LC Method for Analysis of Three Flavonols in Rat Plasma and Urine after Oral Administration of Polygonum aviculare Extract

A high-performance liquid chromatographic method has been developed for the simultaneous analysis of the flavonols myricitrin (1), avicularin (2), and juglanin (3) in rat plasma and urine after oral administration of the total flavonoids from Polygonum aviculare. Samples were prepared by solid-phase extraction then separated on a C₁₈ reversed-phase column by use of a mobile-phase gradient prepared from methanol and aqueous formic acid solution. The flow rate was 1 mL min^?1. Detection was performed at 254 nm. The calibration range was 11–1,100 μg mL^?1 for both 2 and 3 in plasma; in urine the calibration ranges for 1, 2, and 3 were 32–1,600, 11–1,100, and 22–1,100 μg mL^?1, respectively. Intra-day and inter-day RSD were less than 4.33 and 3.62% for 2 and 3, respectively, in plasma, and no more than 4.03 and 2.22% for all the analytes in urine. The analytical sensitivity and selectivity of the assay enabled successful application to pharmacokinetic studies of flavonols 1–3 in rats.     

Synthesis and thermal behavior study of complexes of the type [Pd(μ-X)(4-eb-p-phen)]2 (X = Cl,Br, I,N3, NCO,SCN) and 4-eb-p-phen [bis(4-ethylbenzyl)p-phenylenediimine]

The Schiff base bis(4-ethylbenzyl) p-phenylenediimine, 4-eb-p-phen (1), and six new dimeric Pd(II) complexes of the type [Pd(μ-X)(4-eb-p-phen)]₂ {X = Cl (2), Br (3), I (4), N₃ (5), NCO (6), SCN (7)} have been synthesized and characterized by elemental analysis, IR spectroscopy, and ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 2–7 has been investigated by means of thermogravimetry and differential thermal analysis. From the final decomposition temperatures, the thermal stability of the complexes can be ordered in the following sequence: 3 > 4 > 7 > 2 ≈ 5 > 6. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction (XRD).     

Excited state intramolecular hydrogen atom transfer of phenylethynyl-substituted 2′-hydroxychalcones

(E)-1-[2-Hydroxy-4-(phenylethynyl)phenyl]-3-[4-(phenylethynyl)phenyl]prop-2-en-1-one (1), (E)-1-[2-hydroxy-4-(phenylethynyl)phenyl]-3-phenylprop-2-en-1-one (2), and (E)-1-(2-hydroxyphenyl)-3-[4-(phenylethynyl)phenyl]prop-2-en-1-one (3), which belong to a new class of 2′-hydroxychalcones with phenylethynyl group(s) at the para position of the phenyl ring, were synthesized, and their photochemical properties were investigated. The lowest energy absorption band of 1 peaks at a longer wavelength (383 nm) with a much larger molar extinction coefficient (5.0 × 10⁴ M ^?1 cm^?1) than that of the parent 2′-hydroxychalcone (2′HC) (2.0 × 10⁴ M ^?1 cm^?1 at 318 nm). Upon photoexcitation, all three compounds underwent excited-state intramolecular hydrogen atom transfer (ESIHT) to produce an excited tautomer that emitted fluorescence with a large Stokes shift in the longer wavelength region at 600–700 nm. The quantum yield of the tautomer fluorescence of 1 was not high at 298 K (Φ _f = 9.1 × 10^?5), but was highest among 2′HC and its analogues. The Φ _f values of 1–3 increased 10–30 fold upon reducing the temperature from 298 to 77 K.     

