Our Lab's Research on Tea and Its Bioactive Ingredients
Our lab's research on tea (Camellia sinensis) is extensive and multi-faceted, systematically exploring the journey from leaf to health impact. Our work encompasses the development of extraction techniques, advanced processing, in-depth characterization of tea's bioactive components, and rigorous investigation into their health benefits and underlying molecular mechanisms, particularly in relation to metabolic diseases, gut health, and novel therapeutic applications.
1. Advancements in Tea Extraction, Processing, and Characterization
A significant portion of our research focuses on optimizing and innovating the extraction and processing of tea to enhance its quality and bioactive potential. We have pioneered the use of green extraction technologies, such as combining ultrasound-assisted extraction (UAE) with deep eutectic solvents (DES), to significantly improve the yield of antioxidant polyphenols from green tea (Luo et al., 2020) and theabrownins from dark tea (Liu et al., 2022). Further refining our understanding of extraction, we demonstrated that while treatments like tannase and ultrasound can enhance the in vitro antioxidant activity of green tea extracts, these benefits may not translate to improved in vivo effects, highlighting the importance of in vivo validation for processing techniques (Xu, Meng, et al., 2019; Xu, Zheng, et al., 2019). This work is complemented by our comprehensive review of both conventional and novel techniques for tea polyphenol extraction, purification, and identification, providing a valuable resource for the field (Li, Guo, et al., 2023).
Furthermore, we investigated the biochemical transformations during tea processing. Using multi-omics approaches, we have detailed the dynamic changes in metabolites and proteins during the withering of different tea cultivars, providing a molecular basis for tea quality formation (Ye et al., 2024). We also explored microbial fermentation, demonstrating that inoculating dark tea with Aspergillus niger can accelerate fermentation and improve its flavor by modulating key compounds (Li et al., 2025). Our research also extends to novel applications of tea by-products, showing that fermenting kombucha with tea residues can markedly increase its polyphenol content and antioxidant activity (Zhou, Saimaiti, et al., 2022).
2. Characterization and Health Benefits of Tea's Bioactive Components
Our lab has conducted extensive research on the key bioactive compounds in tea and their health-promoting effects. This includes broad comparative studies, such as systematically evaluating the phenolic profiles and antioxidant capacities of 30 different Chinese tea infusions (Zhao et al., 2019) and their fat-soluble, water-soluble, and bound-insoluble fractions (Tang et al., 2019). We also found that crude polysaccharides from 12 different Chinese teas, particularly Pu-erh, exhibited significant antioxidant and anti-diabetic activities, which were positively correlated with their protein and phenolic content (Guo et al., 2021). We have also published foundational reviews on the chemistry and health benefits of tea major components like L-theanine (Li, Liu, et al., 2022), dark tea pigments and bioactives (Lin et al., 2021; Wang et al., 2022), and epigallocatechin gallate (EGCG) (Gan et al., 2018).
A major focus has been on elucidating the mechanisms behind tea's benefits for metabolic diseases. Through in vivo studies, we have shown that various green teas can prevent obesity and non-alcoholic fatty liver disease (NAFLD) (Zhou, Mao, et al., 2022; Mao et al., 2021). Specifically, we identified theabrownin (TB) from dark tea as having potent preventative and therapeutic effects on NAFLD and obesity, linking its mechanism to the regulation of serotonin-related signaling pathways via the gut-liver axis (Li et al., 2023). In comparative studies on alcoholic fatty liver disease (AFLD), we found that teas like Fried Green Tea and Pu-erh Dark Tea offered significant protection by ameliorating oxidative damage (Li, Mao, Gan, et al., 2021) and that several green teas were particularly effective, with their benefits correlating to their content of gallic acid and catechins (Li, Mao, Zhou, et al., 2021). A broad comparison of 32 Chinese teas further confirmed that dark teas, contrary to in vitro findings, showed the strongest in vivo antioxidant and hepatoprotective activities in an alcohol-induced liver injury model (Cao et al., 2020). This extensive body of work is supported by our comprehensive reviews summarizing the epidemiological, experimental, and clinical evidence for tea's role in managing obesity (Xu et al., 2023), diabetes (Meng et al., 2019), cardiovascular diseases (Cao et al., 2019), cancer (Xu et al., 2020), neurodegenerative diseases (Luo et al., 2023), and hyperuricemia (Chen et al., 2023), all of which detail the underlying molecular mechanisms (Shang et al., 2021; Tang et al., 2019).
