Phenolic compounds in field horsetail (Equisetum arvense L.) as natural antioxidants

In this paper, the study of antioxidant activity and phenolic composition of three different extracts (EtOAc, n-BuOH and H(2)O) of field horsetail (Equisetum arvense L.) is presented. The antioxidant activity has been evaluated measuring the total reducing power (expressed by Ascorbate Equivalent Antioxidant Capacity - AEAC), inhibition of lipid peroxidation, and free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazyl (DPPH radical) and nitric oxide (NO), respectively. In addition, the total flavonoid content (TFC) and phenolic constituents of each extract have been determined. The results obtained show that the highest RSC regarding both DPPH and NO radicals is expressed by EtOAc extract (EC(50)=2.37 microg/mL and EC(50)=90.07 microg/mL, respectively), and the lowest by H(2)O extract (EC(50)=37.2 microg/mL and EC(50)>333.33 microg/mL, respectively). n-BuOH extract showed the highest total reducing power (AEAC=13.40 microg/mL). Differences in the phenolic composition of examined extracts are found comparing the HPLC chemical profiles. Although, isoquercitrin is the main flavonoid in both EtOAc and n-BuOH extracts, a considerable amount of di-E-caffeoyl-meso-tartaric acid was presented in the n-BuOH extract. In H(2)O extract high content of phenolic acids and low percentage of flavonoids were detected.     

Mono‐ and Binuclear Rhodium and Platinum Complexes of 1, 3, 5‐Trimethyl‐1, 3, 5‐triaza‐2σ3λ3‐phosphorin‐4, 6‐dionyloxy‐substituted Calix[4]arenes

The reaction behaviour of 1, 3, 5‐triaza‐2σ³λ³‐phosphorin‐4, 6‐dionyloxy‐substituted calix[4]arenes towards mono‐ and binuclear rhodium and platinum complexes was investigated. Special attention was directed to structure and dynamic behaviour of the products in solution and in the solid state. Depending on the molar ratio of the reactands, the reaction of the tetrakis(triazaphosphorindionyloxy)‐substituted calix[4]arene ( 4 ) and its tert‐butyl‐derivative ( 1 ) with [(cod)RhCl]₂ yielded the mono‐ and disubstituted binuclear rhodium complexes 2 , 3 , and 5 . In all cases, a C₂‐symmetrical structure was proved in solution, apparently caused by a fast intramolecular exchange process between cone conformation and 1, 3‐alternating conformation. The X‐ray crystal structure determination of 5 confirmed [(calixarene)RhCl]₂‐coordination through two opposite phosphorus atoms with a P ⃜P separation of 345 pm. The complex displays crystallographic inversion symmetry, and the Rh₂Cl₂ core is thus exactly planar. Reaction of 1 and of the bis(triazaphosphorindionyloxy)‐bis(methoxy)‐substituted tert‐butyl‐calix‐[4]arene ( 7 ) with (cod)Rh(acac) in equimolar ratio and subsequent reaction with HBF₄ led to the expected cationic monorhodium complexes 5 and 8 , involving 1, 3‐alternating P‐Rh‐P‐coordination. The cone conformation in solution was proved by NMR spectroscopy and characteristic values of the ¹J(PRh) coupling constants in the ³¹P‐NMR‐spectra. Reaction of equimolar amounts of 4 with (cod)Rh(acac) or (nbd)Rh(acac) led, by substitution of the labile coordinated acetylacetonato and after addition of HBF₄, to the corresponding mononuclear cationic complexes 9 and 10 . Only two of the four phosphorus atoms in 9 and 10 are coordinated to the central metal atom. Displacement of either cycloocta‐1, 5‐diene or norbornadiene was not observed. For both compounds, the cone conformation was proved by NMR spectroscopy. Reaction of 4 with (cod)PtCl₂ led to the PtCl₂‐complex ( 11 ). As for all compounds mentioned above, only two phosphorus atoms of the ligand coordinate to platinum, while two phosphorus atoms remain uncoordinated (proved by δ³¹P and characteristic values of ¹J(PPt)). NMR‐spectroscopic evidence was found for the existence of the cone conformation in the cis‐configuration of 11 .     

以方沸石负载Ni(II)催化剂修饰的电极电氧化甲醇Seyed Naser Azizi,Shahram Ghasemi,Neda Salek Gilani简

There is a high overvoltage in the oxidation of methanol in fuel cells, and so modified electrodes are used to decrease it. A modified electrode that used Ni(Ⅱ) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed. Analcime zeolite was synthesized by hydrothermal synthesis, and Ni(Ⅱ) ions were incorporated into the analcime structure, which was then mixed with carbon paste to prepare modified electrode. The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry. The effects of the scan rate of the potential, concentration of methanol, and amount of zeolite were investigated. The rate constant for the catalytic reaction of methanol was 6×10³ cm³ mol^-1 s^-1 from measurements using chronoamperometry. The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.     

