An Overview of Polymeric Nanoplatforms to Deliver Veterinary Antimicrobials.

There is an urgent need to find new solutions for the global dilemma of increasing antibiotic resistance in humans and animals. Modifying the performance of existing antibiotics using the nanocarrier drug delivery system (DDS) is a good option considering economic costs, labor costs, and time investment compared to the development of new antibiotics. Numerous studies on nanomedicine carriers that can be used for humans are available in the literature, but relatively few studies have been reported specifically for veterinary pharmaceutical products. Polymer-based nano-DDS are becoming a research hotspot in the pharmaceutical industry owing to their advantages, such as stability and modifiability. This review presents current research progress on polymer-based nanodelivery systems for veterinary antimicrobial drugs, focusing on the role of polymeric materials in enhancing drug performance. The use of polymer-based nanoformulations improves treatment compliance in livestock and companion animals, thereby reducing the workload of managers. Although promising advances have been made, many obstacles remain to be addressed before nanoformulations can be used in a clinical setting. Some crucial issues currently facing this field, including toxicity, quality control, and mass production, are discussed in this review. With the continuous optimization of nanotechnology, polymer-based DDS has shown its potential in reducing antibiotic resistance to veterinary medicines.

6-benzylaminopurine causes endothelial dysfunctions to human umbilical vein endothelial cells and exacerbates atorvastatin-induced cerebral hemorrhage in zebrafish.

6-benzylaminopurine (6-BA), a multifunctional plant growth regulator, which is frequently used worldwide to improve qualities of various crops, is an important ingredient in production of "toxic bean sprouts." Although there is no direct evidence of adverse effects, its hazardous effects, as well as joint toxicity with other chemicals, have received particular attention and aroused furious debate between proponents and environmental regulators. By use of human umbilical vein endothelial cells (HUVECs), adverse effects of 6-BA to human-derived cells were first demonstrated in this study. A total of 25-50 mg 6-BA/L inhibited proliferation, migration, and formation of tubular-like structures by 50% in vitro. Results of Western blot analyses revealed that exposure to 6-BA differentially modulated the MAPK signal transduction pathway in HUVECs. Specifically, 6-BA decreased phosphorylation of MEK and ERK, but increased phosphorylation of JNK and P38. In addition, 6-BA exacerbated atorvastatin-induced cerebral hemorrhage via increasing hemorrhagic occurrence by 60% and areas by 4 times in zebrafish larvae. In summary, 6-BA elicited toxicity to the endothelial system of HUVECs and zebrafish. This was due, at least in part, to discoordination of MAPK signaling pathway, which should pose potential risks to the cerebral vascular system.

Development of magnetic molecularly imprinted polymers for selective extraction of Benzoxazolinone-type alkaloids from acanthus plants.

Benzoxazolinone-type alkaloids found in Acanthus ebracteatus and Acanthus ilicifolius Linnaeus possess various beneficial properties, such as antileishmanial, antipyretic, analgesic, antibacterial, and antioxidant effects. In this study, we employed a surface imprinting technique on nanomaterials. We utilized functionalized Fe3O4@SiO2NH2 as a scaffold, with 2-benzoxazolinone and 2H-1,4-benzoxazin-3(4H)-one serving as dual templates, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and 2,2-azodiisobutyric nitrile (AIBN) as the initiator. Prior to polymerization, we screened functional monomers using ultraviolet (UV) spectroscopy. The resulting magnetic surface molecular imprinting polymer (Fe3O4@SiO2@MIP) was thoroughly characterized using Fourier transform infrared spectrometry (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). We also conducted assessments of its adsorption isotherms, dynamics, and selective binding capabilities. Our findings indicate that the MIPs exhibited exceptional selective recognition performance. Through meticulous screening and optimization of extraction and separation conditions, we established an LC‒MS/MS method based on magnetic solid-phase extraction technology. The method exhibited a recovery range of 78.80-106.99 % (RSD, 0.46-3.31 %) for 2-benzoxazolinone, with a limit of detection (LOD) and limit of quantification (LOQ) of 2.85 and 9.00 µg L-1, respectively. For 2H-1,4-benzoxazin-3(4H)-one, the method yielded a recovery range of 84.75-103.53 % (RSD, 0.07-5.96 %), with an LOD and LOQ of 3.60 and 12.60 µg L-1, respectively, in real samples. The resulting Fe3O4@SiO2@MIP demonstrated a high capacity for class-specific adsorption.

