Biochemical Characterization of New Gemifloxacin Schiff Base (GMFX-o-phdn) Metal Complexes and Evaluation of Their Antimicrobial Activity against Some Phyto- or Human Pathogens

Abstract

Four novel ligand-metal complexes were synthesized through the reaction of Fe(III), pleaseCo(II), Zn(II), and Zr(IV) with Schiff base gemifloxacin reacted with ortho-phenylenediamine (GMFX-o-phdn) to investigate their biological activities. Elemental analysis, FT-IR, 1H NMR, UV-visible, molar conductance, melting points, magnetic susceptibility, and thermal analyses have been carried out for insuring the chelation process. The antimicrobial activity was carried out against Monilinia fructicola, Aspergillus flavus, Penicillium italicum, Botrytis cinerea, Escherichia coli, Bacillus cereus, Pseudomonas fluorescens, and P. aeruginosa. The radical scavenging activity (RSA%) was in vitro evaluated using ABTS method. FT-IR spectra indicated that GMFX-o-phdn chelated with metal ions as a tetradentate through oxygen of carboxylate group and nitrogen of azomethine group. The data of infrared, 1HNMR, and molar conductivity indicate that GMFX–o-phdn reacted as neutral tetra dentate ligand (N2O2) with metal ions through the two oxygen atoms of the carboxylic group (oxygen containing negative charge) and two nitrogen atoms of azomethine group (each nitrogen containing a lone pair of electrons) (the absent of peak corresponding to ν(COOH) at 1715 cm−1, the shift of azomethine group peak from 1633 cm−1 to around 1570 cm−1, the signal at 11 ppm of COOH and the presence of the chloride ions outside the complex sphere). Thermal analyses (TG-DTG/DTA) exhibited that the decaying of the metal complexes exists in three steps with the final residue metal oxide. The obtained data from DTA curves reflect that the degradation processes were exothermic or endothermic. Results showed that some of the studied complexes exhibited promising antifungal activity against most of the tested fungal pathogens, whereas they showed higher antibacterial activity against E. coli and B. cereus and low activity against P. fluorescens and P. aeruginosa. In addition, GMFX-o-phdn and its metal complexes showed strong antioxidant effect. In particular, the parent ligand and Fe(III) complex showed greater antioxidant capacity at low tested concentrations than that of other metal complexes where their IC50 were 169.7 and 164.6 µg/mL, respectively.

Spectroscopic Analyses and Antimicrobial Activity of Novel Ciprofloxacin and 7-Hydroxy-4-methylcoumarin, the Plant-Based Natural Benzopyrone Derivative

“…These data indicated that CIP ligated as monodetate through the oxygen atom of the COO − group [ 44 , 48 ]. Additionally, the IR spectrum of the HMC ligand shows a very strong band at 1674 cm −1 assignable to the stretching vibration of the cyclic ester ν (C=O); this band is shifted to lower values ( Table 2 ), indicating the coordination of HMC through the oxygen atom of the carbonyl group [ 25 , 26 , 27 , 28 ]. The presence of the broad bands in the range 3489–3411 cm −1 confirms the presence of H 2 O in all complexes [ 48 ].…”

“…The data of the TG and DTG curves of the compounds are listed in Table 5 . The TG-DTG analyses of CIP were studied before [ 28 , 34 ]. Decomposition of HMC started at 50 °C and finished at 600 °C, with two stages.…”

“…The percentage of Zr(IV) was determined by three analytical methods, complexometric titration, thermogravimetry, and atomic absorption. Gravimetric determination was carried out by transforming the solid products into zirconium oxide and also determined by using atomic absorption method [ 15 , 28 ]. Spectrometer model PYE-UNICAM SP 1900 fitted with the corresponding lamp was used for this purposed.…”

“…It functions by inhibiting DNA gyrase, a type II topoisomerase, and topoisomerase IV, enzymes necessary to separate bacterial DNA, thereby inhibiting cell division [ 26 , 27 ]. CIP chelates with the metal ions as a bidentate ligand through the pyridone oxygen and one carboxylate oxygen [ 22 , 28 , 29 , 30 ]. Zr(IV) reacted with sparfloxacin, norfloxacin, moxifloxacin, lomefloxacin, ciprofloxacin, ofloxacin, carbamazebine, ibuprofen, meloxicam, and some tetradentate Schiff-base ligands, forming stable octahedral complexes [ 15 , 21 , 28 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ].…”

“…CIP chelates with the metal ions as a bidentate ligand through the pyridone oxygen and one carboxylate oxygen [ 22 , 28 , 29 , 30 ]. Zr(IV) reacted with sparfloxacin, norfloxacin, moxifloxacin, lomefloxacin, ciprofloxacin, ofloxacin, carbamazebine, ibuprofen, meloxicam, and some tetradentate Schiff-base ligands, forming stable octahedral complexes [ 15 , 21 , 28 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. The complexes exhibit highly significant antibacterial activity for G+ve and G-ve bacteria.…”