Preparative Isolation and Purification of Two Phenylpropanoids from Daphne giraldii Nitsche by HSCCC

Preparative high-speed counter-current chromatography (HSCCC) was successfully applied to purify phenylpropanoids from the stem and root bark of Daphne giraldii Nitsche, a traditional Chinese medicine. Their structures were identified on the basis of ¹H NMR and ¹³C NMR technology. The two-phase solvent system composed of n -hexane–ethyl acetate–methanol–water (2: 3: 0.5: 4, v/v/v/v) was selected for HSCCC. A total of 8.0 mg woonenoside XI (1) and 18.0 mg daphnetin (2) were obtained in one-step separation from 200 mg of the crude extract with purity of 96.0 and 99.1%, respectively, as determined by LC. And the major compound (2) showed antithrombotic activity in vitro.     

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene by using three electroneutral receptors

From extraction experiments and $ \gamma $ -activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3 A^?(aq) + L(nb) $ \Leftrightarrow $ EuL³⁺(nb) + 3A^?(nb) taking place in the two-phase water–nitrobenzene system ( $ {\text{A}}^{ - } = {\text{CF}}_{ 3} {\text{SO}}_{3}^{ - } $ ; L = electroneutral receptors denoted by 1, 2, and 3 – see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the series of 3 < 2 < 1.

Syntheses, crystal structures, and characterization of four homochiral coordination polymers based on two chiral reduced Schiff base ligands

Four homochiral coordination polymers incorporating two chiral reduced Schiff base ligands, namely, [Cu(L¹)(H₂O)]·H₂O (1), [Zn₂(L²)₂] (2), [Co(L²)(H₂O)] (3), and [Ni(L²)(H₂O)] (4) (H₂L¹ = N-(4-carboxyl)benzyl-l-alanine, H₂L² = N-(4-carboxyl)benzyl-l-leucine) have been obtained by hydrothermal methods and characterized by physico-chemical and spectroscopic methods. X-ray crystallographic analysis reveals that complex 1 exhibits a chain structure with 1D channels. Complexes 2–4 all are 3D network structures with 1D channels in which the isobutyl group of the ligand points toward to the channel. Complex 2 displays strong photoluminescent emission in the purple region.     

New copper(II) 2-(alkylamino)troponates

The copper aminotropones Cu[ON(R′)C₇H₄R-4]₂ [R = H, R′ = Me (13), Et (14), n-Pr (15), n-Bu (16), Bz (17), MenOCH₂CH₂ (20); R = i-Pr, R′ = Me (18), n-Pr (19), MenOCH₂CH₂ (21)] have been prepared from the corresponding aminotropones HN(R′)OC₇H₄R-4 (1–7) by reacting with copper(II) acetate in aqueous ethanol. 20, 21 contain the flavourant, menthol, as part of the ligand. The structures of 5 (R = H, R′ = Bz), a hydrogen-bonded dimer, 14 and 20, both incorporating square-planar, four-coordinate copper centres, have been determined by X-ray crystallography. The antibacterial activities of complexes 13, 17, 20 and 21 have been assayed against Staphylococcus waneri, an in vitro model of plaque inhibition effects, and found to be more active than a commercial toothpaste formulation, but less active than the O,O-chelated copper(II) complex of ethylmaltol.     

Syntheses and characterization of a new class of vanadia precursors of oxime-modified oxovanadium(V) isopropoxide,crystal and molecular structure of [VO{ONC10H16}3]

Modification of [VO(OPrⁱ)₃] with oximes in different molar ratios, yielded new class of vanadia precursors, [VO{OPrⁱ}_3?n{L}_n] {where, n = 1–3 and LH = C₉H₁₆C=NOH (1–3) and (CH₃)₂C=NOH (4–6)}.All the products are yellow in colour. (1) and (2) are liquid/viscous liquid, while others are solids. Molecular weight measurements of all these derivatives and the ESI-mass spectral studies of (1), (2), (3) and (5) indicate their monomeric nature. ¹H and ¹³C{¹H} NMR spectra suggest that the oximato moieties are monodentate in solution which was further confirmed by the ⁵¹V NMR signals, appeared in the region expected for tetra-coordinated oxo-vanadium atoms. On ageing, a disproportionation reaction occurs in (1) and some crystals appeared. Single crystal X-ray diffraction analyses of the crystals obtained from (1) as well as from (3) were found to be the same and indicate the presence of side-on {dihapto η ²-(N, O)} binding modes of the oximato ligands, leading to the formation of seven coordination environment around the vanadium atom. Thermogravimetric curve of (1) exhibits multi-step decomposition with the formation of V₂O₅ as the final product at ~850 °C. Sol–gel transformation of (3) yielded (a) VO₂ sintered at 300 °C and (b) V₂O₅ at 600 °C. Similarly, sol–gel transformations of (1) and (2) yielded V₂O₅ (c) and (d) at 600 °C, respectively. Formation of monoclinic phase in (a) and orthorhombic phase in (b), (c) and (d) were confirmed by powder XRD patterns.     

