (5.0 min). Under optimized conditions, Fe3O4@poly(AGA-co-MBA) nanoparticles were applied in the sample preparation for the analysis of 10 aminoglycosides in meat samples by high-performance liquid chromatography-tandem mass spectrometry. The limits of detection (LODs) for the 10 aminoglycosides were in the range of 0.6-23.6 µg kg-1. Satisfactory recoveries of spiked meat samples from 84.6-98.3% with acceptable relative standard deviations from 3.1% to 7.8% were achieved. Compared to other reported methods for the analysis of aminoglycosides, the present work had comparable or higher sensitivities with a simple extraction procedure. The proposed hydrophilic interaction extraction sorbents are promising as powerful alternatives for extracting and enriching aminoglycosides in animal-derived food samples.

Synthesis of dummy-template molecularly imprinted polymer adsorbents for solid phase extraction of aminoglycosides antibiotics from environmental water samples.

A novel dummy molecularly imprinted polymers (DMIPs) for aminoglycoside antibiotics (AAs) was prepared for the first time by precipitation polymerization using raffinose as template molecule, methacrylic acid as functional monomer and trimethylolpropane triacrylate as cross-linker. The obtained DMIPs were characterized in detail, and their adsorbing and recognition performance were evaluated. The results showed that the DMIPs exhibited specific recognition towards six AAs with large adsorption capacity. The dummy molecularly imprinted solid phase extraction (DMISPE) conditions including elution/washing solutions and sample loading volumes were optimized. Under optimum conditions, a convenient and efficient method for the determination of AAs in environmental water samples based on DMISPE coupling with hydrophilic interaction-high performance liquid chromatography-tandem mass spectrometry was established. The developed method showed good linearity with correlation coefficients higher than 0.9921 for all the analytes and good recoveries (70.8-108.3%) with relative standard deviations from 2.6 to 11.4% spiked at three different concentration levels in water samples. The limit of detection (S/N = 3) ranged from 0.006 to 0.6 ng/mL. The results demonstrated good potential of DMIPs for sample pretreatment of trace AAs in environmental water samples.

Simultaneous Determination of Aminoglycoside Residues in Livestock and Fishery Products by Phenylboronic Acid Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry.

A rapid and simple method has been developed for simultaneous determinations of the concentrations of nine aminoglycosides (AGs) in livestock and fishery products using phenylboronic acid (PBA) solid-phase extraction (SPE) clean-up. Unlike the widely employed SPE approaches, based on cation-exchange, PBA SPE relies on the reversible formation of covalent bonds with the analytes. The advantage of using PBA lies in the fact that this compound strongly and stably retains analytes, and the pH of the loading solution can be easily adjusted using a high-concentration buffer. The clean-up conditions, such as the pH of the loading solution and the acetonitrile concentration in the elution and wash solvents, were optimized. The degree of recovery measured for nine AGs in six samples (bovine muscle, bovine liver, milk, chicken egg, fish and shrimp) were in the 73 - 98% range, and the values for the relative standard deviation were 9.3% or less.

Seven chromanoid norbisabolane derivatives from the marine-alga-endophytic fungus Trichoderma asperellum A-YMD-9-2.

An examination of the endophytic fungus Trichoderma asperellum A-YMD-9-2 obtained from the marine red alga Gracilaria verrucosa led to the isolation of seven new chromanoid norbisabolane derivatives, trichobisabolins I-L (1-4) and trichaspsides C-E (5-7). Their structures and relative configurations were established on the basis of spectroscopic techniques, mainly including 1D/2D NMR and MS, and the absolute configuration of 1 was assigned by X-ray crystallographic analysis using Cu Kα radiation. All of these isolates feature a 1,9-epoxy ring system, and 5-7 represent the second occurrence of norbisabolane aminoglycosides. Compounds 1-7 exhibited potent inhibition of several marine phytoplankton species.

Cytotoxic anthracycline and antibacterial tirandamycin analogues from a marine-derived Streptomyces sp. SCSIO 41399.