Tn3-like structures co-harboring of blaCTX-M-65, blaTEM-1 and blaOXA-10 in the plasmids of two Escherichia coli ST1508 strains originating from dairy cattle in China.

The purpose of this study was to determine the level of horizontal transmission of the blaCTX-M-65 gene and the role of its associated mobile genetic elements (MGEs) in the bovine-derived Escherichia coli. After PCR identification, two plasmids carrying blaCTX-M-65 were successfully transferred to the recipient E. coli J53 Azr through conjugation assays and subsequently selected for Whole-Genome sequencing (WGS) analysis. The resistance profiles of these two positive strains and their transconjugants were also determined through antimicrobial susceptibility tests. Whole genome data were acquired using both the PacBio sequencing platform and the Illumina data platform. The annotated results were then submitted to the Genbank database for accession number recording. For comparison, the genetic environment of plasmids carrying the resistance gene blaCTX-M-65 was mapped using the Easyfig software. WGS analysis revealed Tn3-like composite transposons bearing blaCTX-M-65, blaTEM-1, and blaOXA-10 in the IncHI2-type plasmids of these two E. coli ST1508 strains. A phylogenetic tree was generated from all 48 assembled E. coli isolates blaCTX-M-65, blaTEM-1, and blaOXA-10 from the NCBI Pathogen Detection database with our two isolates, showing the relationships and the contribution of SNPs to the diversity between genetic samples. This study suggests that the transmissibility of blaCTX-M-65 on Tn3-like composite transposons contributes to an increased risk of its transmission in E. coli derived from dairy cattle.

Multidrug-Resistant Escherichia coli Isolate of Chinese Bovine Origin Carrying the blaCTX-M-55 Gene Located in IS26-Mediated Composite Translocatable Units.

Elevated detection rates of the blaCTX-M-55 gene in animals have been reported as a result of antibiotic misuse in clinics. To investigate the horizontal transfer mechanism of blaCTX-M-55 and its associated mobile genetic elements (MGEs), we isolated 318 nonrepetitive strains of Escherichia coli (E. coli) from bovine samples in Xinjiang and Gansu provinces, China. All E. coli strains were screened for the CTX-M-55 gene using PCR. The complete genomic data were sequenced using the PacBio triplet sequencing platform and corrected using the Illumina data platform. The genetic environment of the plasmids carrying the resistance blaCTX-M-55 gene was mapped using the software Easyfig2.2.3 for comparison. The results showed that all blaCTX-M-55-positive strains were resistant to multiple antibiotics. Five strains of Escherichia coli carry the blaCTX-M-55 gene, which is adjacent to other resistance genes and is located on the IncHI2-type plasmid. Four of the five blaCTX-M-55-harbor strains carried translocatable units (TUs). All the donor bacteria carrying the blaCTX-M-55 genes could transfer horizontally to the recipient (E. coli J53 Azr). This study demonstrates that the transmission of blaCTX-M-55 is localized on IS26-flanked composite transposons. The cotransmission and prevalence of blaCTX-M-55 with other MDR resistance genes on epidemic plasmids require enhanced monitoring and control.

Synthesis and Antifungal Activity of Derivatives of the Natural Product Griseofulvin against Phytopathogenic Fungi.

