Comprehensive Report on Quercetin (DB04216)

I. Executive Summary

Quercetin (DrugBank ID: DB04216) is a small molecule flavonol, a subclass of the flavonoid group of polyphenols, that is ubiquitously distributed throughout the plant kingdom.[1] Found in a wide array of common foods such as onions, apples, berries, and tea, it is one of the most abundant antioxidants in the human diet.[3] Decades of preclinical research have positioned Quercetin as a compound of significant scientific interest due to its potent and pleiotropic biological activities, including well-documented antioxidant, anti-inflammatory, immunomodulatory, and anticancer properties demonstrated in numerous

in vitro and animal models.[5]

The central scientific challenge and defining characteristic of Quercetin research is the marked disparity between its robust bioactivity in laboratory settings and its often modest or inconsistent efficacy in human clinical trials.[3] This translational gap is overwhelmingly attributed to a challenging pharmacokinetic profile characterized by very low aqueous solubility, poor oral bioavailability, and rapid, extensive first-pass metabolism in the gut and liver.[3] Upon oral ingestion, the parent Quercetin aglycone is rarely detected in systemic circulation; instead, the body is exposed to a complex profile of conjugated metabolites (glucuronides, sulfates, and methylated forms), raising critical questions about which chemical species are responsible for the observed biological effects.[3]