Effect of Quercetin on CYP3A Activity in Chinese Healthy Participants

The aims of this study were to investigate the effect of quercetin on CYP3A activity in vivo. An open, randomized, 2-period crossover experiment was performed in 18 healthy male volunteers. Genotyped data were available from a total of 165 participants. The allelic frequency was 52.5%. Every volunteer ingested orally 500 mg quercetin or placebo once a day for 13 consecutive days. On day 14, a single 7.5-mg midazolam tablet was administrated orally. The plasma concentrations of midazolam and 1-OH-midazolam were determined over 24 hours. The results showed that coadministration of quercetin in CYP3A5*1/*1 and CYP3A5*1/*3 individuals significantly decreased the area under the curve (AUC(0-12 h)) of midazolam (160.88 +/- 45.58 ng.h/mL vs 188.07 +/- 65.75 ng.h/mL, P < .05), significantly decreased the AUC(0-infinity) of midazolam (165.46 +/- 47.15 ng.h/mL vs 211.84 +/- 75.80 ng.h/mL, P < .01), shortened t(1/2) (2.06 +/- 0.51 h vs 2.75 +/- 0.89 h, P < .01), and decreased t(max) significantly (0.48 +/- 0.36 h vs 1.06 +/- 0.69 h, P < .01), respectively. In conclusion, quercetin significantly induced CYP3A activity to substrate midazolam, and the induction was partly related to the CYP3A5 genotype, being more prominent in CYP3A5*1/*1 and CYP3A5*1/*3 individuals.