Natural products are important sources for the discovery of new pesticides. Chemical synthesis and structural modification can lead to pesticides. Despite abundant research in fungicide discovery for crop protection, there is an emerging need for the development of novel antifungal agrochemicals. Herein, 39 diversified griseofulvin derivatives were effectively synthesized from the natural product griseofulvin by diversity-oriented synthesis through the reactions of demethylation, ammonolysis, methylation, nitration, acylation, reduction, and chlorination. Among them, 31 derivatives were novel. All structures were characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometry (HR-MS), and the antifungal activity was investigated against five phytopathogenic fungi. Compounds 5h and 5l had excellent activity against Botrytis cinerea (5h, IC50 = 17.29 ± 0.64 µg/mL) and Alternaria solani (5l, IC50 = 22.52 ± 0.79 µg/mL), respectively. Compound 9 exhibited the more promising activities against three target fungi, especially against Colletotrichum gloeosporioides (IC50 = 7.24 ± 0.66 µg/mL), which is obviously better than positive control hymexazol, thifluzamide, and parent compound griseofulvin. In addition, compound 10 showed significant and extensive activities against four target fungi Cytospora sp. (IC50 = 18.72 ± 0.35 µg/mL), C. gloeosporioides (IC50 = 31.39 ± 1.48 µg/mL), A. solani (IC50 = 40.82 ± 1.04 µg/mL), and Fusarium solani (IC50 = 36.81 ± 0.82 µg/mL). Unexpectedly, 11 and 12, the chlorinated products of compound 9, exhibited the most promising activity against C. gloeosporioides (IC50 = 4.48 ± 0.54 µg/mL for 11, 2.24 ± 0.76 µg/mL for 12). Furthermore, 12 showed remarkable activity against Cytospora sp. (IC50 = 5.85 ± 0.72 µg/mL). Additionally, in vivo antifungal activity against C. gloeosporioides, homology modeling, and docking analysis of 11, 12, and griseofulvin were conducted. All results indicated that 11 and 12 had potency as antifungal agents against C. gloeosporioides, and the modifications of the 2' and 4' positions of griseofulvin should be further explored for higher-activity lead compounds or potential agricultural fungicides.

6-Benzylaminopurine causes lipid dyshomeostasis via disruption of glycerophospholipid metabolism in zebrafish.

6-Benzylaminopurine (6-BA) is ubiquitous in agricultural production and is accessible to humans through diets. The modulation of lipid metabolism by 6-BA has been previously demonstrated in plants and oleaginous microorganisms. Therefore, whether it alters lipid homeostasis in other living organisms requires further investigation. In this study, doses ≥10 mg 6-BA/L caused malformation of the yolk sac, steatosis, and other hepatopathies in zebrafish larvae. Exposure to 25 mg 6-BA/L resulted in increased levels of triglyceride and total cholesterol. Results of transcriptomic analysis indicated that 6-BA alters genes associated with fatty acid and glycerophospholipid metabolism. Among them, the expression levels of hmgcra, elovl7b, and apobb.2 were downregulated, whereas those of lpcat3, bco1l, cyp7al, fabp1b.1, elp6, pde6ha, apoa4b.2_2, sgk1, dgkaa, and mogat2 were upregulated. Correspondingly, a study of the metabolome identified lysophosphatidylcholine (LPC) as the major differentially expressed metabolite in response to 6-BA treatment. Therefore, abnormal accumulation of LPCs and dyshomeostasis of glycerophospholipid metabolism were identified as potential mechanisms causing the toxicity of 6-BA, which should be assessed to understand the risks of 6-BA and the products contaminated by it. ENVIRONMENTAL IMPLICATION: 6-Benzylaminopurine (6-BA), an important residue in "toxic bean sprouts," is ubiquitous in agricultural production and is common in typical diets. Its regulation of lipid metabolism has been demonstrated in plants and oleaginous microorganisms. Whether it alters lipid homeostasis in other organisms and the underlying mechanisms remain largely unknown. The worldwide use of 6-BA and the potential exposure of humans have aroused public attention owing to its hazardous effects; thus, its hazardous effects, particularly those on lipid homeostasis, deserve careful clarification.

Virtual Screening and In Vitro Experimental Verification of LuxS Inhibitors for Escherichia coli O157:H7.

