2% along 720 minutes, PHBV microparticles showed DE of 73.3% (M1R5), http://www.selleckchem.com/products/chir-99021-ct99021-hcl.html 78.6% (M1R10), and 88.9% (M1R20). For PCL microparticles, DE of 52.2, 78.0, and 85.0% was obtained for M2R5, M2R10, and M2R20, respectively. Previous papers reported that a high DE was verified for pharmaceutical dosage forms of immediate release while a lower value was indicative of a controlled release behavior [46, 47]. The release profiles were fitted to mathematical models, and the selection of the best model considered the correlation coefficient (r), the model selection criteria (MSC), and the graphic adjustment. Resveratrol and PHBV/PCL microparticles were better fitted to the biexponential equation (Table 4) than other models. The burst-release apparent rate constant (��) and the slow-release apparent rate constant (��) for resveratrol and PHBV/PCL microparticles are reported in Table 4.

Table 4Release data obtained by fitting the dissolution profiles of pure resveratrol and PHBV/PCL microparticles to the biexponential equation. These results demonstrated that PHBV/PCL microparticles reduced the drug dissolution rate, nevertheless without changing its release model. The first stage of release was initially rapid (burst release) whereas the second stage of release was slow (controlled release). The burst release can help to reach the effective concentration of resveratrol rapidly in plasma, whereas the controlled release would maintain the effective concentration of drug in plasma for a long time [22].

Moreover the poor bioavailability of resveratrol due to its rapid metabolism, including its conjugation with sulfate in the intestinal mucosa, and elimination could be partially avoided by microencapsulation, thus prolonging its biological half-time in vivo. Concerning the mathematical modeling fitting the Korsmeyer-Peppas model, PHBV microparticles showed n values of 1.23 (M1R5), 0.89 (M1R10), and 1.28 (M1R20). For PCL microparticles, n values of 0.65, 0.57, and 0.73 were obtained for M2R5, M2R10, and M2R20, respectively. PHBV microparticles presented values of n greater than 0.85 indicating that the release mechanism is governed by erosion [27]. Considering that PHBV is an aqueous-insoluble polymer, the process can occur by sequential stages of entrance of water and drug release. Otherwise PCL microparticles revealed values of n between 0.43 and 0.85.

These intermediate values are related to an anomalous behavior, a non-Fickian kinetics corresponding to the superposition of diffusion and erosion phenomena [27].3.8. Antioxidant PotentialIn order to explore whether the microencapsulation has influence on antioxidant capacity of resveratrol, HOCl-scavenging activity and ABTS radical cation AV-951 discoloration assay of pure resveratrol and resveratrol-loaded microparticles at the same drug concentrations were compared.