3. Bioavailability, Gut Microbiota Interaction, and Novel Delivery Systems
Recognizing that efficacy depends on bioavailability, our work delves into the metabolic fate of tea compounds. We have reviewed how gut microbiota metabolize green tea catechins (GTCs) into more bioavailable and potent low-molecular-weight metabolites like phenyl-gamma-valerolactones, arguing this is a key step for realizing their health benefits (Liu et al., 2024). Our experimental work showed that oolong tea polysaccharides are effectively fermented by gut microbiota, leading to the proliferation of beneficial genera like Bacteroides and the production of short-chain fatty acids (Wu et al., 2022), and the hepatoprotective effects of oolong and dark teas in AFLD are closely linked to their ability to restore gut microbiota balance (Li, Mao, Zhou, et al., 2021).
To directly overcome poor bioavailability of tea compounds, we have engineered novel delivery systems. In a groundbreaking study, we developed silk fibroin microneedles loaded with epigallocatechin gallate (EGCG). This system effectively mitigated atrazine-induced testicular toxicity in rats by reducing oxidative stress and modulating key apoptosis and necroptosis pathways (Fang et al., 2024). This work, along with our review on nanochemoprevention strategies for EGCG (Yang et al., 2020), positions our lab at the forefront of applying nanotechnology to enhance the therapeutic potential of tea bioactives.
4. Significance and Novelty of Our Work
The significance of our lab's research lies in its comprehensive, "farm-to-function" approach that connects tea processing with its ultimate health benefits through rigorous molecular investigation. The novelty is evident in several key areas:
(1) Technological Innovation: We are pioneers in applying and optimizing green extraction techniques (UAE-DES) for tea, and in using microbial inoculation (Aspergillus niger) as a controlled method to enhance the quality of fermented teas.
(2) Mechanism-Driven Health Research: Rather than simply reporting bioactivities, we delve deep into the molecular mechanisms. Our work identifying the serotonin-gut-liver axis as a target for theabrownin in treating NAFLD is a prime example of this in-depth, hypothesis-driven research.
(3) Bridging Bioavailability and Efficacy: Our focus on the role of gut microbiota in metabolizing tea compounds and our development of novel delivery systems (e.g., EGCG-loaded microneedles) directly address the critical challenge of bioavailability, translating the potential of tea bioactives into practical therapeutic strategies.
(4) Comprehensive and Comparative Analysis: By systematically comparing a wide array of teas for their chemical profiles and in vivo effects against specific diseases, and by publishing numerous authoritative reviews, our research provides valuable, evidence-based guidance for consumers and for the development of targeted functional foods.
In summary, our lab has built a powerful research program that not only catalogues the rich chemistry and health benefits of tea but also actively engineers solutions to enhance its quality, bioavailability, and therapeutic application. This work provides a strong scientific foundation for the development of new functional foods, nutraceuticals, and clinical therapies derived from tea.
Acknowledgement
We would like to thank the hard work and collaboration of all my team members and collaborators involved in this work, especially the great contribution of Prof. Hua-Bin Li and his team from Sun Yat-Sen University.
