ANTIVIRAL ACTIVITY AND FLAVONOID CONTENT OF PROPOLIS FROM CROATIA AND BRAZIL

The flavonoids and phenolic acids and their esters present in propolis are considered to be a rich source of chemopreventive agents, since they possess various biological activities. We investigated water and ethanolic extracts of two chemotypes of propolis (poplar-type from Croatia, and alecrim-type from Brazil) with respect to their chemical composition and antiviral effects. The flavonoid content was anlyzed using two complementary colorimetric methods for flavones/flavonols and flavanones and dihydroflavonols. The samples as well as the main compounds present in propolis: naringenin, quercetin, chrysin, galangin and caffeic acid were tested for inhibitory activity on the replication of influenza viruses A/Germany/27, strain Weybridge (H7N7) and A/Aichi/2/68 (H3N2) in MDCK cells and herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) in MDBK cells. Cytopathic effect was used as a measure of viral replication and the selectivity of inhibition was evaluated. The water and ethanolic extracts from Brazilian propolis as well as naringenin and caffeic acid significantly inhibited the growth of A/Weybridge with selectivity indices (SI) 15, 10, 10 and 6 respectively. None of the tested compounds showed antiviral activity against A/Aichi. Both water propolis extracts from Croatian and Brazilian sources as well as galangin and quercetin exhibited strong anti-HSV-1activity, with SI 20, 16.7, 15 and 10 respectively. The Brazilian water extract of propolis was less effective towards HSV-2 as was quercetin with SI 7.1 and 4 respectively. No correlation between flavonoids content and antiviral activity was observed.