Quercetin is a type of plant-based chemical, or phytochemical, known as a flavonoid (also Phytochemicals). Sources of quercetin include the commonly found apples, red onions, tea leaves, wines, and other related foods. The quercitin can also be found as a supplement for diet. The substance has been found to raise the energy spending in mice, but this lasts only for a short period of less than eight weeks. The effects of the substance on tolerance to exercise in rats have been related to the enhanced mitochondrial biogenesis. The substance also is said to be the aglycone form of numerous other flavonoid, like quercitrin and rutin which found mostly in buckwheat, citrus fruit and onions. Quercetin forms the quercitrin, glycosides and rhamnose together with rutinose and rutin, respectively. Quercetin is in the class of IARC group 3 (with no tangible evidence of carcinogenicity in humans).