Analysis of the composition of Brazilian propolis extracts by chromatography and evaluation of their in vitro activity against Gram-positive bacteria

Brazilian propolis from Sao Paulo state was submitted to extraction using several solvents, resulting in extracts with different composition. These extracts were submitted to Thin Layer Chromatography (TLC). Bioauthographic analysis of the TLC plates identified fractions with inhibitory activity, which were then analysed by High Performance Liquid Chromatography (HPLC). In vitro assays, commonly used to evaluate the activity of propolis against Grain-positive bacteria, were compared to determine which rendered the most consistent results. The bactericidal activity of these extracts were analysed by Serial Dilution in Tubes and Agar Plate Diffusion. Serial Dilution in Tubes obtained the most consistent results, with the Minimal Bactericidal Concentration of the extracts ranging between 2.5 and 20.0 mg/mL, for the species of Gram-positive bacteria tested. The results of the Agar Plate Diffusion were directly proportional to the hydro-solubility of the extracts and did not evaluate their bactericidal activity correctly. The bactericidal activity of this sample of propolis was due to the combined effect of several components that were identified by HPLC and were best extracted using 50% ethanol as a solvent.