Quercetin is a prominent flavonol subclass of flavonoids widely distributed in fruits, vegetables, and grains such as onions, apples, berries, and tea. It exhibits potent antioxidant activity due to its polyphenolic structure featuring five hydroxyl groups that enable free radical scavenging and metal chelation. Research indicates anti-inflammatory, cardioprotective, and potential anticancer effects through modulation of signaling pathways like NF-kB and PI3K/Akt. It undergoes extensive phase II metabolism in humans, forming glucuronides and sulfates with limited bioavailability. Quercetin is commonly used in dietary supplements and studied for its role in preventing oxidative stress-related diseases.