Electrochemical study of the antineoplastic agent etoposide at carbon paste electrode and its determination in spiked human serum by differential pulse voltammetry

The electrochemical oxidation of the antineoplastic agent etoposide was studied at carbon paste electrode in Britton-Robinson buffer solutions over the pH range 2.0-10.0 using cyclic, linear sweep and differential pulse voltammetry. Oxidation of the drug was effected in a single reversible, diffusion-controlled step within the pH range 2.0-4.0, a second oxidation process was produced above pH 4.0. Using differential pulse voltammetry (DPV), the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 3.0 at 0.500 V (vs. Ag/AgCl) on carbon paste electrode. This process could be used to determine etoposide concentrations in the range 2.5 x 10(-7) to 2.5 x 10(-5) M with a detection limit of 1.0 x 10(-7) M. The method was successfully applied to the determination of the drug in spiked human serum.     

Eliminating the Unruh effect of relativistic Dirac fields by partial measurements

The retrieval of lost entanglement for relatively accelerated fermionic observers of a tripartite system by a partial measurement technique has been investigated. From the prospective of the negativities of one-tangles and the π-tangle, we show that the degraded entanglement in noninertial frames with single-mode approximation is completely retrieved by an optimal strength of the partial measurement or the partial measurement reversal. In addition, we find that the optimal one-tangle with respect to inertial and noninertial observers turns out to be the same for an optimal strength of partial measurements at q₀=0 when two accelerated observers move with infinite acceleration.     

Gelatin/Montmorillonite and Gelatin/Polyvinyl Alcohol/Montmorillonite Bionanocomposite Hydrogels: Microstructural,Swelling and Drying Properties

Abstract

Gelatin/montmorillonite bionanocomposite hydrogels containing 0, 5 and 10?wt.% of montmorillonite were prepared via two different techniques, either a cooling or drying method. In addition, gelatin/polyvinyl alcohol/montmorillonite bionanocomposite hydrogels having gelatin/polyvinyl alcohol ratios of 1/1, 1/2 and 2/1, loaded with 0, 5 and 10?wt.% of montmorillonite, were prepared via a cyclic freezing-thawing technique. The microstructural properties of both types of the prepared bionanocomposite hydrogels were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The gel fraction, swelling behavior and drying kinetics of all prepared bionanocomposite hydrogels were also studied. The XRD and SEM results showed a porous structure with a possible exfoliated morphology for both types of the prepared bionanocomposite hydrogels. In addition, the gel fraction of the bionanocomposite hydrogels increased and a more entangled and crosslinked network with a decreased pore size was obtained by increasing the loading level of montmorillonite for both types of the bionanocomposite hydrogels. The swelling ratio and drying rate of both types of the bionanocomposite hydrogels could be increased by decreasing the PVA portion or MMT loading level, while the swelling and drying ability of the gelatin/montmorillonite bionanocomposite hydrogels prepared via the cooling method was higher than those of the corresponding samples prepared via the drying method.     

Natural frequencies of the elastically end restrained non-uniform Timoshenko beam using the power series method

In recent years, the transverse vibration of the uniform Timoshenko beam has become a highly significant research topic. The Timoshenko beam (TB) model is suitable for describing the behavior of the beams under high-frequency excitation load when the wavelength approaches the thickness of the beam because it considers the shear deformation and the rotational inertia effects. In this paper, the natural frequencies of the elastically end constrained nonuniform TB is discussed. For this reason, the nonuniform TB is modeled by an exact and direct modeling technique. The semi-analytical solution based on the power series method is adopted in technique. The effect of the spring supports, different boundary conditions, the non-uniformity in the cross-section of the TB, and other parameters are assessed. The results are shown that the nonuniformity in the cross-section of the beam is impressed on the natural frequencies. On the other hand, the presented formulation not only effectively is easy to use, but also provides the reasonable solution of non-uniform TB, carrying various boundary conditions.     

高频红外碳硫仪测定区域地球化学样品中的硫

高频红外碳硫仪由于便捷高效,常应用于区域地球化学样品中硫的分析检测。本文采用高频红外碳硫仪测定低中高含量的硫,以纯铁屑、锡粒和钨粒为助熔剂,对样品称样量、助熔剂的种类、加入顺序和用量等因素进行探讨,确定了最佳分析岩石、土壤和水系沉积物中硫含量的条件,并且用国家一级标准物质验证了该方法的准确度和精密度。结果表明,当样品和助熔剂的加入顺序和质量分别为：0.05 g样品、0.5 g铁助熔剂、1.7 g钨粒时,土壤和水系沉积物中硫的测定结果最稳定,岩石标准样品额外的加入0.5 g锡改善样品流动性,提高分析准确度。该方法的相对标准偏差（RSD）小于6%（n= 12）,相对误差绝对值小于8%。此方法具有操作简单、高效、稳定性好的特点,适合于大批量区域地球化学样品中硫的检测。     