Aranciamycin K (1) and isotirandamycin B (2) were isolated from a marine-derived Streptomyces sp. SCSIO 41399, along with the previously reported four anthracycline derivatives (3-6), and two known tirandamycin derivatives (7 and 8). Their structures including absolute configurations were determined by extensive analysis of their spectroscopic analysis and ECD calculation method. Most of the isolated compounds were tested for their cytotoxic, antibacterial, and antifungal activities. Compounds 2, 7 and 8 displayed potent bacteriostatic effects against Streptococcus agalactiae with MIC values of 11.5, 5.9 and 5.7 µM, respectively. Besides, compounds 3, 5 and 6 exhibited moderate in vitro cytotoxic activities against the K562 cell lines with IC50 values of 22.0 ± 0.20, 1.80 ± 0.01 and 12.1 ± 0.07 µM, respectively.

A polyvinyl alcohol-coated core-shell magnetic nanoparticle for the extraction of aminoglycoside antibiotics residues from honey samples.

The authors describe magnetic nanoparticles comprising of a Fe3O4 core and a polyvinyl alcohol (PVA) coating for use in dispersive solid phase extraction (DSPE) of aminoglycoside antibiotics (AAs). The sorbent was investigated by Transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), thermo-gravimetric analysis (TGA), nitrogen adsorption-desorption isotherms and so on. The extraction conditions consisting of the proportion of ACN, pH value, buffer concentration and sorbent dosage were optimized. The nanoparticles have a large surface area (73.28 m2 g-1), a high binding capacity (11.33 µmol g-1) and a fast binding time (30 s). The Fe3O4@PVA is shown to be an effective adsorbent for the enrichment of AAs (streptomycin, dihydrostreptomycin and kanamycin) in spiked honey. The limits of detection are as low as 0.993, 0.913 and 1.23 µg kg-1 for streptomycin, dihydrostreptomycin and kanamycin, respectively. The recoveries varied from 82.9% to 100.7% at the three spiking levels tested (40, 400, 4000 µg⋅kg-1). Intra-day and inter-day assay precision were < 12.1% (n = 6) and <12.8% (n = 3) at three spiking levels. These data showed that the method could be applied to the extraction of AAs in honey samples.

Hydrophilic interaction liquid chromatography of aminoglycoside antibiotics with a diol-type stationary phase.

Owing to their pronounced polarity, hydrophilic interaction liquid chromatography (HILIC) can be considered as the elective choice for the LC analysis of aminoglycoside (AG) antibiotics. In the present work, a gradient program was optimized for the first time with a diol-type stationary phase and an evaporative light scattering detector (ELSD), thus allowing the almost complete separation of the nine analysed AGs: spectinomycin, dihydrostreptomycin, streptomycin A, gentamicin C1, amikacin, kanamycin A, paromomycin, apramycin and neomycin. In the optimized analysis conditions, analyte retention was found to be governed by a multimodal mechanism encompassing electrostatic, partitioning and hydrophilic interactions. However, the gradient mode of elution complicated a deep understanding of the influence of each contribution on the retention behaviour. The developed HILIC-ELSD method was applied for the analysis of commercial tablets containing neomycin co-formulated with the polypeptide antibiotic bacitracin. The method was fully validated according to the guidelines enshrined in the International Conference on Harmonization (ICH). The use of the diol-type stationary phase was well suited for implementing a successful 2D-HPLC system. Indeed, in order to cope with the absence of chemoselectivity for the couples amikacin/kanamycin and paromomycin/apramycin, a successful 2D-HPLC method was implemented with the "heart-cut" approach and the use of either heptafluorobutyric (for the former) or perfluorooctanoic acid (for the latter) as the ion-pair reagent in the second RP-LC dimension.

Angucycline Glycosides from Mangrove-Derived Streptomycesdiastaticus subsp. SCSIO GJ056.

Nine new angucycline glycosides designated urdamycins N1⁻N9 (1⁻9), together with two known congener urdamycins A (10) and B (11), were obtained from a mangrove-derived Streptomycesdiastaticus subsp. SCSIO GJ056. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis. The absolute configurations of 6⁻9 were assigned by electronic circular dichroism calculation method. Urdamycins N6 (6) and N9 (9) represent the first naturally occurring (5R, 6R)-angucycline glycosides, which are diastereomers of urdamycins N7 (7) and N8 (8), respectively.

Evanescent wave aptasensor for continuous and online aminoglycoside antibiotics detection based on target binding facilitated fluorescence quenching.

