Caracterização da composição química e atividade biológica de extratos de Alternanthera brasiliana (L.) Kuntze Amarnathaceae

Abstract

Alternanthera brasiliana (Amaranthaceae) is a medicinal plant used in the treatment of inflammation, pain and infectious processes (BROCHADO et al., 2003; MACEDO et al., 2004). Polar extracts of this plant have revealed the presence of carbohydrates and pigments of theclass of betalains (SILVA et al., 2005, GASPARETTO et al., 2010). Already the lipophilic extracts have shown significant amounts of acids and fatty esters, steroids, fatty alcohols and hydrocarbons (PEREIRA, 2007).Recent studies involving other medicinal plants has shown that the extractives content varies with extraction method and the solvent employed (WEINHOLD et al., 2008; BIMAKRA et al., 2011). In these studies, conventional procedures based on solid-liquid extraction have lower levels of extractives than those obtained by more elaborate methods such as solid-liquid extraction using ultrasound and dispersion of the matrix on solid phase (DMFS) (XIAO et al., 2004, SILVA et al., 2009; JADHAV et al., 2009; BIMAKRA et al., 2011). The solid-liquid extraction with ultrasound is based on the use of ultrasonic waves to promote greater penetration of the solvent in the vegetable matrix, allowing more efficient interaction between the constituents of the plant and the solvent (HEMWIMOL et al., 2006). Already dispersion of the solid phase matrix is based on the interaction between the plant material and an adsorbent (florisil, silica, C18, etc.), resulting in disruption of the cell wall facilitating the extraction of chemical substances (BARKER, 2007). The dispersion of the matrix in solid phase is a technique commonly used to study various organic contaminants in several environmental matrixes (BING et al., 2005; PENA et al., 2008), however are very few reports describing the use of plant extracts (CAPRIOTTI et al. 2010). But the class of plant metabolites phenolic acids (ZIAKOVÁ et al., 2003) and isoflavonoids (VISNEVSCHI-NECRASOVA et al., 2009) have been successfully extracted from this technique. These extraction techniques use various types of solvents, being employed, for example, water, ethanol, dichloromethane, ethyl acetate and hexane (BARWICK, 1997; ZHAOet al., 2006; GARCIA et al., 2010). The hexane, although it is advantageous to extract only lipophilic compounds, has some deficiencies for the removal of compounds partly polar (OKOLIet al., 2007; Lai et al., 2009; ORHAN et al., 2009; MONSÁLVEZ et al. in 2010). The dichloromethane and ethyl acetate are used to remove extractives medicinal plants in order to obtain compounds with intermediate polarity (CECHINEL YUNES and SON, 1998). However,because of the toxicity of dichloromethane, the extraction method this solvent has been used in a restricted manner (JABER-VAZDEKIZ et al., 2006). The water and ethanol extract greater amount of hydrophilic components such as carbohydrate and phenolic compound (MARKOM etal., 2007), but high levels of carbohydrates favor the growth of microorganisms (BIELLA et al., 2008). Despite these reports in the literature, no systematic study was conducted to compare different extraction methods and solvents for the determination of extractives in A. brasiliana. The comparison between extraction methods can provide to obtain high amount of active ingredient in less time, with a reduction in reagent consumption and greater preservation of chemical composition.