Validated spectrofluorimetric method for the determination of carbamazepine in pharmaceutical dosage forms after reaction with 4‐chloro‐7‐‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl)

A sensitive and simple spectrofluorimetric method has been developed and validated for the determination of the anti‐epileptic drug carbamazepine (CBZ) in its dosage forms. The method was based on a nucleophilic substitution reaction of CBZ with 4‐chloro‐7‐nitrobenzo‐2‐ oxa‐1,3‐diazole (NBD‐Cl) in borate buffer (pH 9) to form a highly fluorescent derivative that was measured at 530 nm after excitation at 460 nm. Factors affecting the formation of the reaction product were studied and optimized, and the reaction mechanism was postulated. The fluorescence–concentration plot is rectilinear over the range of 0.6–8 µg/mL with limit of detection of 0.06 µg/mL and limit of quantitation of 0.19 µg/mL. The method was applied to the analysis of commercial tablets and the results were in good agreement with those obtained using the reference method. Validation of the analytical procedures was evaluated according to ICH guidelines. Copyright © 2015 John Wiley & Sons, Ltd.     

Application of NMR spectroscopy for assignment of the absolute configuration of 8‐tert‐butyl‐2‐hydroxy‐7‐methoxy‐8‐methyl‐9‐oxa‐6‐azaspiro[4.5]dec‐6‐en‐10‐one

In order to assign the absolute configurations of 8‐tert‐butyl‐2‐hydroxy‐7‐methoxy‐8‐methyl‐9‐oxa‐6‐azaspiro[4.5]dec‐6‐en‐10‐one ( 2a , 2b ), their esters ( 5a , 5b , 5c , 5d ) with (R)‐ or (S)‐2‐methoxyphenylacetic acid ( 4a , 4b ) have been synthesized. The absolute configurations of these compounds have been determined on the basis of NOESY correlations between the protons of the tert‐butyl group and the cyclopentane fragment of the molecules. The crucial part of this analysis was assignment of the absolute configuration at C‐5. Additionally, by calculation of the chemical shift anisotropy, δ^RS, for the relevant protons, it was also possible to confirm the absolute configurations at the C‐2 centres of compounds 2a , 2b and 5a , 5b , 5c , 5d . Chirality, 25:422–426, 2013.© 2013 Wiley Periodicals, Inc.     

Enantiopure 4‐oxazolin‐2‐ones and 4‐methylene‐2‐oxazolidinones as chiral building blocks in a divergent asymmetric synthesis of heterocycles

Enantiopure 3‐((R)‐ and 3‐((S)‐1‐phenylethyl)‐4‐oxazoline‐2‐ones were evaluated as chiral building blocks for the divergent construction of heterocycles with stereogenic quaternary centers. The N‐(R)‐ or N‐(S)‐1‐phenylethyl group of these compounds proved to be an efficient chiral auxiliary for the asymmetric induction of the 4‐ and 5‐positions of the 4‐oxazolin‐2‐one ring through thermal and MW‐promoted nucleophilic conjugated addition to Michael acceptors and alkyl halides. The resulting adducts were transformed via a cascade process into fused six‐membered carbo‐ and heterocycles. The structure of the reaction products depended on the electrophiles and reaction conditions used. Alternative isomeric 4‐methylene‐2‐oxazolidinones served as chiral precursors for a versatile and divergent approach to highly substituted cyclic carbamates. DFT quantum calculations showed that the formation of bicyclic pyranyl compounds was generated by a diastereoselective concerted hetero‐Diels‐Alder cycloaddition.     

HS‐SPME‐GC‐FID method for detection and quantification of Bacillus cereus ATCC 10702 mediated 2‐acetyl‐1‐pyrroline

A rapid micro‐scale solid‐phase micro‐extraction (SPME) procedure coupled with gas‐chromatography with flame ionized detector (GC‐FID) was used to extract parts per billion levels of a principle basmati aroma compound “2‐acetyl‐1‐pyrroline” (2‐AP) from bacterial samples. In present investigation, optimization parameters of bacterial incubation period, sample weight, pre‐incubation time, adsorption time, and temperature, precursors and their concentrations has been studied. In the optimized conditions, detection of 2‐AP produced by Bacillus cereus ATCC10702 using only 0.5 g of sample volume was 85 μg/kg. Along with 2‐AP, 15 other compounds produced by B. cereus were also reported out of which 14 were reported for the first time consisting mainly of (E)?2‐hexenal, pentadecanal, 4‐hydroxy‐2‐butanone, n‐hexanal, 2–6‐nonadienal, 3‐methoxy‐2(5H) furanone and 2‐acetyl‐1‐pyridine and octanal. High recovery of 2‐AP (87 %) from very less amount of B. cereus samples was observed. The method is reproducible fast and can be used for detection of 2‐AP production by B. cereus. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1356–1363, 2014     

