In this study, correlations between electronic structure and the antimalarial activities reported for a group of 21 tetrahydropyridines were evaluated by multivariate methods. Simple and multiple linear regressions, principal component analyses, and linear discriminant analyses were employed to evaluate possible correlations between quantum-mechanical descriptors and pharmacological activity. The results obtained provide useful information on the position of active sites of tetrahydropyridines and identify some specific features associated with active derivatives. Based on these findings, simple substitution rules are proposed for designing more efficient tetrahydropyridine derivatives.

Computational modeling studies of conjugated polymers have been shown to present many challenges. One such challenge is to find ways to reduce the computational cost for these studies without compromising the quality of the results. An approach longly used in the literature for this purpose is replacing long alkyl side chains (with six or more carbons) with a methyl group. This work reports on a theoretical study conducted with the conjugated polymer poly(3-hexylthiophene), which contains a hexyl side chain attached to the monomer, to verify the influence of the size of the alkyl side chain on its electronic structure. The results indicated that, for polymers containing long alkyl side chains, replacement with a propyl group offered full saturation of all properties under review, showing it to be a good approach.

The performance of advanced electronic ceramics is directly related to the synthesis route employed. Sol-gel methods are widely used for this purpose. However, the physicochemical intermediate steps are still not well understood. Better understanding and control of these processes can improve the final quality of samples. In this work, we studied theoretically the formation of metal complexes between citric acid and lithium or barium metal cations with different citric acid/metal proportions, using Density Functional Theory electronic structure calculations. Infrared and Raman scattering spectra were simulated for the more stable geometric configurations. Using this methodology, we identified some features of complexes formed in the synthesis process. Our results show that the complexes can be distinguished by changes in the bands assigned to C=O, COH-, and COO- group vibrations. An estimate of the most stable complexes is made based on total energy.

O desenvolvimento de linhagens resistentes de Plasmodium falciparum tem encorajado a busca por novas drogas antimalariais. A febrifugina é uma substância natural com alta atividade contra o P. falciparum que apresenta propriedade emética e toxicidade para o fígado tal que não permitem o seu uso clínico. A busca por análogos que possam ter uma performance clínica melhor é um tema de pesquisa atual. Nosso objetivo é investigar a estrutura eletrônica teórica de uma família de derivados da febrifugina empregando cálculos semi-empíricos de orbitais moleculares, procurando por índices eletrônicos que possam ajudar a modelar novos derivados mais eficientes. Os resultados teóricos mostram que para as moléculas mais seletivas existe um agrupamento dos valores de determinados índices em intervalos bem definidos. O modelo proposto para se obter alta seletividade foi testado com sucesso.

Plasmodium falciparum resistant strain development has encouraged the search for new antimalarial drugs. Febrifugine is a natural substance with high activity against P. falciparum presenting strong emetic property and liver toxicity, which prevent it from being used as a clinical drug. The search for analogues that could have a better clinical performance is a current topic. We aim to investigate the theoretical electronic structure by means of febrifugine derivative family semi-empirical molecular orbital calculations, seeking the electronic indexes that could help the design of new efficient derivatives. The theoretical results show there is a clustering in well-defined ranges of several electronic indexes of the most selective molecules. The model proposed for achieving high selectivity was tested with success.

Um novo composto, isolado a partir do extrato metanólico das folhas de Paepalanthus argenteus var. argenteus (Bongard) Hensold foi caracterizado como xeractinol, um novo diidroflavonol C-glucosilado. Sua estrutura foi elucidada com base em extensiva análise espectroscópica (RMN uni- e bidimensionais, EM, HREIMS, IV, UV). Cálculos ab initio de estrutura eletrônica corroboram nossa proposição para a estrutura molecular. O diidroflavonol aqui isolado pode servir como marcador taxonômico de Paepalanthus subg. Xeractis, uma vez que este flavonóide não foi encontrado em nenhum outro taxon de Eriocaulaceae.

New compound isolated from methanolic extract from the leaves of Paepalanthus argenteus var. argenteus (Bongard) Hensold was characterized as xeractinol, a new dihydroflavonol C-glucoside. The structure was elucidated on the basis of extensive spectroscopic analysis (1D and 2D NMR, MS, HREIMS, IR and UV). Ab initio electronic structure calculations support our proposal to the molecular structure. The dihydroflavonol herein isolated may serve as taxonomic marker of Paepalanthus subgenus Xeractis, because this flavonoid have not been reported in any other taxon of Eriocaulaceae.