Journal of Tea Science Research, 2024, Vol.14, No.3, 169-181 http://hortherbpublisher.com/index.php/jtsr 169 Review Article Open Access Pathways to Flavor: Decoding the Biosynthesis of Tea Secondary Metabolites KaiqinLin1, YingZhu3, Yichen Zhao2 1 Guizhou Institute of Tea Sciences, Guizhou Academy of Agricultural Sciences, Guiyang, 550006, Guizhou, China 2 Key Laboratory of Plant Resources Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Tea Sciences, Guizhou University, Guiyang, 550025, Guizhou, China 3 Institute of Biotechnology, Guizhou Key Laboratory of Agricultural Biotechnology, Guizhou Academy of Agricultural Sciences & Plant Conservation & Breeding Technology Center, Guiyang, 550006, Guizhou, China Corresponding author: yczhao@gzu.edu.cn Journal of Tea Science Research, 2024, Vol.14, No.3 doi: 10.5376/jtsr.2024.14.0016 Received: 25 Apr., 2024 Accepted: 30 May, 2024 Published: 19 Jun., 2024 Copyright © 2024 Lin et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Lin K.Q., Zhu Y., and Zhao Y.C., 2024, Pathways to flavor: decoding the biosynthesis of tea secondary metabolites, Journal of Tea Science Research, 14(3): 169-181 (doi: 10.5376/jtsr.2024.14.0016) Abstract Tea (Camellia sinensis) is a globally consumed beverage, cherished for its unique flavor and health benefits. The secondary metabolites in tea, such as phenolic compounds, amino acids, alkaloids, and terpenoids, not only contribute to tea's distinctive taste and aroma but also possess significant biological activities, including antioxidant, anti-inflammatory, and anticancer properties. Understanding the biosynthetic pathways of these secondary metabolites is crucial for enhancing tea quality and its health functions. This study systematically analyzes the classification and biosynthetic pathways of tea secondary metabolites, including phenolic compounds (such as flavonoids and catechins), amino acids (such as theanine and glutamic acid), alkaloids (such as caffeine, theobromine, and theophylline), and terpenoids (such as linalool, geraniol, and benzyl alcohol). Additionally, this study discusses the impact of genetic and environmental factors on the synthesis of these tea metabolites and introduces analytical techniques used to study tea metabolites, such as chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy. Through comprehensive analysis, this research provides a scientific basis for future studies aimed at improving tea quality and market competitiveness through metabolite research and outlines future research directions to promote the development of the tea industry. Keywords Tea secondary metabolites; Biosynthetic pathways; Phenolic compounds; Amino acids; Alkaloids; Terpenoids 1 Introduction Tea (Camellia sinensis) is one of the most widely consumed beverages worldwide, valued not only for its refreshing taste but also for its numerous health benefits. The unique flavor and health-promoting properties of tea are primarily attributed to its secondary metabolites, including flavonoids, alkaloids, and terpenoids. These compounds play a crucial role in the plant's defense mechanisms and contribute to the sensory qualities of tea, such as astringency, umami, bitterness, and aroma (Zhao et al., 2021). For example, flavonols, a type of flavonoid, are known to impart bitterness to tea, and their levels can be regulated by environmental factors such as UV radiation and shading (Zhao et al., 2021). These secondary metabolites not only have economic importance in enhancing tea quality but also serve as targets for biotechnological production due to their therapeutic properties (Dziggel et al., 2017). The biosynthesis of secondary metabolites in tea plants involves complex metabolic pathways that are tightly regulated by various genetic and environmental factors. Recent studies have revealed the intricate regulatory networks involved in the production of these compounds. For instance, the synthesis of flavonols in tea leaves is controlled by a network of activating and inhibiting factors, including transcription factors like CsMYB12 and CsbZIP1, which are upregulated by UV-B radiation and downregulated under shading conditions (Zhao et al., 2021). These transcription factors interact with other regulatory proteins to modulate the expression of key biosynthetic genes such as CsFLS and CsUGT78A14, thereby controlling the flavonol content in tea leaves (Zhao et al., 2021). Advances in next-generation sequencing and gene silencing technologies have further elucidated these pathways, making it possible to reconstruct the metabolic pathways of economically relevant secondary metabolites in microbial hosts (Dziggel et al., 2017).
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