Humans can detect and distinguish the five basic taste qualities salty, sour, sweet, umami, and bitter (1). Gustatory stimuli are detected by taste receptor cells, which are organized in groups of 60 -100 cells forming a taste bud. One to multiple taste buds are embedded within morphologically different types of taste papillae distributed over the tongue surface. Each taste bud exhibits a single apical porus exposing the microvilli of the receptor cells to the oral cavity (2).The human TAS2R gene family of bitter receptors belongs to the G protein-coupled receptor superfamily and consists of ϳ25 members (3). The identification of activating bitter compounds for