Helber Barbosa

TEMPERATURE-DEPENDENCE OF THE SOLUBILITY OF SOME ACETANILIDE DERIVATIVES IN SEVERAL ORGANIC AND AQUEOUS SOLVENTS

The thermodynamic functions free energy, enthalpy, and entropy of solution, were evaluated from the solubility data of acetanilide, acetaminophen, and phenacetin, determined at several temperatures in water, octanol, isopropyl myristate, and chloroform. These three organic solvents mutually saturated with water, and finally, in cyclohexane. In the aqueous media, the solubility was determined at pH 7.4 and ionic strength 0.15 mol L−1. The excess free energy and the activity coefficients of the solutes were also determined. The solubility for acetanilide and phenacetin was higher in organic media such as octanol and chloroform than is those obtained in the aqueous media and cyclohexane, while for acetaminophen the solubility was higher in octanol than those obtained in the other solvents.

Thermal and structural study of guava (Psidium guajava L) powders obtained by two dehydration methods

Two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. The powders were characterised by sensory and thermal analyses (TGA-DSC), infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal, morphological and structural characterisations showed a similar behaviour for the two solids. TGA-DSC and IR showed the presence of pectin as the main constituent of solids. A semi-crystalline profile was evidenced by XRD, and lamellar/spherical morphologies were observed by SEM. Sensory analyses revealed an aroma highly related to guava. These value-added food products are an alternative to process guava and avoid loss during postharvest handling.

In vitro analysis regarding the safety of components used in a film-based therapeutic system loaded with meglumine antimoniate and its activity toward Leishmania major experimental infections: a preliminary study.

Abstract Owing to its biocompatibility properties and its ability to promote the scar healing process, chitosan is employed in tissue engineering for the manufacture of formulations. To control the characteristic skin ulcers of cutaneous leishmaniasis (CL), the use of a biopolymeric system that favors the scar healing process and releases an active agent such as meglumine antimoniate may be a better option. For these reasons, here we analyzed the cytotoxic capabilities of excipients [medium molecular weight chitosan (MMWC), lactic acid (LA) and polyvinylpyrrolidone (PVP)], used for the formulation of a film-based therapeutic system that releases meglumine antimoniate and were evaluated on human macrophages [monocyte-derived macrophages (MDMs)], L929 fibroblasts and parasites (Leishmania major promastigotes and intracellular amastigotes). The ability of excipients to modulate the cytokines production involved in the scar healing process was compared with film-based therapeutic system. The efficiency of a film-based therapeutic system loaded with meglumine antimoniate was compared with conventional formulation (Albiventriz®). We found that MMWC was toxic for two parasite forms. In contrast, measurement of interleukin levels did not show any evidence of preferential secretion as a side effect of treating human macrophages with MMWC. Finally, the efficiency of a polymeric film-based therapeutic system that was loaded with meglumine antimoniate could not be determined due to the high degree of toxicity observed in infected MDMs; moreover, these compounds do not induce any apparent immunomodulatory effects. Our findings suggest that the final concentrations of each excipients (MMWC, LA and PVP) that were used in the polymeric film were suitable vehicles for active pharmaceutical compound delivery and did not selectively affect (enhancing or diminishing immune activity) macrophages.

Thermodynamic quantities of solvation and dilution for some acetanilide derivatives in octanol and water mutually saturateds

Based on published thermodynamic quantities for solution, partitioning and sublimation of acetanilide (ACN), acetaminophen (ACP) and Phenacetin (PNC), the thermodynamic quantities for drugs solvation in octanol-saturated water (W(ROH)) and water-saturated octanol (ROH(W)) as well as the drugs dilution in ROH(W) were calculated. The Gibbs energies of solvation were favourable in all cases. The respective enthalpies and entropies were negative indicating an enthalpy-driving for the sol- vation process in all cases. On the other hand, the Gibbs energies of dilution were favourable for ACP and PNC but unfavourable for ACN, whereas the respective enthalpies and entropies were negative for ACP and PNC but positive for ACN indicating enthalpy-driving for the dilution process in the case of the former drugs and entropy-driving for the latter. From the obtained values for the transfer process- es, an interpretation based on solute-solvent interactions was developed.

Design of a Device for Recording Bioelectric Signals with Surface Electrodes, in the Evaluation of the Effect of Ultraviolet Radiation on a Tissue

The accepted methodology by regulatory agencies to determine the efficacy of sunscreen products makes use of healthy human volunteers who are exposed to radiation. In order to find an alternative to these types of evaluations, the effect of exposure to UV radiation was investigated in an ex vivo pig skin model on the bioelectrical signals of the tissue in terms of energy and impedance. A system was implemented using the measurements configuration of 4 electrodes (Two electrostimulation electrodes and two electrodes for the signals acquisition all of them were silver cup electrodes) and a mathematical model was established in relation to electrical change as a function of exposure time. As a result, an attenuation of the energy response signal relative to the non-irradiated tissue was obtained, as well as impedance values after irradiation. This behavior is directly related to damage in the tissue structure. The results allow to conclude that the device can quantify the effect caused by radiation on the electrical properties of an ex vivo tissue and are promising in the understanding of the phenomena associated with the electrical response of a tissue to ultraviolet radiation.