Quercetin is an abundant flavonoid found in edible vegetables, grains and fruits and is used as an ingredient in supplements, beverages, or foods. Pirin (PIR) is a highly conserved nuclear protein (Wendler et al. 1997) which possesses quercetinase activity, transforming quercetin to 2-protocatechuoylphloroglucinol carboxylic acid (2PCPGCA) and carbon monoxide (CO) (Adams & Jia 2005). Quercetin supplements have been promoted for the treatment of a wide spectrum of diseases including cancer but there is insufficient evidence to draw any conclusive proof of its beneficial effects to date (Miles et al. 2014).