ABSTRACT
Four imidazolium-based ionic liquids (IL; 1-butyl-3-methylimidazolium chloride, 1-carboxymethyl-3-methylimidazolium chloride, 1,3-dicarboxymethylimidazolium chloride and 1-(2-hydroxyethyl) -3-methylimidazolium chloride) were tested as compatibilizers of microcrystalline cellulose (MCC). Subsequently, ethanolic IL solutions were prepared; MCC was mixed, and the mixtures were left to evaporate the ethanol at ambient conditions. These modified MCC were characterized and applied as reinforcements (5.0 and 10 phr) in an epoxy resin aiming to manufacture biobased composites with enhanced performances. The IL did not significantly modify the morphological and structural characteristics of such reinforcements. Regarding the thermal stability, the slight increase was associated with the MCC-IL affinity. The IL-modified MCC-epoxy composites presented improved mechanical responses, such as flexural strength (≈22.5%) and toughness behavior (≈18.6%), compared with pure epoxy. Such improvement was also obtained for the viscoelastic response, where the storage modulus at the glassy state depended on the MCC amount and IL type. These differences were associated with stronger hydrogen bonding between IL and epoxy hardener or the IL with MCC, causing a "bridging" effect between MCC and epoxy matrix.
ABSTRACT
In this study we explored the previously established leishmanicidal activity of a complementary set of 24 imidazolium salts (IS), 1-hexadecylimidazole (C16Im) and 1-hexadecylpyridinium chloride (C16PyrCl) against Leishmania (Leishmania) amazonensis and Leishmania (Leishmania) infantum chagasi. Promastigotes of L. amazonensis and L. infantum chagasi were incubated with 0.1 to 100 µM of the compounds and eight of them demonstrated leishmanicidal activity after 48 h - C10MImMeS (IC50 L. amazonensis = 11.6), C16MImPF6(IC50 L. amazonensis = 6.9), C16MImBr (IC50 L. amazonensis = 6), C16M2ImCl (IC50 L. amazonensis = 4.1), C16M4ImCl (IC50 L. amazonensis = 1.8), (C10)2MImCl (IC50 L. amazonensis = 1.9), C16Im (IC50 L. amazonensis = 14.6), and C16PyrCl (IC50 L. amazonensis = 4).The effect of IS on reactive oxygen species production, mitochondrial membrane potential, membrane integrity and morphological alterations of promastigotes was determined, as well as on L. amazonensis-infected macrophages. Their cytotoxicity against macrophages and human erythrocytes was also evaluated. The IS C10MImMeS, C16MImPF6, C16MImBr, C16M2ImCl, C16M4ImCl and (C10)2MImCl, and the compounds C16Im and C16PyrCl killed and inhibited the growth of promastigote forms of L. amazonensis and L. infantum chagasi in a concentration-dependent manner, contributing to a better understanding of the structure-activity relationship of IS against Leishmania. These IS induced ROS production, mitochondrial dysfunction, membrane disruption and morphological alterations in infective forms of L. amazonensis and killed intracellular amastigote forms in very low concentrations (IC50 amastigotes ≤ 0.3), being potential drug candidates against L. amazonensis.
