Determination of Sumatriptan and Zolmitriptan in Presence of Their Corresponding Degradation Products by HPTLC Methods

Accurate, sensitive, and precise high performance thin layer chromatographic (HPTLC) methods were developed and validated for the determination of sumatriptan and zolmitriptan in presence of their degradation products. Sumatriptan was separated from its degradation products and analyzed on TLC silica gel 60 F₂₅₄ plates using chloroform–ethyl acetate–methanol–ammonia (4:3:3:0.1, v/v) as a developing system followed by densitometric measurement of the bands at 228 nm. Zolmitriptan was determined using chloroform–ethyl acetate–methanol–ammonia (3:3:3:1, v/v) as a developing system followed by densitometric measurement at 222 nm. The methods were validated over a range of 0.5–4 μg/spot for sumatriptan and 0.5–3 μg/spot for zolmitriptan. The proposed methods were successfully applied for the determination of the studied drugs in bulk powder and in their pharmaceutical formulations.     

The Radical Cationic Repair Pathway of Cyclobutane Pyrimidine Dimer: The Effect of Sugar‐Phosphate Backbone

Radical cationic repair process of cis–syn thymine dimer has been investigated when (1) sugar‐phosphate backbones were substituted by hydrogen atoms, (2) phosphate group was substituted by two hydrogen atoms each on a sugar ring and (3) sugar‐phosphate backbone was taken into account. The effect of the interactions between N1 and N1′ lone pairs and the C6‐C6′ antibonding orbital are the most important evidences for the cleavage of the C6‐C6′ bond in the first step of radical cationic repair mechanism in the absence of the sugar‐phosphate backbone. The impact of the N1 and N1′ lone pairs on the C6‐C6′ bond cleavage decreases and the energy barrier of the cleavage of that bond significantly increases in the presence of the deoxynucleoside sugars and the sugar‐phosphate backbone.     

Preparation, nano purification, quality control and labeling optimization of [64Cu]-5,10,15,20-tetrakis (penta fluoro phenyl) porphyrin complex as a possible imaging agent

Cu-64 was produced via the ⁶⁸Zn (p,αn)⁶⁴Cu nuclear reaction (≈200 mCi, >95 % chemical yield at 180 μA for 1.1 h irradiation, (radionuclidic purity >96 %, copper-67 as impurity) followed by purification with amino functionalized nano magnetic oxide, Fe₃O₄ aiming to remove trace amount of heavy metal ions from aqueous media due to achieve ultra pure [⁶⁴Cu] CuCl₂ for labeling step. [⁶⁴Cu] labeled 5,10,15,20-tetrakis(penta fluoro phenyl) porphyrin ([⁶⁴Cu]-TFPP) was prepared using freshly prepared [⁶⁴Cu] CuCl₂ (Cu-64; T _1/2 = 12.7 h) and 5,10,15,20-tetrakis(penta fluoro phenyl)porphyrin (H₂TFPP) for 60 min at 100 °C under reflux condition (radiochemical purity: >97 % ITLC, >98 % HPLC, specific activity: 14–16 GBq/mmol). Stability of the complex was checked in final formulation and human serum for 24 h. The partition coefficient was calculated for the compound (log P = 0.73). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and PET imaging up in 2 and 4 h after injection. A detailed comparative pharmacokinetic study performed for ⁶⁴Cu cation and [⁶⁴Cu]-TFPP. The complex is mostly washed out from the circulation through kidneys and liver and can be an interesting tumor imaging/targeting agent due to high specific uptake and rapid excretion through the urinary tract.     

In Silico and Experimental Characterization of Chimeric Bacillus thermocatenulatus Lipase with the Complete Conserved Pentapeptide of Candida rugosa Lipase

Lipases are one of the highest value commercial enzymes as they have broad applications in detergent, food, pharmaceutical, and dairy industries. To provide chimeric Bacillus thermocatenulatus lipase (BTL2), the completely conserved pentapeptide (¹¹²Ala-His-Ser-Gln-Gly¹¹⁶) was replaced with similar sequences (²⁰⁷Gly-Glu-Ser-Ala-Gly²¹¹) of Candida rugosa lipase (CLR) at the nucleophilic elbow region. For this purpose, three mutations including A112G, H113E, and Q115A were inserted in the conserved pentapeptide sequence of btl2 gene. Based on the crystal structures of 2W22, the best structure of opened form of the chimeric lipases were garnered using the MODELLER v9.10 software. The native and chimeric lipases were docked to a set of ligands, and a trial version of Molegro Virtual Docker (MVD) software was used to obtain the energy values. Docking results confirmed chimeric lipase to be better than the native lipase. Following the in silico study, cloning experiments were conducted and expression of native and chimeric btl2 gene in Pichia pastoris was performed. The native and chimeric lipases were purified, and the effect of these mutations on characteristics of chimeric lipase studied and then compared with those of native lipase. Chimeric lipase exhibited 1.6-fold higher activity than the native lipase at 55 °C. The highest percentage of both lipases activity was observed at 60 °C and pH of 8.0. The ion Ca²⁺ slightly inhibited the activity of both lipases, whereas the organic solvent enhanced the lipase stability of chimeric lipase as compared with the native lipase. According to the results, the presence of two glycine residues at the conserved pentapeptide region of this chimeric lipase (¹¹² Gly-Glu-Ser-Ala-Gly ¹¹⁶) may increase the flexibility of the nucleophilic elbow region and affect the enzyme activity level.     

