Antibacterial, Antifungal, Phytotoxic, and Genotoxic Properties of Two Complexes of AgIwith Sulfachloropyridazine (SCP): X-ray Diffraction of [Ag(SCP)]n

Assessment of the biological effect of metal ions and their complexes using Allium cepa and Artemia salina assays: a possible environmental implementation of biological inorganic chemistry

The pollution of aquatic ecosystems due to the elevated concentration of a variety of contaminants, such as metal ions, poses a threat to humankind, as these ecosystems are in high relevance with human activities and survivability. The exposure in heavy metal ions is responsible for many severe chronic and pathogenic diseases and some types of cancer as well. Metal ions of the groups 11 (Cu, Ag, Au), 12 (Zn, Cd, Hg), 14 (Sn, Pb) and 15 (Sb, Bi) highly interfere with proteins leading to DNA damage and oxidative stress. While, the detection of these contaminants is mainly based on physicochemical analysis, the chemical determination, however, is deemed ineffective in some cases because of their complex nature. The development of biological models for the evaluation of the presence of metal ions is an attractive solution, which provides more insights regarding their effects. The present work critically reviews the reports published regarding the toxicity assessment of heavy metal ions through Allium cepa and Artemia salina assays. The in vivo toxicity of the agents is not only dose depended, but it is also strongly affected by their ligand type. However, there is no comprehensive study which compares the biological effect of chemical agents against Allium cepa and Artemia salina. Reports that include metal ions and complexes interaction with either Allium cepa or Artemia salina bio-indicators are included in the review.

N,N′-Diarylformamidine Dithiocarbamate Ag(I) Cluster and Coordination Polymer

An Ag(I)formamidine cluster Ag6L16 (1) and an Ag(I)formamidine coordination polymer Ag7(L2)2 2 (L1 = N,N′-bis(2,6-disopropylphenyl) formamidine dithiocarbamate and L2 = N,N′-mesityl formamidine dithiocarbamate) have been synthesized from the reactions of L1 and L2 with AgNO3 respectively. The complexes were characterized using spectroscopic and analytical methods, including single-crystal X-ray diffraction. In the structure of 1, a six vertex distorted square bi-pyramidal octahedron is formed from an Ag6 core. The N,N′-bis(2,6-disopropylphenyl) formamidine dithiocarbamate ligands stabilize this core through two main –CS2 bridging modes giving a propeller like structure. In the structure of 2, each of the two Ag(I) centers are bridged by two N,N′-mesityl formamidine dithiocarbamate ligands forming 8-member Ag2(CS2)2 metallacycles with an inversion center in the middle of the Ag—Ag argentophilic bond. The metallacycles are connected through Ag—S bonds forming ribbons in the crystallographic a-axis. The Ag(I) centers are coordinated to two N,N′-mesitylformamidine dithiocarbamates through the dithiocarbamate S atoms. The thermal decomposition of complexes 1 and 2 had similar thermograms with one major weight loss activity and the formation of elemental silver particles thereafter.

Silver nanoparticles stabilized with propolis show reduced toxicity and potential activity against fungal infections

Aim: Elucidate the antifungal efficacy of biologically synthesized silver nanoparticles with ethanolic propolis extract (AgNPs PE) against the planktonic forms and biofilms of clinically important fungi. Materials & methods: AgNPs were synthesized, characterized and evaluated for cytotoxicity, mutagenicity and antimicrobial activity. Results: AgNPs PE displayed a colloidal appearance, good stability and size of 2.0–40.0 nm. AgNPs PE demonstrated lower cytotoxicity and nonmutagenic potential. In addition, AgNPs PE displayed antifungal properties against all tested isolates, inhibiting growth at concentrations lower than the cytotoxic effect. Mature biofilms treated for 48 h with AgNPs PE showed significant reduction of viable cells, metabolic activity and total biomass. Conclusion: This is the first time that AgNPs have been synthesized from an ethanolic extract of propolis only, proving antifungal, antibiofilm, atoxic and nonmutagenic properties.

Synthesis and Antimicrobial Activity of 2-Trifluoroacetonylbenzoxazole Ligands and Their Metal Complexes

Three 2-fluoroacetonylbenzoxazole ligands 1a-c and their new Zn(II) complexes 2a-c have been synthesized. In addition, syntheses of new metal [Mg(II), Ni(II), Cu(II), Pd(II), and Ag(I)] complexes from 1a have been also described. The molecular and crystal structures of six metal complexes 2b and 2d-h were determined by single-crystal X-ray diffraction analyses. Their antibacterial activities against six Gram-positive and six Gram-negative bacteria were evaluated by minimum inhibitory concentrations (MIC), which were compared with those of appropriate antibiotics and silver nitrate. The results indicate that some metal compounds have more antibacterial effects in comparison with free ligands and have preferred antibacterial activities that may have potential pharmaceutical applications. Noticeably, the Ag(I) complex 2h exhibited low MIC value of 0.7 µM against Pseudomonas aeruginosa, which was even superior to the reference drug, Norfloxacin with that of 1.5 µM. Against P. aeruginosa, 2h is bacteriostatic, exerts the cell surface damage observed by scanning electron microscopy (SEM) and is less likely to develop resistance. The new 2h has been found to display effective antimicrobial activity against a series of bacteria.

