Different Profiles of Quercetin Metabolites in Rat Plasma: Comparison of Two Administration Methods

Abstract

The bioavailability of polyphenols in human and rodents has been discussed regarding their biological activity. We found different metabolite profiles of quercetin in rat plasma between two administration procedures. A single intragastric administration (50 mg/kg) resulted in the appearance of a variety of metabolites in the plasma, whereas only a major fraction was detected by free access (1% quercetin). The methylated/non-methylated metabolites ratio was much higher in the free access group. Mass spectrometric analyses showed that the fraction from free access contained highly conjugated quercetin metabolites such as sulfo-glucuronides of quercetin and methylquercetin. The metabolite profile of human plasma after an intake of onion was similar to that with intragastric administration in rats. In vitro oxidation of human low-density lipoprotein showed that methylation of the catechol moiety of quercetin significantly attenuated the antioxidative activity. These results might provide information about the bioavailability of quercetin when conducting animal experiments.

The flavonoid quercetin induces acute vasodilator effects in healthy volunteers: Correlation with beta-glucuronidase activity

“…Interestingly, the metabolic profile after pure quercetin reported herein seems to be different from that after quercetin rich foods in humans [16,26,36] which includes quercetin-3 -O-sulfate, quercetin-3-O-glucuronide, isorhamnetin-3-O-glucuronide, quercetin diglucuronide and quercetin glucuronide sulfate while the aglycones are undetected. Similarly, different metabolites of quercetin were found in rat plasma after a single intragastric administration compared to those after free access mixed with food [37]. Thus, quercetin administration, as a capsule to humans or as an intragastrical suspension to rats, results mainly in an increase of Q3GA with minor increases in other metabolites including the aglycones.…”

Interference of flavonoids with enzymatic assays for the determination of free fatty acid and triglyceride levels

“…2). Quercetin-3- O -glucuronide is the major metabolite found in human and rat plasma [12, 14, 15]. It was previously shown that plasma concentrations of quercetin metabolites could inhibit myeloperoxidase [12].…”

Hepatic Nrf2 expression is altered by quercetin supplementation in X-irradiated rats

“…Experimental quercetin supplementation has been used to counteract oxidative stress in a number of forms, including dissolved in water (14), ethanol (15) or propylen glycol (12), or food-supplemented (12). Quercetin has been used as pre-treatment to radiation in mice (16) and other flavonoids have been tested both prior to and following irradiation (17).…”