Azo dyes account for 60–70% of all dyes known to date. Understanding the factors that affect the direction of keto–enol tautomerism in azo dyes through spectral measurements is crucial to their potential applications. This review encompasses the most important spectroscopic studies of different azo dyes categorized by their structures within the last few years (2010–2014). It is concluded that the stability of the keto and enol forms largely arises from the ability to establish intra-molecular and inter-molecular hydrogen bonding, respectively. There are many factors that affect the keto or enol form, for example, polar solvent, high temperature, neutral pH and electron withdrawing substituents favor the keto form through intramolecular hydrogen bonding, whereas, nonpolar solvent, low temperature, high pH and electron donating groups favor the enol form through intermolecular hydrogen bonding. Encapsulation inside nanocaged microheterogenous systems creates a rigid environment that stabilizes the enol form mostly, while in the solid state, most of the tautomeric equilibrium lies in favor of the keto form. Understanding of keto–enol tautomerism in azo dyes helps to probe solvation dynamics, to tune the pK_a values in chemical sensing, and to explain proton transfer in the excited state.

Organic pollutants, especially those found in water bodies, pose a direct threat to various aquatic organisms as well as humans. A variety of different remediation approaches, including chemical and biological methods, have been developed for the degradation of various organic pollutants. However, comparative mechanistic studies of pollutant degradation by these different systems are almost non-existent. In this study, the degradation of a model thiazole pollutant, thioflavin T (ThT), was carried out in the presence of either an advanced oxidation process (ultraviolet (UV) + H₂O₂) or a chloroperoxidase enzyme system (CPO + H₂O₂). The degradation was followed both spectrophotometrically and using liquid chromatography-mass spectroscopy (LC-MS), and the products formed were identified using tandem liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS). The results show that the two remediation approaches produced different sets of intermediates, with only one common species (a demethylated form of ThT). This suggests that different degradation schemes were operating in the two systems. Interestingly, one of the major intermediates produced by the CPO + H₂O₂ system was a chlorinated form of thioflavin. Phytotoxicity studies showed that the CPO + H₂O₂-treated ThT solution was significantly (p <0.05) less toxic than the UV + H₂O₂-treated ThT solution. This is the first time that a comparative mechanistic study showing in detail the intermediates generated in chemical and biological remediation methods has been presented. Furthermore, the results show that different remediation systems have very different degradation schemes and result in products having different toxicities.

Liver cancer remains among the leading causes of cancer-related deaths worldwide. This is due to many reasons, including limitations of available drugs, late diagnosis due to the overlapping symptoms with many other liver diseases, and lack of effective screening modalities. Compared to conventional chemotherapy, targeted drug delivery systems are advantageous in many ways, as they minimize drug resistance and improve therapeutic value for cancer patients. Nanomaterials, in general, and nanoparticles, in particular, possess nm size, which provides a high surface area for a great extent of functionalization to be used for the targeted delivery of cancer drugs. Amongst the different formulations of nanoparticles, magnetic nanoparticles (MNPs) have unique chemical and physical characteristics and magnetic behavior, making them preferable candidates as a core for drug delivery systems. To maintain the nanosized structure of MNPs, a polymeric coating is usually applied to maintain the nanoparticles dispersed in the solution. Moreover, the polymeric coating provides a plate form for carrying drug molecules on its surface. In the present study, poly(ethylene glycol) (PEG)-coated MNPs were successfully synthesized, where the optimum concentration of PEG on the surface of the MNPs was investigated. The PEG-coated MNPs were further coated with crocetin at different concentrations. The crocetin-coated pegylated MNPs were evaluated in vitro using a hepatic cell line (HepG2) for up to 72 h. Results showed good release kinetics under acidic and neutral conditions. The optimally prepared drug delivery system showed a high potential for reducing the HepG2 cell proliferation in vitro using an MTT assay. The calculated IC50 for Cro-PEG-MNPs were 0.1019, 0.0903, and 0.0462 mg/mL of 5×, 10× and 20×, respectively.

Background: Anthranilic acid is an active compound with diverse biological activities such as anti-inflammatory, antineoplastic, anti-malarial and α-glucosidase inhibitory properties. It can also chelate transition metals to form complexes with applications as antipathogens, photoluminescent materials, corrosion inhibitors, and catalysts. Results: Anthranilic acid complexes (1–10) of Zn(II), Bi(III), Ag(I), Fe(II), Co(II), Cu(II), Mn(II), Al, Ni(II), and Cr(III) were synthesized and characterized using thermogravimetric (TGA), elemental analysis, FT-IR, UV–vis spectrometry, mass spectrometry and magnetic susceptibility. The morphology and size of metal complex (1–10) particles were determined by scanning electron microscope (SEM) and the surface area was determined by BET analysis. TGA and CHN analysis data indicated that the stoichiometries of complexes were 1:2 metal/ligand except for Ag(I), Al and Bi. Furthermore, DFT study was performed to optimize the structure of selected complexes. The complexes (1–10) were evaluated for their catalytic activity in the reduction of 4-nitrophenol (4-NP), antibacterial activity against S. aureus, P. aeroginosa and E. coli as well as their antifungal activity against F. solani and A. niger. The complexes were also tested against the second-stage juveniles (J₂) root-knot nematodes. Conclusion: Co(II) complex 5 and Cu(II) complex 6 showed high catalytic activity for the reduction of 4-NP to 4-aminophenol (4-AP). Ag(I) complex 3 showed the best activity against the pathogens that were tested namely clinically important bacteria S. aureus, P. aeroginosa and E. coli, commercially important fungi F. solani and A. niger and J₂ root-knot nematodes M. javanica.