Darstellung und Sulfurierung von 4,5-Benzo-2-{[2-(dimethylamino)ethyl]methyl-amino}-3-methyl-1,3,2-oxazaphosphorinan-6-on; Molekülstruktur eines Tetracarbonylmolybdän(0)-Chelatkomplexes

4,5-Benzo-2-{[2-(dimethylamino)ethyl]methylamino}-3-methyl-1,3,2-oxazaphosphorinan-6-one – Preparation, Sulfuration, and Molecular Structure of a Tetracarbonyl Molybdenum Derivative The synthesis of the title compound 4 is described. It reacts with sulfur to yield the thiophosphoryl derivative 5 . The structure of the molybdenum(0) complex 6 , containing 4 as a bidentate ligand, was established by X-ray analysis and is compared to that of the related 2-{[2-(dimethylamino)ethyl]methyl-amino}-1,3,2-benzodioxaphosphole-tetracarbonylchromium(0)-complex 7 [1]. 6 , similarly to 7 , shows a nearly rectangular ?bite”? angle, with 4 functioning as a chelating ligand, coordinating to Mo(0) via P(III) and the nitrogen atom of the NMe₂ group. The heterocyclic part of the ligand displays a distorted envelope configuration.     

An unusual way of formation of spirophosphoranes during the oxidative addition of hexafluoroacctone to σ5P-σ3P-diphosphorus compounds,and in the reaction of 2-chloro-l,2-dimethyl-3-phenyl-2-phenylseleno-l,3,5σ5-diazaphosphetidin-4-one with bis(2-chloroethyl)amine hydrochloride/ triethylamine

The reaction of (chloromethyl)dichlorophosphine 1 with N,N′-dimethyl-N,N′-bis(trimethylsilyl)urea 2 furnished the σ⁵P-σ³P-diphosphorus compound 3 . The reaction of 3 with hexafluoroacetone proceeded in an unusual fashion, with the rupture of the P? P bond, resulting in 4,4-bis(trifluoromethyl)-3-chloro-2-hexfluoroisopropoxy-2-oxo-1,2-oxaphosphetane 7 and the spirophosphorane 4-chloromethyl-1,3,5,7-tetramethyl-1,3,5,7-tetraaza-4σ⁵-phosphaspiro-[3,3]heptan-2,6-dione 8 . The reaction of 2-chloro-1,2-dimethyl-3-phenyl-2-phenylseleno-1,3,2σ⁵-diazaphosphetidin-4-one 9 with bis(2-chloroethyl)amine hydrochloride/triethylamine 10 also proceeded in an unexpected fashion, leading to the spirophosphorane 11 as the only identified product. Single-crystal X-ray structure analyses of compounds 8 and 11 were conducted. The coordination geometry at phosphorus in both compounds shows a large deviation from idealized forms. This distortion arises mainly from the presence of the four-membered rings.     

A biocompatible composite based on poly(ε‐caprolactone fumarate) and hydroxyapatite

Fabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and ¹H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd.     

Radical of filters in BL‐algebras

In this paper, the notion of the radical of a filter in BL‐algebras is defined and several characterizations of the radical of a filter are given. Also we prove that A/F is an MV‐algebra if and only if D_s(A) ? F. After that we define the notion of semi maximal filter in BL‐algebras and we state and prove some theorems which determine the relationship between this notion and the other types of filters of a BL‐algebra. Moreover, we prove that A/F is a semi simple BL‐algebra if and only if F is a semi maximal filter of A. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Investigation of the electronic structure and the structural stability of selected penicillins by density functional calculations of 14N nuclear quadrupole resonance parameters

A computational study was carried out by density functional theory (DFT) to investigate the relative stability and reactivity in three selected penicillins: penicillin-G, penicillin-V and carbenicillin. The geometry of the investigated molecules was optimized at the B3LYP/6-31G(d) level of theory. Then, the nuclear quadrupole resonance (NQR) parameters of ¹⁴N and ²H nuclei and natural bond orbital (NBO) analysis in these molecules were calculated on the geometrically optimized models at the B3LYP level using 6-311++G(d,p) basis sets in the gas phase. The NBO analysis shows that the occupancy of the LP(N) decreases with increasing p character of the lone pair of nitrogen. A comparison between the results obtained for these penicillins and related 6-APA structures of them indicates that the presence of a bulky side group in the acyl side chain can lead to more stability of the β-lactam ring. On the other hand, NBO analysis was applied to rationalize the ¹⁴N NQR parameters in the charge distribution around nitrogen atoms. Inspection of the present results illustrates that the largest component of EFG tensor (q _zz ), the nuclear quadrupole coupling constant, C _Q, and the NQR frequency values of nitrogens decrease with decreasing occupancy values of LP(N). We suggest that the reason for this trend can be found in increasing contribution of delocalized electrons of nitrogen in the intramolecular interactions and hence stability of these structures increases in the order: PG < PV < CA. Finally, a good relationship is found between most of the calculated ²H NQR parameters and the related intramolecular hydrogen bonds.     

A quantum chemistry study of ruthenabenzene complexes

The electronic structure and properties of the ruthenabenzenes and substituted ruthenabenzenes have been explored using the hybrid density functional B3LYP theory. Systematic studies on the substituent effect in para-substituted ruthenabenzenes complexes have been studied. The following substituents were taken into consideration: H, NO₂, CN, CHO, COOH, F, CH₃, OH, and NH₂. Basic measures of aromatic character were derived from the structure and nucleus-independent chemical shift (NICS). The NICS calculations indicate a correlation between NICS(1.5) and the hardness in all species. The atoms in molecule analysis indicates a correlation between r(Ru-C) bonds and the electron density of bond critical point in all species.