Introduction to Quercetin Quercetin: A Powerful Flavonoid with Anti-Inflammatory and Antioxidant Properties. Quercetin is a flavonoid found in many fruits, vegetables, and grains known for its anti-inflammatory and antioxidant properties. It's been particularly useful in combating inflammation due to illness or injury. Not only that, it acts as an antioxidant to protect the body from oxidative damage caused by free radicals. Quercetin has also been shown to have potential anti-cancer properties.