Enterohemorrhagic Escherichia coli O157:H7 is an important foodborne pathogen that forms biofilms. In this study, three quorum-sensing (QS) inhibitors (M414-3326, 3254-3286, and L413-0180) were obtained through virtual screening, and their in vitro antibiofilm activities were validated. Briefly, the three-dimensional structure model of LuxS was constructed and characterized using the SWISS-MODEL. High-affinity inhibitors were screened from the ChemDiv database (1,535,478 compounds) using LuxS as a ligand. Five compounds (L449-1159, L368-0079, M414-3326, 3254-3286, and L413-0180) with a good inhibitory effect (50% inhibitory concentration <10 µM) on type II QS signal molecule autoinducer-2 (AI-2) were obtained using a AI-2 bioluminescence assay. The absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties predicated that the five compounds had high intestinal absorption levels (high) and plasma protein binding (absorbent strong) and did not inhibit the metabolism of CYP2D6 metabolic enzymes. In addition, molecular dynamics simulation showed that compounds L449-1159 and L368-0079 could not stably bind with LuxS. Thus, these compounds were excluded. Furthermore, surface plasmon resonance results showed that the three compounds could specifically bind to LuxS. IN addition, the three compounds could effectively inhibit the biofilm formation without affecting the growth and metabolism of the bacteria. Finally, the reverse transcription-quantitative PCR results showed that the three compounds downregulated the expression of the LuxS gene. Overall, these results revealed that the three compounds obtained through virtual screening could inhibit biofilm formation of E. coli O157:H7 and are potential LuxS inhibitors that can be used to treat E. coli O157:H7 infections. IMPORTANCE E. coli O157:H7 is a foodborne pathogen of public health importance. Quorum sensing (QS) is a form of bacterial communication that can regulate various group behaviors, including biofilm formation. Here, we identified three QS AI-2 inhibitors (M414-3326, 3254-3286, and L413-0180) that can stably and specifically bind to LuxS protein. The three QS AI-2 inhibitors inhibited biofilm formation without affecting the growth and metabolic activity of E. coli O157:H7. The three QS AI-2 inhibitors are promising agents for treating E. coli O157:H7 infections. Further studies to identify the mechanism of the three QS AI-2 inhibitors are needed to develop new drugs to overcome antibiotic resistance.

Recent Progress of Electrospun Herbal Medicine Nanofibers.

Herbal medicine has a long history of medical efficacy with low toxicity, side effects and good biocompatibility. However, the bioavailability of the extract of raw herbs and bioactive compounds is poor because of their low water solubility. In order to overcome the solubility issues, electrospinning technology can offer a delivery alternative to resolve them. The electrospun fibers have the advantages of high specific surface area, high porosity, excellent mechanical strength and flexible structures. At the same time, various natural and synthetic polymer-bound fibers can mimic extracellular matrix applications in different medical fields. In this paper, the development of electrospinning technology and polymers used for incorporating herbal medicine into electrospun nanofibers are reviewed. Finally, the recent progress of the applications of these herbal medicine nanofibers in biomedical (drug delivery, wound dressing, tissue engineering) and food fields along with their future prospects is discussed.

Mechanism of Synergy between Piceatannol and Ciprofloxacin against Staphylococcus aureus.

Piceatannol (PIC) is a natural stilbene extracted from grape skins that exhibits biological activities such as antibacterial, antitumor, and antioxidant activities. The present study was carried out to further investigate the effect of PIC on the antibacterial activity of different antibiotics and to reveal the antibacterial mechanism of PIC. We found that PIC had an inhibitory effect against Staphylococcus aureus (S. aureus); its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 128 µg/mL and 256 µg/ mL, respectively. Additionally, we measured the fractional inhibitory concentration (FIC) of PIC combined with antibiotics via the checkerboard method. The results showed that when PIC and ciprofloxacin (CIP) were combined, they displayed a synergistic effect against S. aureus. Moreover, this synergistic effect was verified by time-kill assays. Further, the results of the membrane permeability assay and proton motive force assay revealed that PIC could enhance the sensitivity of S. aureus to CIP by dissipating the bacterial proton motive force (PMF), particularly the ∆ψ component, rather than increasing membrane permeability. PIC also inhibited bacterial adenosine triphosphate (ATP) synthesis and was less likely to induce bacterial resistance but exhibited slight hemolytic activity on mammalian erythrocytes. In summary, the combination of PIC and CIP is expected to become a new drug combination to combat S. aureus.

Novel quorum sensing inhibitor Echinatin as an antibacterial synergist against Escherichia coli.

A new antibacterial strategy based on inhibiting bacterial quorum sensing (QS) has emerged as a promising method of attenuating bacterial pathogenicity and preventing bacterial resistance to antibiotics. In this study, we screened Echinatin (Ech) with high-efficiency anti-QS from 13 flavonoids through the AI-2 bioluminescence assay. Additionally, crystal violet (CV) staining combined with confocal laser scanning microscopy (CLSM) was used to evaluate the effect of anti-biofilm against Escherichia coli (E. coli). Further, the antibacterial synergistic effect of Ech and marketed antibiotics were measured by broth dilution and Alamar Blue Assay. It was found that Ech interfered with the phenotype of QS, including biofilm formation, exopolysaccharide (EPS) production, and motility, without affecting bacterial growth and metabolic activity. Moreover, qRT-PCR exhibited that Ech significantly reduced the expression of QS-regulated genes (luxS, pfs, lsrB, lsrK, lsrR, flhC, flhD, fliC, csgD, and stx2). More important, Ech with currently marketed colistin antibiotics (including colistin B and colistin E) showed significantly synergistically increased antibacterial activity in overcoming antibiotic resistance of E. coli. In summary, these results suggested the potent anti-QS and novel antibacterial synergist candidate of Ech for treating E. coli infections.

