G. M. S. P. Guilhon

Metodologias empregadas em estudos de avaliação da atividade alelopática em condições de laboratório: revisão crítica

Nas ultimas decadas, tem proliferado a formacao de grupos de pesquisa dedicados aos estudos na area de alelopatia, em diferentes partes do mundo. O Brasil nao ficou imune a essa tendencia; prova disso sao os numeros cada vez maiores de artigos cientificos publicados em periodicos nacionais e internacionais. O fato de a alelopatia ser uma ciencia relativamente jovem, podendo ser considerada em sua fase juvenil de desenvolvimento, tem propiciado a proliferacao de tecnicas de estudos diversificadas e muitas vezes carentes de embasamento. Adicionalmente, essa peculiaridade dificulta o entendimento das grandezas expressas e do valor biologico que os resultados apresentados podem significar. Uniformizar os procedimentos e, sem duvida alguma, ponto de partida quando se pensa na dimensao que a alelopatia pode representar em futuro proximo. Neste trabalho, foram revisados criticamente os protocolos pertinentes aos processos empregados nos bioensaios desenvolvidos para caracterizar as propriedades alelopaticas de extratos brutos e de substâncias quimicas. Ao mesmo tempo, os pontos fortes e as limitacoes de cada procedimento sao apresentados.

Activity of the julocrotine, a glutarimide alkaloid from Croton pullei var. glabrior, on Leishmania (L.) amazonensis

The antiproliferative effect of julocrotine, an alkaloid isolated from Croton pullei var. glabrior (Euphorbiaceae), was studied in the macrophage amastigote and promastigote stages of the protozoan Leishmania (L.) amazonensis, which causes cutaneous leishmaniasis in the New World. Julocrotine showed a dose-dependent effect against the amastigote and promastigote forms, where 79xa0μM julocrotine inhibited promastigote growth by 54%, with an IC50 of 67xa0μM. To analyze the antiamastigote activity of the drug, murine peritoneal macrophages infected with L. amazonensis promastigotes were treated with different concentrations of julocrotine. An 80% inhibition of amastigote development was observed using 79xa0μM julocrotine for 72xa0h, with an IC50 of 19.8xa0μM. In addition, ultrastructural observation of the parasites showed a significant reduction in the number of amastigotes in the parasitophorous vacuoles and morphological changes in promastigotes, such as swelling of the mitochondrion, chromatin condensation, presence of membranous structures near the Golgi complex, and some vesicle bodies in the flagellar pocket. A colorimetric assay (MTT), which measures cytotoxic metabolic activity, showed that macrophages maintain their viability after treatment with the drug. These results suggest that julocrotine effectively inhibits the growth of parasites and does not have any cytototoxic effects on the host cell.

Flavonoids and other compounds from Ouratea ferruginea (Ochnaceae) as anticancer and chemopreventive agents.

The chemical study of the extracts from leaves and stems of Ouratea ferruginea allowed the identification of a new isoflavone, 5-hydroxy-7,3′4′5′-tetramethoxyisoflavone, and twenty two known compounds, including friedelin, 3β-friedelinol, lupeone, a mixture of sitosterol, stigmasterol and campesterol, sitosteryl- and stigmasteryl-3-O-β-D-glucopyranosides, 5,4′-dihydroxy-7,5′,3′-trimethoxyisoflavone, 5,4′-dihydroxy-7,3′-di-methoxyisoflavone (7,3′-di-O-methylorobol), 5,7,4′-trihydroxy-3′,5′-dimethoxyisoflavone (piscigenin), 2R,3R-epicatechin, syringic acid, 2,6-dimethoxybenzoquinone, 2,6-dimethoxyhydroquinone, syringic and ferulic aldehyde, a mixture of vanillic acid, 1-hydroxy-2-methoxy-4-(1E-3-hydroxy-1-propenyl)-benzene and 3,5-dimethoxy-4-hydroxy-dihydrocinamaldehyde, besides amenthoflavone and 7-O-methylamenthoflavone (sequoiaflavone) which are considered as chemotaxonomic markers of Ouratea. The structures were identified by IR, 1H- and 13C-NMR and GC-MS, HPLC-MS, besides comparison with literature data. The inhibitory effects of 5,4′-dihydroxy-7,5′,3′-trimethoxyisoflavone, 7,3′-di-O-methylorobol, piscigenin and 7-O-methylamenthoflavone on cytochrome P450-dependent 7-ethoxycoumarin O-deethylase (ECOD) and glutathione S-transferase (GST) were evaluated in vitro. The 5,4′-dihydroxy-7,5′,3′-trimethoxy-isoflavone was the best inhibitor, inhibiting almost 75% of GST activity. Sequoiaflavone was the most potent inhibitor, inhibiting ECOD assay in 75%. These activities allow us to consider both these flavonoids as potential anticancer and chemopreventive agents.

