Journal of Tea Science Research, 2024, Vol.14, No.3, 169-181 http://hortherbpublisher.com/index.php/jtsr 170 This study aims to decode the biosynthetic pathways of secondary metabolites in tea leaves, with a particular focus on understanding the regulatory mechanisms involved in their biosynthesis. By synthesizing current research findings, this study provides a comprehensive overview of the genetic and environmental factors influencing the biosynthesis of key secondary metabolites in tea plants. Additionally, the research explores the potential of biotechnological approaches to produce these valuable compounds in microbial systems. Through these analyses, gaps and shortcomings in the current body of knowledge are identified, and future research directions and potential solutions are proposed, aiming to provide a theoretical basis and technical support for the production and quality improvement of tea secondary metabolites. Future research will focus on integrating multi-omics data, systematically analyzing metabolic pathways through systems biology, and developing novel bioreactors to drive innovation and sustainable development in the tea industry. 2 Classification of Major Secondary Metabolites in Tea 2.1 Phenolic compounds in tea Phenolic compounds are a significant class of secondary metabolites in tea, contributing to its antioxidant properties and overall health benefits. High-performance liquid chromatography-mass spectrometry (HPLC-MS(n)) has been effectively utilized to analyze over 30 phenolic compounds in both green and black tea. These compounds include catechin derivatives, flavonols, theaflavins, and their various gallate derivatives, as well as quercetin and kaempferol glycosides, and quinic acid esters of gallic acid and hydroxycinnamates. Phenolic compounds, particularly flavonoids, are known for their clinical properties such as anti-atherosclerotic, anti-inflammatory, antitumor, and antiviral activities (Saboon et al., 2019). The presence of these compounds in tea underscores its potential as a natural antioxidant source, playing a crucial role in neutralizing free radicals and contributing to the prevention of various diseases. 2.2 Amino acid compounds in tea Amino acids are important substances contributing to the flavor of tea. At present, 26 kinds of free amino acids have been identified from tea, including 20 protein source amino acids and 6 non-protein source amino acids, among which the content of non-protein source amino acid theanine can account for more than 50% of the total amino acid content. This was followed by glutamic acid, arginine, serine and aspartic acid (Yu and Yang, 2020). Among them, L-Theanine is the most abundant and representative amino acid in tea, accounting for more than half of the total free amino acids in tea and 1%-4% of dry tea (Deng et al., 2009; Tang et al., 2020). It is one of the characteristic components of tea and the main substance that determines the fresh and refreshing taste of green tea. The content and proportion of amino acids in tea have an important effect on the quality and nutritional value of tea. Because amino acids themselves are taste and aroma substances, the composition and content of amino acids in fresh tea leaves are different, which affects the quality of tea. 2.3 Alkaloids in tea Alkaloids are another important group of secondary metabolites found in tea, with caffeine and theobromine being the most prominent. These purine alkaloids are identified using HPLC-MS(n) based on their retention time, absorbance spectrum, and MS fragmentation pattern. Alkaloids in tea are primarily known for their stimulant properties, with caffeine being the most well-known for its ability to enhance alertness and reduce fatigue. Additionally, alkaloids possess various pharmacological activities, including anesthetic properties, which contribute to the therapeutic potential of tea. The presence of these compounds not only adds to the flavor profile of tea but also enhances its functional benefits as a beverage. 2.4 Terpenoids in tea Terpenoids are a diverse class of secondary metabolites also present in tea, contributing to its aroma and potential health benefits. These compounds are known for their antibacterial, anti-inflammatory, anticancer, antimalarial, and antiviral activities. The terpenoids in tea include various compounds that play a role in the unique fragrance and therapeutic properties of tea. Their pharmacological activities make them valuable in both traditional
RkJQdWJsaXNoZXIy MjQ4ODYzNA==