Processes of Electrospun Polyvinylidene Fluoride-Based Nanofibers, Their Piezoelectric Properties, and Several Fantastic Applications.

Since the third scientific and technological revolution, electronic information technology has developed rapidly, and piezoelectric materials that can convert mechanical energy into electrical energy have become a research hotspot. Among them, piezoelectric polymers are widely used in various fields such as water treatment, biomedicine, and flexible sensors due to their good flexibility and weak toxicity. However, compared with ceramic piezoelectric materials, the piezoelectric properties of polymers are poor, so it is very important to improve the piezoelectric properties of polymers. Electrospinning technology can improve the piezoelectric properties of piezoelectric polymers by adjusting electrospinning parameters to control the piezoelectrically active phase transition of polymers. In addition, the prepared nanofibrous membrane is also a good substrate for supporting piezoelectric functional particles, which can also effectively improve the piezoelectric properties of polymers by doping particles. This paper reviews the piezoelectric properties of various electrospun piezoelectric polymer membranes, especially polyvinylidene fluoride (PVDF)-based electrospun nanofibrous membranes (NFs). Additionally, this paper introduces the various methods for increasing piezoelectric properties from the perspective of structure and species. Finally, the applications of NFs in the fields of biology, energy, and photocatalysis are discussed, and the future research directions and development are prospected.

[Thermal proteome profiling: a technique for a comprehensive assessment of protein status].

Thermal proteome profiling (TPP) is a combination of cellular thermal shift assay (CETSA) and quantitative mass spectrometry (MS), also termed as MS-CETSA. TPP determines the stability of the entire proteome by measuring the content of soluble proteins in cells or cell lysates at different heating temperatures. Proteins can change their thermostability when interacting with small molecules (e.g., drugs or metabolites), nucleic acids, or other proteins or posttranslational modification, while TPP can identify target proteins based on the difference in thermostability with or without ligand-binding. At present, TPP has been applied to identify the targets and off-targets of drugs and interrogate protein-metabolite and protein-protein interactions. Due to limited understanding of this technology, this review introduced the principles, methods, applications, advantages and limitations of TPP.

Novel Antibiofilm Inhibitor Ginkgetin as an Antibacterial Synergist against Escherichia coli.

As an opportunistic pathogen, Escherichia coli (E. coli) forms biofilm that increases the virulence of bacteria and antibiotic resistance, posing a serious threat to human and animal health. Recently, ginkgetin (Gin) has been discovered to have antiinflammatory, antioxidant, and antitumor properties. In the present study, we evaluated the antibiofilm and antibacterial synergist of Gin against E. coli. Additionally, Alamar Blue assay combined with confocal laser scanning microscope (CLSM) and crystal violet (CV) staining was used to evaluate the effect of antibiofilm and antibacterial synergist against E. coli. Results showed that Gin reduces biofilm formation, exopolysaccharide (EPS) production, and motility against E. coli without limiting its growth and metabolic activity. Furthermore, we identified the inhibitory effect of Gin on AI-2 signaling molecule production, which showed apparent anti-quorum sensing (QS) properties. The qRT-PCR also indicated that Gin reduced the transcription of curli-related genes (csgA, csgD), flagella-formation genes (flhC, flhD, fliC, fliM), and QS-related genes (luxS, lsrB, lsrK, lsrR). Moreover, Gin showed obvious antibacterial synergism to overcome antibiotic resistance in E. coli with marketed antibiotics, including gentamicin, colistin B, and colistin E. These results suggested the potent antibiofilm and novel antibacterial synergist effect of Gin for treating E. coli infections.

Licarin-B Exhibits Activity Against the Toxoplasma gondii RH Strain by Damaging Mitochondria and Activating Autophagy.

