Insecticidal Activity and Free Radical Scavenging Properties of Isolated Phytoconstituents from the Saudi Plant Nuxia oppositifolia (Hochst.)

Chromatographic purification of the alcoholic extract from the aerial parts of the Saudi plant Nuxia oppositifolia (Hochst.), Benth., resulted in five isolated phenolic compounds. Two flavones, hispidulin (1) and jaceosidin (2), and the phenylethanoid glycosides, verbascoside (3), isoverbascoside (4), and conandroside (5), were identified and their chemical structures were determined by spectroscopic analyses. The insecticidal activity of compounds 1 and 2, in addition to 11 compounds isolated in a previous research (6–16), was evaluated against the Yellow Fever mosquito, Aedes aegypti. Four compounds displayed adulticidal activity with LD₅₀ values of 2–2.3 μg/mosquito. Free radical scavenging properties of the plant extracts and compounds (1–5) were evaluated by measuring the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate radical cation (ABTS^•+) scavenging activity. All compounds exhibited notable activity, compared with the positive control, l-Ascorbic acid. This study suggests that N. oppositifolia could be a promising source of secondary metabolites, some with lethal adulticidal effect against Ae. aegypti.     

Phosphanimin- und Phosphaniminato-Komplexe von Eisen. Die Kristallstrukturen von [FeCl3(Me3SiNPEt3)], [FeCl2(Me3SiNPEt3)]2, [FeCl2(NPEt3)]2 und [Fe(O2C?CH3)2(NPEt3)]2

Phosphanimine and Phosphoraneiminato Complexes of Iron. The Crystal Structures of [FeCl₃(Me₃SiNPEt₃)], [FeCl₂(Me₃SiNPEt₃)]₂, [FeCl₂(NPEt₃)]₂, and [Fe(O₂C? CH₃)₂(NPEt₃)]₂ The phosphanimine complexes [FeCl₃(Me₃SiNPEt₃)] (red-orange) and [FeCl₂(Me₃SiNPEt₃)]₂ (colourless) have been prepared by reactions of Me₃SiNPEt₃ with FeCl₃ and FeCl₂, respectively, in CH₂Cl₂ suspensions. Thermal decomposition of these donor-acceptor complexes in boiling toluene leads to the phosphoraneiminato complex [FeCl₂(NPEt₃)]₂ (black), whereas [Fe(O₂C? CH₃)₂(NPEt₃)]₂ (brown) is formed from iron(II) acetate and Me₃SiNPEt₃ in boiling acetonitrile. The complexes are characterized by IR spectroscopy and by crystal structure determinations. [FeCl₃(Me₃SiNPEt₃)] (1) : Space group P2₁/c, Z = 8, structure determination with 4 673 unique reflections, R = 0.033. Lattice dimensions at ?15°C: a = 1 607.8, b = 1 602.0, c = 1 417.2 pm, β = 106.56°. 1 forms monomeric molecules with tetrahedrally coordinated iron atoms. Bond lengths in average: Fe? N = 196.9 pm, Fe? Cl = 219.7 pm. [FeCl₂(Me₃SiNPEt₃)]₂ (2) : Space group P2₁/c, Z = 4, structure determination with 4 992 unique reflections, R = 0.048. Lattice dimensions at 20°C: a = 1 457.9, b = 1 685.4, c = 1 507.3 pm, β = 116.74°. 2 forms dimeric molecules, which are associated by chloro bridges. The iron atoms are tetrahedrally coordinated with trans positions of the phosphanimine ligands. Both lengths in average: Fe? N = 202.2 pm, Fe? Cl_terminal = 224.7 pm, Fe? Cl bridge = 241.0 pm. [FeCl₂(NPEt₃)]2 (3): Space group P2₁/n, Z = 2, structure determination with 2763 unique reflections, R = 0.039. Lattice dimensions at ?70°C: a = 799.1, b = 1009.0, c = 1441.9 pm, β = 93.45°. 3 forms centrosymmetric dimeric molecules, in which the tetrahedrally coordinated iron atoms are associated by the nitrogen atoms of the phosphoraneiminato ligands. Bond lengths in average: Fe? N = 191.4 pm, Fe? Cl = 222.7 pm. [Fe(O₂C? CH₃)₂(NPEt₃]2 (4): Space group P2₁/n, Z = 2, structure determination with 3005 observed unique reflections, R = 0.034. Lattice dimensions at -65°C: a = 886.4, b = 1444.6 pm, β = 90.60°. 4 forms centrosymmetric dimeric molecules, in which the octahedrally coordinated iron atoms are associated by the nitrogen atoms of the phosphoraneiminato ligands with bond lengths Fe? N of 191.9 and 195.0 pm. The acetate groups are coordinated in a chelating fashion.     

