School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Biochem Biophys Res Commun. 2011 Feb 25;405(4):620-5. doi: 10.1016/j.bbrc.2011.01.079. Epub 2011 Jan 25.
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.
儿茶素有广泛的生理功能，是绿茶主要的味觉成分。尽管儿茶素表现出强烈的苦味，但儿茶素的苦味受体尚未完全被了解。本研究的目的是鉴定主要绿茶儿茶素（如(-)-表儿茶素（EC）、(-)-表儿茶素没食子酸酯（ECg）、(-)-表没食子儿茶素（EGC）和(-)-表没食子儿茶素没食子酸酯（EGCg）的受体。通过使用表达人苦味受体的培养细胞的基于细胞的测定，观察到 hTAS2R39 表达细胞对 300μM 的 ECg 或 EGCg 有明显的反应，这两种儿茶素在人类中引起强烈的苦味。在测试的儿茶素中，hTAS2R39 表达细胞对 ECg 的反应最强，其次是 EGCg。由于细胞对 EC 和 EGC 的反应远弱于 ECg 和 EGCg，因此强烈假定没食子酰基参与了苦味强度。这一发现与人类感官研究中获得的味觉强度观察结果相似。我们的结果表明 hTAS2R39 参与了人类对儿茶素的检测，表明可以使用表达 hTAS2R39 的细胞来评估茶儿茶素的苦味。
