Characterization of L-phenylalanine metabolism to acetophenone and 1-phenylethanol in the flowers of Camellia sinensis using stable isotope labeling |
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Authors: | Dong Fang Yang Ziyin Baldermann Susanne Kajitani Yutaka Ota Shogo Kasuga Hisae Imazeki Yumi Ohnishi Toshiyuki Watanabe Naoharu |
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Affiliation: | a Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan b Corporate Research & Development Division, Takasago International Corporation, 4-11, Nishiyawata 1-chome, Hiratsuka City, Kanagawa 254-0073, Japan |
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Abstract: | Acetophenone (AP) and 1-phenylethanol (1PE) are the two major endogenous volatile compounds in flowers of Camellia sinensis var. Yabukita. Until now no information has been available on the biosynthesis of AP and 1PE in plants. Here we propose that AP and 1PE are derived from L-phenylalanine (L-Phe), based on feeding experiments using stable isotope-labeled precursors L-[(2)H(8)]Phe and L-[(13)C(9)]Phe. The subacid conditions in the flowers result in more hydrogenation than dehydrogenation in the transformation between AP and 1PE. Due to the action of some enzyme(s) responsible for the formation of (R)-1PE from AP in the flowers, (R)-1PE is the dominant endogenous steroisomer of 1PE. The modification of 1PE into nonvolatile glycosidic forms is one of the reasons for why only a little 1PE is released from the flowers. The levels of AP, 1PE, and glycosides of 1PE increase during floral development, whereas the level of L-Phe decreases. These metabolites occur mostly in the anthers. |
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Keywords: | AIP, 2-aminoindan-2-phosphonic acid AP, acetophenone CA, cinnamic acid HPPA, 3-hydroxy-3-phenylpropionic acid MSTFA, N-methyl-N-(trimethylsilyl) trifluoroacetamide PAA, phenyllactic acid PAL, phenylalanine ammonia-lyase 1-PE, 1-phenylethanol smallcaps" >l-Phe, smallcaps" >l-phenylalanine PPA, phenylpyruvic acid PVPP, polyvinylpolypyrrolidone SPME, solid phase microextraction |
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