Cao, S. Y., Li, B. Y., Gan, R. Y., Mao, Q. Q., Wang, Y. F., Shang, A., Meng, J. M., Xu, X. Y., Wei, X. L., & Li, H. B. (2020). The In Vivo Antioxidant and Hepatoprotective Actions of Selected Chinese Teas. Foods, 9(3), 262. http://dx.doi.org/10.3390/foods9030262
Cao, S. Y., Zhao, C. N., Gan, R. Y., Xu, X. Y., Wei, X. L., Corke, H., Atanasov, A. G., & Li, H. B. (2019). Effects and Mechanisms of Tea and Its Bioactive Compounds for the Prevention and Treatment of Cardiovascular Diseases: An Updated Review. Antioxidants, 8(6), 166. http://dx.doi.org/10.3390/antiox8060166
Chen, Y., Luo, L. Y., Hu, S. S., Gan, R. Y., & Zeng, L. (2023). The chemistry, processing, and preclinical anti-hyperuricemia potential of tea: a comprehensive review. Critical Reviews in Food Science and Nutrition, 63(24), 7065-7090. http://dx.doi.org/10.1080/10408398.2022.2040417
Fang, C. Y., Li, Y. C., He, G. Y., Gan, R. Y., Luo, F., Lei, L. J., Hou, X., & Ye, Y. L. (2024). Silk fibroin microneedles loaded with epigallocatechin gallate mitigate atrazine-induced testicular toxicity. Journal of Hazardous Materials, 480, 136252. http://dx.doi.org/10.1016/j.jhazmat.2024.136252
Gan, R. Y., Li, H. B., Sui, Z. Q., & Corke, H. (2018). Absorption, metabolism, anti-cancer effect and molecular targets of epigallocatechin gallate (EGCG): An updated review. Critical Reviews in Food Science and Nutrition, 58(6), 924-941. http://dx.doi.org/10.1080/10408398.2016.1231168
Guo, H., Fu, M. X., Wu, D. T., Zhao, Y. X., Li, H., Li, H. B., & Gan, R. Y. (2021). Structural Characteristics of Crude Polysaccharides from 12 Selected Chinese Teas, and Their Antioxidant and Anti-Diabetic Activities. Antioxidants, 10(10), 1562. http://dx.doi.org/10.3390/antiox10101562
Li, B. Y., Mao, Q. Q., Gan, R. Y., Cao, S. Y., Xu, X. Y., Luo, M., Li, H. Y., & Li, H. B. (2021). Protective effects of tea extracts against alcoholic fatty liver disease in mice via modulating cytochrome P450 2E1 expression and ameliorating oxidative damage. Food Science & Nutrition, 9(10), 5626-5640. http://dx.doi.org/10.1002/fsn3.2526
Li, B. Y., Mao, Q. Q., Zhou, D. D., Luo, M., Gan, R. Y., Li, H. Y., Huang, S. Y., Saimaiti, A., Shang, A., & Li, H. B. (2021). Effects of Tea against Alcoholic Fatty Liver Disease by Modulating Gut Microbiota in Chronic Alcohol-Exposed Mice. Foods, 10(6), 1232. http://dx.doi.org/10.3390/foods10061232
Li, H., Guo, H., Luo, Q., Wu, D. T., Zou, L., Liu, Y., Li, H. B., & Gan, R. Y. (2023). Current extraction, purification, and identification techniques of tea polyphenols: An updated review. Critical Reviews in Food Science and Nutrition, 63(19), 3912-3930. http://dx.doi.org/10.1080/10408398.2021.1995843
Li, H. Y., Huang, S. Y., Zhou, D. D., Xiong, R. G., Luo, M., Saimaiti, A., Han, M. K., Gan, R. Y., Zhu, H. L., & Li, H. B. (2023). Theabrownin inhibits obesity and non-alcoholic fatty liver disease in mice via serotonin-related signaling pathways and gut-liver axis. Journal of Advanced Research, 52, 59-72. http://dx.doi.org/10.1016/j.jare.2023.01.008
Li, M. Y., Du, S. C., Xiao, Y., Wu, Y. P., Zhong, K., Huang, Y. N., Gan, R. Y., & Gao, H. (2025). Enhancing the quality of dark tea through fermentation with Aspergillus niger: Unveiling aroma and taste characteristics. Food Microbiology, 128, 104721. http://dx.doi.org/10.1016/j.fm.2025.104721
