Abstract:

Propolis extracts were prepared by extraction with different solvents and were subjected to assay of antifungal activity against Penicillium italicum and determination of components (i.e. total flavonoids and phenols). In addition, the correlation between the inhibitory rate and the contents of total flavonoids and phenols was analyzed. The results showed that among five extracts of propolis with different solvents, both the ethyl acetate extract and the alcohol extract presented the highest inhibitory rate, 100% ± 0%, but the former contained more total flavonoids than the latter did. The correlation coefficient between the inhibitory rate and the content of total flavonoids was higher than that between the inhibitory rate and the content of total phenols. According to these results, we concluded that the ethyl acetate extract has stronger antifungal activity than the alcohol extract do. Subsequently, the antifungal activity of this ethyl acetate extract was further investigated, as well as the effects of pH and temperature on the stability of the antifungal activity. The results showed that the ethyl acetate extract of propolis exhibited strong inhibitory effects against mycelial growth and spore germination of Penicillium italicum in a concentration-dependent manner. After being heated for 30 min at different temperatures of 25 to 100 ℃,the ethyl acetate extract still retained marked inhibitory effect, and no differences were found in heating temperatures. In the range of pH 3.6 to 7.6, the antifungal activity of the ethyl acetate extract firstly increased and reached a maximum at pH 5.2 and then fell down.

Key words: ethyl acetate extract of propolis, Penicillium italicum, antifungal activity, stability