Potencial alelopático de Myrcia guianensis.

O uso do fogo e de roçadeira para controle de plantas daninhas em pastagens tem se mostrado pouco efetivo. Já o uso de herbicidas sintéticos, embora mais eficaz no controle de plantas daninhas, tem sido questionado quanto ao impacto ambiental. Portanto, a busca de compostos naturais para possível utilização como herbicida é de fundamental importância. Esses fatos motivaram o presente estudo, que teve como objetivos isolar, identificar e caracterizar a atividade alelopática potencial de substâncias químicas produzidas por Myrcia guianensis (pedra-ume-caá). Foram analisados os efeitos potenciais alelopáticos de extratos brutos, partições, óleo essencial e das substâncias químicas isoladas (ácido gálico e ácido protocatecuico) sobre a germinação e o desenvolvimento da radícula e do hipocótilo das plantas daninhas Mimosa pudica (malícia) e Senna obtusifolia (mata-pasto) em pastagens. Os extratos brutos e as partições foram analisados em concentração de 1%; o óleo essencial, em concentrações de 1, 5, 10, 15 e 20 ppm; e as substâncias isoladas, em concentrações de 15, 30, 45 e 60 ppm. A espécie malícia se mostrou mais sensível aos efeitos alelopáticos dos extratos brutos e das partições. O óleo essencial inibiu a germinação da malícia e estimulou a germinação no mata-pasto. A atividade alelopática das substâncias químicas isoladas esteve associada à concentração, e a atividade mais intensa foi em 60 ppm

Effect of leguminous lectins on the growth of Rhizobium tropici CIAT899.

201

Cytotoxicity and genotoxicity of Vernonia condensata Baker aqueous extracts in an Allium cepa test system and C2C12 cell culture

Vernonia condensata Baker is a medicinal species widely used by the Brazilian population for its analgesic, hepatoprotective and digestive properties. This study aimed to investigate the cytotoxic and genotoxic effects of V. condensata aqueous extracts using Allium cepa test system and in vitro micronucleus test. Fresh V. condensata leaves were collected, dried and ground, and aqueous extracts were prepared at concentrations of 1500; 3000; and 6000 µg/ml of dry extract. In the A. cepa test, ten repetitions were used per treatment. Distilled water was used as negative control and sodium azide (2M) as positive control. The onion bulbs were rooted in distilled water for 72 h and then exposed to the extracts for 24 h. The roots were collected and fixed in Carnoy’s solution (3:1) for 24 h. Smear slides were prepared of the root apical meristems and 2000 cells/concentration was analyzed, measuring the mitotic index, micronuclei frequency and mitotic abnormalities of A. cepa. In vitro cytotoxicity and genotoxicity were also performed using the murine myoblast cell line C2C12. In vivo data demonstrated that an increase in the concentration of V. condensata aqueous extracts caused cytotoxic and genotoxic effects in meristematic cells of A. cepa. A concentration of 1500 µg/ml showed no cytotoxic or genotoxic effects, while 3000 µg/ml resulted in mitotic abnormalities and a decline in the mitotic index, indicating cytotoxicity. The 6000 µg/ml aqueous extract showed cytotoxicity and genotoxicity, increasing mitotic abnormalities and micronuclei frequencies in the A. cepa test. An IC50 value of 15.610 µg/mL was obtained for C2C12 cell line and the doses of 6000 µg/mL and 12000 µg/mL of Vernonia extract induced genotoxicity. The data of the present study reveals that V. condensate extract should be used with parsimony, once that it can bring unwanted side effects, which can be dangerous

Cytotoxicity and genotoxicity of Vernonia condensata Baker aqueous extracts in an Allium cepa test system and C2C12 cell culture

692-701Vernonia condensata Baker is a medicinal species widely used by the Brazilian population for its analgesic, hepatoprotective and digestive properties. This study aimed to investigate the cytotoxic and genotoxic effects of V. condensata aqueous extracts using Allium cepa test system and in vitro micronucleus test. Fresh V. condensata leaves were collected, dried and ground, and aqueous extracts were prepared at concentrations of 1500; 3000; and 6000 µg/ml of dry extract. In the A. cepa test, ten repetitions were used per treatment. Distilled water was used as negative control and sodium azide (2M) as positive control. The onion bulbs were rooted in distilled water for 72 h and then exposed to the extracts for 24 h. The roots were collected and fixed in Carnoy’s solution (3:1) for 24 h. Smear slides were prepared of the root apical meristems and 2000 cells/concentration was analyzed, measuring the mitotic index, micronuclei frequency and mitotic abnormalities of A. cepa. In vitro cytotoxicity and genotoxicity were also performed using the murine myoblast cell line C2C12. In vivo data demonstrated that an increase in the concentration of V. condensata aqueous extracts caused cytotoxic and genotoxic effects in meristematic cells of A. cepa. A concentration of 1500 µg/ml showed no cytotoxic or genotoxic effects, while 3000 µg/ml resulted in mitotic abnormalities and a decline in the mitotic index, indicating cytotoxicity. The 6000 µg/ml aqueous extract showed cytotoxicity and genotoxicity, increasing mitotic abnormalities and micronuclei frequencies in the A. cepa test. An IC50 value of 15.610 µg/mL was obtained for C2C12 cell line and the doses of 6000 µg/mL and 12000 µg/mL of Vernonia extract induced genotoxicity. The data of the present study reveals that V. condensate extract should be used with parsimony, once that it can bring unwanted side effects, which can be dangerous

Bioensaios de alelopatia com substâncias químicas isoladas de Brachiaria brizantha em função das variações do ph.

Disponível também on-line

Isotopic Composition of Light Nuclei in Cosmic Rays: Results from AMS-01

The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper we present measurements of the isotopic ratios 2H/4He, 3He/4He, 6Li/7Li, 7Be/(9Be+10Be) and 10B/11B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.Comment: To appear in ApJ. 12 pages, 11 figures, 6 table