HPLC and LC-MS Analysis of Quercetin Metabolites in Rat Organs

There is much epidemiological evidence that diets rich in fruit and vegetables tend to show protective effects against cardiovascular diseases, aging, cancer, diabetes. This protective effect is hypothesized to be due to polyphenols, which are the major antioxidants in plant foods. Polyphenols are extensively metabolized and these metabolites may act as the active ingredients rather than the precursors in food, thus being beneficial for human health. Pure polyphenols like quercetin, catechin and naringenin were injected through intraperitoneal injections into male rats at doses ranging from 50 mg/kg of body weight daily for 3 days and were sacrificed 2 hours after the last injection. The liver, kidney, heart, and brain were harvested. This research focuses on quercetin and its metabolic activity; homogenized solutions of the organs after treatment with with quercetin were prepared for further analysis with HPLC and LC-MS for monitoring the polyphenols. These organ extracts of quercetin were further treated with the enzyme β-glucuronidase and the enzyme activity was analyzed using HPLC. The HPLC separated quercetin and its metabolites in the extracts. It also helped in determination of the concentration of quercetin and its metabolites. This confirmed that liver had the highest concentration of quercetin amongst all the organs and thus liver was considered as the primary organ for polyphenol metabolism. Further on with the enzyme hydrolysis it was confirmed that glucuronides were the major metabolites of quercetin conjugates. The metabolites of quercetin were identified by LC-MS analysis by comparing the obtained mass spectra by the literature mass spectra. Thus, HPLC and LC-MS analysis demonstrated necessary sensitivity and selectivity to confirm and quantify polyphenols and their metabolites in the extracts