Croatica Chemica Acta, Vol. 78 No. 3, 2005.
Original scientific paper
Monitoring Flavonoid Metabolism in Human Cells by Exploiting Fluorescence Elicited upon Quercetin/Protein Interactions
Herwig O. Gutzeit
Sergey V. Tokalov
Jutta Ludwig-Müller
Gordana Rusak
Abstract
Despite the wealth of information concerning biological effects of flavonoids, a systematic approach to analyzing the molecular targets is still lacking and, for this reason, a rational evaluation of the risks or benefits of flavonoid-containing foods or of possible pharmaceutical applications is difficult. We have exploited the property of quercetin to elicit fluorescence when bound to specific target proteins and assayed several flavonoids with different modifications (methylation, hydroxylation, glycosylation). Quercetin target proteins can be visualized in living cells, but in vital human leukaemia cells (HL-60) the fluorescence decreases rapidly after labelling, while metabolically inactive apoptotic cells retain the fluorescence. These cytological differences were apparent under the fluorescent microscope and were quantified using flow cytometry. Metabolic conversion of quercetin in vital cells was confirmed and quantified by HPLC analysis. While apoptotic cells still contained considerable amounts of quercetin, vital cells rapidly metabolized the flavonoid (e.g., by methylation or glycosylation). Biochemical results
are consistent with the cytological observations and support the conclusion that quercetin becomes rapidly converted to non-fluorogenic metabolites in vital cells. Loss of fluorescence in vital cells allows convenient monitoring and quantifying of the dynamics of quercetin metabolism in human cells.
Keywords
quercetin; protein targets; flavonoid/protein fluorescence; flavonoid metabolism; leukaemia cells
Hrčak ID:
39
URI
Publication date:
15.9.2005.
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