Identification of key metabolites of tectorigenin in rat urine by HPLC-MS(n)

This is a report about the identification of key metabolites of tectorigenin in rat urine using high-performance liquid chromatography-electrospray ionization ion trap tandem mass spectrometric method (HPLC-ESI-MS(n)). Six healthy rats were administered a single dose (80 mg/kg) of tectorigenin by oral gavage. Urine was sampled for 0-24 h and centrifuged at 12,000 rpm for 10 min to obtain the supernatants, then the supernatants were purified by solid-phase extraction with a C(18) cartridge. The chromatographic separation was carried out on a reversed-phase C(18) column with a gradient elution program whereas acetonitrile-0.1% formic acid water was used as mobile phase. Mass spectra were acquired in negative ionization mode and a data-dependant scan was used for the identification of the key metabolites of tectorigenin in the urine samples. As a result, four phase II metabolites and the parent drug tectorigenin were found and identified in rat urine for the first time.     

Pattern recognition of Chinese flue-cured tobaccos by an improved and simplified K-nearest neighbors classification algorithm on near infrared spectra

In tobacco industry of China, tobacco leaves are classified and managed in terms of their cultivation areas and plant parts of tobacco-stalks. However, sometimes intentionally or involuntary mislabeling cultivation areas, blending tobacco plant parts would occur into tobacco market. The error will affect the style and quality of cigarettes. In the present work, more than 1000 Chinese flue-cured tobacco leaf samples, which have 12 genotypes and cultivated from 5 to 10 regions of China in 2003 and 2004, have been discriminated by means of an improved and simplified KNN classification algorithm (IS-KNN) based on near infrared (NIR) spectra. An original method of optimizing number of significant principal components (PCs) based on analysis of error and cross-validation was advanced. Compared with conventional pattern recognition methods KNN, NN, LDA and PLS-DA, IS-KNN exhibits good adaptability in discrimination of complicated Chinese flue-cured tobaccos. The practice in this work shows that optimized number of PCs and performance of classification models are closely relative to complicated extent of samples but not to number of categories or samples. The results demonstrated the usefulness of NIR spectra combined with chemometrics as an objective and rapid method for the authentication and identification of tobacco leaves or other kinds of powder samples.     

Preparation of 3,6-dibenzoylacenapthene in the presence of Lewis acidic ionic liquids

The reactivity of Lewis acidic ionic liquids for the acylation of acenaphthene to 3,6-dibenzoylacenaphthene was investigated. Ionic liquids of different alkyl chain length and metal chloride were synthesized and tested for the reaction to discuss the effects of Lewis acidity of the ionic liquid on the alkylation. Pure 3,6-dibenzoylacenaphthene was obtained and the structure of 3,6-dibenzoylacenaphthene was identified by GC/MS, FT-IR and ¹H NMR spectra. [Emim]C1/A1C1₃ ionic liquid was found to be the most active catalyst in the acylation. The yield of 3,6-dibenzoylacenaphthene was up to 89.6% and the selectivity towards 3,6-dibenzoylacenaphthene was up to 92.2%. The experiment shows that [Emim]Cl/AlCl₃ can be used as both catalyst and solvent, it is reusable and environmentally friendly for the preparation of 3,6-dibenzoylacenaphthene.     

Construction of metal–organic frameworks with transitional metals based on the 3,5-bis(4-pyridyl)-1H-1,2,4-triazole ligand

