Chromatography Detects Toxins in Tea Samples

Pyrrolizidine alkaloids (PAs) and their related compounds, PA N-oxides (PANOs), are natural chemicals produced by certain plants. Researchers at the Handan Municipal Centre for Disease Prevention and Control in China tested 63 tea samples—including green tea, lightly fermented tea, semi-fermented tea, and fully fermented tea—to find out how much risk these compounds might pose to people through their diet. The team used high-performance liquid chromatography coupled to tandem mass spectroscopy (HPLC–MS/MS) to separate and identify PAs and PANOs in the tea samples. To assess how risky this level of exposure might be for people's health, the study used a method called the margin of exposure (MoE) approach. In simple terms, an MoE score of 10,000 or higher is considered a low health risk. A paper based on their research was published in the journal ACS Omega.¹

What Are Pyrrolizidine Alkaloids (PAs) and Pyrrolizidine Alkaloid N-oxides (PANOs)?

Pas and their related compounds PANOs are natural chemicals made by plants. More than 6,000 plant species can produce these substances when they're under stress, and most of these plants belong to three main families: Boraginaceae, Asteraceae, and Fabaceae.²Rather than directly harming liver cells, PAs cause damage by triggering hemolysis, the breakdown of red blood cells, within the liver.³

When tea is brewed, more than 50% of the PAs and more than 75% of the PANOs found in the dry tea leaves pass into the actual cup of tea.⁴Research teams from Europe, the Americas, and Asia have studied how risky it might be for people to be exposed to PAs and PANOs through tea. Their findings suggest that certain groups of people could face potential health risks, and in some cases, the levels detected went beyond the maximum limits considered safe.^5-7

How Prevalent Are PAs/PANOs in the Tea Samples Tested, and What Level of Health Risk Do They Pose to Consumers?

Out of the 25 Pas and PANOs tested, four of them—lycopsamine N-oxide, intermedine N-oxide, senkirkine, and lasiocarpine—showed up in more than 10 samples. One fermented tea sample even contained six of these compounds at the same time. Overall, about 78% of the samples tested positive for PAs or PANOs, with an average amount of 17.67 micrograms per kilogram.¹

Using a Monte Carlo simulation to estimate safety margins, the researchers found only a 0.2% chance that the safety margin would drop below the commonly used safety threshold of 10,000. However, based on typical (median) levels of these compounds, drinking the tea regularly for more than 94 days in a row would bring the safety margin below that 10,000 threshold.¹

“Overall,” write the authors of the paper,¹ “the findings indicate that high-level tea consumers are subject to potential PA/PANO exposure risks. To gain a more thorough understanding, we plan to further investigate the dynamic metabolic profiles of PAs/PANOs in vivo, which constitute the next step of our research program. Previous studies have suggested that the transfer rate of PAs from dry tea to infusion typically ranges above 50%. Consequently, our calculated exposure levels and the associated risk may be overestimated.”

The research team suggests that, going forward, researchers should investigate how different tea-processing techniques and brewing methods affect how much PA/PANO ends up in the final cup of tea. This would help create a more accurate picture of how much people are exposed to these compounds when they drink tea.¹

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References

1. Ding, G.; Liu, M.; Lian, Y. et al. Pyrrolizidine Alkaloids in Tea and Dietary Exposure Assessment of Tea Intake. ACS Omega 2026, 11 (35), 53487-53493. DOI: 10.1021/acsomega.6c06636
2. Kaltner, F.; Gottschalk, C.; de Vries, E. Transfer of Pyrrolizidine and Tropane Alkaloids from Tea and Herbal Tea to Infusions. Food Chem.2025, 489, 145026. DOI: 10.1016/j.foodchem.2025.145026
3. Huang, T. Y.;Song, Z. J.; Zhang, C. B. et al.Deciphering the Distinct Vascular Liver Injury Induced by Pyrrolizidine Alkaloids: From the Invasive Species to Health Hazard. J. Agric. Food Chem. 2025, 73 (49), 31543-31558. DOI: 10.1021/acs.jafc.5c09270
4. Han, H.; Jiang, C.; Wang, C. et al. Dissipation Pattern and Conversion of Pyrrolizidine Alkaloids (PAs) and Pyrrolizidine Alkaloid N-oxides (PANOs) During Tea Manufacturing and Brewing. Food Chem. 2022, 390, 133183. DOI: 10.1016/j.foodchem.2022.133183
5. Abdallah, L. A.; Merhi, A.; Hayeck, N. et al.Pyrrolizidine Alkaloid Contamination in Loose Tea and its Health Risk Assessment. Food Chem. Toxicol. 2026, 207, 115826. DOI: 10.1016/j.fct.2025.115826
6. Mädge, I.; Cramer, L.; Rahaus, I. et al. Pyrrolizidine Alkaloids in Herbal Teas for Infants, Pregnant or Lactating Women. Food Chem. 2015, 187, 491-498. DOI: 10.1016/j.foodchem.2015.04.067
7. Lu, Y.-S.; Qiu, J.; Mu, X.-Y. et al. Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review. Foods 2024, 13, 536. DOI: 10.3390/foods13040536