Xanthones from the Roots of Moutabea guianensis Aubl.

The phytochemical investigation of Moutabea guianensis roots led to the isolation of five polyoxygenated xanthones, including two new ones named moutabeone B (1,8-dihydroxy-4,5,6,7-tetramethoxyxanthone) and moutabeone C (1-hydroxy-4,5,6,7,8-pentamethoxyxanthone), along with the three known xanthones, 1,8-dihydroxy-4,6-dimethoxyxanthone, 1,8-dihydroxy-4,5,6-trimethoxyxanthone and augustin A (1,8-dihydroxy-4,6,7-trimethoxyxanthone). Structural characterization of all compounds was established on the basis of spectroscopic methods, mainly 1D and 2D nuclear magnetic resonance (NMR) and comparison with literature data. The antioxidant activity of compounds was tested through a thin layer chromatography (TLC) bioautography assay using 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH·) as detection reagent. All tested compounds were more active (DL < 0.13–0.03 µg) than Trolox (DL < 0.15 µg), used as reference standard.

Bioensaios de atividade alelopática dos esteroides espinasterol, espinasterona e glicopiranosil espinasterol

Tres esteroides (espinasterol, espinasterona e glicopiranosil espinasterol) foram isolados do caule de Moutabea guianensis, planta de origem amazonica. Suas estruturas foram determinadas a partir das analises de RMN e por comparacao com dados espectroscopicos da literatura. Foram avaliadas as atividades alelopaticas das tres substâncias em duas plantas invasoras de pastagens comuns da regiao amazonica: Mimosa pudica (malicia) e Senna obtusifolia (mata-pasto). A substância glicopiranosil espinasterol foi mais ativa no ensaio de desenvolvimento da radicula, inibindo a especie Senna obtusifolia em 75%; o espinasterol inibiu em 22% o desenvolvimento do hipocotilo de Senna obtusifolia; e no bioensaio de germinacao de sementes as substâncias espinasterol e espinasterona proporcionaram 10% de inibicao em Mimosa pudica. A partir desses resultados, observou-se que a diferenca de substituintes observada na posicao-3 dos esteroides e capaz de alterar a atividade alelopatica. O grupo glicosil na posicao-3 elevou a atividade alelopatica de forma mais expressiva no bioensaio de desenvolvimento de radicula da especie malicia, quando comparado aos esteroides hidroxilado e carbonilado. Este e o primeiro estudo quimico e alelopatico do genero Moutabea.

Using LC and Hierarchical Cluster Analysis as Tools to Distinguish Timbó Collections into Two Deguelia Species: A Contribution to Chemotaxonomy

The species Deguelia utilis and Deguelia rufescens var. urucu, popularly known as “timbó,” have been used for many years as rotenone sources in insecticide formulations. In this work, a method was developed and validated using a high-performance liquid chromatography-photodiode array (HPLC-PDA) system, and results were analyzed using hierarchical cluster analysis (HCA). By quantifying the major rotenoids of these species, it was possible to establish a linear relation between them. The ratio between the concentrations of rotenone and deguelin for D. utilis is approximately 1:0.8, respectively, while for D. rufescens var. urucu it is 2:1. These results may help to distinguish these species contributing to their taxonomic identification.