Synthesis, characterization and biological studies of a cobalt(III) complex of sulfathiazole

The emergence of old and new antibiotic resistance created in the last decades revealed a substantial medical need for new classes of antimicrobial agents. The antimicrobial activity of sulfa drugs is often enhanced by complexation with metal ions, which is in concordance with the well-known importance of metal ions in biological systems. Besides, sulfonamides and its derivatives constitute an important class of drugs, with several types of pharmacological agents possessing antibacterial, anti-carbonic anhydrase, diuretic, hypoglycemic, antithyroid, antiviral and anticancer activities, among others. The purpose of this work has been the obtainment, characterization and determination of biological properties (antibacterial, antifungal, mutagenicity and phytotoxicity) of a new Co(III)-sulfathiazole complex: Costz, besides of its interaction with bovine serum albumin (BSA). The reaction between sodium sulfathiazole (Nastz) and cobalt(II) chloride in the presence of H₂O₂ leads to a brown solid, [Co^III(stz)₂OH(H₂O)₃], (Costz). The structure of this compound has been examined by means of elemental analyses, FT-IR, ¹H NMR, UV-Visible spectrometric methods and thermal studies. The Co(III) ion, which exhibits a distorted octahedral environment, could coordinate with the N thiazolic atom of sulfathiazolate. The complex quenched partially the native fluorescence of bovine serum albumin (BSA), suggesting a specific interaction with the protein. The Costz complex showed, in vitro, a moderate antifungal activity against Aspergillus fumigatus and A. flavus. As antibacterial, Costz displayed, in vitro, enhanced activity respective to the ligand against Pseudomonas aeruginosa. Costz did not show mutagenic properties with the Ames test. In the Allium cepa test the complex showed cytotoxic properties but not genotoxic ones. These results may be auspicious, however, further biological studies are needed to consider the complex Costz as a possible drug in the future.

Antimicrobial evaluation of new metallic complexes with xylitol active against P. aeruginosa and C. albicans: MIC determination, post-agent effect and Zn-uptake

Xylitol (xylH5) is metabolized via the pentose pathway in humans, but it is unsuitable as an energy source for many microorganisms where it produces a xylitol-induced growth inhibition and disturbance in protein synthesis. For this reason, xylitol is used in the prophylaxis of several infections. In the search of better antimicrobial agents, new copper and zinc complexes with xylitol were synthesized and characterized by analytical and spectrosco pic methods: Na2[Cu3(xylH−4)2]·NaCl·4.5H2O (Cu-xyl) and [Zn4(xylH−4)2(H2O)2]·NaCl·3H2O (Zn-xyl). Both copper and zinc complexes presented higher MIC against Pseudomona aeruginosa than the free xylitol while two different behaviors were found against Candida albicans depending on the complex. The growth curves showed that Cu-xyl presented lower activity than the free ligand during all the studied period. In the case of Znxyl the growth curves showed that the inhibition of the microorganism growth in the first stage was equivalent to that of xylitol but in the second stage (after 18 h) Zn-xyl inhibited more. Besides, the PAE (post agent effect)obtained for Zn-xyl and xyl showed that the recovery from the damage of microbial cells had a delay of 14 and 13 h respectively. This behavior could be useful in prophylaxis treatments for infectious diseases where it is important that the antimicrobial effect lasts longer. With the aim to understand the microbiological activities the analysis of the particle size, lipophilicity and Zn uptake was performed.

Synthesis, characterization, microbiological evaluation, genotoxicity and synergism tests of new nano silver complexes with sulfamoxole: X-ray diffraction of [Ag2(SMX)2]·DMSO

The synthesis and microbiological evaluation of two new Ag(I) complexes with sulfamoxole (SMX), [Ag2(SMX)2]·H2O and [Ag4(SCN)3(SMX)]·H2O are described. Both were characterized by elemental analysis, thermogravimetry, powder and single crystal X-ray diffraction, NMR, Raman and experimental and theoretical IR spectroscopies. Their antibacterial and antifungal properties were evaluated by agar and broth dilution assays, respectively. In addition, synergism tests for Pseudomonas aeruginosa were performed, and genotoxicity studies were carried out employing the Allium cepa test. Both complexes displayed good activity against Escherichia coli, Staphylococcus aureus, P. aeruginosa, and 10 fungi strains, with lower minimum inhibitory concentrations (MICs) than that of free SMX in all cases. The nanometrical crystallite particle size determined from XRPD, DLS and TEM might explain the good microbiological activity in spite of the low solubility of both complexes. The fractional inhibitory concentration (FIC) calculated from the P. aeruginosa test data indicated that the activity of the complexes is not due to synergism of the free components in the concentration ratios studied. Moreover, none of the complexes displayed cytotoxic effects on onions in the concentration range tested, and chromosome aberrations were not observed.