T. Walle et al., QUERCETIN, A POTENT AND SPECIFIC INHIBITOR OF THE HUMAN P-FORM PHENOLSULFOTRANSFERASE, Biochemical pharmacology, 50(5), 1995, pp. 731-734
The natural product quercetin was a potent inhibitor of the human P-fo
rm phenolsulfotransferase with an IC50 value of 0.10+/-0.03 mu M (mean
+/-SEM; N = 5), which was three to four orders of magnitude more poten
t than its inhibition of other human sulfotransferases. The inhibition
was noncompetitive with a K-i value of 0.10 mu M. The potency and mec
hanism of this inhibition appear similar to those of the current stand
ard P-form inhibitor, 2,6-dichloro-4-nitrophenol. Among other flavonoi
ds examined, kaempferol was found to have an IC50 value of 0.39 +/- 0.
07 mu M, naringenin 10.6 +/- 1.6 mu M and naringin 265 +/- 90 mu M (N
= 3). These observations suggest the potential for clinically importan
t pharmacologic and toxicologic interactions by flavonoid-containing f
oods and beverages.