Analysis of propolis from the continental and Adriatic regions of Croatia.

Thin-layer chromatography of ethanolic extract of propolis (EEP) from the continental and Adriatic regions of Croatia showed that 72.2% of propolis samples contain galangin, 88.8% of samples contain kaempferol, naringenin and apigenin and 66.6% of samples contain caffeic acid. Caffeic acid, pinocembrin, galangin, chrysin and naringenin were analyzed by HPLC. In all samples, pinocembrin was the dominant flavonoid. In samples from the Adriatic region, concentration of pinocembrin ranged from 0.03 to 6.14% (x = 2.87%) and in the continental region samples from 0 to 4.74% (x = 2.84%). Chrysin was found in all propolis samples in a concentration ranging from 0.22 to 5.32% (x = 1.86%) in the continental region samples and from 0.03 to 3.64% (x = 1.96%) in samples from the Adriatic region. Chrysin was followed by naringenin, ranging from 0 to 1.14% (x = 0.42%) in samples from the Adriatic region and from 0.22 to 2.41% (x = 0.60%) in the continental region samples. Concentration of caffeic acid ranged from 0 to 10.11% (x = 2.69%) in the Adriatic region samples and from 0.27 to 2.67% (x = 1.37%) in samples from the continental region of Croatia. Results of HPLC analyses suggest that propolis samples collected from various parts of Croatia do not differ markedly in contents of chrysin, pinocembrin, naringenin and galangin but differ in the concentration of caffeic acid. All EEPs significantly inhibited the growth of Bacillus subtilis in comparison with the control (80% ethanol) (p < 0.05), showing inhibition zones of 16 +/- 2 mm for samples from the continental region, and of 18 +/- 3 mm for samples from the Adriatic region. There was no significant difference in antimicrobial activity of EEPs from the continental and Adriatic regions of Croatia, suggesting that bactericidal activity depends on synergism of all phenolic compounds.