RESUMO
The absolute configuration and solution-state conformers of three peperomin-type secolignans isolated from Peperomia blanda (Piperaceae) are unambiguously determined by using vibrational circular dichroism (VCD) spectroscopy associated with density functional theory (DFT) calculations. Advantages of VCD over the electronic form of CD for the analysis of diastereomers are also discussed. This work extends our growing knowledge about secondary metabolites within the Piperaceae family species while providing a definitive and straightforward method to assess the absolute stereochemistry of secolignans.
Assuntos
Produtos Biológicos/química , Lignanas/química , Peperomia/química , Produtos Biológicos/isolamento & purificação , Dicroísmo Circular , Lignanas/isolamento & purificação , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação Molecular , Teoria Quântica , EstereoisomerismoRESUMO
Corydines, isocorydines, and analogous aporphine alkaloids were isolated from the leaves of Aristolochia lagesiana var. intermedia, together with three bisaporphine salts (lagesianines B-D). Their structures were determined by chemical derivatizations and spectroscopic analyses. Lagesianines B and C are the first examples of N-CH(2)-N' and C-2-O-C-1' linked dimeric aporphine alkaloids, respectively, while the monomeric units of lagesianine D, which has a carbon skeleton, are linked through C-7-C-5'via an ethane-1,2-diol group (C-7-CHOHCHOH-C-5').
Assuntos
Aporfinas/química , Aporfinas/isolamento & purificação , Aristolochia/química , Espectroscopia de Ressonância MagnéticaRESUMO
Holostylis reniformis biosynthesizes 8-8' linked lignans without 9,9'-oxygenation. To elucidate the biosynthetic pathways to these lignans, the reputed precursors [U-(14)C]phenylalanine, [9-(3)H(1)]coniferyl alcohol, and [9-(3)H(1)]isoeugenol were administered to roots of the plant, which led to the incorporation of (3)H and (14)C into ten 2,7' linked-lignans (aryltetralone lignans) and two 7,7'-epoxylignans (furan lignans). These administration experiments demonstrated that the lignans were propenylphenol-derived and that H. reniformis can exhibit regioselective control over radical-radical coupling (via isoeugenol radicals). Regiospecific control over propenylphenol-derived lignan biosynthesis was observed, together with diastereoselective control of C2-C7' bond formation for the aryltetralone lignans (7'R). These experiments provide evidence that isoeugenol is a biosynthetic intermediate to the aryltetralone and furan lignans.
Assuntos
Antimaláricos/metabolismo , Aristolochiaceae/metabolismo , Lignanas/biossíntese , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância Magnética , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria UltravioletaRESUMO
(8S,8'R,9S)-, (8R,8'R,9R)-, and (8R,8'R,9S)-cubebins, together with (8R,8'R,8''R,8'''R,9R,9''S)-bicubebin, were isolated from Aristolochia lagesiana and Aristolochia pubescens. Their structures were determined by spectroscopic methods, including 1H and 13C NMR spectroscopy at low temperatures, and by chemical transformations.
Assuntos
Aristolochia/química , Lignanas/química , Extratos Vegetais/química , Plantas Medicinais , 4-Butirolactona/química , 4-Butirolactona/farmacologia , Dicroísmo Circular , Lignanas/isolamento & purificação , Lignanas/farmacologia , Espectroscopia de Ressonância Magnética , Conformação MolecularRESUMO
Acetone and ethanol extracts of the tubercula and several compounds isolated from Aristolochia pubescens (Willd) were bioassayed on velvetbean caterpillars, Anticarsia gemmatalis (Hübner), for evaluation of the insecticidal activities. Of the extracts subjected to bioassay, the acetone extract showed the highest activity. (-)-Cubebin did not show activity against soybean caterpillars, whereas aristolochic acid and ent-kaur-15-en-17-ol increased the larval period. These compounds, and (+)-eudesmin and (+)-sesamin, reduced the viability of this period, giving rise to malformed adults. These extracts and compounds are therefore potential botanical insecticide agents for the control of velvetbean caterpillars in soybean crops.
Assuntos
Aristolochia/química , Inseticidas/toxicidade , Larva/efeitos dos fármacos , Lepidópteros/efeitos dos fármacos , Extratos Vegetais/toxicidade , Animais , Ácidos Aristolóquicos/toxicidade , Bioensaio , Dioxóis/toxicidade , Diterpenos/toxicidade , Furanos/toxicidade , Lignanas/toxicidadeRESUMO
From the acetone and ethanol extracts of the tubercula of Aristolochia pubescens, two diterpene esters of aristolochic acids were isolated, together with 23 known compounds. The structures of the compounds were determined on the basis of spectroscopic analysis.