Cristiane C. Nascimento

One-step preparation of CdS nanocrystals supported on thiolated silica-gel matrix and evaluation of photocatalytic performance

Here we report the use of a thiol-functionalized silica-gel to prepare supported CdS nanocrystals by a facile one-step procedure. Upon changing the relative proportion of the matrix we obtained nanocrystals with different average sizes and size distributions, as evidenced by spectroscopic measurements as well as TEM images. Photoluminescence spectra also indicated that the main effect of the matrix is related to the size control since the spectral profiles were found to be strongly dependent on the excitation wavelength. The performance of the material in the photocatalytic degradation of two commercial dyes (methylene blue and rhodamine 6G) has been tested under sunlight radiation, showing promising results. Almost complete decolorization has been observed after 80 min of exposure, with no adsorption on the silica surface.

Characterization, phase solubility and molecular modeling of α-cyclodextrin/pyrimethamine inclusion complex

An inclusion complex between the dihydrofolate reductase inhibitor pyrimethamine (PYR) and alpha-cyclodextrin (alpha-CD) was prepared and characterized. From the phase-solubility diagram, a linear increase of PYR solubility was verified as a function of alpha-CD concentration, suggesting the formation of a soluble complex. A 1:1 host-guest stoichiometry can be proposed according to the Jobs plot, obtained from the difference of PYR fluorescence intensity in the presence and absence of alpha-CD. Differential scanning calorimetry (DSC) measurements provided additional evidences of complexation such as the absence of the endothermic peak assigned to the melting of the drug. The inclusion mode characterized by two-dimensional (1)H NMR spectroscopy (ROESY) involves penetration of the p-chlorophenyl ring into the alpha-CD cavity, in agreement to the orientation optimized by molecular modeling methods.

Development and characterization of microencapsules containing spray dried powder obtained from Brazilian brown, green and red propolis

The aim of this study was to obtain dried powders from the brown, green and red varieties of the Brazilian propolis by spray drying, using gum arabic and maltodextrin as encapsulating materials. Propolis microparticles were evaluated for particle size, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), moisture, water activity, solubility, hygroscopicity, encapsulation efficiency, total phenolic content, flavonoids and antioxidant activity (DPPH, ABTS+, FRAP, ORAC). Bioactive compounds were determined by UPHLC-QqQ-MS/MS. The results showed that the microparticles presented spherical forms, smooth surfaces, amorphous characteristics, low water activity, moisture and hygroscopicity, high solubility, good encapsulation efficiency, good antioxidant activity, although a reduction in total phenolics and flavonoids from the non-encapsulated propolis. The most important compounds in propolis powders were artepillin C, kaempferide, p-coumaric acid, luteolin, chlorogenic acid, kaempferol and caffeic acid. Spray-drying of propolis is a viable option to increase its use in food and pharmaceutical applications.