title: Enantiomeric and quantitative analysis of volatile terpenoids in different teas (Camellia sinensis).
abstract: Volatile terpenoids play important roles in the formation of tea aroma quality due to their pleasant scents and low odor thresholds. Most volatile terpenoids contain stereogenic centers, which results in various stereo distributions of their enantiomers and diastereoisomers in different types of tea. However, the distribution characteristics of terpenoid enantiomers in teas were still unclear, which poses an obstacle to the scientific understanding of tea aroma. In this work, a new and efficient analysis approach based on headspace solid phase microextraction (HS-SPME)-chiral gas chromatography-mass spectrometry (GC-MS) was established to analyze 12 pairs of familiar terpenoid enantiomers in different teas. The extraction efficiency of the HS-SPME method to extract volatile terpenoids in teas was the greatest when using CAR-DVB-PDMS (50/30μm) fibers and 1:10 proportions between tea and boiling water at a 50°C extraction temperature for 40min, and the stability observation of enantiomeric ratios of the terpenoids well proved the feasibility of the extraction method. The favorable limits of detection, limits of quantitation, repeatability, linearity, and concentration ranges of each terpenoid enantiomer demonstrated the repeatability and reliability of the analytical approach. The enantiomeric and quantitative analyses indicated that S-limonene, S-linalool, (2S, 5S)-linalool oxide A, (2S, 5R)-linalool oxide B, R-4-terpineol, (2S, 5R)-linalool oxide C, (2S, 5S)-linalool oxide D, S-α-terpineol, R-α-ionone, peak 1 of theaspirane A and peak 2 of theaspirane B were the major terpenoid components in most Chinese teas; instead, higher proportions of the opposite enantiomers of the above terpenoids were frequently detected in black teas with large leaf origin and Indonesia white teas. Besides, great diversities of enantiomeric ratios and concentrations among different teas were observed. Furthermore, partial least-squares discriminant analyses were performed to distinguish the concentration differences of the terpenoid enantiomers among different teas; the analysis results indicated that highly significant concentration differences existed between large and small leaf origins of black teas, and significant differences of the concentrations of linalool oxides A-C were observed between green, white and dark teas. The successful application of this chiral analysis technique of tea aroma will lay a scientific foundation for further quality assessment, botanical origin determination and authenticity assessment of teas.
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China; Graduate School of Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Chen-Yang
authors.initials: CY
authors.lastname: Shao
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China. Electronic address: teachem108@hotmail.com.
authors.forename: Hai-Peng
authors.initials: HP
authors.lastname: Lv
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
authors.forename: Wei-Dong
authors.initials: WD
authors.lastname: Dai
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
authors.forename: Li
authors.initials: L
authors.lastname: Guo
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
authors.forename: Jun-Feng
authors.initials: JF
authors.lastname: Tan
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
authors.forename: Qun-Hua
authors.initials: QH
authors.lastname: Peng
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China. Electronic address: linzhi@caas.cn.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Lin
mesh_terms: D028241:Camellia sinensis / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D052617:Solid Phase Microextraction; D013237:Stereoisomerism; D013662:Tea / Q000737:chemistry*; D013729:Terpenes / Q000032:analysis / Q000737:chemistry
chemical_list: D013662:Tea; D013729:Terpenes
keywords: Chiral GC–MS; Enantiomeric ratio; HS-SPME; Tea; Volatile terpenoids