Characterizing Theabrownins in Dark Tea Using Ultraviolet-Visible and Infrared Spectroscopy

A new study examined the theabrownins (TBs) in dark tea, which helped uncover the beverage’s potential health benefits for humans. The study, which was conducted in Hubei University of Technology, and its findings were published in the Journal of the Science of Food and Agriculture (1).

Dark tea, unlike other major tea types in China, undergoes microbial fermentation during production, giving it distinct flavors and properties. Recently, there has been a surge in research on the health benefits of dark tea, suggesting its potential as a merging of medicine and food substances (2). Another study published in 2023 introduces the chemical composition, biological activities, and potential health effects of dark tea, while also addressing future directions and challenges in its development (2).

The research team, led by Xiaoqiang Chen at the Hubei University of Technology, continued this research. To further examine the potential of health benefits of dark tea, the research team examined the industrialization of theabrownins (TBs), a crucial component in dark tea (1). Their findings demonstrated the complex nature of TBs and pave the way for large-scale TB production.

Dark tea, particularly Pu-erh ripe tea, is renowned for its rich content of TBs, yet industrial production of these compounds has remained an ongoing challenge. Chen and his team tackled this challenge by extracting TBs from Pu-erh ripe tea and refining the process to obtain a TB isolate (1).

The researchers used an extraction process to remove the caffeine, theaflavin, catechin, and saponin using trichloromethane, ethyl acetate, and n-butanol. Subsequently, column chromatography with a macroporous resin HPD-750 was employed, eluting with a gradient of ethanol aqueous solution (1). Their approach resulted in four distinct fractions: TBs-FC1; TBs-FC2; TBs-FC3; and TBs-FC4.

These fractions are distinguished based on their chemical composition. All contain polysaccharides but do not contain small molecules such as catechins, caffeine, and theaflavins (1). The researchers also examined their molecular weights, finding that they ranged from 23.380 kDa to 123.000 kDa. This indicates that they are complexes of TBs and tea polysaccharide conjugates (TPCs) (1).

Utilizing ultraviolet-visible (UV-visible) and infrared (IR) spectra, the researchers characterized the properties of TBs and TPCs within these fractions. Notably, the zeta potentials of these complexes ranged from −13.40 mV to −38.80 mV in aqueous solutions across a pH range of 3.0–9.0 (1).

Based on their results, the researchers showed that TBs do not exist independently but rather in a combined state with total phenolic compounds (TPCs) in dark tea. This revelation is important because it sheds light on the theoretical foundation for the industrial-scale production of TBs (1).

The implications of this research extend beyond the realms of tea production. TBs are known for their antioxidant properties and potential health benefits, including anti-inflammatory and anti-cancer effects (1). By unlocking their industrial potential, researchers aim to harness these bioactive compounds for pharmaceutical and nutraceutical purposes, promising a brighter future for both tea enthusiasts and health-conscious consumers worldwide (1).

As a result, Chen and the rest of the research team have not only advanced our understanding of TBs, but they have also expanded on previous research that has explored the health benefits of dark tea.

References

(1) Chen, X.; Wang, M.; Wang, Z.; et al. Theabrownins in Dark Tea Form Complexes with Tea Polysaccharide Conjugates. J. Sci. Food Agric. 2024, ASAP. DOI: 10.1002/jsfa.13431

(2) Pan, H.; Le, M.; He, C.; et al. Dark Tea: A Popular Beverage with Possible Medicinal Application. Chin. Herb Med. 2023, 15 (4), 614. DOI: 10.1016/j.chmed.2022.08.005