Search Results

You are looking at 1 - 2 of 2 items for

  • Author or Editor: Luiz Pires x
  • Refine by Access: All Content x
Clear All Modify Search

This report investigates the effect of sampling by the volumetric ring method on pore size number and shape distributions. Soil porosity was analyzed using the micromorphological image analysis technique, which helped to explain soil structure changes near the border of samples collected in cylinders and provided detailed information about pore shape, number, and size distribution variations along the samples. Compaction due to sampling affects mainly large irregular and rounded pores of the soils utilized in this study. When evaluating inaccuracies in density measurements due to the compacted regions caused by the sampling device the average soil bulk density for each soil resulted in the ranges of 1.72 ± 0.05 g.cm −3 for Geric Ferralsol soil, 1.66 ± 0.03 g.cm −3 for Eutric Nitosol soil and 1.33 ± 0.05 g.cm −3 for Rhodic Ferralsol soil, respectively. When calculating the average soil bulk density over smaller regions, e.g. in the center of each sample (area of 17.14 mm 2 ) results reduced to 1.64 ± 0.05 g.cm −3 with Geric Ferralsol soil, 1.56 ± 0.03 g.cm −3 with Eutric Nitosol soil and 1.29 ± 0.10 g.cm −3 with Rhodic Ferralsol soil, respectively. These results clearly indicate the effect of sampling by the volumetric ring method. The use of image analysis was essential to explain compaction differences close to the border of the samples collected using cylinders (volumetric ring method) and provided detailed information about pore shape and size distribution variations within soil samples. The results are useful as indicators of the consequences of sampling on the quality of soil samples.

Restricted access

Quercetin-PVP K25 solid dispersions

Preparation, thermal characterization and antioxidant activity

Journal of Thermal Analysis and Calorimetry
Authors: Ana Rita de Mello Costa, Flávia Silva Marquiafável, Mirela Mara de Oliveira Lima Leite Vaz, Bruno Alves Rocha, Paula Carolina Pires Bueno, Pedro Luiz M Amaral, Hernane da Silva Barud, and Andresa Ap Berreta-Silva

Abstract

Quercetin is a flavonoid very well studied and has already entered clinical trials emerging as prospective anticancer drug candidate. In addition, quercetin has being reported to its free-radical scavenging activity and suggests potential uses for the prevention and treatment of pathologies as atherosclerosis, chronic inflammation, and others. However, quercetin is sparingly soluble in water, which may be responsible for its limited absorption upon oral administration. The solid dispersion of quercetin with polyvinylpyrrolidone Kollidon® 25 (PVP K25) suggests an interesting way to increase quercetin solubility, antioxidant activity, and consequently bioavailability. Then, the purpose of this study was to prepare solid dispersions of quercetin with PVP K25 and evaluate their thermal characterization, antioxidant activity and quercetin improvement solubility. For this purpose, quercetin-PVP K25 solutions were dried and quercetin-PVP K25 solids were obtained. The formation of quercetin-PVP K25 solid dispersion was evaluated by solubility studies, powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetry (TG), and antioxidant activity. It was observed that PVP K25 was able to provide quercetin clear aqueous solutions and that quercetin solubility was increased in a PVP K25 concentration dependent manner, improving solubility even 436-fold the pure quercetin. The results obtained with XRD, FT-IR, DSC, and TG demonstrated possible quercetin-PVP K25 solid dispersion formation. Besides, the antioxidant activity of the quercetin-PVP K25 solid dispersions dissolved in aqueous solution and pure quercetin dissolved in methanol showed IC50 value of 0.61 ± 0.03 and 1.00 ± 0.02 μg/mL, respectively, demonstrating that the solid dispersions presented a significant increase in antioxidant activity (P < 0.05). Putting results together, it was possible to conclude there was the formation of quercetin-PVP K25 solid dispersion.

Restricted access