Electrochemical behavior of 5-type phosphodiesterase inhibitory drugs in solid state by voltammetry of immobilized microparticles

Journal of Solid State Electrochemistry - Evaluation of electrochemical behavior of 5-type phosphodiesterase inhibitory drugs is of major concern since they have been added illegally as adulterants...     

Vibrational spectroscopic studies,theoretical aspects,and X-ray analysis of xanthenodiones (1,8-dioxooctahydroxanthenes)

Compounds containing a pyran moiety fused to two cyclohexen-2-one rings are collectively called xanthenodiones (1,8-dioxooctahydroxanthenes). With the aim of increasing the knowledge about the structures of xanthenodiones, in the present investigation two xanthenodiones, namely 9-(4-hydroxy-3-methoxyphenyl)-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione ( 1 ) and 9-(4-hydroxyphenyl)-3,6-diisopropyl 3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione ( 2 ), were synthesized. Their structures were investigated by nuclear magnetic resonance, single-crystal X-ray diffraction, infrared (IR), and Raman spectroscopy techniques along with mass spectrometry. In addition, a computational study was carried out involving vibrational spectroscopy, which allowed us to assign vibrational modes and their shifts as lattice environment. Even though compound 2 has two stereocenters, it crystallized in a centrosymmetric space group (P2₁/c) as expected from its achiral synthesis. This compound also crystallized as monohydrate and the presence of water molecule did not change the conformation of the target compounds.     

HPLC–UV method for temozolomide determination in complex biological matrices: Application for in vitro,ex vivo and in vivo studies

A high‐performance liquid chromatography method for temozolomide (TMZ) determination in complex biological matrices was developed and validated for application in in vitro, ex vivo and in vivo studies of new nanotechnology‐based systems for TMZ nasal delivery. The method was able to quantify TMZ in nanoemulsions, following cellular uptake, in the porcine nasal mucosa and in mouse plasma and brain. Analyses were performed on a C₁₈ column at 35°C, under UV detection at 330 nm. The mobile phase was methanol–acetic acid 0.5% (30:70, v/v), eluted at an isocratic flow rate of 1.1 mL/min. The method was found to be specific, precise, accurate, robust and linear (0.05 to 5 μg/mL) for TMZ determination in all matrices. No interference of TMZ degradation products was found under various stress conditions such as acidic, alkaline, oxidative, light and thermal exposure, demonstrating stability. The method was applied for the quantification of TMZ in different matrices, i.e. the efficiency of nanoemulsions in vitro in increasing TMZ cellular uptake, ex vivo TMZ permeation and retention in the porcine nasal mucosa tissue, and for in vivo TMZ quantification in mouse brain following intranasal nanoemulsion administration compared with free TMZ.     

Allelopathic effect of the ethanol extract and fractions of the aerial parts of Lippia alba (Verbenaceae)

Lippia alba, belonging to the Verbenaceae family, is one of the most commonly utilized medicinal plants in folk medicine. The allelopathic activity was assessed using seeds of Lactuca sativa (lettuce) and Allium cepa (onion) by assessing the growth of the radicle and hypocotyl. The tests showed allelopathic efficiency in inhibiting the growth of lettuce and onion seeds. The best results for allelopathic activity were presented by the dichloromethane (DCM) fraction of the fresh plant, which inhibited radicle (23.04–100% lettuce and 64.17–66.36% onion) and hypocotyl (16.77–100% lettuce and 65.10–69.43% onion) formation, and as well as the DCM fraction of the dry plant, which also inhibited radicle (30.74–82.83% lettuce and 63.50–93.67% onion) and hypocotyl (24.12–70% lettuce and 69.07–79.95% onion) formation. Based on these results, it was found that the aerial parts of L. alba are rich in bioactive substances, suggesting the possibility of using of L. alba as a natural herbicide.     

A geometric singular perturbation theory approach to constrained differential equations

This paper is concerned with a geometric study of ()‐parameter families of constrained differential systems, where . Our main results say that the dynamics of such a family close to the impasse set is equivalent to the dynamics of a multiple time scale singular perturbation problem (that is a singularly perturbed system containing several small parameters). This enables us to use a geometric theory for multiscale systems in order to describe the behaviour of such a family close to the impasse set. We think that a systematic program towards a combination between geometric singular perturbation theory and constrained systems and problems involving persistence of typical minimal sets are currently emergent. Some illustrations and applications of the main results are provided.     

Cellulose nanofibers from curaua fibers

Curaua nanofibers extracted under different conditions were investigated. The raw fibers were mercerized with NaOH solutions; they were then submitted to acid hydrolysis using three different types of acids (H₂SO₄, a mixture of H₂SO₄/HCl and HCl). The fibers were analyzed by cellulose, lignin and hemicellulose contents; viscometry, X-ray diffraction (XRD) and thermal stability by thermogravimetric analysis (TG). The nanofibers were morphologically characterized by transmission electron microscopy (TEM) and their surface charges in suspensions were estimated by Zeta-potential. Their degree of polymerization (DP) was characterized by viscometry, crystallinity by XRD and thermal stability by TG. Increasing the NaOH solution concentration in the mercerization, there was a decrease of hemicellulose and lignin contents and consequently an increase of cellulose content. XRD patterns presented changes in the crystal structure from cellulose I to cellulose II when the fibers were mercerized with 17.5% NaOH solution. All curaua nanofibers presented a rod-like shape, an average diameter (D) of 6–10 nm and length (L) of 80–170 nm, with an aspect ratio (L/D) of around 13–17. The mercerization of fibers with NaOH solutions influenced the crystallinity index and thermal stability of the resulting nanofibers. The fibers mercerized with NaOH solution 17.5% resulted in more crystalline nanofibers, but thermally less stable and inferior DP. The aggregation state increases with the amount of HCl introduced into the extraction, due to the decrease of surface charges (as verified by Zeta Potential analysis). However, this release presented nanofibers with better thermal stability than those whose acid hydrolysis was carried out using only H₂SO₄.     

Gibbs free energy of transfer of a methylene group on {UCON + (sodium or potassium) phosphate salts} aqueous two-phase systems: Hydrophobicity effects

The Gibbs free energy of transfer of a suitable hydrophobic probe can be regarded as a measure of the relative hydrophobicity of the different phases. The methylene group (CH₂) can be considered hydrophobic, and thus be a suitable probe for hydrophobicity. In this work, the partition coefficients of a series of five dinitrophenylated-amino acids were experimentally determined, at 23 °C, in three different tie-lines of the biphasic systems: (UCON + K₂HPO₄), (UCON + potassium phosphate buffer, pH 7), (UCON + KH₂PO₄), (UCON + Na₂HPO₄), (UCON + sodium phosphate buffer, pH 7), and (UCON + NaH₂PO₄). The Gibbs free energy of transfer of CH₂ units were calculated from the partition coefficients and used to compare the relative hydrophobicity of the equilibrium phases. The largest relative hydrophobicity was found for the ATPS formed by dihydrogen phosphate salts.