All‐Manganese‐Based Binder‐Free Stretchable Lithium‐Ion Batteries

Advanced electrode materials with bendability and stretchability are critical for the rapid development of fully flexible/stretchable lithium‐ion batteries. However, the sufficiently stretchable lithium‐ion battery is still underdeveloped that is one of the biggest challenges preventing from realizing fully deformable power sources. Here, a low‐temperature hydrothermal synthesis of a cathode material for stretchable lithium‐ion battery is reported by the in situ growth of LiMn₂O₄ (LMO) nanocrystals inside 3D carbon nanotube (CNT) film networks. The LMO/CNT film composite has demonstrated the chemical bonding between the LMO active materials and CNT scaffolds, which is the most important characteristic of the stretchable electrodes. When coupled with a wrinkled MnO_x /CNT film anode, a binder‐free, all‐manganese‐based stretchable full battery cell is assembled which delivers a high average specific capacity of ≈97 mA h g^?1 and stabilizes after over 300 cycles with an enormous strain of 100%. Furthermore, combining with other merits such as low cost, natural abundance, and environmentally friendly, the all‐manganese design is expected to accelerate the practical applications of stretchable lithium‐ion batteries for fully flexible and biomedical electronics.     

Enantioselective resolution of 4‐chloromandelic acid by liquid–liquid extraction using 2‐chloro‐N‐carbobenzyloxy‐L‐amino acid

A liquid–liquid extraction resolution of 4‐chloro‐mandelic acid (4‐ClMA) was studied by using 2‐chloro‐N‐carbobenzyloxy‐L‐amino acid (2‐Cl‐Z‐AA) as a chiral extractant. Important factors affecting the extraction efficiency were investigated, including the type of chiral extractant, pH value of aqueous phase, initial concentration of chiral extractant in organic phase, initial concentration of 4‐ClMA in aqueous phase, and resolution temperature. It was observed that the concentration of (R)‐4‐ClMA was much higher than that of (S)‐4‐ClMA in organic phase due to a higher stability of the complex formed between (R)‐4‐ClMA and 2‐Cl‐Z‐AA. A separation factor (α) of 3.05 was obtained at 0.02 mol/L 2‐Cl‐Z‐Valine dissolved in dichloromethane, pH of 2.0, concentration of 4‐ClMA of 0.11 mmol/Land T of 296.7K.     

Bio‐Nanotechnology in High‐Performance Supercapacitors

The use of bio‐nanotechnology for the fabrication of diverse functional nanomaterials with precisely controlled morphologies and microstructures is attracting considerable attention due to its sustainability and renewability. As one of the key energy storage devices, supercapacitor (SC) requires the active electrode material to have high specific surface area, interconnected porous structure, excellent electronic conductivity, and appropriate heteroatom doping for promoting the transfer of electrons and electrolyte ions. The combination of bio‐technology and SC will open up a new avenue for the large‐scale fabrication of high performance functional energy storage devices. In this review, the most state‐of‐the‐art research progress in bio‐nanotechnological fabrication of different nanomaterials, including carbon materials, metal oxides, conducting polymers, and their corresponding composites are reviewed with the following three bio‐nanotechnical approaches covered: (1) biomass carbonization technologies; (2) bio‐template methods; and (3) bio‐complex technologies, while also highlighting their applications as functional SC electrodes.     

Roles of mouse sperm‐associated alpha‐L‐fucosidases in fertilization

Sperm‐associated α‐L ‐fucosidases have been implicated in fertilization in many species. Previously, we documented the existence of α‐L ‐fucosidase in mouse cauda epididymal contents, and showed that sperm‐associated α‐L ‐fucosidase is cryptically stored within the acrosome and reappears within the sperm equatorial segment after the acrosome reaction. The enrichment of sperm membrane‐associated α‐L ‐fucosidase within the equatorial segment of acrosome‐reacted cells implicates its roles during fertilization. Here, we document the absence of α‐L ‐fucosidase in mouse oocytes and early embryos, and define roles of sperm associated α‐L ‐fucosidase in fertilization using specific inhibitors and competitors. Mouse sperm were pretreated with deoxyfuconojirimycin (DFJ, an inhibitor of α‐L ‐fucosidase) or with anti‐fucosidase antibody; alternatively, mouse oocytes were pretreated with purified human liver α‐L ‐fucosidase. Five‐millimolar DFJ did not inhibit sperm–zona pellucida (ZP) binding, membrane binding, or fusion and penetration, but anti‐fucosidase antibody and purified human liver α‐L ‐fucosidase significantly decreased the frequency of these events. To evaluate sperm‐associated α‐L ‐fucosidase enzyme activity in post‐fusion events, DFJ‐pretreated sperm were microinjected into oocytes, and 2‐pronuclear (2‐PN) embryos were treated with 5 mM DFJ with no significant effects, suggesting that α‐L ‐fucosidase enzyme activity does not play a role in post‐fusion events and/or early embryo development in mice. The recognition and binding of mouse sperm to the ZP and oolemma involves the glycoprotein structure of α‐L ‐fucosidase, but not its catalytic action. These observations suggest that deficits in fucosidase protein and/or the presence of anti‐fucosidase antibody may be responsible for some types of infertility. Mol. Reprod. Dev. 80: 273–285, 2013. © 2013 Wiley Periodicals, Inc.     

