The influence of dietary sunflower honey, propolis, and a flavonoid extract of propolis was examined on drug-metabolizing enzyme activities in rat liver and on microsome-mediated binding of benzo[a]pyrene to DNA. Characterization of flavonoids present in sunflower honey and propolis was achieved in order to assess the relative effects of different components of honey and propolis. Honey and propolis contained the same major flavonoids, pinocembrin, chrysin, galangin, and pinobanksin. The concentration of flavonoids was higher in propolis. Sunflower honey produced no significant changes on phase I and phase II enzyme activities and no modification of in vitro binding of benzo[a]pyrene to DNA. Propolis treatment produced an increase of ethoxyresorufin deethylase, pentoxyresorufin depentylase, ethoxycoumarin deethylase, glutathione transferase, and epoxide hydrolase activities. A flavonoid extract from propolis slightly enhanced only few enzyme activities, ethoxycoumarin deethylase and epoxide hydrolase. The induction pattern was similar to that observed with pinocembrin (a major flavonoid of propolis) administered solely. Binding of benzo[a]pyrene to DNA by microsomes from rats fed with propolis or a flavonoid extract from propolis was not significantly modified. These results contribute to identification of food or foodstuffs that can modify drug-metabolizing enzymes and binding of carcinogens to DNA. Keywords: Sunflower honey; propolis; flavonoids; drug-metabolizing enzymes; benzo[a]pyrene−DNA binding

The flavonoids of sunflower honey were isolated and analyzed by different methods: RP-TLC, RP-HPLC/UV-Vis (diode array detection) using post-column derivatization, GC/SM. Five main compounds were identified as pinocembrin (5,7-dihydroxyflavanone), pinobanksin (3,5,7-trihydroxyflavanone), chrysin (5,7-dihydroxyflavone), galangin (3,5,7-trihydroxyflavone) and quercetin (3,5,7,3',4'-pentahydroxy flavone). Two minor flavonoids were also detected: tectochrysin (5 hydroxy-7-methoxyflavone) and kaempferol (3,.5,7,4'-tetrahydroxy flavone). All these compounds had been previously reported in propolis, another hive product. Honey is a source of flavonoids in the human diet. Flavonoid structures may provide an index of floral origin with further study.

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