Non-aqueous synthesis of nano-sized aluminium(III) isopropoxide derivatives with 8-hydroxyquinoline and their sol–gel transformation to nano-sized δ-alumina

Non-aqueous reactions of aluminum isopropoxide with 8-hydroxyquinoline (Hq = HONH₆C₉) in 1:1, 1:2 and 1:3 molar ratios in anhydrous benzene yield complexes of the type [q_nAl(OPrⁱ)_3?n] {where n = 1 (1), n = 2 (2), n = 3 (3)}. Progress of the reactions were monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All the products were fluorescent green powders, sparingly soluble in CHCl₃. They were characterized by elemental analysis, FT-IR and (¹H, ¹³C and ²⁷Al) NMR studies. The ESI mass spectral studies indicate dimeric nature for (1) and (2) and monomeric nature for the compound (3). The XRD spectra of (1–3) showed crystalline nature with the average particle size of 45, 32 and 27 nm respectively, as evaluated from Debye–Scherrer equation. The XRD spectrum of (3) also suggests the formation of β-crystalline polymorphs of Alq₃. The SEM images appear to indicate granular morphology for (1) and formation of cylindrical shaped rods for (2) and (3). Sol–gel hydrolysis of (1), (2) or (3) in presence of a strong acid as well as of the precursor, Al(OPrⁱ)₃,without acid or base catalyst, followed by sintering at 950 °C yielded tetragonal primitive phase of nano-sized δ-alumina in all the cases, as reflected by their powder X-ray diffraction pattern. The IR, SEM and EDX studies also support the formation of transition alumina.     

Identification of Iridoids,Flavonoids and Triterpenes from the Methanolic Extract of Melampyrum bihariense A. Kern. and the Antioxidant Activity of the Extract

Melampyrum bihariense A. Kern. (Scrophulariaceae), a plant species used in traditional medicine for the treatment of rheumatic disorders and skin infections, was investigated with regard to its antioxidant activity and identification of its bioactive chemical constituents. The crude methanolic extract of the aerial parts of M. bihariense was examined by the spectrophotometric DPPH (1,1-diphenyl-2-picrylhydrazyl) and ferric reducing antioxidant power methods. The free radical scavenging capacity (SC₅₀) of the extract was found by the DPPH method to be 27.10 mg mL^?1, and the ferric reducing ability equivalent to ascorbic acid at 50 mg mL^?1 was 0.709 μg mL^?1. The chemical composition of this highly effective in the methanolic extract was analysed, and the main compounds were isolated through solvent–solvent partition, and multiple chromatographic separations, including column chromatography, vacuum liquid chromatography, centrifugal planar chromatography and preparative thin-layer chromatography. The structures were established by one- and two-dimensional NMR and liquid chromatography-mass spectrometry. The iridoids aucubin (1), 8-epi-loganin (2) and mussaenoside (3), the flavones apigenin and luteolin and the triterpene acids ursolic acid and oleanolic acid were identified; components 2, 3, ursolic acid and oleanolic acid for the first time in this species. The present study reveals that M. bihariense exerts antioxidant activity, and the iridoids, flavonoids and triterpene acids may be the main bioactive constituents of its methanolic extract.     

