Sparfloxacin–metal complexes as antifungal agents – Their synthesis, characterization and antimicrobial activities

Gemifloxacin-transition metal complexes as therapeutic candidates: antimicrobial, antifungal, anti-enzymatic, and docking studies of newly synthesized complexes

In the era of acquired microbial resistance (AMR), resulting in the ineffectiveness of antibiotics is of keen interest for researchers in current scenarios. Ten novel metal complexes of gemifloxacin have been synthesized by reacting it with essential and trace elements in a 2:1 ratio predetermined conducto-metrically. As these metals are either present in the body or co-administered as metallic supplements can alter the level of antibiotics. Therefore, Metal complexes of Gemifloxacin, an important member of the fluoroquinolone family, were synthesized. The possible coordination of gemifloxacin with these metals has been proposed by the electronic and elemental data obtained through molar conductance, elemental analysis, and spectroscopic techniques like ultraviolet-visible (UV-Vis), infrared (IR), and proton-nuclear magnetic resonance (1H NMR) studies. In the light of these studies, the monoanionic bidentate ligand behavior of gemifloxacin in complexation with metals has been revealed. For in-vitro microbial studies, these newly synthesized complexes were tested against eleven different bacteria including Gram + ve and Gram -ve organisms, and one fungal strain. The results were compared with the parent drug by applying ANOVA through SPSS software version 22. Therefore, it has been found that among all synthesized metal complexes, the G-M01 complex exhibits increased activity against B. subtilis, P. mirabilis, E. coli, K. pneumonia, and C. freundii. Complex G-M02, G-M03, G-M04, and G-M10 show more pronounced activity than Gemifloxacin against S. aureus and M. luteus. Moreover, the binding orientations of the synthesized metal complexes into the binding site of the urease enzyme revealed that all the docked metal complexes oriented away from the Ni bi-center, and the inactivation of urease is due to their interaction with entrance flap residues.

Spectral, thermal, antimicrobial studies for silver(I) complexes of pyrazolone derivatives

Background

Synthesize new complexes of Ag(I) to enhance efficacy or stability and also, pharmacological activities on the operation of pyrazolone's biological properties.

Results

Efficient and high yielding pathways starting from the versatile and readily available 3-methyl-1-phenyl-5-pyrazolone by Knoevenagel condensation of a sequence of 4-arylidene-3-methyl-1-phenyl-5-pyrazolone derivatives (2a-c) have been formed by the reaction of various substituted aromatic aldehydes Used as ligands to synthesize Ag(I) chelates. Synthesized compounds and their complexes have been characterized by elemental analysis, magnetic and spectroscopic methods (IR, ¹³C, ¹HNMR, mass) and thermal analysis. The spectrophotometric determinations suggest distorted octaedral geometry for all complexes. Both ligands and their metal complexes have also been tested for their antibacterial and antifungal efficacy.

Conclusions

Newly synthesized compounds have shown potent antimicrobial activity. The results showed that the complex 's high activity was higher than its free ligands, and that Ag(I)-L₃ had the highest activity.

A new calcium(II) complex of marbofloxacin showing much lower acute toxicity with retained antibacterial activity

Marbofloxacin (MB) is a newly developed veterinary drug with broad-spectrum antibacterial activity. In this study, a new calcium(II)-based complex of marbofloxacin, MB-Ca, was synthesized and structurally characterized by IR, ESI-MS, UV-Vis and single crystal X-ray diffraction analysis. The characterization of this complex in solution state indicated that the coordinated MB-Ca was partly retained, along with the monomeric and dimeric forms of MB. It also showed satisfactory water solubility (1.89 mg/mL), comparing with MB (2.82 mg/mL) at 35 °C. The in vitro antibacterial activity of MB-Ca was also screened towards a series of typical pathogenic bacteria, and determined by the methods of turbidimetry and disc diffusion. The results indicated it showed comparable antibacterial activity to MB. However, it exhibited higher inhibitive ability in vitro on DNA gyrase than MB alone. Furthermore, MB-Ca showed significantly lower acute toxicity (LD₅₀, 3186 mg/kg) than MB (LD₅₀, 1294 mg/kg) in mice, based on the in vivo acute toxicity test. The histopathological examination on the major organs of the mice by the oral administration of MB-Ca did not show obvious organic lesions, which is similar to those treated by MB. The research results suggest that MB-Ca could be further developed into a new promising metal-based veterinary drug and a better substitute of MB, showing unabated antibacterial activity along with lower toxicity.

