The genus Aristolochia, an important source of physiologically active compounds that belong to different chemical classes, is the subject of research in numerous pharmacological and chemical studies. This genus contains a large number of terpenoid compounds, particularly diterpenes. This work presents a compilation of the 13C-NMR data of 57 diterpenoids described between 1981 and 2007 which were isolated from Aristolochia species. The compounds are arranged skeletonwise in each section, according to their structures, i.e., clerodane, labdane, and kaurane derivatives. A brief discussion on the 13C chemical shifts of these diterpenes is also included.

Polythiophene (PTh) and its derivatives are polymer-based materials with aπ-conjugation framework. PTh is a useful photoelectric material and can be used in organic semiconductor devices, such as PLED, OLED, and solar cells. Their properties are based on molecular structure; the derivatives contain different substitutes in the 3 and 5 positions, such as electron-donating or electron-withdrawing groups. All molecular geometries were optimized at B3LYP/6-31G(d,p) level of theory. The energy gap (Egap) between the HOMO and LUMO levels is related to theπ-conjugation in the PTh polymer backbone. In this study, the DFT calculations were performed for the nonsubstituted and 3,5-substituted variants to investigate the stability geometries and electrical properties. The theoretical calculations show that the substituted forms are stable, have lowEgap, and are in good agreement with the experimental observations.

Recebido em 8/10/09; aceito em 13/5/10; publicado na web em 17/9/10 CHEMICAL STUDY AND ANTIBACTERIAL ACTIVITY OF STEM OF Aristolochia esperanzae Kuntze (ARISTOLOCHIACEAE). From the ethanolic extract of the stem of A. esperanzae ethyl and methyl fatty acid esters, fatty acids, aristolochic I and II acids, and β-cubebin were isolated. In addiction asarinin, populifolic and 2-oxo-populifolic acids, aristolactams AIa and AII, and sitosterol 3-O-β-D-glucopyranoside were also isolated and firstly described in the species. Asarinin and β-cubebin showed antibacterial activity against Bacillus cereus and aristolochic acid I against Staphylococcus aureus and Listeria monocitogenes.Keywords: Aristolochia esperanzae; aristolochic acids; antibacterial activity. INTRODUÇÃOAristolochia esperanzae Kuntze (Aristolochiaceae) tem como sinônimo A. boliviensis O. Kuntze, 1 sendo encontrada na América do Sul e conhecida popularmente no Brasil como cipó-mil-homens.2 Levantamentos etnofarmacológicos indicam o uso de extratos desta espécie no tratamento de artrite reumatoide e de diversas outras doenças.3 Por outro lado, a comercialização de ervas medicinais contendo extratos de espécies do gênero Aristolochia é proibida em muitos países, devido as suas propriedades nefrotóxicas, carcinogênicas e mutagênicas, 4 que podem levar tanto à nefropatia progressiva quanto ao câncer urotelial em humanos. 5O gênero Aristolochia tem sido documentado quimicamente desde 1951, 6 revelando principalmente a presença de terpenoides, lignoides, flavonoides, ácidos graxos e constituintes nitrogenados (alcaloides e nitrofenantrenos).7 A literatura registra estudos fitoquímicos das folhas e raízes de A. esperanzae, 8 das quais foram isolados diterpenos dos tipos clerodano e labdano, triterpenos, lignanas dos tipos dibenzilbutirolactona, furofurano tetra-hidrofurano e 4-aril-tetralona, ácidos aristolóquicos e aristolactamas. O presente trabalho descreve o estudo fitoquímico do caule (cerne e cascas) de A. esperanzae, resultando no isolamento de asarinina (1), ácido pupolifólico (2), ácido 2-oxo-pupolifólico (3), ácido aristolóquico II (4), aristolactama AII (5), aristolactama AIa (6), (8R,8'R,9S)-cubebina ou β-cubebina (7), ácido aristolóquico I (8), sitosterol-3-O-β-D-glicopiranosídeo (9) e estigmastan-3,5,22-trieno (10), conforme Figura 1. Os compostos 4, 7 e 8 haviam sido anteriormente isolados nas folhas e raízes da planta e os demais estão sendo descritos pela primeira vez na espé-cie. Além disto, este estudo foi acompanhado por testes de atividade antibacteriana de seus extratos, frações e fitoconstituintes isolados. PARTE EXPERIMENTAL Procedimentos geraisOs pontos de fusão não corrigidos foram determinados em aparelho Mettler FP80 SNR H22439. As análises por espectroscopia de absorção na região do infravermelho (IV) foram realizadas em espectrômetro Perkin Elmer Spectrum One (ATR). As análises por cromatografia a gás acoplada à espectrometria de massas (CG/EM) foram realizadas em um cromatógrafo CG Varian 3800, acoplado a um espectrômetro de massas Va...

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This work describes the configurational and conformational analyses of 1,6,7-triacetoxy-8,13-epoxy-14-labden-11-one, a labdane diterpenoid isolated from Plectranthus ornatus. Its relative stereochemistry was previously proposed by comparison with 1 H and 13 C NMR data of forskolin (2); however, the configurations of C-8 and C-13 have not been confirmed. Correlations between 13 C NMR experimental data and HF/6-31G* calculated values of carbon chemical shifts were performed for configurational and conformational analyses. This procedure was formerly applied to the configurational analysis of 2. Among the seven different forskolin-type structures investigated, the 13 C NMR data of 2 correlated best with those with the same stereochemistry of 2 described in the literature. Thus, the same procedure was considered valid for configurational analysis of the labdane diterpenoid isolated from P. ornatus. The relative stereochemistry of this compound based on theoretical calculations was similar to the structure previously proposed, but the best results were obtained considering configurational inversion at C-13.