Enantioselective iodolactonization catalyzed by chiral quaternary ammonium salts derived from cinchonidine

Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent.     

Competitive disproportionation and demethylation of toluene on Mg-containing Y zeolites

On Mg-containing Y zeolites toluene undergoes disproportionation and demethylation. The relative importance of the two processes is discussed.

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Mg- Y . .

     

Neosappanone A, a xanthine oxidase (XO) inhibitory dimeric methanodibenzoxocinone with a new carbon skeleton from Caesalpinia sappan

A novel dimeric methanodibenzoxocinone, named neosappanone A (1), possessing a unique unprecedented novel carbon framework, has been isolated from the heartwood of Caesalpinia sappan L. of Vietnam, and its structure was elucidated on the basis of spectroscopic analysis. Neosappanone A (1) competitively inhibited xanthine oxidase in a concentration-dependent manner (IC₅₀, 29.7 μM; K_i, 16.3 μM).     

Mechanism of o-xylene conversion on magnesium modifications of Y zeolite

o-Xylene conversions has been investigated in the presence of MgNaY zeolites with different Si/Al ratios and degrees of exchange. Disproportionation proceeds to a higher degree than does isomerization. The distribution of reaction products is attributed to geometric factors. The results are in agreement with a monomolecular mechanism of isomerization.

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- MgNaY Si/Al . , , . . .

     

多壁碳纳米管-Nafion复合膜修饰玻碳电极测定硝苯地平的研究

研制了以Nafion分散羧基化多壁碳纳米管的化学修饰电极(Nafion-MWCNTs/GC),研究了硝苯地平(NIF)在修饰电极上的电化学行为和测定方法。实验结果表明,在0.1mol/LNH3-NH4Cl(pH9.6)溶液中,Nafion-MWCNTs/GC,对NIF具有明显的催化和增敏作用,还原峰电位由-0.85V(裸电极)正移到-0.75V(vs.AgCl/Ag)(修饰电极),灵敏度增加约7倍。对各种实验条件进行了优化。定量测定的线性范围为2.5×10-7~4.5×10-5mol/L,r为0.9974;检出限为8.0×10-8mol/L。探讨了NIF在Nafion-MWCNTs/GC上的电极过程和反应机理,测得在本体系中参与反应的质子数和电子转移数均为4,电子转移系数α为0.41。对NIF药片进行了测定,回收率为94.5%~101.0%。     

海口市正常儿童头发中四种微量元素含量

用电感耦合等离子体发射光谱法（ＩＣＰ－ＡＥＳ），测定了海口市２６６例正常儿童头发中锌、铁、阵、铜四种微量元素的含量，计算出海口市儿童四各微量元素的正常范围。并与其它地区文献报道值进行了比较。     

Y2O3涂层负载Pd整体式催化剂的制备和催化性能

以Y(NO3)3为前驱体制备了Y2O3涂层的堇青石蜂窝陶瓷载体.扫描电子显微镜、X射线能谱和超声波振荡等表征结果表明,Y2O3涂层不但具有良好的抗振荡性和粘结强度,而且具有很强的吸附催化剂活性组分(H2PdCl4)的能力,适合制备负载型Pd催化剂.以甲苯和乙酸乙酯完全燃烧为模型反应考察了催化剂的活性,发现以Y2O3涂层堇青石蜂窝陶瓷为载体的整体式Pd/Y2O3催化剂具有良好的催化活性和热稳定性,甲苯和乙酸乙酯催化燃烧的T99分别为210和300℃;催化剂经900℃焙烧4 h后,T99仅提高20℃,表明催化剂具有很高的热稳定性.催化剂的X射线衍射、拉曼光谱和程序升温还原结果表明,Pd/Y2O3催化剂经低温焙烧时,Y2O3和PdO均高度分散在堇青石蜂窝陶瓷的表面,而高温焙烧使催化剂活性组分PdO晶粒增大,从而导致催化剂活性下降.