The biosensors capable for on-site continuous and online monitoring of pollutants in environment are highly desired due to their practical importance and convenience. The group specific detection of pollutants is especially attractive due to the diversity of environmental pollutants. Here we devise an evanescent wave aptasensor based on target binding facilitated fluorescence quenching (FQ-EWA) for the online continuous and group-specific detection of aminoglycoside antibiotics (AMGAs). In FQ-EWA, a fluorophore labeled DNA aptamer selected against kanamycin was used for both the target recognition in solution and signal transduction on optical fiber of EWA. The aptamers form multiple-strand complex (M-Apt) in the absence of AMGAs. The binding between AMGA and the aptamer disrupts M-Apt and leads to the formation of AMGA -aptamer complex (AMGA-Apt). The photo-induced electron transfer between the fluorophore and AMGA partially quenches the fluorescence of AMGA-Apt. The structure-selective absorption of AMGA-Apt over M-Apt on the graphene oxide further quenches the fluorescence of AMGA-Apt. Meanwhile, the unbound aptamers in solution assemble with the unlabeled aptamers immobilized on the fiber to form M-Apt. The amount of M-Apt on the fiber is inversely proportional to the concentration of AMGAs, enabling the signal-off detection of AMGAs from 200nM to 200µM with a detection limit of 26nM. The whole detection process is carried out in an online mode without any offline operation, providing a great benefit for system automation and miniaturization. FQ-EWA also shows great surface regeneration capability and enables the continuous detection more than 60 times.

Development of multiple monolithic fiber solid-phase microextraction and liquid chromatography-tandem mass spectrometry method for the sensitive monitoring of aminoglycosides in honey and milk samples.

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples was developed using multiple monolithic fiber solid-phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly(methacrylic acid-co-ethylenedimethacrylate) monolith as the extraction medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation-exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10-0.30 and 0.23-0.59 µg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2-11%.

Evaluation of hydrophilic interaction liquid chromatography-tandem mass spectrometry and extraction with molecularly imprinted polymers for determination of aminoglycosides in milk and milk-based functional foods.

An analytical method for the determination of eleven aminoglycosides in different types of milk and milk-based functional products has been optimized and validated. A hydrophilic interaction chromatography (HILIC) column was proposed for the separation of analytes by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A commercially molecularly imprinted polymer has been used for the solid phase extraction of the analytes, in order to achieve high selectivity in the sample treatment. The proposed method was characterized for different types of milk (whole cow milk, skimmed cow milk, whole goat milk) and functional dairy products, such as follow-on milk, Omega 3-enriched milk and isoflavones-enriched milk. Matrix effect was studied in the different matrices, being lower than │15│% in all cases, showing that the proposed procedure provided very clean extracts. Limits of quantification in the range 4.2-49µgkg-1 were estimated, well below the maximum residue limits established by the European Union. Recoveries ranged from 70% to 106% with RSD lower than 13%, in compliance with the current legislation. The combination of HILIC to solve the difficulties of the separation of these very polar compounds in reverse phase with the use of MISPE for sample treatment and MS/MS detection provided a very sensitive, highly selective, robust and useful method for identification and quantification of aminoglycoside residues in different types of milk and milk-based products.

Antimicrobial Spirotetronate Metabolites from Marine-Derived Micromonospora harpali SCSIO GJ089.

Two new spirotetronate aglycones, 22-dehydroxymethyl-kijanolide (1) and 8-hydroxy-22-dehydroxymethyl-kijanolide (2), along with seven new spirotetronate glycosides, microsporanates A-F (3-8) and tetrocarcin P (9), together with three known tetrocarcins [tetrocarcins A (10), B (11), and AC6H (12)], were isolated from fermentation broths of the marine-derived Micromonospora harpali SCSIO GJ089. The structures of 1-9 were elucidated on the basis of 1D and 2D NMR and MS spectroscopic data. Compounds 3-8 feature an α,ß-unsaturated carbonyl moiety within their spirotetronate skeletons. Moreover, compounds 3-12 displayed strong to moderate antibacterial activities against Gram positive bacteria Bacillus thuringiensis BT01 and B. subtilis BS01 with MIC values ranging from 0.016 to 8.0 µg/mL.

Biosynthetic pathways of aminoglycosides and their engineering.