Quinolone derivatives and their antifungal activities: An overview

More than 300 million people suffer from the incidence of life-threatening invasive fungal infections, resulting in over 1.35 million deaths annually. Currently, the antifungal agents available in clinics are rather limited, and the rapid development of resistance to the existing antifungal drugs has further aggravated mortality. Quinolones possess a broad spectrum of chemotherapeutic properties and demonstrate considerable antifungal activities as well. Various quinolone derivatives have been screened for their antifungal activities, and some of them exhibit excellent potency against both drug-susceptible and drug-resistant fungi. This review aims to outline the recent advances in quinolone derivatives as potential antifungal agents and summarize the structure-activity relationship, to provide insights for the rational design of more active candidates.

Gallium(iii) and iron(iii) complexes of quinolone antimicrobials

Iron is an essential nutrient for many microbes. According to the "Trojan Horse Hypothesis", biological systems have difficulties distinguishing between Fe(3+) and Ga(3+), which constitutes the antimicrobial efficacy of the gallium(iii) ion. Nine novel tris(quinolono)gallium(iii) complexes and their corresponding iron(iii) analogs have been synthesized and fully characterized. Quinolone antimicrobial agents from three drug generations were used in this study: ciprofloxacin, enoxacin, fleroxacin, levofloxacin, lomefloxacin, nalidixic acid, norfloxacin, oxolinic acid, and pipemidic acid. The antimicrobial efficacy of the tris(quinolono)gallium(iii) complexes was studied against E. faecalis and S. aureus (both Gram-positive), as well as E. coli, K. pneumonia, and P. aeruginosa (all Gram-negative) in direct comparison to the tris(quinolono)iron(iii) complexes and the corresponding free quinolone ligands at various concentrations. For the tris(quinolono)gallium(iii) complexes, no combinational antimicrobial effects between Ga(3+) and the quinolone antimicrobial agents were observed.

Highly sensitive “turn-on” fluorescence probe for the detection of sparfloxacin in human serum using silica-functionalized CdTe quantum dots

The hydrophilic carboxyl-capped CdTe@SiO₂ quantum dots (SQDs) can served as a “turn-on” photoluminescence (PL) probe for highly sensitive and selective detection of sparfloxacin in human serum.

Interaction of vanadium (IV) solvates (L) with second-generation fluoroquinolone antibacterial drug ciprofloxacin: spectroscopic, structure, thermal analyses, kinetics and biological evaluation (L=An, DMF, Py and Et3N)

The preparation and characterization of the new solid complexes [VO(CIP)2L]SO4⋅nH2O, where L=aniline (An), dimethylformamide (DMF), pyridine (Py) and triethylamine (Et3N) in the reaction of ciprofloxacin (CIP) with VO(SO4)2·2H2O in ethanol. The isolated complexes have been characterized with their melting points, elemental analysis, IR spectroscopy, magnetic properties, conductance measurements, UV-Vis. and (1)H NMR spectroscopic methods and thermal analyses. The results supported the formation of the complexes and indicated that ciprofloxacin reacts as a bidentate ligand bound to the vanadium ion through the pyridone oxygen and one carboxylato oxygen. The activation energies, E(*); entropies, ΔS(*); enthalpies, ΔH(*); Gibbs free energies, ΔG(*), of the thermal decomposition reactions have been derived from thermo gravimetric (TGA) and differential thermo gravimetric (DTG) curves, using Coats-Redfern and Horowitz-Metzeger methods. The lowest energy model structure of each complex has been proposed by using the density functional theory (DFT) at the B3LYP/CEP-31G level of theory. The ligand and their metal complexes were also evaluated for their antibacterial activity against several bacterial species, such as Bacillus Subtilis (B. Subtilis), Staphylococcus aureus (S. aureus), Nesseria Gonorrhoeae (N. Gonorrhoeae), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli).