Based on the versatile ligand 3,5-bis(4-pyridyl)-1H-1,2,4-triazole (Hbpt) derived from an in situ metal/ligand reaction, a series of coordination compounds CoCl₄(H₃bpt)(H₂O) (1), Cu(H₂bpt)₂(SO₄)₂(H₂O)₆ (2), [Ag(bpt)]_n (3), [Co(Hbpt)(pa)]_n (4), [Co(Hbpt)(pda)]_n (5) and [Cu(Hbpt)(pda)(H₂O)]_n (6) have been constructed (pa = phthalate, pda = 1,3-phenylenediacetate). The structures of these targeted complexes have been characterized by X-ray single-crystal diffraction techniques. Structural analysis reveals that Hbpt adopts versatile coordination modes to arrange the metal ions in 0-D point, simple (4,4) layers and dinuclear core chains in 1–3, which are further extended via the benzenedicarboxylate connectors to give rise to a variety of coordination networks such as (4,4), (4¹² · 6³), (6⁴ · 8²) topologies in 4–6. The supramolecular organization through hydrogen bonds is analyzed for these complexes and thermal stability of these crystalline materials has been explored by TG-DTG.     

Electrophoretic separation with 2-mm inner diameter fused-silica microcolumn packed with quartz microncrystals and its application

The feasibility of a microcolumn electrophoresis technique was investigated with a 100 mm length, 2 mm I.D. fused-silica microcolumn packed with uniform quartz microncrystals prepared by hydrothermal synthesis. To evaluate the separation technique, tryptophan, phenylalanine and tyrosine were primarily separated by the microcolumn electrophoresis and detected at 216 nm without derivatization by an ordinary spectrophotometer. The separation conditions of the amino acids were optimized. With 1.5 mmol/L disodium phosphate buffer solution (pH 11.5) containing 25% (v/v) methanol and 10% (v/v) acetonitrile, the three amino acids were separated and the separation efficiency of tryptophan was 4.5 × 10⁴ plates/m. The limits of detection were 0.035, 0.22 and 0.20 μmol/L, respectively. The sample capacity of the electrophoretic microcolumn achieved 35 μL. The proposed method was used to determine these amino acids in compound amino acid injection samples without derivatization. For the simplicity and portability of the microcolumn electrophoresis, it is studied as one of the high-performance separation techniques for an in situ and real-time electrokinetic flow analysis system. For its high detection sensitivity and large sample capacity, it can be developed for preparative electrophoresis.     

Tailoring noise frequency spectrum to improve NIR determinations

Near infrared spectroscopy (NIR) contains excessive background noise and weak analytical signals caused by near infrared overtones and combinations. That makes it difficult to achieve quantitative determinations of low concentration samples by NIR. A simple chemometric approach has been established to modify the noise frequency spectrum to improve NIR determinations. The proposed method is to multiply one Savitzky-Golay filtered NIR spectrum with another reference spectrum added with thermal noises before the other Savitzky-Golay filter. Since Savitzky-Golay filter is a kind of low-pass filter and cannot eliminate low frequency components of NIR spectrum, using one step or two consecutive Savitzky-Golay filter procedures cannot improve the determination of NIR greatly. Meanwhile, significant improvement is achieved via the Savitzky-Golay filtered NIR spectrum processed with the multiplication alteration before the other Savitzky-Golay filter. The frequency range of the modified noise spectrum shifts toward higher frequency regime via multiplication operation. So the second Savitzky-Golay filter is able to provide better filtering efficiency to obtain satisfied result. The improvement of NIR determination with tailoring noise frequency spectrum technique was demonstrated by both simulated dataset and two measured NIR spectral datasets. It is expected that noise frequency spectrum technique will be adopted mostly in applications where quantitative determination of low concentration sample is crucial.     

Investigation on the photophysical processes in nanosized photocatalytic thin films using planar solid-state devices

The photophysical processes for three nanosized photocatalytic oxides, titanium dioxide (TiO₂) thin film, tin dioxide (SnO₂) thin film, and layered TiO₂/SnO₂ thin film, have been examined in planar solid-state devices. It is found that, for SnO₂ thin film, the dissociation of the photogenerated excitons can take place both on the film surface and inside the film, while for TiO₂ thin film, almost all excitons dissociate on the film surface. Such a difference is proposed to account for the higher photocatalytic activity of TiO₂ over SnO₂, since it is experimentally shown that the excitons dissociate in SnO₂ thin film as efficiently as they do in TiO₂ thin film. For layered TiO₂/SnO₂ thin film, when it is illuminated by a beam of UV light, it is suggested that there exists a local electrostatic field at the SnO₂ side of the interface, mainly formed by those holes efficiently photogenerated and then localized in SnO₂ thin film. The photo-induced local electrostatic field is believed to facilitate hole–electron separation on TiO₂ thin film and therefore increase the photocatalytic activity of the layered thin film over single TiO₂ thin film.     