Despite decades long clinical usage, aminoglycosides still remain a valuable pharmaceutical source for fighting Gram-negative bacterial pathogens, and their newly identified bioactivities are also renewing interest in this old class of antibiotics. As Nature's gift, some aminoglycosides possess natural defensive structural elements that can circumvent drug resistance mechanisms. Thus, a detailed understanding of aminoglycoside biosynthesis will enable us to apply Nature's biosynthetic strategy towards expanding structural diversity in order to produce novel and more robust aminoglycoside analogs. The engineered biosynthesis of novel aminoglycosides is required not only to develop effective therapeutics against the emerging 'superbugs' but also to reinvigorate antibiotic lead discovery in readiness for the emerging post-antibiotic era.

A fluorescent glycosyl-imprinted polymer for pH and temperature regulated sensing of target glycopeptide antibiotic.

This paper demonstrates a new strategy for developing a fluorescent glycosyl-imprinted polymer for pH and temperature regulated sensing of target glycopeptide antibiotic. The technique provides amino modified Mn-doped ZnS QDs as fluorescent supports, 4-vinylphenylbronic acid as a covalent monomer, N-isopropyl acrylamide as a thermo-responsive monomer in combination with acrylamide as a non-covalent monomer, and glycosyl moiety of a glycopeptide antibiotic as a template to produce fluorescent molecularly imprinted polymer (FMIP) in aqueous solution. The FMIP can alter its functional moieties and structure with pH and temperature stimulation. This allows recognition of target molecules through control of pH and temperature. The fluorescence intensity of the FMIP was enhanced gradually as the concentration of telavancin increased, and showed selective recognition toward the target glycopeptide antibiotic preferentially among other antibiotics. Using the FMIP as a sensing material, good linear correlations were obtained over the concentration range of 3.0-300.0µg/L and with a low limit of detection of 1.0µg/L. The analysis results of telavancin in real samples were consistent with that obtained by liquid chromatography tandem mass spectrometry.

Urea-formaldehyde monolithic column for hydrophilic in-tube solid-phase microextraction of aminoglycosides.

A novel urea-formaldehyde (UF) monolithic column has been developed and exploited as a sorbent for hydrophilic in-tube solid-phase microextraction (in-tube SPME) of aminoglycosides (AGs). Because of the innate hydrophilicity, UF monolith showed high extraction efficiency towards these hydrophilic analytes. The adsorption capacities for target compounds dissolved in water/ACN (1:1, v/v) were in the range of 5.18-7.36µg/cm. Due to the lack of a chromophore, evaporative light scattering detector (ELSD) was selected as the detector for AGs, and coupled with the online in-tube SPME-HPLC system. Several factors of the online system, such as trifluoroacetic acid (TFA) and ACN percentage in the sampling solution, ionic strength in the sample solution, elution volume, sampling and elution flow rate, were optimized with respect to the extraction efficiencies. Under the optimized conditions, the limits of detection (LODs) of streptomycin, tobramycin and neomycin were discovered in the range of 3.0-5.2µg/kg. The recoveries were ranged from 82.1 to 96.7% with relative standard deviations (RSDs) of 2.3-5.1% (n=4) at spiking levels of 50, 200 and 500µg/kg, respectively. The excellent applicability of the UF monolithic column was examined by the determination of streptomycin in practical tilapia samples, which showed the potential advantages for the analysis of polar analytes in complicated samples.

Two-dimensional solid-phase extraction strategy for the selective enrichment of aminoglycosides in milk.

An orthogonal two-dimensional solid-phase extraction strategy was established for the selective enrichment of three aminoglycosides including spectinomycin, streptomycin, and dihydrostreptomycin in milk. A reversed-phase liquid chromatography material (C18 ) and a weak cation-exchange material (TGA) were integrated in a single solid-phase extraction cartridge. The feasibility of two-dimensional clean-up procedure that experienced two-step adsorption, two-step rinsing, and two-step elution was systematically investigated. Based on the orthogonality of reversed-phase and weak cation-exchange procedures, the two-dimensional solid-phase extraction strategy could minimize the interference from the hydrophobic matrix existing in traditional reversed-phase solid-phase extraction. In addition, high ionic strength in the extracts could be effectively removed before the second dimension of weak cation-exchange solid-phase extraction. Combined with liquid chromatography and tandem mass spectrometry, the optimized procedure was validated according to the European Union Commission directive 2002/657/EC. A good performance was achieved in terms of linearity, recovery, precision, decision limit, and detection capability in milk. Finally, the optimized two-dimensional clean-up procedure incorporated with liquid chromatography and tandem mass spectrometry was successfully applied to the rapid monitoring of aminoglycoside residues in milk.