Extraction of methyl xanthines and their UHPLC–DAD determination in consumable beverages used in Eastern province of Saudi Arabia

Coffee and tea are the most widely consumed beverages worldwide. However, the consumer may be unaware of the exact amount of methyl xanthine (MX, i.e. caffeine [C], theobromine [TB] and theophylline [TH]) consumed, as most of the products do not list the proper amounts. This may lead to serious risks including cardiovascular, kidney and stimulant effects. The aim of the study was to determine the MX amount in ready-to-use beverages (coffee and tea) collected from various outlets in the city of Al-Khobar, Saudi Arabia. Forty different samples of espresso, black coffee and red tea were collected. A fast, reliable and efficient UHPLC–DAD method was developed and validated for MX determination. Total lipids were extracted and fractionated in order to determine glycolipids, phospholipids and neutral lipids. The r² value for the method was 0.980–0.988 in a linearity range of 0.5–200 ppm. The range for MX (C [0.02–2.39 mg/ml], TB [0.00–0.10 mg/ml] and TH [0.00–0.004 mg/ml]) and total lipids was 1–5 g. The amount of glycolipids (3.1 g) was higher among the lipid fractions followed by phospholipids (1.8 g) and neutral lipids (0.25 g). In general, espresso beverages (20–30 ml) contained high amounts of MX whereas black coffee beverages contained high amount of lipids. Most of the beverages expressed C, TB, TH, lipids or their fractions; however, the product with high amounts of MX and lipids at the same time was espresso (brands Chemistry and Wogard). Although the MX and lipid levels in these beverages well below the allowed limits, care must still be taken, especially when using the beverages with high serving volumes (200–250 ml) or coffee prepared via the filter method i.e. black coffee, using a high temperature for a longer time.     

Purcell Effect and Nonlinear Behavior of the Emission in a Periodic Structure Composed of InAs Monolayers Embedded in a GaAs Matrix

Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time‐resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super‐radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near‐quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non‐monotonic dependence of intensity on direction, with a maximum observed at approximately 40°. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures.     

HPLC with fluorescence detection assay of perampanel,a novel AMPA receptor antagonist,in human plasma for clinical pharmacokinetic studies

Perampanel (Fycompa®), a novel α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor antagonist, is registered for the adjunctive treatment of patients (aged ≥12 years) with refractory partial‐onset seizures. To support therapeutic drug monitoring, a simple high‐performance liquid chromatography (HPLC) assay with fluorescence detection was developed to determine perampanel concentrations in human plasma and validated to support clinical trials. Human plasma samples (1.0 mL) were processed by liquid extraction using diethyl ether, followed by chromatographic separation on a YMC Pack Pro C₁₈ column (150 × 4.6 mm i.d., 5 µm) with isocratic elution of acetonitrile–water–acetic acid–sodium acetate (840:560:3:1.8, v/v/v/w) at a flow rate of 1.0 mL/min. Column eluent was monitored at excitation and emission wavelengths of 290 and 430 nm, respectively. The assay was linear (range 1.0–500 ng/mL) and this could be extended to 25 µg/mL by 50‐fold dilution integrity. No endogenous peaks were detected in the elution of analytes in drug‐free blank human plasma from six individuals and no interference was observed with co‐medications tested. Intra‐ and inter‐batch reproducibility studies demonstrated accuracy and precision within the acceptance criteria of bioanalytical guidelines. Validation data demonstrated that our assay is simple, selective, reproducible and suitable for therapeutic drug monitoring of perampanel. Copyright © 2015 John Wiley & Sons, Ltd.     

Beyond Stereoselectivity,Switchable Catalysis: Some of the Last Frontier Challenges in Ring‐Opening Polymerization of Cyclic Esters

Metal‐based catalysts and initiators have played a pivotal role in the ring‐opening polymerization (ROP) of cyclic esters, thanks to their high activity and remarkable ability to control precisely the architectures of the resulting polyesters in terms of molar mass, dispersity, microstructure, or tacticity. Today, after two decades of extensive research, the field is slowly reaching maturity. However, several challenges remain, while original concepts have emerged around new types or new applications of catalysis. This Review is not intended to comprehensively cover all of these aspects. Rather, it provides a personal overview of the very recent progress achieved in some selected, important aspects of ROP catalysis—stereocontrol and switchable catalysis. Hence, the first part addresses the development of new metal‐based catalysts for the isoselective ROP of racemic lactide towards stereoblock copolymers, and the use of syndioselective ROP metal catalysts to control the monomer sequence in copolymers. A second part covers the development of ROP catalysts—primarily metal‐based catalysts, but also organocatalysts—that can be externally regulated by the use of chemical or photo stimuli to switch them between two states with different catalytic abilities. Current challenges and opportunities are highlighted.     

Development of an LC‐MS/MS method for determining the pharmacokinetics of clonidine following oral administration of Zhenju antihypertensive compound

Zhenju antihypertensive compound (ZJAHC) is a combined Chinese–Western medicine formula including clonidine (CLO), hydrochlorothiazide (HCT), rutin, Chrysanthemum indicum extract and pearl powder. Compared with CLO preparations, ZJAHC shows improved activities and decreased adverse effects. It is believed that the side effects of CLO are caused by its high peak plasma concentration. Hence, study of the influence of ZJAHC on the pharmacokinetic behaviors of clonidine seems essential. In present study, the plasma concentrations of CLO were determined with a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method. The MS/MS transitions monitored for clonidine and internal standard were 230.2 → 213.1 and 152.2 → 110.2, respectively. The analyte was quantified in a single run within 3 min. The pharmacokinetic study showed that the area under the plasma concentration–time curve of CLO in ZJAHC (60 µg/kg CLO) was similar to that of CLO‐HCT‐high (120 µg/kg CLO) but the peak concentration was much lower than that in CLO‐HCT‐high. ZJAHC could enhance the bioavailability without greatly increasing peak concentration of clonidine. This comprehensive effect of enhancing the bioavailability and avoiding the high peak plasma concentration for CLO might mainly result from the co‐contribution of Western medicine and traditional Chinese medicine (TCM), while the effect of TCM was stronger than that of Western medicine. Copyright © 2014 John Wiley & Sons, Ltd.     

Fused vs. spiro: Kinetic,not thermodynamic preference may direct the reaction of α-carbonyl oxonium ylides

Rh(II)-catalyzed decomposition of certain cyclic α-diazocarbonyl compounds in the presence of cyclic ethers has been shown to give bicyclic ring expansion products. These are thought to arise from a [1,4]-alkyl shift toward the carbonyl oxygen atom and are in contrast with the recently observed spirocyclic products of a Stevens-type [1,2]-alkyl shift within the postulated oxonium ylide intermediate. Quantum chemical calculations performed at the B3LYP/6-31G* level of theory showed that the former reaction pathway (toward fused bicycles) is kinetically preferred.     

Studies on metabolism of total glucosides of paeony from Paeoniae Radix Alba in rats by UPLC‐Q‐TOF‐MS/MS

Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd.     

Facile non‐lithographic route to highly aligned silica nanopatterns using unidirectionally aligned polystyrene‐block‐polydimethylsiloxane films

Thin films (monolayer and bilayer) of cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self‐assembly were exposed to ultraviolet‐ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center‐to‐center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear‐alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1058–1064