2-(Diphenylphosphino)benzoate-functionalized diiron ethane-1,2-dithiolate complexes with uncoordinated or coordinated phosphine ligand

Abstract

Treatment of the starting complex [Fe₂(CO)₆{μ-SCH₂CH(CH₂OH)S}] (1) with 2-(diphenylphosphino)benzoic acid in the presence of N,N’-dicyclohexylcarbodiimide and 4-dimethylaminopyridine gave the corresponding ester derivative [Fe₂(CO)₆{μ-SCH₂CH(CH₂O₂CC₆H₄PPh₂-2)S}] (2) in 92% yield. Further treatment of complex 2 with one equivalent of Me₃NO · 2?H₂O as the decarbonylating agent yielded diphenylphosphino-substituted complex [Fe₂(CO)₅{μ-SCH₂CH(CH₂O₂CC₆H₄PPh₂-2)S}] (3) in 79% yield. Both complexes were characterized by elemental analysis, spectroscopy, as well as by X-ray crystallography. Additionally, the electrochemical properties of these complexes were studied by cyclic voltammetry.     

Structural features of an acidic polysaccharide with the potential of promoting osteoblast differentiation from Lycium ruthenicum Murr.

Abstract

The enhanced osteoblast differentiation is beneficial to the prevention of osteoporosis. In this study, a homogeneous polysaccharide (LRP-S2A) with the potential of promoting osteoblast differentiation was obtained from the fruits of Lycium ruthenicum, a traditional herb for treatment of postmenopausal metabolic disorders. Structural identification indicated that LRP-S2A, with a relative molecular weight of 2.65 × 10⁶ Da and an uronic acid content of 41.8%, contained Rha, Ara, Gal, Glc and GlcA in a molar ratio of 1.00 : 2.07 : 0.57 : 2.59 : 4.33 and was composed of a backbone consisting of 6-O-Me-α-(1→4)-D-GlcpA, 2-O-acetyl-α-(1→4)-D-Glcp, α-(1→2,4)-L-Rhap, β-(1→3)-D-Galp andα-(1→3,5)-L-Araf, and some branches consisting of 6-O-Me-α-(1→4)-D-GlcpA and terminal α-L-Araf. These results suggested that LRP-S2A with the potential of promoting osteoblast differentiation was a new acidic polysaccharide.     

Flavonoid compounds and antibacterial mechanisms of different parts of white guava (Psidium guajava L. cv. Pearl)

Abstract

The flavonoid compositions, extracted from leaves, peel and flesh of white guava (Psidium guajava L. cv. Pearl), were identified and quantified by UPLC-ESI-QTOF-MS, HPLC-ESI-MS/MS and HPLC. The main components of three extracts all were quercetin-glycosides, but the proportion and content of quercetin-hexoside and quercetin-pentoside in each extract were different. Based on the measurements of MIC, MBC value and time killing curve, it emerged that 3 flavonoid extracts of white guava had good antibacterial effects on four pathogenic bacteria. White guava leaves flavonoids (WGLF) concentrations of 5.00?mg/mL and 0.625?mg/mL could change the micro-morphology of Escherichia coli and Staphylococcus aureus. It suggested that the antibacterial mechanism of WGLF on gram-positive and gram-negative bacteria was to destroy the structure and function of the cell membrane. It is indicated that the flavonoid extracts from white guava is a potential natural antimicrobial agent.