1,3,5‐Trihydroxy‐13,13‐dimethyl‐2H‐pyran [7,6‐b] xanthone directly targets heat shock protein 27 in hepatocellular carcinoma

We previously showed that the small molecule 1,3,5‐trihydroxy‐13,13‐dimethyl‐2H‐pyran [7,6‐b] xanthone (TDP) induces apoptosis in hepatocellular carcinoma (HCC) by suppressing Hsp27 expression, although the mechanism is not fully understood. To investigate the functional association between TDP and Hsp27 protein in HCC, recombinant Hsp27 protein was incubated with TDP at room temperature, and assayed by mass spectrum (MS) and natural electrophoresis. TDP effectively stimulated Hsp27 to form aggregates ex vitro, leading to suppression of its chaperone activity. The aggregates were degraded by the ubiquitin–proteasome (UPS) pathway. TDP directly interacted with Asp17 and Phe55 in chain C of Hsp27 on the basis of bioinformatic prediction. In conclusion, Hsp27 is a direct target of TDP in its anti‐cancer activity, which provides strong support for a clinical application.

     

High‐Performance Liquid Chromatographic Enantioseparation of Unusual Isoxazoline‐Fused 2‐Aminocyclopentanecarboxylic Acids on (+)‐(18‐Crown‐6)‐2,3,11,12‐Tetracarboxylic Acid‐Based Chiral Stationary Phases

The enantiomers of four unusual isoxazoline‐fused 2‐aminocyclopentanecarboxylic acids were directly separated on chiral stationary phases containing (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid as chiral selector. The nature of the alcoholic modifier (MeOH, EtOH, IPA) exerted a great effect on the retention, whereas the selectivity and resolution did not change substantially. Two types of dependence of retention on alcohol content were detected: k₁ increased continuously with increasing alcohol content or a U‐shaped retention curve was observed. A comparison of the chromatographic data obtained with HCOOH, AcOH, TFA, HClO₄, H₂SO₄, or H₃PO₄ as acidic modifier at a constant concentration demonstrated that in most cases, larger k values were obtained on the application of AcOH or HCOOH, and an increase of the acid content resulted in a decrease of retention. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes and selector. The sequence of elution of the enantiomers was determined in all cases. Chirality 24:817‐824, 2012. © 2012 Wiley Periodicals, Inc.     

Synthesis and Olfactory Characterization of Silicon‐Containing Derivatives of the Acyclic Lily‐of‐the‐Valley Odorant 5,7,7‐Trimethyl‐4‐methylideneoctanal

5‐Methyl‐4‐methylidene‐6‐(trimethylsilyl)hexanal ( 1b ), a sila analog of the acyclic lily‐of‐the‐valley odorant 5,7,7‐trimethyl‐4‐methylideneoctanal ( 1a ), and the Si‐containing derivatives 2 – 6 were prepared in multistep syntheses, starting from Cl₃SiH and Cl₂SiMe₂, respectively. Compounds 1b, 2 – 6 , and their new precursors were characterized by elemental analyses (C, H, N) and NMR spectroscopic studies (¹H, ¹³C, ¹⁵N, and ²⁹Si). To gain more information about the structure? odor correlation in the family of lily‐of‐the‐valley or ‘muguet’ odorants, C/Si analogs 1a / 1b and derivatives 2 – 6 were evaluated for their olfactory properties.     