Toxoplasma gondii is an obligate intracellular pathogen that infects warm-blooded animals and humans. However, side effects limit toxoplasmosis treatment, and new drugs with high efficiency and low toxicity need to be developed. Natural products found in plants have become a useful source of drugs for toxoplasmosis. In this study, twenty natural compounds were screened for anti-T. gondii activity by Giemsa staining or real-time fluorescence quantitative polymerase chain reaction (qPCR) in vitro. Among these, licarin-B from nutmeg exhibited excellent anti-T. gondii activity, inhibiting T. gondii invasion and proliferation in a dose-dependent manner, with an EC50 of 14.05 ± 3.96 µg/mL. In the in vivo, licarin-B treatment significantly reduced the parasite burden in tissues compared to no treatment, protected the 90% infected mice from to death at 50 mg/kg.bw. Flow cytometry analysis suggested a significant reduction in T. gondii survival after licarin-B treatment. Ultrastructural changes in T. gondii were observed by transmission electron microscopy (TEM), as licarin-B induced mitochondrial swelling and formation of cytoplasmic vacuoles, an autophagosome-like double-membrane structure and extensive clefts around the T. gondii nucleus. Furthermore, MitoTracker Red CMXRos, MDC, and DAPI staining showed that licarin-B promoted mitochondrial damage, autophagosome formation, and nuclear disintegration, which were consistent with the TEM observations. Together, these findings indicate that licarin-B is a promising anti-T. gondii agent that potentially functions by damaging mitochondria and activating autophagy, leading to T. gondii death.

Distribution and elimination of quinocetone and its major metabolites in Cherry Valley ducks.

We examined the tissue distribution and elimination of quinocetone (QCT) and its major metabolites 1-desoxyquinocetone (1-DQCT), di-desoxyquinocetone (BDQCT), and 3-methyl-quinoxaline-2-carboxylic (MQCA) in ducks. The analytes were simultaneously quantitated using a UPLC-MS/MS method after oral administration of QCT at 100 mg·kg-1 day-1 for 7 days. We found that QCT and its major metabolites were widely distributed in duck tissues. The concentrations indicated that the primary compound in the liver, kidney, and heart was MQCA and the primary compound in the stomach, intestine, spleen, and lung was QCT. We also identified that MQCA was the most appropriate compound for QCT residue monitoring. The liver and kidney are the primary QCT target organs in ducks, and this study provides clear monitoring tools and important data to evaluate its safety.

Determination and pharmacokinetics study of oxyclozanide suspension in cattle by LC-MS/MS.

BACKGROUND: Oxyclozanide is an anthelmintic drug that is widely used to treat fasciolosis. However, the pharmacokinetics of oxyclozanide in cattle are not yet clearly understood. The present study was designed to develop a sensitive method to determine oxyclozanide levels in cattle plasma using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and to study its pharmacokinetics for application in cattle. RESULTS: A simple and rapid HPLC-MS/MS analytical method was established and validated to quantify oxyclozanide levels in cattle plasma using niclosamide as the internal standard (IS) in negative ion mode. Chromatographic separation of the analytes was achieved using a C18 analytical column (75 × 4.6 mm, 2.7 µm) at 30 °C. The mobile phase comprised 0.01% v/v acetic acid (HOAc) diluted in water:acetonitrile (MeCN) (90:10% v/v) and 5 mM ammonium formate in methanol (MeOH):MeCN (75:25, v/v) at a 10:90 ratio (v/v) and was delivered at a flow rate of 0.4 mL min- 1. A good linear response across the concentration range of 0.02048-25.600 µg/mL was achieved (r2 = 0.994). The method was validated with respect to linearity, matrix effect, accuracy, precision, recovery and stability. The lower limit of quantification (LLOQ) was 0.020 µg/mL, and the extraction recovery was > 98% for oxyclozanide. The inter- and intra-day accuracy and precision of the method showed the relative standard deviation (RSD) less than 10%. The method was successfully applied to an assessment of the pharmacokinetics of oxyclozanide in cattle plasma. In healthy cattle, a single oral dose of an oxyclozanide suspension followed the one-compartment model, with a half-life (T1/2) of 64.40 ± 30.18 h, a plasma clearance rate (CL/F) of 11.426 ± 2.442 mL/h/kg, and an average area under the curve (AUC) of 965.608 ± 220.097 h*µg/mL. The peak concentration (Cmax) was 15.870 ± 2.855 µg/mL, which occurred at a peak time (Tmax) = 22.032 ± 3.343 h. CONCLUSIONS: A reliable, accurate HPLC-MS/MS analytical method was established in our study and successful applied to study the pharmacokinetics of oxyclozanide in cattle plasma. These results will be useful for further evaluations of the pharmacokinetic properties of oxyclozanide or for monitoring therapeutic drugs in animals.

