Nora S. Abdel-Kader

Antibacterial effect of some benzopyrone derivatives

The Schiff base derivatives of benzopyran-4-one are characterized by imine groups which have biological activities such as antimicrobial, antifungal and antitumoral. The aim of this study was therefore to evaluate the toxicity of Schiff bases towards bacterial cells. Escherichia coli as Gram-negative bacteria and Staphylococcus capitis as Gram-positive bacteria were exposed to different concentrations of Schiff bases. For assessment of toxicity a 96-well turbidimetric procedure, capable of testing the antimicrobial properties on a single microplate, was used. Analysis of the growth curves showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria was higher than that on Gram-positive. Furthermore the presence of hydroxylic groups is correlated with an increased antibacterial effect.

Spectroscopic and biological activities studies of bivalent transition metal complexes of Schiff bases derived from condensation of 1,4-phenylenediamine and benzopyrone derivatives.

Many tools of analysis such as elemental analyses, infrared, ultraviolet-visible, electron spin resonance (ESR) and thermal analysis, as well as conductivity and magnetic susceptibility measurements were used to elucidate the structures of the newly prepared Co(II), Ni(II) and Cu(II) complexes with Schiff bases derived from the condensation of 1,4-phenylenediamine with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzo-pyran-4-one (H2L) or 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one (H4L). The data showed that all formed complexes are 1:1 or 2:2 (M:L) and non-electrolyte chelates. The Co(II) and Cu(II) complexes of the two Schiff bases were screened for antibacterial activities by the disk diffusion method. The antibacterial activity was screened using Escherichia coli and Staphylococcus capitis but the antifungal activity was examined by using Aspergillus flavus and Candida albicans. The Results showed that the tested complexes have antibacterial, except CuH4L, but not antifungal activities.

Synthesis, spectral, thermal and magnetic studies of Mn(II), Ni(II) and Cu(II) complexes with some benzopyran-4-one Schiff bases

The Schiff bases of N(2)O(2) dibasic ligands, H(2)La and H(2)Lb are prepared by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one. Also tetra basic ligands, H(4)La and H(4)Lb are prepared by the condensation of aliphatic amines (a) and (b) with 6-formyl-5,7-dihydroxy-2-methylbenzopyran-4-one. New complexes of H(4)La and H(4)Lb with metal ions Mn(II), Ni(II) and Cu(II) are synthesized, in addition Mn(II) complexes with ligands H(2)La and H(2)Lb are also synthesized. Elemental and thermal analyses, infrared, ultraviolet-visible as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The structures of copper(II) complexes are also assigned based upon ESR spectra study. All the complexes separated with the stoichiometric ratio (1:1) (M:L) except Mn-H(4)La and Mn-H(4)Lb with (2:1) (M:L) molar ratio. In metal chelates of the type 1:1 (M:L), the Schiff bases behave as a dinegative N(2)O(2) tetradentate ligands. Moreover in 2:1 (M:L) complexes, the Schiff base molecules act as mono negative bidentate ligand and binuclear complex is then formed. The Schiff bases were assayed by the disc diffusion method for antibacterial activity against Staphylococcus aureus and Escherichia coli. The antifungal activity of the Schiff bases was also evaluated against the fungi Aspergillus flavus and Candida albicans.

Microplate assay for screening the antibacterial activity of Schiff bases derived from substituted benzopyran-4-one

Schiff bases (SB(1)-SB(3)) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB(1)), p-phenylenediamine (SB(2)) and o-phenylenediamine (SB(3)), while Schiff bases (SB(4)-SB(6)) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB(4)), p-phenylenediamine (SB(5)) and o-phenylenediamine (SB(6)). Schiff bases were characterized using elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH(3) on position five have higher antibacterial activity than that containing hydroxy group on the same position.

Synthesis and characterization of tetradentate bis -Schiff base complexes of di- and tri-valent transition metals

The bis-Schiff bases of N2O2 dibasic ligands, H2La and H2Lb are synthesized by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzo-pyran-4-one. The ligands are characterized using elemental analysis, IR, UV–Vis, 1H-NMR and mass spectroscopy. The ionization constant pKa values are determined spectrophotometrically. The 1H-NMR spectra of the ligands show the presence of phenolic coordinating groups. New complexes of H2La and H2Lb with metal ions Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) are synthesized. Elemental analyses, infrared, ultraviolet-visible, electron spin resonance and thermal analysis, as well as conductivity and magnetic susceptibility measurements, are used to elucidate the structures of the newly prepared metal complexes. Thermal degradation studies for some complexes show that the final product is the metal oxide. A square planar geometry is suggested for the Cu(II), Zn(II) (for H2La and H2Lb) and Ni(II) (for H2La) complexes; an octahedral geometry for the Co(II), Cr(III), Fe(III) (for H2La and H2Lb), and Ni(II) (for H2Lb) complexes. The coordination sites are two azomethine nitrogens and two phenolic oxygens in the tetradentate Schiff bases.

Synthesis, Characterization of La(III), Nd(III), and Er(III) Complexes with Schiff Bases Derived from Benzopyran-4-one and Thier Fluorescence Study

The Schiff bases, L1, L2, and L3, are synthesized from the condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one (L) with 2-aminopyridine (1), p-phenylenediamine (2), and o-phenylenediamine (3). The prepared Schiff bases react with lanthanum (III), neodymium (III), and erbium (III) nitrate to give complexes with stoichiometric ratio (1 : 1) (ligand : metal). The binuclear complexes of Er(III) with L3 and the three metal ions with L2 are separated. The complexes have been characterized by elemental analysis, molar conductance, electronic absorption, and infrared, 1H-NMR spectral studies. The presence of hydrated and coordinated water molecules is inferred from thermogravimetric analysis. Thermal degradation studies show that the final product is the metal oxide. The luminescence properties of the Nd(III) and Er(III) complexes in dimethylformamide (DMF) solutions were investigated.

Bioluminescence-Sensing Assay for Microbial Growth Recognition

The conventional methods for microbial viability quantification require cultivation and are laborious. There is consequently a widespread need for cultivation-free methods. The adenosine triphosphate (ATP) bioluminescence-sensing assay is considered an extremely effective biosensor; hence ATP is the energy currency of all living microbes and can be used as a rapid indicator of microbial viability. We developed an ATP bioluminescence-sensing assay to detect microbial viability. A bioluminescent recombinant E. coli strain was used with luciferase extracted from transformed bacteria. Results showed that there is a direct correlation between the bioluminescence intensity of the ATP bioluminescence-sensing assay and the microbial viability. Bacterial counts from food samples were detected using the developed sensing assay and validated by the traditional plate-counting method. Compared with the plate-counting method, ATP bioluminescence-sensing assay is a more rapid and efficient approach for detecting microbial viability.