Asymmetrically simultaneous synthesis of L‐homophenylalanine and N6‐protected‐2‐oxo‐6‐amino‐hexanoic acid by engineered Escherichia coli aspartate aminotransferase

L ‐Homophenylalanine (L ‐HPA) and N⁶‐protected‐2‐oxo‐6‐amino‐hexanoic acid (N⁶‐protected‐OAHA) can be used as building blocks for the manufacture of angiotensin‐converting enzyme inhibitors. To synthesize L ‐HPA and N⁶‐protected‐OAHA simultaneously from 2‐oxo‐4‐phenylbutanoic acid (OPBA) and N⁶‐protected‐L ‐lysine, several variants of Escherichia coli aspartate aminotransferase (AAT) were developed by site‐directed mutagenesis and their catalytic activities were investigated. Three kinds of N⁶‐protected‐L ‐lysine were tested as potential amino donors for the bioconversion process. AAT variants of R292E/L18H and R292E/L18T exhibited specific activities of 0.70±0.01 U/mg protein and 0.67±0.02 U/mg protein to 2‐amino‐6‐tert‐butoxycarbonylamino‐hexanoic acid (BOC‐lysine) and 2‐amino‐6‐(2,2,2‐trifluoro‐acetylamino)‐hexanoic acid, respectively. E. coli cells expressing R292E/L18H variant were able to convert OPBA and BOC‐lysine to L ‐HPA and 2‐oxo‐6‐tert‐butoxycarbonylamino‐hexanoic acid (BOC‐OAHA) with 96.2% yield in 8 h. This is the first report demonstrating a process for the simultaneous production of two useful building blocks, L ‐HPA and BOC‐OAHA. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Epigallocatechin‐3‐O‐gallate up‐regulates microRNA‐199a‐3p expression by down‐regulating the expression of cyclooxygenase‐2 in stimulated human osteoarthritis chondrocytes

Osteoarthritis (OA) is a most common form of arthritis worldwide leading to significant disability. MicroRNAs (miRNAs) are non‐coding RNAs involved in various aspects of cartilage development, homoeostasis and pathology. Several miRNAs have been identified which have shown to regulate expression of target genes relevant to OA pathogenesis such as matrix metalloproteinase (MMP)‐13, cyclooxygenase (COX)‐2, etc. Epigallocatechin‐3‐O‐gallate (EGCG), the most abundant and active polyphenol in green tea, has been reported to have anti‐arthritic effects, however, the role of EGCG in the regulation of miRNAs has not been investigated in OA. Here, we showed that EGCG inhibits COX‐2 mRNA/protein expression or prostaglandin E₂ (PGE₂) production via up‐regulating microRNA hsa‐miR‐199a‐3p expression in interleukin (IL)‐1β‐stimulated human OA chondrocytes. This negative co‐regulation of hsa‐miR‐199a‐3p and COX‐2 by EGCG was confirmed by transfection of OA chondrocytes with anti‐miR‐199a‐3p. Transfection of OA chondrocytes with anti‐miR‐199a‐3p significantly enhanced COX‐2 expression and PGE₂ production (P < 0.001), while EGCG treatment significantly inhibited anti‐miR‐199a‐3p transfection‐induced COX‐2 expression or PGE₂ production in a dose‐dependent manner. These results were further re‐validated by co‐treatment of these transfection OA chondrocytes with IL‐1β and EGCG. EGCG treatment consistently up‐regulated the IL‐1β‐decreased hsa‐miR‐199a‐3p expression (P < 0.05) and significantly inhibited the IL‐1β‐induced COX‐2 expression/PGE₂ production (P < 0.05) in OA chondrocytes transfected with anti‐hsa‐miR‐199a‐3p. Taken together, these results clearly indicate that EGCG inhibits COX‐2 expression/PGE₂ production via up‐regulation of hsa‐miR‐199a‐3p expression. These novel pharmacological actions of EGCG on IL‐1β‐stimulated human OA chondrocytes provide new suggestions that EGCG or EGCG‐derived compounds inhibit cartilage breakdown or pain by up‐regulating the expression of microRNAs in human chondrocytes.     

The special optical properties and application of the heterocyclic compound diethyl 6‐anilino‐5H‐2,3‐dithia‐5,7‐diazacyclopenta(cd)indene‐1,4‐dicarboxylate

The heterocyclic compound diethyl 6‐anilino‐5H‐2,3‐dithia‐5,7‐diazacyclopenta(cd)indene‐1,4‐dicarboxylate (D1) was found to form highly emissive aggregates in polar solvents, and the aggregate emission can be tuned by the simple addition of water to a dimethylsulfoxide solution. A theoretical study based on Density functional theory (DFT) calculations, shows that intermolecular interactions of D1 with solvent may be potential factors in the fluorescence change. In addition, the phenyl ring in D1 plays an important role because of its response to solvent. In the non‐aggregated state, deprotonation of the N–H of D1 can proceed easily on the addition of base, and the deprotonated compound might interact with Ag⁺, resulting in a significant change in color and fluorescence quenching, which make it a potential chemosensor for the selective detection of trace amounts of Ag⁺. Copyright © 2013 John Wiley & Sons, Ltd.