Li, M. Y., Liu, H. Y., Wu, D. T., Kenaan, A., Geng, F., Li, H. B., Gunaratne, A., Li, H., & Gan, R. Y. (2022). L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications. Frontiers in Nutrition, 9, 853846. http://dx.doi.org/10.3389/fnut.2022.853846
Lin, F. J., Wei, X. L., Liu, H. Y., Li, H., Xia, Y., Wu, D. T., Zhang, P. Z., Gandhi, G. R., Li, H. B., & Gan, R. Y. (2021). State-of-the-art review of dark tea: From chemistry to health benefits. Trends in Food Science & Technology, 109, 126-138. http://dx.doi.org/10.1016/j.tifs.2021.01.030
Liu, C., Gan, R. Y., Chen, D. W., Zheng, L., Ng, S. B., & Rietjens, I. M. (2024). Gut microbiota-mediated metabolism of green tea catechins and the biological consequences: An updated review. Critical Reviews in Food Science and Nutrition, 64(20), 7067-7084. http://dx.doi.org/10.1080/10408398.2023.2180478
Liu, Y., Liu, H. Y., Yang, X., Zhu, F., Wu, D. T., Li, H. B., & Gan, R. Y. (2022). Green extraction, chemical composition, and in vitro antioxidant activity of theabrownins from Kangzhuan dark tea. Current Research in Food Science, 5, 1944-1954. http://dx.doi.org/10.1016/j.crfs.2022.10.019
Luo, M., Gan, R. Y., Li, B. Y., Mao, Q. Q., Shang, A. O., Xu, X. Y., Li, H. Y., & Li, H. B. (2023). Effects and Mechanisms of Tea on Parkinson's Disease, Alzheimer's Disease and Depression. Food Reviews International, 39(1), 278-306. http://dx.doi.org/10.1080/87559129.2021.1904413
Luo, Q., Zhang, J. R., Li, H. B., Wu, D. T., Geng, F., Corke, H., Wei, X. L., & Gan, R. Y. (2020). Green Extraction of Antioxidant Polyphenols from Green Tea (Camellia sinensis). Antioxidants, 9(9), 785. http://dx.doi.org/10.3390/antiox9090785
Mao, Q. Q., Li, B. Y., Meng, J. M., Gan, R. Y., Xu, X. Y., Gu, Y. Y., Wang, X. H., & Li, H. B. (2021). Effects of several tea extracts on nonalcoholic fatty liver disease in mice fed with a high-fat diet. Food Science & Nutrition, 9(6), 2954-2967. http://dx.doi.org/10.1002/fsn3.2255
Meng, J. M., Cao, S. Y., Wei, X. L., Gan, R. Y., Wang, Y. F., Cai, S. X., Xu, X. Y., Zhang, P. Z., & Li, H. B. (2019). Effects and Mechanisms of Tea for the Prevention and Management of Diabetes Mellitus and Diabetic Complications: An Updated Review. Antioxidants, 8(6), 170. http://dx.doi.org/10.3390/antiox8060170
Shang, A., Li, J. H., Zhou, D. D., Gan, R. Y., & Li, H. B. (2021). Molecular mechanisms underlying health benefits of tea compounds. Free Radical Biology and Medicine, 172, 181-200. http://dx.doi.org/10.1016/j.freeradbiomed.2021.06.006
Tang, G. Y., Meng, X., Gan, R. Y., Zhao, C. N., Liu, Q., Feng, Y. B., Li, S., Wei, X. L., Atanasov, A. G., Corke, H., & Li, H. B. (2019). Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review. International Journal of Molecular Sciences, 20(24), 6196. http://dx.doi.org/10.3390/ijms20246196
Tang, G. Y., Zhao, C. N., Xu, X. Y., Gan, R. Y., Cao, S. Y., Liu, Q., Shang, A., Mao, Q. Q., & Li, H. B. (2019). Phytochemical Composition and Antioxidant Capacity of 30 Chinese Teas. Antioxidants, 8(6), 180. http://dx.doi.org/10.3390/antiox8060180
