Key words antibacterial activity; fluorinated benzoxazole; metal complex; trifluoroacetylBacterial infection remains a serious threat to human lives due to rapid development of resistance to the existing antibiotics. In order to prevent this major medical problem, the discovery of new types of antimicrobial agents is a very important but challenging task.1,2) Transition metal complexes have received great attention because many drugs such as antibiotics and quinolone antibiotics possess better pharmaceutical properties when they are in the form of metal complexes. 3-7)Benzoxazole heterocycle system is an important pharmacophore and privileged structure in the medicinal chemistry. 8-10)Its derivatives and particularly, 2-substituted benzoxazoles exert various biological activities such as antimicrobial, antiviral, antifungal, and anticancer. [11][12][13][14][15] In previous studies, we have identified 2-trifluoroacetonylbenzoxazole (1a) with in vitro antimicrobial activity against Helicobacter pylori and Escherichia coli (Ec) from our compound library of trifluoromethyl ketones obtained by our developed reactions. 16,17) The heteroaryl-substituted alkenol systems such as 1a are known to chelate some metal ions such as aluminum 18) and to form a stable six-membered metal complexes in a bidentate mode, where the complexes were reinforced by a positive inductive effect of the heterocyclic moiety and a negative inductive effect of the CF 3 groups. [19][20][21][22][23] In the light of these knowledge, three 2-fluoroacetonylbenzoxazole ligands 1a-c and their new Zn(II) complexes 2a-c have been synthesized in order to check how the metal ion binding may influence their antibacterial activity (Chart 1). In addition, syntheses of new metal [Mg(II), Ni(II), Cu(II), Pd(II), and Ag(I)] complexes 2d-h from 1a have been also described ( Table 1). The structures of six metal complexes 2b and 2d-h were determined by single-crystal X-ray diffraction analyses. In vitro antimicrobial activities of the ligands 1a-c and their metal complexes 2a-h were investigated against six Gram-positive (G(+)) and six Gram-negative (G(−)) bacteria and the results were compared with those of silver nitrate and appropriate antibiotics such as Kanamycin, Gentamicin, Norfloxacin, and/or Linezolid. The most potent Ag(I) complex 2h is bacteriostatic, disrupts membrane integrity observed by scanning electron microscopy (SEM) and is less likely to develop resistance development against Pseudomonas aeruginosa (Pa). Results and DiscussionChemistry First, three benzoxazole ligands 1a-c and their new Zn(II) complexes 2a-c have been prepared in order to investigate the relationship of the ligands and their Zn(II) complexes with their antibacterial activities.Our synthetic protocol to obtain the ligand 1a consists of a trifluoroacetylation of 2-methylbenzoxazole with trifluoroacetic anhydride (TFAA) in the presence of pyridine 24) (Chart 1). The Zn(II) complex 2a was prepared by the reaction of 1a with zinc dust in MeCN in 78% yield, consisting of 1a with zinc(...
Use of intercostal transthoracic trocars is safe and effective not only for complicated laparoscopic hepatectomy but also for hemispherical wedge resections of subcapsular hepatic tumors located in segment VII or VIII.
Background/Aim: Multidrug resistance (MDR) represents a significant impediment to successful cancer treatment. In this study, novel metal [Zn(II), Cu(II), Mg(II), Ni(II), Pd(II), and Ag(I)] complexes of 2-trifluoroacetonylbenzoxazole previously synthesized and characterized by our group were tested for their MDR-reversing activity in comparison with the free ligands in L5178Y mouse Tlymphoma (MDR) cells transfected with human ATP-binding cassette sub-family B member 1 (ABCB1; P-glycoprotein) gene. Materials and Methods: Cytotoxic and antiproliferative effects of the complexes were assessed by the thiazolyl blue tetrazolium bromide (MTT) method. Modulation of ABCB1 activity was measured by rhodamine 123 accumulation assay using flow cytometry. The apoptosis-inducing activity of some complexes was also tested on the multidrug resistant L5178Y mouse T-lymphoma cells, using the annexin-V/propidium iodide assay. Results: When compared to the free ligand, a remarkable enhancement in MDR reversal and cytotoxic activity was found for the Zn(II) and Cu(II) complexes. The activity of the complexes proved to be up to 29-and 5-fold higher than that of the ligands and the ABCB1 inhibitor verapamil as positive control, respectively. The complexes possessed a remarkable potential to induce apoptosis of MDR cells. Conclusion: Our results suggest that the Zn(II) and Cu(II) complexes display significant MDRreversing activity in a dose-dependent manner and possess strong cytotoxic activity and a remarkable potential to induce apoptosis in MDR L5178Y mouse T-lymphoma cells.
Background: Most pancreatic cancers are found at progressive stages when they cannot be surgically removed. Therefore, a highly accurate early detection method is urgently needed. Methods: This study analyzed serum from Japanese patients who suffered from pancreatic ductal adenocarcinoma (PDAC) and aimed to establish a PDAC-diagnostic system with metabolites in serum. Two groups of metabolites, primary metabolites (PM) and phospholipids (PL), were analyzed using liquid chromatography/electrospray ionization mass spectrometry. A support vector machine was employed to establish a machine learning-based diagnostic algorithm. Results: Integrating PM and PL databases improved cancer diagnostic accuracy and the area under the receiver operating characteristic curve. It was more effective than the algorithm based on either PM or PL database, or single metabolites as a biomarker. Subsequently, 36 statistically significant metabolites were fed into the algorithm as a collective biomarker, which improved results by accomplishing 97.4% and was further validated by additional serum. Interestingly, specific clusters of metabolites from patients with preoperative neoadjuvant chemotherapy (NAC) showed different patterns from those without NAC and were somewhat comparable to those of the control. Conclusion: We propose an efficient screening system for PDAC with high accuracy by liquid biopsy and potential biomarkers useful for assessing NAC performance.
Bacteria often show resistance against antibiotics due to various mechanisms such as the expression of efflux pumps, biofilm formation, or bacterial quorum sensing (QS) controls. For successful therapy, the discovery of alternative agents is crucial. The objective of this study was to evaluate the efflux pump, anti-biofilm, and QS inhibiting, as well as antibacterial effects of 2-trifluoroacetonylbenzoxazole ligands (1–3) and their metal complexes (4–12) in bacteria. The ligand 2 and its Zn(II) complex 5, and furthermore the Cu(II) complex 7 of ligand 1, exerted remarkable antibacterial activity on the Staphylococcus aureus 272123 (MRSA) strain. In the minimum inhibitory concentration (MIC) reduction assay the ligand 3, the Zn(II) complex 5 of ligand 2, and the Cu(II), Ni(II), Mg(II), Fe(III) complexes (7, 8, 9, 12) of ligand 1 enhanced the antibacterial activity of ciprofloxacin in MRSA. An increased ethidium bromide accumulation was detected for ligand 3 in MRSA while the Fe(III) complex 12 of ligand 1 decreased the biofilm formation of the reference S. aureus ATCC 25923 strain. The Zn(II) and Ag(II) complexes (3 and 4) of ligand 1 and ligand 3 inhibited the QS. Based on our results, the ligands and their metal complexes could be potential alternative drugs in the treatment of infectious diseases.
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