Avaliação das atividades antibacteriana e antioxidante de Croton heliotropiifolius Kunte e Croton blanchetianus Baill.

Abstract

Croton heliotropiifolius Kunte and Croton blanchetianus Baill (Euphorbiaceae) are medicinal plants native of northeast Brazil. Known popularly as "velame'' and “marmeleiro'', these plants are commonly used as teas, infusions, poultices and laxatives. The therapeutic potential of these species results from the presence of several secondary metabolites such as alkaloids, flavonoids and terpenoids. This paper describes the chemical composition, the antibacterial and modulating activities of essential oils, and the antioxidant activity of leaf ethanolic extracts of these species. Essential oils were extracted from fresh leaves by hydrodistillation and the chemical constituents were identified by GC/MS. Eucalyptol (16.9%), βcaryophyllene (15.9%) and germacrene-D (14.5%) were the main essential oils extracted from C. heliotropiifolius, and cedrol (28.4%), eucalyptol (17.4%) and α-pinene (10.5%) from C. Blanchetianus. Ethanol leaf extracts were obtained by the exhaustive cold extraction method and analyzed phytochemically. Classes of metabolites such as tannins, flavonoids, flavonones, flavonols, flavonoids, catechins and xanthones were indentified on these extracts. Subsequently, the antioxidant activity of these extracts were evaluated according to the free radical sequestration potential by DPPH (1,1-difenil-2-picril-hidrazila). Antibacterial activity of the essential oils was evaluated by the direct interaction and Agar diffusion methods, and indirectly with aminoglycoside antibiotics, by broth microdilution and growth of standard and multidrug-resistant Gram positive and Gram negative bacteria strains. Preliminary results of the antibacterial activity showed that both oils were more effective on Bacillus cereus Grampositive strain. In verifying the minimum inhibitory concentration (MIC), it was observed that the essential oil of C. heliotropiifolius showed no inhibitory activity, except on the multidrugresistant Staphylococcus aureus (MR 358) strain for MIC=512μg/mL. Croton blanchetianus essential oil inhibited more significantly Staphylococcus aureus for MIC=64 μg/mL. Croton blanchetianus oil increased synergistically the activity of amikacin, kanamycin and gentamicin on Bacillus cereus strain. In vitro antioxidant tests by DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical sequestering, showed antioxidant activity for both extracts, and leaf extract of C. blanchetianus were the most efficient, with EC50=6.5 ± 0.5 µg/mL.