In vitro activity of propolis against Streptococcus pyogenes

Propolis, a multifunctional substance used by bees to maintain the safety o f their hives, is popular for its therapeutic potential against some micro- organisms. Ethanolic extracts of two propolis specimens, collected from dif ferent. areas within a region in the north-west of Italy, were examined to evaluate their antimicrobial activity against 46 Streptococcus pyogenes str ains. By both agar dilution and agar diffusion methods, the minimal inhibit ory concentration (MIC) and minimal bactericidal concentration (MBC) were l ess than or equal to 234 mu g ml(-1), corresponding to a one in 512 dilutio n of the 12% (w/v) extracts. One of the two propolis samples was more activ e and this extract was shown to be richer in the flavonoids pinocembrin and galangin using HPLC. Therefore, with a simple microbiological assay techni que, in particular the agar dilution method, it was possible to standardize the analysis of propolis samples to identify the quality parameters of thi s natural product before use for medical treatment.