title: Evaluation of the bitterness of green tea catechins by a cell-based assay with the human bitter taste receptor hTAS2R39.
abstract: Catechins have a broad range of physiological functions and act as the main taste ingredient of green tea. Although catechins show a strong bitterness, the bitter taste receptor for catechins has not been fully understood. The objective of this study was to identify the receptor for the major green tea catechins such as (-)-epicatechin (EC), (-)-epicatechin gallate (ECg), (-)-epigallocatechin (EGC), and (-)-epigallocatechin gallate (EGCg). By the cell-based assay using cultured cells expressing human bitter taste receptor, a clear response of hTAS2R39-expressing cells was observed to 300μM of either ECg or EGCg, which elicit a strong bitterness in humans. The response of hTAS2R39-expressing cells to ECg was the strongest among the tested catechins, followed by EGCg. Because the cellular response to EC and EGC is much weaker than those of ECg and EGCg, galloyl groups was strongly supposed to be involved in the bitter intensity. This finding is similar to the observations of taste intensity obtained from a human sensory study. Our results suggest the participation of hTAS2R39 in the detection of catechins in humans, indicating the possibility that bitterness of tea catechins can be evaluated by using cells expressing hTAS2R39.
authors.affiliation: School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Narukawa
authors.forename: Chiaki
authors.initials: C
authors.lastname: Noga
authors.forename: Yohei
authors.initials: Y
authors.lastname: Ueno
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sato
authors.forename: Takumi
authors.initials: T
authors.lastname: Misaka
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis*; D057809:HEK293 Cells; D006801:Humans; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D013649:Taste / Q000502:physiology*; D013662:Tea / Q000737:chemistry*
chemical_list: D011956:Receptors, Cell Surface; C557300:TAS2R39 protein, human; D013662:Tea; D002392:Catechin; C062669:epicatechin gallate; C045651:epigallocatechin gallate