Investigação do potencial químico e biológico de Vernonia condensata Baker (Asteraceae)

Abstract

Vernonia condensata Baker (Asteraceae), known as necroton, is used in traditional medicine as an analgesic, liver detoxifying and antimicrobial. The aim of the present study was to evaluate the chemical and biological potential of this plant, ordering to provide new information for better scientific understanding of its medicinal use. Dried and powdered leaves were exhaustively extracted with ethanol by static maceration. The ethanol extract has been partitioned, obtaining the hexane, dichloromethane, in ethyl acetate and butanol fractions. The phytochemical screening was performed by classical identification chemical reactions for the major classes of special metabolites. The content of total phenols and flavonoids were determined by spectrophotometry. The antioxidant activity was determined by 2,2-diphenyl-1-picryl-hidrazil (DPPH) assay, bioautography with DPPH, reducing power of Fe+3 and thiobarbituric acid (TBA) test, while the antibacterial potential was investigated by ágar diffusion method and by Minimal Inhibitory Concentration (MIC) determination through the microdilution method. The acute toxicity was established by 50% lethal dose (LD50). The antinociceptive activity was evaluated by writhing, formalin and hot plate tests, while the anti-inflammatory activity by paw edema and pleurisy methods. Data were expressed as mean  standard error and the analysis of variance followed by Newman-Keuls, Bonferroni or Tukey tests was used to measure the degree of significance (p < 0.05). Tannins, flavonoids, coumarins, saponins terpenes and steroids were detected. The total phenolic content ranged from 0.19 to 23.11 g/100 g, while the total flavonoids from 0.13 to 4.10 g/100 g. The EC50 of DPPH method ranged from 4.28 to 75.10 μg/mL and bioautography showed the presence of antioxidant components. The reduction power of Fe+3 was 19.98 ± 0.42 to 336.48 ± 11.05 μg/mL and the lipid peroxidation test showed significant effect at different concentrations. The ethanol extract was nontoxic at the doses tested and reduced the writhing and the paw licking time also increasing the latency time on the hot plate, presenting, in this way, antinociceptive activity. Moreover, the paw edema volume and the number of leukocytes in the pleural exudate were reduced, demonstrating the anti-inflammatory activity of the extract. Considering the antibacterial activity, the MIC values showed that the evaluated fractions were active in major or minor level against the reference strains tested. The MIC data were consistent with those observed in preliminary screening step using the diffusion method. Through the determination of the Minimal Bactericidal Concentration (MBC) was possible to classify the bacteriostatic or bactericidal effects of the ethanol extract and fractions tested. The results obtained in the present study indicated that V. condensata is an important source of bioactives substances with antioxidant, antibacterial, antinociceptive and antiinflammatory properties and may be a promising alternative to therapeutic applications.