In vitro anti-Leishmania activity of T6 synthetic compound encapsulated in yeast-derived ß-(1,3)-d-glucan particles.

The objective of this study was to encapsulate a synthetic compound, the 4-[(2E)-N'-(2,2'-bithienyl-5-methylene)hydra-zinecarbonyl]-6,7-dihydro-1-phenyl-1H-pyrazolo[3,4-d]pyridazin-7-one (T6) in glucan-rich particles mainly composed by the cell wall of Saccharomyces cerevisiae (GPs) and to study their individual and combined activity on Leishmania infantum. The possible mechanism of action of T6 was also investigated. Our results showed the activity of T6 compound in both promastigote (IC50 = 2.5 µg/mL) and intracellular amastigote (IC50 = 1.23 µg/mL) forms. We also found activity against intracellular amastigote forms (IC50 = 8.20 µg/mL) when the T6 compound was encapsulated in GPs. Another interesting finding was the fact that T6 encapsulated in GPs showed a significant decrease in J774A1 macrophage toxicity (CC50 ≥ 18.53 µg/mL) compared to the T6 compound alone (IC50 = 2.27 µg/mL). Through electron microscopy and biochemical methodologies, we verified that the activity of T6 in promastigote forms of L. infantum was characterized by events of cell death by apoptosis like increased ROS production, cell shrinkage, phosphatidylserine exposure and DNA fragmentation. We conclude that T6 can be considered a promising anti-Leishmania compound, and that the use of GPs for drug encapsulation is an interesting approach to the development of new effective and less toxic formulations.

A dissolução in vitro na previsão da absorção oral de fármacos em formas farmacêuticas de liberação modificada / Dissolution studies in vitro as a prognostic tool for oral absorption of modified release pharmaceutical dosage forms

Pretende-se com o presente trabalho abordar os aspectos teóricos e práticos dos estudos de dissolução das formas farmacêuticas sólidas orais de liberação modificada, em três partes. Na primeira parte faz-se referência à classificação, interesse terapêutico e teoria da liberação do fármaco. Na segunda parte abordam-se as teorias de dissolução, os modelos de liberação, os sistemas de dissolução e sua validação, as especificações e critérios de aceitação dos ensaios de dissolução e ainda os fatores condicionates da dissolução, liberação e absorção. Na terceira parte confrontam-se as condições em que são efetuados os ensaios de dissolução com os parâmetros fisiológicos, fazendo referência aos meios de dissolução e composição do lume do trato gastrintestinal e ao modelos hidrodinâmicos