Unexpected hydroxyl radical production in brewed tea under sunlight

Linjun Qin; Lili Yang; Manabu Shiraiwa; Francesco Faiola; Huan Zhong; Christian Sonne; Yujue Yang; Shuting Liu; Guorui Liu; Minghui Zheng; Guibin Jiang

doi:10.1093/pnasnexus/pgae015

Unexpected hydroxyl radical production in brewed tea under sunlight

PNAS Nexus. 2024 Jan 16;3(1):pgae015. doi: 10.1093/pnasnexus/pgae015. eCollection 2024 Jan.

Authors

Linjun Qin^{1

2}, Lili Yang^{1

2}, Manabu Shiraiwa³, Francesco Faiola^{1

2}, Huan Zhong⁴, Christian Sonne⁵, Yujue Yang^{1

2}, Shuting Liu^{1

2}, Guorui Liu^{1

2

6}, Minghui Zheng^{1

2

6}, Guibin Jiang^{1

2

6}

Affiliations

¹ State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
² College of Resources and Environment, University of the Chinese Academy of Sciences, Beijing 100190, China.
³ Department of Chemistry, University of California, Irvine, CA 92697, USA.
⁴ State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
⁵ Department for Bioscience, Arctic Research Centre, Aarhus University, Roskilde DK-4000, Denmark.
⁶ Institute of Environment and Health, Hangzhou Institute for Advanced Study, University of the Chinese Academy of Sciences, Hangzhou 310024, China.

Abstract

Tea is one of the world's most popular and widely consumed beverages. It is a common pastime to enjoy a cup of tea in the sunshine. However, little attention has been given to understanding the possible photochemical reactions occurring beneath the calm surface of brewed tea. Epigallocatechin gallate (EGCG), which is widely used in food and beverages, is the most significant active ingredient found in tea. In this study, we investigated the presence of free radicals in both an aqueous EGCG solution and brewed tea under simulated sunlight conditions. To our surprise, we unexpectedly observed the production of hydroxyl radicals (•OH) in brewed tea. It was found that sunlight irradiation played a critical role in the formation of •OH, independent of the presence of metal ions. Furthermore, we demonstrated that the •OH generated from the EGCG aqueous solution induced cell cytotoxicity and DNA damage in vitro. Considering the crucial role of •OH in various fields, including human health and the environment, it is important to further explore the practical implications of •OH production in brewed tea under sunlight. In summary, our study unveils the unexpected formation of •OH in brewed tea and emphasizes the significance of sunlight-induced reactions. The observed cytotoxic and DNA-damaging effects of •OH emphasize the importance of understanding the potential health consequences associated with tea consumption. Further research in this area will contribute to a better understanding of the broader implications of •OH production in brewed tea under sunlight.