The aim of this investigation was to study the methylation of quercetin and fisetin, 2 chemically related flavonoids, in human liver and to this purpose, an assay, was set-up to measure the rates of quercetin and fisetin methylation in human liver. The methylation rates (pmol/min/mg) Of quercetin and fisetin were measured in 10 liver samples and the mean +/- SD and the median were 170 +/- 30 and 177 (quercetin) and 183 15 and 178 (fisetin). The rates of quercetin and fisetin methylation were not different (p = 0.283). The fold of variation among samples as 2 (quercetin) and 1.3 (fisetin). Methytransferase towards quercetin and fisetin followed Michaelis-Menten kinetics, and the K-m values were 2.6 +/- 0.3 (quercetin) and 8,6 +/- 0.7 muM (fisetin. p = 0.009) and the V-max values were 187 +/- 20 (quercetin) and 276 +/- 33 pmol/min/mg (fisetin, p = 0.009). Two. 4 and 8 mul of red Chianti wine added to the incubation mixture reduced the rate of quercetin methylation to 75 +/- 4%, 65 +/- 9% and 59 +/- 9%, respectively, and that of fisetin methylation to 62 +/- 3%, 51 +/- 3% and 44 +/- 4%. respectively. In conclusion. quercetin and fisetin are methylated in human liver and their rates of methylation have a limited variation among subjects.
Methylation of quercetin and fisetin, flavonoids widely distributed in edible vegetables, fruits and wine, by human liver
PIETRABISSA, ANDREA;
2002-01-01
Abstract
The aim of this investigation was to study the methylation of quercetin and fisetin, 2 chemically related flavonoids, in human liver and to this purpose, an assay, was set-up to measure the rates of quercetin and fisetin methylation in human liver. The methylation rates (pmol/min/mg) Of quercetin and fisetin were measured in 10 liver samples and the mean +/- SD and the median were 170 +/- 30 and 177 (quercetin) and 183 15 and 178 (fisetin). The rates of quercetin and fisetin methylation were not different (p = 0.283). The fold of variation among samples as 2 (quercetin) and 1.3 (fisetin). Methytransferase towards quercetin and fisetin followed Michaelis-Menten kinetics, and the K-m values were 2.6 +/- 0.3 (quercetin) and 8,6 +/- 0.7 muM (fisetin. p = 0.009) and the V-max values were 187 +/- 20 (quercetin) and 276 +/- 33 pmol/min/mg (fisetin, p = 0.009). Two. 4 and 8 mul of red Chianti wine added to the incubation mixture reduced the rate of quercetin methylation to 75 +/- 4%, 65 +/- 9% and 59 +/- 9%, respectively, and that of fisetin methylation to 62 +/- 3%, 51 +/- 3% and 44 +/- 4%. respectively. In conclusion. quercetin and fisetin are methylated in human liver and their rates of methylation have a limited variation among subjects.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.