Two new isoflavonoids from Bowdichia virgilioides

Two new isoflavonoids 7,8,4'-trimethoxyisoflavone and 7,8,4'-trimethoxyisoflavanone and calycosin (7,3'-hydroxy-4'-methoxyisoflavone) were isolated from the wood of the leguminous tree Bowdichia virgilioides by usual chromatographic procedures. Besides these compounds the pterocarpane (-)-maackianin, isoliquiritigenin (4,2',4'-trihydroxychalcone), and the hydrobenzylfurane derivative bowdenol were also obtained. The structures of these new compounds were determinated by MS and 1D and 2D NMR spectral analysis.     

Optimization of solid-phase microextraction procedures for the determination of tricyclic antidepressants and anticonvulsants in plasma samples by liquid chromatography

Simple, sensitive, and reproducible off-line solid-phase microextraction and liquid chromatography (SPME/LC) methods are described for the determination of seven anticonvulsants and tricyclic antidepressants in human plasma. Factorial design and simplex methodology were applied in the optimization of the SPME procedure for tricyclic antidepressants analyses. Important factors in the SPME efficiency are discussed, such as the fiber coatings (both lab-made and commercial), extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The development of the lab-made fiber coatings, namely, octadecylsilane, aminosilane, and polyurethane, are further described and applied to anticonvulsants analyses. The investigated plasmatic range for the evaluated anticonvulsants, using CW-TPR fiber, were the following: phenylethylmalonamide (3.00–40.0 μg mL⁻¹), phenobarbital (5.00–40.0 μg mL⁻¹), primidone (3.00–40.0 μg mL⁻¹), carbamazepine and carbamazepine-epoxide (2.00–24.0 μg mL⁻¹), phenytoin (2.00–40.0 μg mL⁻¹), and lamotrigine (0.50–12.0 μg mL⁻¹). The antidepressants’ linear plasmatic concentration ranged from 75.0 to 500 ng mL⁻¹ for imipramine, amitriptyline, and desipramine, and from 50.0 to 500 ng mL⁻¹ for nortriptyline, being in all cases, the limit of quantification represented by the lowest value. The precision (interassays) for all investigated drugs in plasma sample spiked with different concentrations of each analyte and submitted to the described procedures were lower than 15%. The off-line SPME/LC methodologies developed allow anticonvulsants and antidepressants analyses from therapeutic to toxic levels for therapeutic drug monitoring.     

Design of an NO photoinduced releaser xerogel based on the controlled nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF6)2 (cyclam=1,4,8,11-tetraazacyclotetradecane)

The immobilization and properties of the nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF(6))(2), RuNO, entrapped in a silica matrix by the sol-gel process is reported herein. The entrapped nitrosyl complex was characterized by spectroscopic (UV-vis, infrared (IR), X-ray photoelectron, and (13)C and (29)Si MAS NMR) and electrochemical techniques. The entrapped species exhibit one characteristic absorption band in the UV-vis region of the electronic spectrum at 354 nm and one IR nu(NO) stretching band at 1865 cm(-1), as does the RuNO species in aqueous solution. Our results show that trans-[Ru(NO)Cl(cyclam)](PF(6))(2) can be entrapped in a SiO(2) matrix with preservation of the molecular structure. However, in a SiO(2)/SiNH(2) matrix, the complex undergoes a nucleophilic attack by the amine group at the nitrosonium. Irradiation of the complex, entrapped in the SiO(2) matrix, with light of 334 nm, resulted in NO release. The material was regenerated to its initial nitrosyl form by reaction with nitric oxide.     

On the synthesis and structures of the complexes [RuCl(L)(dppb)(N–N)]PF6 (L = CO,py or 4-NH2py; dppb = 1,4-bis(diphenylphosphino)butane; N–N = 2,2′-bipyridine or 1,10-phenanthroline) and [(dppb)(CO)Cl2-Ru-pz-RuCl2(CO)(dppb)] (pz = pyrazine)

The “Ru(P–P)” unit (P–P = diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl₂Ru-pz-RuCl₂(CO)(dppb)] (pz = pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF₆ (N–N = diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF₆ were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl₂(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and ³¹P{¹H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography.     

Oxidation Mechanism of 1-Methyl-tryptophan and Tryptophan on Glassy Carbon Electrode: A Comparative Study

The anodic behaviour of 1-methyl-tryptophan (1-mTrp) in aqueous electrolytes was investigated on a glassy carbon electrode (GCE), using voltammetric techniques. The oxidation of 1-mTrp was associated with an electrochemical-chemical (EC) mechanism: one electron and one proton were removed of C2 to form an intermediate radical, 1-mTrp⋅. This was followed by a two-way reaction, producing a 1-mTrp dimer and/or reaction with water to form a final hydroxylated product. The oxidation mechanism of 1-mTrp proposed was also compared with the anodic oxidation Trp on GCE. Differential pulse voltammetry was also explored for quantification of Trp and 1-mTrp in neutral medium with low detection limits, on an anodically pre-treated GCE.