Synthesis, characterization and chelating properties of tannin-8-hydroxy quinoline - formaldehyde polymer

Tannin obtained from Eucalyptus plant, condensed with formaldehyde and then 8-hydroxy quinoline. The so called obtained polymer designated as TFQ was used for metal chelate formation. Thus Transition metal chelates of TFQ with Zn+2, Co+2, Cu+2, Ni+2 and Mn+2 metal ions were prepared. The ligand TFQ and its all five metal chelates were characterized by nitrogen content, IR, UV-Visible spectral studies, magnetic moments and thermogravimetry. The antimicrobial activity of all the samples has also been monitored against common microbes.

Permeation characteristics of tetracyclines in parallel artificial membrane permeation assay II: Effect of divalent metal ions and mucin

<p class="ADMETabstracttext">The bioavailability of tetracyclines is markedly decreased when co-administered with antacids, milk, or food containing Ca²⁺. Previously, it was suggested that the effective intestinal permeation of tetracycline (TC) was decreased due to Ca²⁺ linked mucin binding in the mucosal side. In the present study, we investigated the effect of Ca²⁺, Mg²⁺, and mucin on the membrane permeation of six tetracyclines (TC, oxytetracycline (OTC), minocycline (MINO), doxycycline (DOXY), demeclocycline (DMCTC), and chlortetracycline (CTC)). The membrane permeability values (P_e) of tetracyclines were measured by the parallel artificial membrane permeation assay (PAMPA) using soybean lecithin – decane (SL–PAMPA) and octanol (OCT–PAMPA) membranes. In SL–PAMPA, Ca²⁺ markedly decreased the P_e values of all tetracyclines. In OCT–PAMPA, Ca²⁺ increased the P_e values of TC, CTC, and DMCTC, but not DOXY, OTC, and MINO. Mg²⁺ decreased the P_e values of all tetracyclines in both SL–PAMPA and OCT–PAMPA (except for CTC in OCT–PAMPA). The addition of mucin had little or no effect in all cases. In contrast to the previously suggested mechanism, the results of the present study suggested that Ca²⁺ chelate formation decreased the membrane permeation of tetracyclines, irrespective of Ca²⁺ linked mucin binding. Molecular speciation analysis suggested that the permeation of TC – metal chelates was negligibly small in SL-PAMPA.</p>

Kinetics, DFT Study and Antibacterial Activity of Zinc(II) and Copper(II) Terpyridine Complexes

The kinetics of ligand substitution reactions between zinc(II) and copper(II) terpyridine complexes and biologically relevant nucleophiles were investigated at pH 7.38 as a function of nucleophile concentration. Substitution reactions include two steps of consecutive displacement of the chlorido ligands. The order of reactivity of the investigated nucleophiles for the first reaction step is: glutathione (GSH) &gt; &gt; DL-aspartic acid (DL-Asp) &gt; guanosine-5’-monophosphate (5’-GMP) &gt; inosine-5’-monophosphate (5’-IMP) &gt; L-methionine (L-Met) (for [CuCl₂(terpy)]), while for [ZnCl₂(terpy)] order is: DL-Asp &gt; GSH &gt; 5’-GMP &gt; 5’-IMP &gt; &gt; L-Met. Chelate formation and pre-equilibrium were obtained for the substitution process between [ZnCl₂(terpy)] complex and glutathione. Activation parameters support an associative mechanism A or I_a for the both reaction steps. The best antibacterial effect was exhibited against <em>Sarcina lutea, </em>and stronger antibacterial activity of [CuCl₂(terpy)] complex than [ZnCl₂(terpy)] was observed. In order to verify the structural geometries of investigated complexes in crystal and solute forms, their structures were optimized by DFT method. Based on energetic stability of complexes, it can be concluded that both of complexes make hydrates very easy, but the bond between water molecule and metal ion is pretty week.