Wang, S. A., Qiu, Y., Gan, R. Y., & Zhu, F. (2022). Chemical constituents and biological properties of Pu-erh tea. Food Research International, 154, 110899. http://dx.doi.org/10.1016/j.foodres.2021.110899
Wu, D. T., Liu, W., Yuan, Q., Gan, R. Y., Hu, Y. C., Wang, S. P., & Zou, L. (2022). Dynamic variations in physicochemical characteristics of oolong tea polysaccharides during simulated digestion and fecal fermentation in vitro. Food Chemistry-X, 14, 100288. http://dx.doi.org/10.1016/j.fochx.2022.100288
Xu, X. Y., Meng, J. M., Mao, Q. Q., Shang, A., Li, B. Y., Zhao, C. N., Tang, G. Y., Cao, S. Y., Wei, X. L., Gan, R. Y., Corke, H., & Li, H. B. (2019). Effects of Tannase and Ultrasound Treatment on the Bioactive Compounds and Antioxidant Activity of Green Tea Extract. Antioxidants, 8(9), 362. http://dx.doi.org/10.3390/antiox8090362
Xu, X. Y., Zheng, J., Meng, J. M., Gan, R. Y., Mao, Q. Q., Shang, A., Li, B. Y., Wei, X. L., & Li, H. B. (2019). Effects of Food Processing on In Vivo Antioxidant and Hepatoprotective Properties of Green Tea Extracts. Antioxidants, 8(12), 572. http://dx.doi.org/10.3390/antiox8120572
Xu, X. Y., Zhao, C. N., Cao, S. Y., Tang, G. Y., Gan, R. Y., & Li, H. B. (2020). Effects and mechanisms of tea for the prevention and management of cancers: An updated review. Critical Reviews in Food Science and Nutrition, 60(10), 1693-1705. http://dx.doi.org/10.1080/10408398.2019.1588223
Xu, X. Y., Zhao, C. N., Li, B. Y., Tang, G. Y., Shang, A., Gan, R. Y., Feng, Y. B., & Li, H. B. (2023). Effects and mechanisms of tea on obesity. Critical Reviews in Food Science and Nutrition, 63(19), 3716-3733. http://dx.doi.org/10.1080/10408398.2021.1992748
Yang, Q. Q., Wei, X. L., Fang, Y. P., Gan, R. Y., Wang, M., Ge, Y. Y., Zhang, D., Cheng, L. Z., & Corke, H. (2020). Nanochemoprevention with therapeutic benefits: An updated review focused on epigallocatechin gallate delivery. Critical Reviews in Food Science and Nutrition, 60(8), 1243-1264. http://dx.doi.org/10.1080/10408398.2019.1565490
Ye, Y. L., Gong, Y. Y., Huang, P., Luo, F., Gan, R. Y., & Fang, C. Y. (2024). Dynamic changes in the non-volatile and flavour compounds in withered tea leaves of three different colour cultivars based on multi-omics. Food Chemistry, 449, 139281. http://dx.doi.org/10.1016/j.foodchem.2024.139281
Zhao, C. N., Tang, G. Y., Cao, S. Y., Xu, X. Y., Gan, R. Y., Liu, Q., Mao, Q. Q., Shang, A., & Li, H. B. (2019). Phenolic Profiles and Antioxidant Activities of 30 Tea Infusions from Green, Black, Oolong, White, Yellow and Dark Teas. Antioxidants, 8(7), 215. http://dx.doi.org/10.3390/antiox8070215
Zhou, D. D., Mao, Q. Q., Li, B. Y., Saimaiti, A., Huang, S. Y., Xiong, R. G., Shang, A., Luo, M., Li, H. Y., Gan, R. Y., Li, H. B., & Li, S. (2022). Effects of Different Green Teas on Obesity and Non-Alcoholic Fatty Liver Disease Induced by a High-Fat Diet in Mice. Frontiers in Nutrition, 9, 929210. http://dx.doi.org/10.3389/fnut.2022.929210
Zhou, D. D., Saimaiti, A., Luo, M., Huang, S. Y., Xiong, R. G., Shang, A., Gan, R. Y., & Li, H. B. (2022). Fermentation with Tea Residues Enhances Antioxidant Activities and Polyphenol Contents in Kombucha Beverages. Antioxidants, 11(1), 155. http://dx.doi.org/10.3390/antiox11010155