Antifungal Activity of Griseofulvin Derivatives against Phytopathogenic Fungi in Vitro and in Vivo and Three-Dimensional Quantitative Structure-Activity Relationship Analysis.

With environmental pollution, residual hazards accumulate and severe drug resistance and many other problems appear; some highly toxic drugs have been banned, and antifungal agents are far from satisfactory. Natural products play an important role in the discovery and development of new pesticides. The natural product griseofulvin (1) has been known as an antifungal agent in the treatment of dermatomycoses for decades. In this study, a series of new griseofulvin derivatives were synthesized with good yields. Their structures were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry (electrospray ionization). The antifungal activities of griseofulvin analogues were first evaluated against five phytopathogenic fungi ( Cytospora sp., Colletotrichum gloeosporioides, Botrytis cinerea, Alternaria solani, and Fusarium solani) in vitro. Of significance is that most of them showed excellent antifungal activities against C. gloeosporioides. The antifungal activities of the four best compounds (6a, 6c, 6e, and 6f) against C. gloeosporioides were further investigated in vivo using infected apples. The results suggested that compounds 6c, 6e, and 6f [half-maximal inhibitory concentration (IC50) = 47.25 ± 1.46, 49.44 ± 1.50, and 53.63 ± 1.74 µg/mL, respectively] were better than thiophanate-methyl (IC50 = 69.66 ± 6.07 µg/mL). Furthermore, comparative molecular field analysis was performed on the basis of the antifungal activity results of all 22 of the compounds against C. gloeosporioides in vitro. The three-dimensional coefficient contour plots revealed that the suitable bulky and electronegative acyl-substituted groups seem to be more favorable for increasing activity at the 4' position of griseofulvin. The structure-activity relationships were also discussed. Griseofulvin derivatives can be used for the development of highly effective and safe agricultural fungicides.

Target animal safety testing of an oral salicylanilide suspension, oxyclozanide, for the treatment of fascioliasis in bovine in China.

The aim of this study was to determine the potential toxicity risk of an oxyclozanide suspension to the target animal, bovine. In this experiment, 32 Simmental beef cattle were fattened and fed a full-price diet without antimicrobial agents. The test cattle were divided into 4 groups, which were treated with 0, 1, 3, and 5 times the recommended dosage through continuous intermittent oral administration at intervals of 2 days. The body weight of the cattle was recorded before and after the experiment, and the weight changes were calculated. The safety of the drugs was evaluated by weight gain, observation of clinical toxicity, haematology, clinical chemistry and histopathology. The results showed that the cattle had different degrees of diarrhoea, loss of appetite and depression after administration. The results of clinicopathology had no significant effect. The results of pathological examination showed that there was a certain degree of damage in the 5 times recommended dose group. The recommended dose was safe to use. Thus, the recommended dose should be given by a single oral administration to ensure the safe use of this drug in the clinic.

Au-Catalyzed Intermolecular [2+2] Cycloadditions between Chloroalkynes and Unactivated Alkenes.

The [2+2] cycloaddition is a versatile strategy for the synthesis of strained cyclobutenes of high synthetic value. In this study, two efficient intermolecular [2+2] cycloadditions between two different types of chloroalkynes and unactivated alkene are realized with gold catalysis. Of significance is that the reaction works with challenging monosubstituted unactivated alkenes, which is unprecedented in gold catalysis and scarcely documented in other metal-catalyzed/promoted reactions; moreover, the reaction exhibits excellent regioselectivities, which are much better than those reported in literature. With 1,2-disubstituted unactivated alkenes, the reaction is largely stereospecific. The cyclobutene products can be prepared in nearly gram scale and readily undergo further reactions including various cross-coupling reactions using the C(sp2)-Cl and/or C(sp2)-SPh bond, which in turn substantially broaden the scope of accessible cyclobutenes and enhance the synthetic utility of this bimolecular reaction.