Genotoxic action of the sesquiterpene lactone centratherin on mammalian cells in vitro and in vivo.

Centratherin is a sesquiterpene lactone known for its antimicrobial, anti-inflammatory, and trypanocidal activities. The aim of this study was to determine the clastogenic and cytotoxic potential of centratherin in human lymphocytes and in mice. Human lymphocytes in culture were submitted to either continuous treatment or treatment during G(2) phase of the cell cycle. After continuous treatment the 0.2 microg/ml concentration induced a significant increase in total of chromosomal aberrations (CA) and sister chromatid exchange compared to control, and it reduced the mitotic index (MI). In the treatment during G(2) phase, centratherin induced a significant increase in the frequency of CA for all concentrations tested (0.1, 0.3, and 0.5 microg/ml). In the in vivo test system all three concentrations tested in mice (3.3, 6.7, and 13.3 mg/kg b.w.) induced a significant increase in CA compared to the negative control. On the basis of these results, centratherin showed clastogenic and cytotoxic activity on in vitro and in vivo mammalian systems.

Inhibition of inflammatory cytokine production and lymphocyte proliferation by structurally different sesquiterpene lactones correlates with their effect on activation of NF-kappaB.

Many sesquiterpene lactones (Sls) are known to possess anti-inflammatory activities. To gain further insight into their structure-activity relationships and the molecular mechanism of action, four germacranolide sesquiterpene lactones which differ in the skeleton and the number of reactive centers (4beta,15-epoxy-miller-9E-enolide (1), 15-acetoxy-eremantholide B (2), a mixture of 15-(isovaleroyl)/15-(2-methyl-butyryl)-2alpha-acetoxy-miguanin (3), and 15-(2-hydroxy)-isobutyryloxy-micrantholide (4)) were investigated for their effect on production of proinflammatory cytokines (interleukin-1beta [IL-1beta], IL-6, and tumor necrosis factor-alpha [TNF-alpha]) as well as proliferation of concanavalin A (Con A) and lipopolysaccharide (LPS)-stimulated mouse lymphocytes. Compounds 1 and 3 which possess an alpha-methylene-gamma-lactone function and a conjugated carbonyl group induced a half-maximal inhibition of cytokine synthesis in adherent mouse peritoneal exudate cells at micromolar concentrations (IC(50) 0.69-1.70 microM), while compound 4 which contains only an alpha-methylene-gamma-lactone residue was less active (IC(50) > or 38 microM). Interestingly, compound 2, which carries only a conjugated keto group, displayed a potency similar to those of the bifunctional compounds 1 and 3. All four Sls suppressed proliferation of murine lymphocyte at IC(50) concentrations between 0.22 and 5.03 microM. The rank order of potency was 1 = 2 > 3 > 4. Generally, the growth of LPS-stimulated cells was more strongly influenced than those of Con A-activated lymphocytes. This effect was particularly pronounced with 4. Inhibitory concentrations correlated well with those necessary for inhibition of the transcription factor nuclear factor kappaB (NF-kappaB) observed in a previous investigation. Therefore, it can be assumed that NF-kappaB may be involved in the suppressive effect of Sls on cytokine production and lymphocyte proliferation.

Inhibition of transcription factor NF-kappaB by sesquiterpene lactones: a proposed molecular mechanism of action.

Many sesquiterpene lactones (SLs) possess considerable anti-inflammatory activity. They inhibit the transcription factor NF-kappaB by selectively alkylating its p65 subunit probably by reacting with cysteine residues. Here we assayed 28 sesquiterpene lactones for their ability to inhibit NF-kappaB. The majority of the potent NF-kappaB inhibitors possess two reactive centers in form of an alpha-methylene-gamma-lactone group and an alpha,beta- or alpha,beta,gamma,delta-unsaturated carbonyl group. Based on computer molecular modelling we propose a molecular mechanism of action, which is able to explain the p65 selectivity of the SLs and the observed correlation of high activity with alkylant bifunctionality. A single bifunctional SL molecule can alkylate the cysteine residue (Cys 38) in the DNA binding loop 1 (L1) and a further cysteine (Cys 120) in the nearby E' region. This cross link alters the position of tyrosine 36 and additional amino acids in such a way that their specific interactions with the DNA become impossible. We also created a model for monofunctional SLs.

Genotoxicity of the natural cercaricides "sucupira" oil and eremanthine in mammalian cells in vitro and in vivo.

"Sucupira" oil and the lactone eremanthine, extracted from Pterodon pubescens and Eremanthus elaeagnus, respectively, are known for their cercaricidal action in experimental animals. Because of their biological effect, they have the potential to be used for the prophylaxis of schistosomiasis caused by Schistosoma mansoni. To test the clastogenicity of these agents, "sucupira" oil, either pure or diluted in corn oil, was tested in vivo on Wistar rat bone marrow cells following dermal application. Metaphase analysis showed that the compound did not induce a significant increase in the frequencies of chromosomal aberrations. When eremanthine was tested on BALB/c mice following gavage at doses of 100, 200, and 300 mg/kg bw, it did not induce structural or numerical chromosomal aberrations. In the in vitro treatment of human lymphocyte cultures, eremanthine also did not cause any increase in chromosomal aberrations or sister chromatid exchanges at the following concentrations in culture medium: 1.25, 2.50, and 5.00 micrograms/ml. From these results, under our experimental conditions, neither "sucupira" oil nor eremanthine showed clastogenic effects on mammalian cells in vivo or in vitro.

Quimioprofilaxia da esquistossomose: atividade moluscicida de produtos naturais - ensaios com caramulos adultos e desovas. / Chemoprophylaxis of schistosomiasis: molluscacidal activity of natural products - assays with adult snails and oviposition

Sao apresentados os dados relativos a atividade moluscicida de 159 extratos, de 84 plantas brasileiras, sobre Biomphalaria glabrata, o mais importante hospedeiro intermediario do Schistosoma mansoni no Brasil. Setenta e oito (49,0%) dos extratos mostraram atividade contra caramujos ou desovas, porem, somente vinte e nove (18,2%)foram ativos sobre ambos. Os extratos de duas especies de vegetais (Mikania hirsutissima e Qualea multiflora) foram letais aos caramujos adultos, na concentracao de 10 ppm