Chemically bonded multiwalled carbon nanotubes as efficient material for solid phase extraction of some metal ions in food samples

Multiwalled carbon nanotubes chemically functionalized with 2-((3-silylpropylimino) methyl) phenol (SPIMP-MWCNT) and successfully applied for the solid phase extraction (SPE) of some metal ions in food samples. The influences of the analytical parameters including pH, amounts of solid phase, eluent conditions (type, volume and concentrations), sample volume and interference of some metal ions on the recoveries of ions Cu²⁺, Pb²⁺, Fe²⁺, Ni²⁺ and Zn²⁺ ion were investigated. The metal ions retained on SPIMP-MWCNT was eluted using 6?mL of 4?mol?L^?1 HNO₃ solution and their content was determined by flame atomic absorption spectrometry (FAAS) with recoveries more than 95% and relative standard deviations (n?=?5) between 2.4–3.4% for both reproducibility and repeatability. The detection limit of this metal ions was between 1.0–2.6?ng?mL^?1 (3S _b , n?=?10) and their preconcentration factor was 100, while their loading capacity was above 32.9?mg?g^?1 of SPIMP-MWCNT. The proposed method was successfully applied for the preconcentration and determination of analytes in different samples.     

氨三乙酸、缬氨酸、亮氨酸的三元过渡金属配合物：合成和生物学应用

以氨三乙酸HNTA2-为主要配体,缬氨酸(valine)或亮氨酸(leucine)为次要配体在微酸性介质中合成了Ni(Ⅱ),Cu(Ⅱ),and Zn(Ⅱ)的三元配合物。用元素分析、热分析、FTIR,UV-Vis分光光度法,磁性测量和质谱法表征了合成的三元配合物。结果表明,三元配合物可在金属(M):氨三乙酸(HNTA)∶缬氨酸(valine)或亮氨酸(leucine)=1∶1∶1时制得,其分子结构为[M(HNTA)(valine)(H2O)2].1.5H2O and[M(HNTA)(leucine)(H2O)2].1.5H2O(其中M=Ni(Ⅱ)or Cu(Ⅱ))和H2[Zn(NTA)(valine)(H2O)]H2O。标题三元过渡金属配合物为八面体对称构型。同时研究了该三元配合物对大肠杆菌,金黄色葡萄球菌,白色念珠菌,黄曲霉菌(菌株从开罗大学理学院微分析中心获得)的抗菌活性。根据推荐的知名方法用标准的抗菌和抗真菌剂进行体外测试(in vitro)以评估我们的新制备的配合物对细菌和真菌物种的生长抑制活性。     

Novel modified carbon nanotubes as a selective sorbent for preconcentration and determination of trace copper ions in fruit samples

In this work, multiwalled carbon nanotubes were reacted with N‐[3‐(triet‐hoxysilyl)propyl]isonicotinamide to prepare pyridine‐functionalized carbon nanotubes. This novel sorbent was characterized by infrared spectroscopy, thermal and elemental analysis, and scanning electron microscopy. Functionalized carbon nanotubes were applied for the preconcentration and determination of copper ions using flame atomic absorption spectrometry. Various parameters such as sample pH, flow rate, eluent type and concentration, and its volume were optimized. Under optimal experimental conditions, the limit of detection, the relative standard deviation, and the recovery of the method were 0.65 ng/mL, 3.2% and 99.4%, respectively. After validating the method using standard reference materials, the new sorbent was applied for the extraction and determination of trace copper(II) ions in fruit samples.     

Applications of intelligent methods in various types of heat exchangers: a review

Journal of Thermal Analysis and Calorimetry - Heat exchangers are applicable in different industries and technologies, and their performance is influenced by different parameters. In addition to...     

A comparative study of the adsorption equilibrium of progesterone by a carbon black and a commercial activated carbon

In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon black and a commercial activated carbon has been studied. The corresponding equilibrium isotherms have been analyzed according to a previously proposed model which establishes a kinetic law satisfactorily fitting the C versus t isotherms. The analysis of the experimental data points out the existence of two well-defined sections in the equilibrium isotherms. A general equation including these two processes has been proposed, the global adsorption process being fitted to such equation. From the values of the kinetic equilibrium constant so obtained, values of standard average adsorption enthalpy () and entropy () have been calculated. Finally, information related to variations of differential adsorption enthalpy () and entropy () with the surface coverage fraction (θ) was obtained by using the corresponding Clausius-Clapeyron equations.     

Synthesis and antiviral screening of 2-(propylthio)-7-substituted-thiazolo[5,4-d]pyrimidines as anti-bovine viral diarrhea virus agents

7-Chloro-2-(propylthio)thiazolo[5,4-d]pyrimidine 4 was prepared and used as a precursor for synthesizing new derivatives of thiazolo[5,4-d]pyrimidine through the nucleophilic displacement of the chlorine atom by different types of amino derivatives. Reaction of compound 4 with primary and secondary amines produced the corresponding substituted amino derivatives. Reaction of 4 with hydrazine hydrate then followed by condensation with aromatic aldehydes afforded hydrazone derivatives. Reaction of 4 with hydrazine hydrate then followed by reaction with isothiocyanates gave the disubstituted thiosemicarbazides. Finally, treatment of 4 with hydrazine derivatives afforded the novel disubstituted hydrazine derivatives. Preliminary antiviral screening on the bovine viral diarrhea virus (BVDV) was carried out, which was classified as a member of the same family of Hepatitis C virus. The results indicated that some of the tested compounds exhibited anti-BVDV activity which may be suitable for a new lead molecule to design more potent anti-BVDV agents.