Antibacterial activity of the essential oil and main components of two Dracocephalum species from Iran

The antibacterial activity of Dracocephalum polychaetum and D. surmandinum essential oils and two main components were investigated. Essential oils of the plants were analysed by GC and GC-MS. Twenty-three components were characterised in the essential oil of D. polychaetum. The oil was rich in oxygenated (73.1%) and hydrocarbon (25.0%) monoterpenes including perilla aldehyde (63.4 %) and limonene (22.1%) as the major constituents. From 25 identified compounds (97.8%) in the oil of D. surmandinum perilla aldehyde (54.3%) and limonene (30.1%) were the main constituents. The bioassays exhibited that all of the Gram-positive and Gram-negative bacteria tested were highly inhibited in the presence of the oils and main components investigated. The most sensitive microorganism to the oils was found to be Staphylococcus epidermidis with the lowest MIC value of 0.3?mgmL(-1). The resistant Gram-negative Pseudomonas aeruginosa was highly inhibited by the oil of D. polychaetum with MIC value of 2.4?mgmL(-1).     

Reverse micelle-mediated dispersive liquid-liquid microextraction of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid

A supramolecular solvent consisting of reverse micelles of decanoic acid, dispersed in a continuous phase of tetrahydrofuran:water, was proposed as an efficient microextraction technique for extraction of selected chlorophenoxy acid herbicides from water samples prior to high-performance liquid chromatography UV determination. The disperser solvent (1.0 mL tetrahydrofuran) containing 20 mg decanoic acid was rapidly injected into 10.0 mL of water sample. After centrifugation, the reverse micelle-rich phase (25 ± 0.5 μL) was floated at top of the home-designed centrifuge tube. The solvent was collected and 20 μL of it was injected into high-performance liquid chromatography for analysis. The results showed that the in situ solvent formation and extraction process can be completed in a few seconds. Under the optimal conditions, limits of detection of the method for 4-chloro-2-methylphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid were in the range of 0.5-0.8 μg L(-1) and the repeatability of the proposed method, expressed as relative standard deviation, varied in the range of 2.5-3.2%. Linearity was found to be in the range of 1-200 μg L(-1) and the preconcentration factors were between 148 and 157. The mean percentage recoveries exceeded 92.0% for all the spiking levels in real water samples.     

High temperature oxidation resistance and corrosion properties of dip coated silica coating by sol gel method on stainless steel

Silica coating for the protection of stainless steel (SS) surfaces was prepared using tetraethoxysilane and methyltriethoxysilane as precursors via an acid-catalysed (H₂SO₄) sol?Cgel method and was deposited on ferritic SS AISI 430 by dip coating. The surface morphology was studied using a scanning electron microscope equipped with energy-dispersive X-ray, phase analysis was carried out by X-ray diffraction, and isothermal oxidation was carried out at 800?°C for 200?h. Corrosion properties were examined by electrochemical impedance spectroscopy and resistance polarization methods in an aqueous medium containing 3.5?wt?% NaCl. The results indicated that silica coating improved high-temperature oxidation resistance of AISI 430 in chloride media.     

High-throughput quantification of palladium in water samples by ion pair based-surfactant assisted microextraction

A novel method for the determination of palladium as a metal ion model was developed by ion pair based surfactant-assisted microextraction (IP-SAME) and inductively coupled plasma-optical detection (ICP-OES). In this methodology, a cationic surfactant was used in extraction process. It has two fundamental functions: (1) the formation of an emulsified phase and (2) the ion pair formation with Pd(II) in the presence of iodide ions and making PdI₄²⁻$\text{Pd}{{\text{I}}_4}^{2-}$ extractable into organic phase (active microextraction). The effective parameters on the extraction recovery such as the types of extraction solvent and the surfactant, surfactant concentration, KI amount and HCl concentration of the sample were investigated and optimized. In the proposed approach, tetradecyl trimethyl ammonium bromide (TTAB) was used as emulsifier and ion pairing agent, and 1-octanol was selected as extraction solvent. Under the optimum conditions, the enhancement factor as large as 146 was obtained. The detection limit for palladium was 0.2 μg L⁻¹, and the relative standard deviation (RSD) was 4.1% (n = 5, C = 10.0 μg L⁻¹). The proposed method was applied for extraction and determination of palladium in different water samples.     

