Reações de cicloadição : uma abordagem teórica e aplicações em síntese orgânica

Este artigo aborda os principais aspectos teóricos das reações de cicloadição, considerando a teoria de orbitais moleculares e a teoria de perturbações. Além disso, as reações de Diels-Alder e as reações 1,3-dipolares (cicloadições térmicas [4+2]) são detalhadas e exemplos de aplicações dessas reações são apresentados.This review reports the theoretical approach of the main aspects of cycloaddition reactions, considering the molecular orbital and perturbation theories. Moreover, Diels-Alder and 1,3-dipolar reactions (thermal [4+2] cycloadditions) are detailed and some examples of their application are described

Estudos Artísticos

Os quinze artigos que aqui se reúnem, nesta edição da Revista Croma, são também as propostas para uma nova política, esclarecida, crítica, e mais exigente. Podem observar-se padrões de intervenção, que partem de algumas dimensões comuns: a interpelação do observador, a criação de novos públicos, a proposta de contribuir para uma mudança alargada, partindo de questões a que não são alheias as problemáticas contemporâneas. As questões de género, a emancipação pós-colonial, a sustentabilidade, as migrações, a massificação, a globalização, o fim das ideologias e a ascensão do populismo, entre outras, constituem os contextos da atualidadeinfo:eu-repo/semantics/publishedVersio

Estudos Artísticos

A arte inclui no seu sistema os mesmos processos que reproduzem o poder ou que renovam as suas retóricas através de astúcias de resistência. Criou-se me tempos a proposta radical de uma arte emancipada, independente de referencialidade para além dos valores plásticos. Esta radicalidade escondia afinal um conformismo otimista e modernista: a arte “abstrata” era conservadora, decorativa, e não incomodava afinal ninguém. Aqui se mostra a oportunidade deste desafio, da chamada de artigos que esta Revista Croma 14 convocou: o desafio é entrar no caleidoscópio das ilusões sem perder o norte, sem abdicar do sentido último da cultura, que é mais humanidade, mais inteira, mais consciente.info:eu-repo/semantics/publishedVersio

Soft Agglomerates of Pantoprazole Gastro-resistant Microparticles for Oral Administration and Intestinal Release

Soft agglomerates containing pantoprazole gastro-resistant microparticles were prepared for an oral delayed-release solid dosage form. A new technique was used to agglomerate the microparticles: enteric microparticles of pantoprazole, non-agglomerating per se, were blended with mannitol/lecithin spray-dried microparticles, i.e., excipient microparticles. The blend was agglomerated by tumbling or sieve vibration. In order to elucidate the agglomerate formation, the effect of factors such as the amount of lecithin in the excipient microparticles, the ratio between pantoprazole and excipient microparticles and the agglomeration method were investigated by factorial design. Twelve batches of agglomerates presenting differing yield, drug loading, morphology, mechanical and release properties were prepared. The concentration of lecithin in the excipient microparticles was crucial for the agglomeration process. The biopharmaceutical characteristics of pantoprazole microparticles, i.e. their delayed-release properties, were not affected by the agglomeration process

Soft agglomerates of pantoprazole gastro-resistant microparticles for oral administration and intestinal release

Soft agglomerates containing pantoprazole gastro-resistant microparticles were prepared for an oral delayed-release solid dosage form. A new technique was used to agglomerate the microparticles: enteric microparticles of pantoprazole, non-agglomerating per se, were blended with mannitol/lecithin spray-dried microparticles, i.e. excipient microparticles. The blend was agglomerated by tumbling or sieve vibration. In order to elucidate the agglomerate formation, the effect of factors such as the amount of lecithin in the excipient microparticles, the ratio between pantoprazole and excipient microparticles and the agglomeration method were investigated by factorial design. Twelve batches of agglomerates presenting differing yield, drug loading, morphology, mechanical and release properties were prepared. The concentration of lecithin in the excipient microparticles was crucial for the agglomeration process. The biopharmaceutical characteristics of pantoprazole microparticles, i.e. their delayed-release properties, were not affected by the agglomeration proces

Nose-to-brain delivery of simvastatin mediated by chitosan-coated lipid-core nanocapsules allows for the treatment of glioblastoma in vivo

Glioblastoma is the most common and lethal malignant brain tumor. Despite simvastatin (SVT) showing potential anticancer properties, its antitumoral effect against glioblastoma appears limited when the conventional oral administration route is selected. As a consequence, nose-to-brain delivery has been proposed as an alternative route to deliver SVT into the brain. This study aimed to prepare chitosan-coated simvastatin-loaded lipid-core nanocapsules (LNCSVT-chit) suitable for nose-to-brain delivery and capable of fostering antitumor effects against glioblastoma both in vitro and in vivo. Results showed that the nanocapsules present adequate particle size (mean diameter below 200 nm), narrow particle size distribution (PDI < 0.2), positive zeta potential and high encapsulation efficiency (nearly 100%). In vitro cytotoxicity of LNCSVT-chit was comparable to non-encapsulated SVT in C6 rat glioma cells, whereas LNCSVT-chit were more cytotoxic than non-encapsulated SVT after 72 h of incubation against U-138 MG human glioblastoma cell line. In studies carried out in rats, LNCSVT-chit significantly enhanced the amount of drug in rat brain tissue after intranasal administration (2.4-fold) when compared with free SVT. Moreover, LNCSVT-chit promoted a significant decrease in tumor growth and malignancy in glioma-bearing rats in comparison to control and free SVT groups. Additionally, LNCSVT-chit did not cause any toxicity in treated rats. Considered overall, the results demonstrated that the nose-to-brain administration of LNCSVT-chit represents a novel potential strategy for glioblastoma treatment