Specificity of 15N NMR chemical shifts to the nature of substituents and tautomerism in substituted pyridine N-oxides

¹H, ¹³C, and ¹⁵N NMR chemical shifts have been measured for 2-aminopyridine N-oxide (1), its eleven derivatives (2–10, 13, 14), and 3-Cl and 3-Br substituted 4-nitropyridine N-oxides (11, 12). δ(¹⁵N) of pyridine ring nitrogen in 2-acetylaminopyridine N-oxides are 5.9–11.5 ppm deshielded from those in 2-aminopyridine N-oxides. When amino and acetylamino substituents are in 4-position, δ(¹⁵N) of ring nitrogen is 21.3 ppm deshielded in the acetylated derivative. The strong resonance interaction between 2-amino and 5-nitro groups reflects in the decrease of amino nitrogen shielding about 5.3–17.9 ppm. Also, ¹H and ¹³C NMR spectral data are in agreement with ¹⁵N NMR results reflected as deshielded amino protons and carbons C-2 and C-5. The pyridine nitrogen chemical shift in all amino- and acetylamino derivatives vary between ?101.2 and ?126.7 ppm, which has been connected with the tautomeric balance in our earlier studies.     

Anion-directed organized assemblies of protonated pyrazole-based ionic salts

The reactions of 3(5)-(4-methoxyphenyl)-5(3)-phenyl-1H-pyrazole (L ¹ ) with nitric acid and 5-(4-benzyloxyphenyl)-3-(furan-2-yl)-1H-pyrazole(L ² ) with hydrochloric acid produced [HL ¹ · NO₃] (Salt-1) and [HL ² · Cl] (Salt-2). The structures of Salt-1 and Salt-2 were determined by single crystal X-diffraction. In Salt-1, HL ¹ showed [2 + 2] binding of NO₃ ^? ions in the solid state to form dimer architecture with R ₁ ² (4) and R ₄ ⁴ (14) graph sets. An anion directed one-dimensional anion-assisted helical chain with active participation of the chloride ion and protonated pyrazole via N–H···Cl hydrogen bonding in Salt-2. In addition, the protonated HL ² molecules interacted with each other through weak C–H···π interactions resulting in the formation of another one-dimensional helical chain.     

Synthesis,spectroscopic characterization,X-ray crystal structure,biological screening and catalytic studies of organotin(IV) carboxylates of 3-(4-cyanophenyl) acrylic acid

A series of six organotin(IV) carboxylates [Me₂SnL₂] (1), [n-Bu₂SnL₂] (2), [n-Oct₂SnL₂] (3), [Me₃SnL] (4), n-Bu₃SnL (5) and [Ph₃SnL] (6), where L = 3-(4-cyanophenyl) acrylic acid have been synthesized and characterized by elemental analysis, FT-IR and NMR (¹H, ¹³C). The complex (4) was also analyzed by single crystal X-ray analysis which showed distorted trigonal bipyramidal geometry with polymeric bridging behavior. The complexes 1–6 were screened for antimicrobial activities and cytotoxicity. The results showed significant activity with few exceptions. The catalytic activity of complexes was assessed in transesterification reaction of Brassica campestris oil (triglycerides) to produce biodiesel (fatty acid methyl esters). The results showed that triorganotin(IV) complexes exhibited good catalytic activity than their di-analogues.     

Theoretical study on the singlet and triplet potential energy surfaces of NH (X3Σ−) + HCNO reaction

