Antioxidant activity of Spathodea campanulata (Bignoneaceae) extracts / Atividade antioxidante de extratos de Spathodea campanulata (Bignoneaceae)

Spathodea campanulata is used in traditional medicine in Africa as diuretic and anti-inflammatory. Although few studies have reported the mechanism of antioxidant action, this study evidenced the antioxidant activity of S. campanulata bark and flower extracts and their possible mechanism of action. Ethanol extracts of S. campanulata bark and flowers showed antioxidant activity on lipid peroxidation of liver microsome induced by Fe3+-ascorbic acid. Bark extract was 5 times more efficient than flower extract. The antioxidant activity of flower extract, previously complexed with increasing concentrations of Fe3+ (20 - 100 µM) which resulted in antioxidant activity loss, was shown to be related to iron complex formation. In contrast, the antioxidant activity of bark extract was not inhibited by the previous incubation with Fe3+, although complexation was demonstrated by spectral analysis of the solution. These results suggest an antioxidant mechanism other than Fe3+ complex formation. Therefore, the antioxidant mechanisms of S. campanulata flower and bark extracts are distinct from each other, reflecting the extract heterogeneous composition and the mechanism of action.

Spathodea campanulata é usada na medicina popular na África como diurético e antiinflamatório. Embora poucos estudos relatem o mecanismo de ação antioxidante, neste trabalho foi evidenciado a atividade antioxidante dos extratos da casca e da flor da S. campanulata e o possível mecanismo de ação. Os extratos etanólicos da casca e da flor da S. campanulata mostrou possuir atividade antioxidante sobre a lipoperoxidação de microssoma hepático induzida por Fe3+-ácido ascórbico. O extrato da casca foi 5 vezes mais eficiente que da flor. O extrato da flor foi previamente complexado com concentrações crescentes de Fe3+ (20 - 100 µM) o qual resultou na perda da atividade antioxidante, demonstrando que esta está relacionada com a formação de complexo com o ferro. Por outro lado, a atividade antioxidante do extrato da casca não foi inibida pela prévia incubação com o ferro, embora haja a formação do complexo evidenciado pela análise espectral da solução. Estes resultados sugerem que o mecanismo antioxidante seja outro que não a complexação com o Fe3+. Portanto, o mecanismo antioxidante dos extratos da flor e da casca da S. campanulata é distinto entre si o que reflete a composição heterogênica do extrato e o mecanismo de ação.

Inhibition of L-glutamate and GABA synaptosome uptake by crotoxin, the major neurotoxin from Crotalus durissus terrificus venom

This paper describes a brief study on the crotoxin mechanism of action, regarding the transport of GABA and L-glutamate in rats cortico-cerebral synaptosomes and in heterologous systems, such as COS-7 cells expressing gabaergic transporters, and C6 glioma cells and Xenopus oocytes expressing glutamatergic transporters. Crotoxin concentrations over 1 µM caused an inhibitory effect of ³H-L-glutamate and ³H-GABA, and reversibly inhibited L-glutamate uptake by C6 glioma cells. When COS-7 cells were assayed, no inhibition of the ³H-GABA transport could be evidenced. Crotoxin kept its inhibitory effect on neurotransmitters uptake even when Ca2+ ions were removed from the medium, therefore, independently of its PLA2 activity. In addition, high concentrations (2 mM) of BPB did not avoid the action of crotoxin on the neurotransmitters uptake. Crotoxin also inhibited ³H-L-glutamate, independently on Na+ channel blockade by TTX. In addition, an evaluation of the lactic dehydrogenase activity indicated that uptake inhibition does not involve a hydrolytic action of crotoxin upon the membrane. We may also suggest that crotoxin acts, at least partially, altering the electrogenic equilibrium, as evidenced by confocal microscopy, when a fluorescent probe was used to verify cell permeability on C6 glioma cells in presence of crotoxin.