The fast peroxyoxalate-chemiluminescence of 3-1-aza-4,10-dithia-7-oxacyclododecane as a novel fluorophore

Due to their multiple selectivities, high sensitivity, and instrumental simplicity peroxyoxalate chemiluminescence (PO-CL) reactions have been used as powerful detection systems in several separation techniques. However many of the PO-CL reactions have slow kinetics and impose extra flow elements in separation systems to obtain acceptable band resolution, overcome the peak broadening and observe the reaction in a reasonable time window at maximum emission intensity. Therefore slow chemiluminescence reactions cannot be used in constructing miniaturized separation systems. To achieve the fast and intense PO-CL reactions (suitable for miniaturized separation systems) careful selection of the fluorophore molecule and the reaction conditions is of great importance. In this work, the time-dependent light emission of the fast chemiluminescence (CL) arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with H₂O₂ in the presence of 3-1-aza-4,10-dithia-7-oxacyclododecane (L) as a novel fluorophore, and imidazole as catalyst, has been studied in ethyl acetate solution. To find the best time-intensity emission curves the concentration of TCPO, imidazole, hydrogen peroxide and L were optimized. The maximum CL intensity and minimum reaction time were obtained at the concentration of 0.2 M H₂O₂, 2.0×10^?3 M TCPO, 1.0×10^?3 M fluorophore and 5.0×10^?3 imidazole. Under the optimum experimental condition, the entire CL reaction is completed in less than 3 s.     

Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium–Schiff’s base complex

A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10^–7 mol L^–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample. Received: 1 December 2000 / Revised: 19 April 2001 / Accepted: 30 April 2001     

Immobilization of platinum nanoparticles on the functionalized chitosan particles: an efficient catalyst for reduction of nitro compounds and tandem reductive Ugi reactions

Molecular Diversity - In this work, we reported a facile synthesis of Pt nanoparticles (NPs) on proline-functionalized cross-linked chitosan particles to catalyze the reduction of R-NO2 to R-NH2 in...     

Effect of gold nanoparticles synthesized using the aqueous extract of Satureja hortensis leaf on enhancing the shelf life and removing Escherichia coli O157:H7 and Listeria monocytogenes in minced camel's meat: The role of nanotechnology in the food industry

Because herbal nanoparticles have antimicrobial properties, researchers have tried to synthesize them to aid in increasing the shelf time of food and food products. In this regard, gold nanoparticles (AuNPs) synthesized by plants are particularly important. In this study, fresh and clean leaves of Satureja hortensis were selected for the synthesis of AuNPs. We also evaluated the efficacy of these nanoparticles to increase the shelf life of and remove Escherichia coli O157:H7 and Listeria monocytogenes from minced camel's meat. The nanoparticles were analyzed by UV–visible spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction tests. The FT-IR spectroscopy results demonstrated that the antioxidant compounds in the plant were the sources of reducing power, reducing gold ions to AuNPs. FE-SEM and TEM images revealed the size of the nanoparticles to be 22.26 nm. The 2,2-diphenyl-1-picrylhydrazyl test revealed similar antioxidant potentials for S. hortensis, AuNPs, and butylated hydroxytoluene. S. hortensis and AuNPs had high cell viability dose-dependently against the human umbilical vein endothelial cell line. At the beginning of the food industry part of this experiment, all samples of control, S. hortensis, and AuNPs were preserved at 4°C for 20 days. During these 20 days, the sensory, chemical, and microbiological parameters were assessed for all samples. AuNPs significantly inhibited the growth of E. coli and L. monocytogenes. In addition, AuNPs significantly increased the protein carbonyl content, thiobarbituric acid reactive substances, pH, peroxide value, total volatile base nitrogen, and sensory attributes (color, odor, and overall acceptability). The best results were seen in AuNPs (1%). These findings reveal that the inclusion of S. hortensis extract improves the solubility of AuNPs, which led to a notable enhancement in their preservative and antibacterial effects.     

The immobilized Ni(II)‐thiourea complex on silica‐layered copper ferrite: A novel and reusable nanocatalyst for one‐pot reductive‐acetylation of nitroarenes

In this study, magnetically nanoparticles of CuFe₂O₄@SiO₂@PTMS@Tu@Ni(II) as novel and reusable catalyst were prepared. Synthesis of the Ni (II)‐nanocatalyst was carried out through the complexation of Ni(OAc)₂·4H₂O with the immobilized thiourea on silica‐layered CuFe₂O₄. The prepared nanocomposite system was then characterized using SEM, EDX, XRD, VSM, ICP‐OES, Raman, UV–Vis and FT‐IR analyses. Catalytic activity of the Ni(II)‐CuFe₂O₄ system was investigated towards rapid reduction of aromatic nitro compounds to arylamines with sodium borohydride as well as one‐pot reductive‐acetylation of nitroarenes to acetanilides with NaBH₄/Ac₂O system without the isolation of intermediate arylamines. All reactions were carried out in H₂O within 3–7 min to afford the products arylamines/acetanilides in high to excellent yields. Reusability of the Ni(II)‐nanocatalyst was examined for seven consecutive cycles without the significant loss of the catalytic activity.