Both the singlet and triplet potential energy surfaces (PESs) of the NH (X³Σ^?) + HCNO reaction have been investigated at the BMC-CCSD level based on the UB3LYP/6-311++G(d, p) structures. The results show that the title reaction is more favorable through the singlet potential energy surface than the triplet one. For the singlet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the most feasible association of NH (X³Σ^?) with HCNO is found to be a non-barrier nitrogen-to-carbon attack forming the adduct a (trans-HNCHNO), which can isomerize to the adduct b (cis-HNCHNO). The most feasible channel is that the 1, 3-H shift with N2–H2 and C–N1 bonds cleavage associated with the N1–H2 bond formation of adduct a leads to the product P ₁ (HCN + HNO). Moreover, P ₂ (HNC + HNO) should be the competitive product. The other products, including P ₃ (NH₂ + NCO) and P ₄ (N₂H₂ + CO), are minor products. The product P ₁ can be obtained through two competitive channels Path 1: R → a → P ₁ and Path 3: R → b → d → P ₁ , whereas the product P ₂ can be formed through Path 2: R → b → d → P ₂ . At high temperatures, the nitrogen-to-nitrogen approach may become feasible. For the triplet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the Path 10: R → ³ a → ³ a ₁ → P ₁ should be the most feasible pathway due to the less reaction steps and lower barriers. These conclusions will have impacts on further experimental investigations.     

Assembly of triorganotin chloride with selenite ligands to macrocyclic,zigzag, helical,and linear structures: syntheses,characterizations, and crystal structures of [R3Sn(O2SeC6H4-4-Et)] n and [R3Sn(O2SeC6H4-2-Et)] n (R = Me,C6H5) complexes

Four new triorganotin(IV) complexes, [R₃Sn(O₂SeC₆H₄-4-Et)]₄ (R = Me 1), [R₃Sn(O₂SeC₆H₄-4-Et)] _n (R = Ph 2), [R₃Sn(O₂SeC₆H₄-2-Et)] _n (R = Me 3; Ph 4) have been synthesized by the treatment of 4-ethylbenzeneseleninic acid, 2-ethylbenzeneseleninic acid, and the corresponding triorganotin(IV) chloride with sodium ethoxide in methanol. All of the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy, TGA, and X-ray crystallography. Crystal structures show that all of the complexes are generated by the bidentate oxygen atoms and the five-coordinated tin centers with trigonal bipyramid geometry. The structural analyses reveal that complex 1 has a centrosymmetric tetranuclear triorganotin selenite with 16-membered macrocycle, which is formed by trimethyltin and ligand alternate linking. A series of C–H···O and π–π stacking interactions in complex 1 play an important function in the supramolecular aggregation. Complex 3 has two 1D spring-like chiral helical chains and crystallizes in the monoclinic space group P2₁, which is chiral. Complex 2 and 4 are both 1D infinite neutral chain polymers and complex 2 forms a 2D supramolecular framework through intermolecular C–H···O interactions.     

Synthesis,antifungal and insecticidal activity of novel [1,2,4]triazolo[4,3-<Emphasis Type="Italic">a</Emphasis>]pyridine derivatives containing a sulfide substructure

A series of [1,2,4]triazolo[4,3-a]pyridine derivatives bearing a sulfide substructure was designed, synthesized and characterized via ¹H·NMR, ¹³C·NMR, IR and elemental analyses. Bioassay Results indicated some of the derivatives displayed good fungicidal activity on Rhizoctonia cerealis, moderated insecticidal activity against Plutella xylostella and good insecticidal activity on Helicoverpa armigera. The inhibitory effects of compounds 4g and 4u against Rhizotonia cerealis were 70.9% at 50 μg mL^?1; the IC₅₀ values of compounds 4d and 4s against Plutella xylostella were 43.87 and 50.75 μg mL^?1, respectively. And the IC₅₀ values of compounds 4d, 4q, and 4s on Helicoverpa armigera were 58.3, 77.14 and 65.31 μg mL^?1, respectively, which were better than that of commercial chlorpyrifos (103.77 μg mL^?1).     