Synthesis, characterization and antimicrobial investigation of some moxifloxacin metal complexes

The new complexes of moxifloxacin (MOX), with Ti(IV), Y(III), Pd(II) and Ce(IV) have been synthesized. These complexes were then characterized by melting point, magnetic studies and spectroscopic techniques involving infrared spectra (IR), UV-Vis, (1)H NMR. C, H, N and halogen elemental analysis and thermal behavior of complexes also investigated. The results suggested that the molar ratio for all complexes is M: MOX=1:2 where moxifloxacin acts as a bidentate via one of the oxygen atoms of the carboxylate group and through the ring carbonyl group and the complexes have the following formula [Ti(MOX)(2)](SO(4))(2)·7H(2)O, [Y(MOX)(2)Cl(2)]Cl·12H(2)O, [Pd(MOX)(2)(H(2)O)(2)]Cl(2)·6H(2)O and [Ce(MOX)(2)](SO(4))(2)·2H(2)O. The activation energies, E*, enthalpies, ΔH*, entropies, ΔS* and Gibbs free energies, ΔG*, of the thermal decomposition reactions have been derived from thermogravimetric (TGA) and differential thermogravimetric (DrTG) curves, using Coats-Redfern (CR) and Horowitz-Metzger (HM) methods. The antimicrobial activity of these complexes has been evaluated against three Gram-positive and three Gram-negative bacteria and compared with the reference drug moxifloxacin. The antibacterial activity of Ti(IV) complex is significant for E. coli K32 and highly significant for S. aureus K1, B. subtilis K22, Br. otitidis K76, P. aeruginosa SW1 and K. oxytoca K42 compared with free moxifloxacin.

Synthesis of acyclovir and HBG analogues having nicotinonitrile and its 2-methyloxy 1,2,3-triazole

Reaction of pyridin-2(1H)-one 1 with 4-bromobutylacetate (2), (2-acetoxyethoxy)methyl bromide (3) gave the corresponding nicotinonitrile O-acyclonucleosides, 4 and 5, respectively. Deacetylation of 4 and 5 gave the corresponding deprotected acyclonucleosides 6 and 7, respectively. Treatment of pyridin-2(1H)-one 1 with 1,3-dichloropropan-2-ol (8), epichlorohydrin (10) and allyl bromide (12) gave the corresponding nicotinonitrile O-acyclonucleosides 9, 11, and 13, respectively. Furthermore, reaction of pyridin-2(1H)-one 1 with the propargyl bromide (14) gave the corresponding 2-O-propargyl derivative 15, which was reacted via [3+2] cycloaddition with 4-azidobutyl acetate (16) and [(2-acetoxyethoxy)methyl]azide (17) to give the corresponding 1,2,3-triazole derivatives 18 and 19, respectively. The structures of the new synthesized compounds were characterized by using IR, (1)H, (13)C NMR spectra, and microanalysis. Selected members of these compounds were screened for antibacterial activity.

Synthesis, structural characterization and antimicrobial activity evaluation of metal complexes of sparfloxacin

The synthesis and characterization of binary Cu(II)- (1), Co(II)- (2), Ni(II)- (3), Mn(II)- (4), Cr(III)- (5), Fe(III)- (6), La(III)- (7), UO(2)(VI)- (8) complexes with sparfloxacin (HL(1)) and ternary Cu(II)- (9), Co(II)- (10), Ni(II)- (11), Mn(II)- (12), Cr(III)- (13), Fe(III)- (14), La(III)- (15), UO(2)(VI)- (16) complexes with sparfloxacin (HL(1)) and DL-alanine (H(2)L(2)) complexes are reported using elemental analysis, molar conductance, magnetic susceptibility, IR, UV-Vis, thermal analysis and (1)H-NMR spectral studies. The molar conductance measurements of all the complexes in DMF solution correspond to non-electrolytic nature. All complexes were of the high-spin type and found to have six-coordinate octahedral geometry except the Cu(II) complexes which were four coordinate, square planar and U- and La-atoms in the uranyl and lanthanide have a pentagonal bipyramidal coordination sphere. The antimicrobial activity of these complexes has been screened against two gram-positive and two gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with reference drug sparfloxacin. All the binary and ternary complexes showed remarkable potential antimicrobial activity higher than the recommended standard agents. Ni(II)- and Mn(II) complexes exhibited higher potency as compared to the parent drug against gram-negative bacteria.