Complexation and Fluorescence of Tricyclic Basic Dyes Encapsulated in Cucurbiturils

Tricyclic basic dyes (proflavine, acridine orange, pyronine, pyronine Y, oxonine, thionine and methylene blue) often form one‐to‐one or two‐to‐one complexes with CB[7] and CB[8], respectively. In the case of pyronine Y, the complexes with CB[7] and CB[8] have a one‐to‐one and three‐to‐one stoichiometry, respectively. The binding constants for CB[7] complexes range from 3.07×10⁶ to 1.70×10⁷ m ^?1. In the case of CB[8], the association constant varies between 3.24×10¹³ and 2.50×10¹⁶ m ^?2. Overall, these binding constants are four orders of magnitude higher than those reported for the same dyes in β and γ‐cyclodextrins. Formation of the host–guest complexes leads to an increase in the fluorescence quantum yields in the case of CB[7], while the dimeric or trimeric dye encapsulated in CB[8] are remarkably less fluorescent than the same dye in diluted solutions.     

Adsorption of 1,3‐Benzenedithiol and 1,3‐Benzenedimethanethiol on Gold Surfaces

The adsorption characteristics of 1,3‐benzenedithiol (1,3‐BDT) and 1,3‐benzenedimethanethiol (1,3‐BDMT) on Au surfaces are investigated by means of surface‐enhanced Raman scattering, UV/Vis absorption spectroscopy, and cyclic voltammetry (CV). 1,3‐BDMT is found to adsorb via two S–Au linkages at concentrations below monolayer coverage, but to have an upright geometry as the concentration increases on Au nanoparticles. On the other hand, 1,3‐BDT is found to adsorb by forming two S–Au linkages, regardless of concentration, based on the disappearance of the ν(SH)_free stretching band. Because of the absence of the methylene unit, 1,3‐BDT appeares not to self‐assemble efficiently on Au surfaces. The UV/Vis absorption spectroscopy and CV techniques are also applied to check the formation of self‐assembled monolayers of 1,3‐BDT and 1,3‐BDMT on Au. Density functional theory calculations based on a simple adsorption model using an Au₈ cluster are performed to better understand the nature of the adsorption characteristics of 1,3‐BDT and 1,3‐BDMT on Au surfaces.     

Electrocatalytic Oxidation of Glucose at Carbon Nanotubes Supported PtRu Nanoparticles and Its Detection

PtRu nanoparticles were supported on multiwall carbon nanotubes (MWNTs), which were further fabricated as an electrode for nonenzymatic glucose sensing. Transmission electron microscope and X‐ray diffraction patterns were used for characterization of the PtRu nanoparticles on MWNTs. Cyclic voltammetry and chronopotentiometry were applied to investigate the performance of the PtRu/MWNTs nanocomposite electrode for nonenzymatic oxidation of glucose. The PtRu/MWNTs electrode shows high electrocatalytic activity towards the oxidation of glucose in 0.1 M NaOH solution and thus can be used to selectively detect glucose. Under the optimal potential (+0.55 V vs. Ag/AgCl), the biosensor effectively performs a selective electrochemical analysis of glucose in the presence of common interferents, such as ascorbic acid (AA), dopamine (DP) and uric acid (UA). Wide linear calibration ranging from 1 mM to 15 mM, high sensitivity of 28.26 μA cm^?2 mM^?1, low detection limit of 2.5×10^?5 M, and fast response time of 10 s were achieved for the detection of glucose at the PtRu/MWNTs electrode.     

Preparation of Novel Arrays Silver Nanoparticles Modified Polyrutin Coat‐Paraffin‐Impregnated Graphite Electrode for Tyrosine and Tryptophan's Oxidation

A novel array silver nanoparticles and Rutin complex film modified paraffin‐impregnated graphite electrode was proposed in this work (denoted as Ag/Rutin/WGE). The characteristics were investigated by the field emission scanning electron microscopy (FE‐SEM), infrared spectra (IR), UV‐visible (UV), X‐ray photoelectron spectroscopy (XPS) and electrochemical techniques. Silver ions were gradually chelated by polyrutin film at 4′‐oxo‐5′‐OH and 5‐OH‐4‐oxo sites accompanying adsorption, then. Silver nanoparticles were highly‐dispersed electrodeposited on polyrutin film. The electrochemical behaviors of tyrosine (Tyr) and tryptophan (Trp) were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Ag/Rutin/WGE electrode shows overlapping catalysis for the oxidation of Tyr and Trp. The linear response of Tyr and Trp were 0.3–10.0 and 0.7–70.0 μM with detection limit of 0.07 and 0.1 μM in a signal‐to‐noise ratio of 3.     