Molecular Interaction Studies and Phytochemical Characterization of Mentha pulegium L. Constituents with Multiple Biological Utilities as Antioxidant,Antimicrobial, Anticancer and Anti-Hemolytic Agents

Multiple biological functions of Mentha pulegium extract were evaluated in the current work. Phytochemical components of the M. pulegium extract were detected by Gas Chromatography-Mass Spectrometry (GC-MS) and High-performance liquid chromatography (HPLC). Moreover, M. pulegium extract was estimated for antioxidant potential by 2,2-Diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical scavenging, antimicrobial activity by well diffusion, and anticoagulant activity via prothrombin time (PT) and activated partial thromboplastin time (APTT). GC-MS analysis detected compounds including cholesterol margarate, stigmast-5-en-3-ol, 19-nor-4-androstenediol, androstan-17-one, pulegone-1,2-epoxide, isochiapin B, dotriacontane, hexadecanoic acid and neophytadiene. Chrysoeriol (15.36 µg/mL) was followed by kaempferol (11.14 µg/mL) and 7-OH flavone (10.14 µg/mL), catechin (4.11 µg/mL), hisperdin (3.05 µg/mL), and luteolin (2.36 µg/mL) were detected by HPLC as flavonoids, in addition to ferulic (13.19 µg/mL), cinnamic (12.69 µg/mL), caffeic (11.45 µg/mL), pyrogallol (9.36 µg/mL), p-coumaric (5.06 µg/mL) and salicylic (4.17 µg/mL) as phenolics. Antioxidant activity was detected with IC₅₀ 18 µg/mL, hemolysis inhibition was recorded as 79.8% at 1000 μg/mL, and PT and APTT were at 21.5 s and 49.5 s, respectively, at 50 μg/mL of M. pulegium extract. The acute toxicity of M. pulegium extract was recorded against PC3 (IC₅₀ 97.99 µg/mL) and MCF7 (IC₅₀ 80.21 µg/mL). Antimicrobial activity of M. pulegium extract was documented against Bacillus subtilis, Escherichia coli, Pseudomonas aureus, Candida albicans, Pseudomonas aeruginosa, but not against black fungus Mucor circinelloides. Molecular docking was applied using MOE (Molecular Operating Environment) to explain the biological activity of neophytadiene, luteolin, chrysoeriol and kaempferol. These compounds could be suitable for the development of novel pharmacological agents for treatment of cancer and bacterial infections.     

Phenolic Constituents from Wendlandia tinctoria var. grandis (Roxb.) DC. Stem Deciphering Pharmacological Potentials against Oxidation,Hyperglycemia, and Diarrhea: Phyto-Pharmacological and Computational Approaches

Wendlandia tinctoria var. grandis (Roxb.) DC. (Family: Rubiaceae) is a semi-evergreen shrub distributed over tropical and subtropical Asia. The present research intended to explore the pharmacological potential of the stem extract of W. tinctoria, focusing on the antioxidant, hypoglycemic, and antidiarrheal properties, and to isolate various secondary metabolites as mediators of such activities. A total of eight phenolic compounds were isolated from the dichloromethane soluble fraction of the stem extract of this plant, which were characterized by electrospray ionization (ESI) mass spectrometric and ¹H NMR spectroscopic data as liquiritigenin (1), naringenin (2), apigenin (3), kaempferol (4), glabridin (5), ferulic acid (6), 4-hydroxybenzoic acid (7), and 4-hydroxybenzaldehyde (8). The dichloromethane soluble fraction exhibited the highest phenolic content (289.87 ± 0.47 mg of GAE/g of dried extract) and the highest scavenging activity (IC₅₀ = 18.83 ± 0.07 µg/mL) against the DPPH free radical. All of the isolated compounds, except 4-hydroxybenzaldehyde, exerted a higher antioxidant effect (IC₅₀ = 6.20 ± 0.10 to 16.11 ± 0.02 μg/mL) than the standard butylated hydroxytoluene (BHT) (IC₅₀ = 17.09 ± 0.01 μg/mL). Significant hypoglycemic and antidiarrheal activities of the methanolic crude extract at both doses (200 mg/kg bw and 400 mg/kg bw) were observed in a time-dependent manner. Furthermore, the computational modeling study supported the current in vitro and in vivo findings, and the isolated constituents had a higher or comparable binding affinity for glutathione reductase and urase oxidase enzymes, glucose transporter 3 (GLUT 3), and kappa-opioid receptor, inferring potential antioxidant, hypoglycemic, and antidiarrheal properties, respectively. This is the first report of all of these phenolic compounds being isolated from this plant species and even the first demonstration of the plant stem extract’s antioxidant, hypoglycemic, and antidiarrheal potentials. According to the current findings, the W. tinctoria stem could be a potential natural remedy for treating oxidative stress, hyperglycemia, and diarrhea. Nevertheless, further extensive investigation is crucial for thorough phytochemical screening and determining the precise mechanisms of action of the plant-derived bioactive metabolites against broad-spectrum molecular targets.