1,4-Dihydropyridine/BF3OEt2 for the reduction of imines: Influences of the amount of added BF3OEt2 and the substitution at N-1 and C-4 of the dihydropyridine ring

We have evaluated four 1,4-dihydropyridines (DHPs 1a, 1b, 1c and 1d) as reducing agents, which presented free (hydrogenated) or phenyl-substituted N-1 and C-4 positions of the DHP ring. Reactions combining each of the DHP and different amounts of BF₃OEt₂ were evaluated for the reduction of imine 2a (N-benzylideneaniline). DHP simultaneously substituted at N-1 and C-4 (1a), and DHP substituted at C-4 (1b) gave lower yields for reduction of 2a in comparison with DHPs 1c and 1d (both unsubstituted at the C-4 position). By evaluating the amount of added BF₃OEt₂ to the reaction mixture, we have found that DHP 1c (substituted at N-1) provided its best yield for amine 3a (82%) when associated with stoichiometric amounts BF₃OEt₂, while DHP 1d (N-1- and C-4-unsubstituted derivative) was more effective (90% yield) with catalytic quantities of the Lewis acid. The reaction system using DHP 1c under stoichiometric BF₃OEt₂ could also be successfully applied with additional imine examples and under reductive amination conditions.     

Investigation of the compatibility between kaempferol and excipients by thermal,spectroscopic and chemometric methods

Journal of Thermal Analysis and Calorimetry - Compatibility is an important step in pre-formulation studies during the development of solid dosage forms. In the present study, we used thermal...     

Fish oil preparation inhibits leukocyte recruitment and bands that characterize inflamed tissue in a model of phenol-induced skin inflammation: percutaneous penetration of a topically applied preparation demonstrated by photoacoustic spectroscopy

Abstract

Fish oil (FO) is a natural source of omega-3 fatty acids, with well-established beneficial effects in inflammatory diseases when FO is orally administered. This study investigated the effects of a topically applied FO preparation (FOP) on phenol-induced ear edema and evaluated the percutaneous penetration of FOP in ear tissue. After applying phenol, groups of mice received FOP on the ear. After 1?h, ear tissue was collected to determine the percent inhibition of edema, myeloperoxidase activity, and to perform photoacoustic spectroscopy (PAS). Treatment with FOP did not reduce edema, but reduced myeloperoxidase activity. The FOP decreased the area of bands that characterize inflamed tissue and penetrated into the tissue. These results indicated an inhibitory effect of FOP on leukocyte recruitment in phenol-induced ear edema. These data support the applicability of PAS as a non-destructive method for evaluating the inflammatory response, percutaneous penetration and antiinflammatory activity of compounds.     

Phenolic characterization of Northeast Portuguese propolis: usual and unusual compounds

In this study, an ethanolic extract from Portuguese propolis was prepared, fractionated by high-performance liquid chromatography, and the identification of the phenolic compounds was done by electrospray mass spectrometry in the negative mode. This technical approach allowed the identification of 37 phenolic compounds, which included not only the typical phenolic acids and flavonoids found in propolis from temperate zones but also several compounds in which its occurrence have never been referred to in the literature. Four of the novel phenolic compounds were methylated and/or esterified or hydroxylated derivatives of common poplar flavonoids, although six peculiar derivatives of pinocembrin/pinobanksin, containing a phenylpropanoic acid derivative moiety in their structure, were also identified. Furthermore, the Portuguese propolis sample was shown to contain a p-coumaric ester derivative dimer.     

Electrochemical sensor for estriol hormone detection in biological and environmental samples

A stable conducting film for sensing using reduced graphene oxide (RGO), gold nanoparticles (GNPs), and potato starch (PS) is proposed. The characterization of the nanomaterials was obtained by ultraviolet and visible spectroscopy, dynamic light scattering, zeta potential, Fourier transform infrared spectroscopy, atomic force microscopy, and cyclic voltammetry. The voltammetric behavior of the RGO-GNPs-PS/GCE electrodes was studied in the presence of estriol and the results showed a high anodic peak current at 0.64 V. Under optimal conditions, an analytical curve was obtained, in which the anodic peak estriol was linear in the range from 1.5 to 22 μmol L^?1, with a detection limit of 0.48 μmol L^?1. The modified electrodes were applied for determination of estriol in environmental and biological samples. The proposed electrode was used for estriol determination in water and urine samples, which presented a recovery range from 92.1 to 106%, showing that RGO-GNPs-PS/GCE is a viable alternative for the detection of estriol and can be attractive for several electrochemical applications.     

Development and evaluation of microencapsulated sunscreen

The aim of the present study was to carry out stability tests and in vitro sun protection factor (SPF) evaluations of formulations containing free or microencapsulated chemical sun filters to improve their use. To this end, three formulations were developed and subjected to stability studies. The most stable formulation was chosen as a vehicle for free and microencapsulated chemical sun filters, and subjected to further stability studies and in vitro SPF assays. The SPF values were approximately 12 and 11 for formulations containing free and encapsulated sun filters, respectively, and both types were stable under stress. Chemical sun filters can be microencapsulated, which may aid in generating innovative sunscreen formulations.     

Inclusion of Benzaldehyde Semicarbazone into β-Cyclodextrin Produces a Very Effective Anticonvulsant Formulation

Aryl semicarbazones can be considered a novel class of compounds presenting anticonvulsant activity. In order to improve the efficiency and bioavailability of benzaldehyde semicarbazone (BS) we used the host–guest strategy and β-cyclodextrin (β-CD) to prepare a BS/β-CD 1:1 inclusion compound, which was characterized by thermal analyses (TG, DTG, DSC), XRD powder pattern diffraction analyses, infrared data and ¹H, ¹³C, 2D-ROESY NMR and ¹H relaxation times. The BS/β-CD inclusion compound was tested in rats using the maximum electroshock (MES) screen. The minimum dose necessary to produce anticonvulsant activity decreased from 100 mg/Kg (ip or vo) for the free semicarbazone to 25 mg/Kg/vo (75%) and 15 mg/Kg/ip (85%), indicating that the host–guest strategy that uses β-CD and BS is very effective and could be successfully employed in the preparation of pharmaceutical formulationof anticonvulsants.     

激波与涡对相互作用的实验研究

在方截面激波管中进行了平面运动激波和涡对的二维相互作用实验，研究了激波与同向涡对、激波与反向涡对相互作用的非定常过程．根据实验照片，分析讨论了作用过程中激波的变形，二次激波和三波点的形成、演变，激波与激波的相互作用，以及旋涡结构的变化等．实验表明，激波通过涡核时，激波发生剧烈变形，旋涡强度增大，涡核形状改变．