The synthesis of some new imidazole and triazole derivatives: crystal Structure and DFT-TDDFT investigation on electronic structure

A series of new N′-3-(1H-imidazol-1-yl)propylcarbamoyl-4-halogenebenzo hydrazonate (3a–b) were obtained by reaction Ethyl 2-((4-halogene phenyl) (ethoxy) methylene) hydrazinecarboxylate (1) and N-(3-aminopropyl)imidazole (2) at 120–140 °C. Compounds (4a–b) were obtained by the reaction compound 1 and N-(3-aminopropyl)imidazole (2) at 160–180 °C. The structures of compounds 3,4 have been inferred through UV–Vis, IR, ¹H/¹³C NMR, mass spectrometry, elemental analyses, and X-ray crystallography. DFT level 6-31G (d) calculations provided structural information. The electronic structure of compound 3a has been studied by DFT level 6-31G (d) calculations using the X-ray data. The results are accordance with X-ray data.     

Synthesis and characterization of palladium(II) complexes [PdX2(p-diben)] (X = Cl,Br, I,N3, or NCO; p-diben = N,N′-bis(4-dimethylaminobenzylidene)ethane-1,2-diamine): crystal structure of [Pd(N3)2(p-diben)]

Five new complexes of general formula [PdX₂(p-diben)], where p-diben = N,N′-bis(4-dimethylaminobenzylidene)ethane-1,2-diamine) (1) and X = Cl (2), Br (3), I (4), N₃ (5), or CNO (6), were synthesized and characterized by physicochemical and spectroscopic methods. The crystal structure of compound (5) was determined by single-crystal X-ray diffraction. Complexes 2–6 were characterized as N,N-chelated products. The crystal structure confirmed this formulation for [Pd(N₃)₂(p-diben)], besides showing the isomerism inversion of one of the C=N bonds, caused by Pd(II) coordination.     

Novel deep-cavity calix[4]arene derivatives with large s-triazine conjugate systems: synthesis and complexation for dyes

Two novel deep-cavity calix[4]arenes 3 and 4 with large s-triazine π-conjugate systems were designed and synthesized in high yields by reacting calix[4]arene with mono phenyl-substituted cyanuric chloride or further substitution with aniline. The liquid–liquid extraction experiment showed that they possessed excellent extraction abilities towards one cationic and three anionic dyes (Orange I, methylene blue, neutral red, brilliant green). The highest extraction percentage of compound 4 was 88.8 % for brilliant green. The complexation UV–Vis spectra of compounds 3 and 4 with four dyes indicated the existences of complexation action between hosts and guests with 1:1 ratio of complexation in DMSO solution. The association constants suggested that the larger π-conjugate system of compound 4 possessed the stronger complexation abilities than that of compound 3. The association constant of compound 4 with BG was as high as 8.1 × 10⁶ M^?1.     

Thermochemical and structural properties of anthraquinones

We have investigated the energetic, structural, and other physical–chemical properties (aromaticity, intrinsic strain, hydrogen bond interaction) of 1,4-anthraquinone (1), its better known isomer 9,10-anthraquinone (2) and the derivatives 9-hydroxy-1,4-anthraquinone (3) and 9-methoxy-1,4-anthraquinone (4). In particular, the standard enthalpy of formation in the gas phase at 298.15 K of 1,4-anthraquinone was determined [ $\Updelta_{\text{f}}^{{}} H_{\text{m}}^{\text{o}} \left( {{\text{g}},{\mathbf{1}}} \right) \, = \, - 4 4. 9 { } \pm { 5}. 7\;{\text{kJ}}\;{\text{mol}}^{ - 1} ]$ . Using isodesmic/homodesmotic reaction schemes, we have experimentally estimated: (i) the stabilization energy of 1 (162.2 ± 7.2 kJ mol^?1) and 2 (193.2 ± 5.2 kJ mol^?1), (ii) strength of intramolecular hydrogen bonding in 3 (HB = 79.8 ± 10.8 kJ mol^?1), and (iii) additional strain energy due to peri-oxygen interaction in 4 (?34.2 ± 7.6 kJ mol^?1). A computational study of these species, at the B3LYP/6-311++G(3df,2p) level, sheds light on structural, aromatic, intrinsic strain, or hydrogen bond effects and further confirmed the consistency of the experimental results.