Rapid determination of sterols in vegetable oils by CEC using methacrylate ester‐based monolithic columns

A method for the determination of sterols in vegetable oils by CEC with UV–Vis detection, using methacrylate ester‐based monolithic columns, has been developed. To prepare the columns, polymerization mixtures containing monomers of different hydrophobicities were tried. The influence of composition of polymerization mixture was optimized in terms of porogenic solvent, monomers/porogens and monomer/crosslinker ratios. The composition of the mobile phase was also studied. The optimum monolith was obtained with lauryl methacrylate monomer at 60:40% (wt:wt) lauryl methacrylate/ethylene dimethacrylate ratio and 60 wt% porogens with 20 wt% of 1,4‐butanediol (12 wt% 1,4‐butanediol in the polymerization mixture). Excellent resolution between sterols was achieved in less than 7 min with an 85:10:5 v/v/v ACN–2‐propanol–water buffer containing 5 mM Tris at pH 8.0. The limits of detection were lower than 0.04 mM, and inter‐day and column‐to‐column reproducibilities at 0.75 mM were better than 6.2%. The method was applied to the determination of sterols in vegetable oils with different botanical origins and to detect olive oil adulteration with sunflower and soybean oils.     

Two New Spirostanol Saponins from Reineckia carnea

Two new spirostanol saponins, (1β,3β,5β,25S)‐spirostan‐1,3‐diol 1‐(β‐D ‐xylopyranoside) ( 1 ) and (1β,3β,5β,25S)‐spirostan‐1,3‐diol 1‐[α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranoside] ( 2 ), along with two known compounds, (1β,3β,5β,25S)‐spirostan‐1,3‐diol 1‐[α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐xylopyranoside] ( 3 ) and (1β,3β,4β,5β,25S)‐spirostan‐1,3,4,5‐tetrol 5‐(β‐D ‐glucopyranoside) ( 4 ) were isolated from the whole plant of Reineckia carnea. The structures of the new steroids were determined by detailed analysis of their 1D‐ and 2D‐NMR spectra and chemical methods, and by comparison with spectral data of known compounds. Compounds 3 and 4 were isolated from the genus Reineckia for the first time.     

Furostane‐Type Steroidal Saponins from the Roots of Chlorophytum borivilianum

Four new furostanol steroid saponins, borivilianosides A–D ( 1 – 4 , resp.), corresponding to (3β,5α,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐hydroxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐galactopyranoside ( 1 ), (3β,5α,22R,25R)‐ 26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐galactopyranoside ( 2 ), (3β,5α,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→2)]‐O‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 3 ), and (3β,5α,25R)‐26‐(β‐D ‐glucopyranosyloxy)furost‐20(22)‐en‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→2)]‐O‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 4 ), together with the known tribuluside A and (3β,5α,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→2)‐O‐[β‐D ‐xylopyranosyl‐(1→3)]‐O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐galactopyranoside were isolated from the dried roots of Chlorophytum borivilianum Sant and Fern . Their structures were elucidated by 2D ‐NMR analyses (COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry.     

Syntheses and Structural Characterization of 1D Coordination Polymers of Transition‐Metal Atoms Containing 2,4‐Pyridinedicarboxylate Bridges

By employing one bridging ligand, 2,4‐pyridinedicarboxylate (2,4‐pda^2?), three one‐dimensional (1D) coordination polymers of [Cu(2,4‐pda)(H₂O)₂]_∞ ( 1 ), {[Cu₄(2,4‐pda)₄(H₂O)₈]·3H₂O}_∞ ( 2 ), and {[Cd(2,4‐pda)(H₂O)₃]·H₂O}_∞ ( 3 ) were synthesized. A simple zigzag polymeric chain is observed for both 1 and 3 , but a railroad‐like zigzag polymeric chain is observed for 2. Almost all water molecules, whether coordinated or not, are involved in hydrogen bonding interactions and help to tie up the 1D polymeric chains of 1‐3 into a three‐dimensional (3D) network. A comparison about the coordination geometries in all similar coordination polymers available to date is also included.     

Adsorptive Voltammetric Behaviors of Resveratrol at Graphite Electrode and its Determination in Tablet Dosage Form

The adsorptive voltammetric behavior of resveratrol was studied at a graphite electrode in B‐R buffer (pH = 6.0) solution using adsorptive cyclic voltammetric technique. The oxidation of resveratrol is an irreversible adsorption controlled process. The oxidation mechanism was proposed and discussed in this work. The dependence of the current on pH and the concentration and nature of buffer were investigated to optimize the experimental conditions for the determination of resveratrol. It was found that in the range of 8.0 × 10^?9 ～ 2.0 × 10^?6 mol/L, the currents measured by differential pulse voltammetries presented a good linear property as a function of the concentrations of resveratrol. In addition, validation parameters, such as reproducibility, sensitivity and recovery were evaluated as well. The proposed method was also successfully applied for the determination of resveratrol in Chinese patent medicine with good results.     

Synthesis of condensed pyridones by using a new ring switching reaction

A new ring‐switching reaction of enaminoesters behaving as bisnucleophiles towards other enaminoesters behaving as biselectrophiles is described. By starting from pyroglutamic derivatives, this reaction provided easy access to methyl 5‐oxo‐1,2,3,5‐tetrahydro‐3‐indolizinecarboxylates substituted by an aminoester side chain in position 6.