Nelson Alvarenga

Bioactive Triterpenes and Related Compounds from Celastraceae

Abstract The Celastraceae family is a source of important bioactive secondary metabolites. Among the compounds isolated from their species, triterpenes and triterpenoid quinonemethides are of great interest, due to the wide range of biological activities showed by those compounds. At the present time, great interest had been devoted to the study of the species of the family searching for new candidates or prototypes of drugs than could contribute to the fight against diseases like AIDS and cancer. The isolated compounds show mainly antimicrobial, cytotoxic, antitumoral, antiviral, antiinflamatory, hepatoprotective, antifeedant and insecticidal activities. This review covers the literature from 1997 up to August 2002 and contains discussions on chemistry and biological activity of triterpenes, triterpenoid quinonemethides and other related compounds. Emphasis has been dedicated to compounds that shown some kind of biological activity and with structure – activity relationships if any. The high potential of these compounds as therapeutical agents is also emphasized.

X-Ray Analysis of Volubilide, a New Decacyclic Diels-Alder C20-C30 Adduct from Hyppocratea volubilis L.

Abstract A new Diels–Alder adduct, 1, has been isolated from Hyppocratea volubilis L. and its structure determined by means of 1H and 13C NMR spectroscopic studies including H-C heteronuclear correlation (HETCOR), and long-range correlation with inverse detection (HMBC). The absolute configuration was determined by X-ray analysis.

A new lupane caffeoyl ester from Hippocratea volubilis.

The extract of the rootbark of Hippocratea volubilis afforded a new triterpene caffeoyl ester, lupeol caffeate (1). Its structure was determined by means of spectroscopic evidence.

Leishmanicidal activity of Maytenus illicifolia roots.

In vitro evaluation of leishmanicidal activity of aqueous and ethanolic extracts of Maytenus illicifolia against three species of Leishmania. The root extracts showed differential activity against parasites, whereas the aerial part of the extracts was inactive.

Chemical Composition of the Essential Oil of Aristolochia gibertii Hooker from Paraguay

Abstract The chemical composition of the essential oils from leaves and stems of Aristolochia gibertii Hooker collected in Paraguay was investigated by GC and GC/MS. The composition of both oils consisted mainly of sesquiterpenes and a small percentage of monoterpenes; 46 constituents being identified in total. The major component was bicyclogermacrene (26.8% in leaves and 15.0% in stems) followed by (E)-nerolidol (17.5% in leaves and 7.1% in stems), limonene (0.4% in leaves and 11.1% in stems), germacrene D (8.5% in leaves and 7.3% in stems) and spathulenol (3.4% in leaves and 7.3% in stems).

In vitro antiprotozoal activity of (S)-cis-Verbenol against Leishmania spp. and Trypanosoma cruzi

(S)-cis-Verbenol, a monoterpene frequently found as a component of essential oils, was assayed against Leishmania amazonensis, Leishmania infantum, Leishmania brasiliensis and against two strains of Trypanosoma cruzi. The cytotoxicity of the compound was also assayed against human fibroblast cells using a colorimetric method. Benznidazole was used as reference drug against T. cruzi and amphotericin B was used against Leishmania spp. The compound showed good activity against the trypanosomes, being more active against the CL Brenner strain, with an IC50 value of 8.3μg/mL. Against Leishmania, the IC50 values were between 2.1 and 3.8μg/mL. The compound showed no cytotoxicity against human fibroblasts at the concentrations assayed and was 100-500 times more toxic for the parasites than for the human cells, as indicated by the selectivity indexes. The results open interesting perspectives about the potential of (S)-cis-Verbenol and other individual components of essential oils for the treatment of these diseases.

Antibacterial activity of the alkaloid extract and isolated compounds from Croton bonplandianum Baill. (Euphorbiaceae)

A atividade antibacteriana do extrato alcaloidal das folhas de Croton bonplandianum Baill., alem dos principais compostos isolados, esparsiflorina e crotsparina, foi testada contra Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae e Pseudomonas aeruginosa. Foi utilizado o metodo de microdiluicao em placa empregando resazurina como indicador da viabilidade celular. Os compostos isolados foram identificados por tecnicas espectroscopicas, principalmente RMN 1D e 2D. O extrato alcaloidal foi ativo principalmente contra S. aureus e P. aeruginosa. Crotsparina mostrou-se inativa contra todos os micro-organismos testados, enquanto esparsiflorina apresentou atividade moderada, a qual foi similar a do extrato bruto. Pseudomonas aeruginosa foi a mais sensivel das bacterias testadas, com CIM de 0,141 mg/mL. Os resultados sugerem que a atividade do extrato pode ser devida em grande medida pela presenca de esparsiflorina. Apesar de a CIM da esparsiflorina nao ter se aproximado daquela apresentada pelos agentes antimicrobianos em uso clinico, tal composto ainda pode compor um prototipo interessante para o desenvolvimento de novas substâncias antibacterianas.