Determination of Pyrrolizidine Alkaloids in Teas and Herbal Teas by LC-MS/MS

Importance of the Topic

Pyrrolizidine alkaloids (PAs) are plant secondary metabolites with hepatotoxic and carcinogenic properties. They frequently contaminate teas and herbal infusions through co-harvested weeds in the Asteraceae, Boraginaceae, and Fabaceae families. Reliable detection of PAs in consumer products is critical for food safety, regulatory compliance, and public health protection.

Objectives and Overview of the Study

This work aims to establish a robust LC-MS/MS procedure for quantifying multiple PAs in teas and herbal extracts. The study assesses contamination patterns across various tea types, compares extraction protocols, and evaluates temporal changes in PA levels between 2016/17 and 2018/19.

Methodology and Instrumentation

Sample preparation follows the German Federal Institute for Risk Assessment (BfR) protocol, using acid or hot-water extraction depending on matrix. Cleanup employs C18 solid-phase extraction cartridges. Chromatographic separation utilizes C18 reversed-phase UHPLC with gradient elution; a phenyl-hexyl column is employed when co-eluting isomeric pairs cannot be resolved. MS/MS transitions are optimized per compound, with unresolved isomers reported as sum parameters.

Instrumental Setup

• Shimadzu Nexera UHPLC system
• Shimadzu 8060 triple quadrupole mass spectrometer
• C18 and phenyl-hexyl analytical columns
• Electrospray ionization in positive mode

Main Results and Discussion

Analysis of samples from 2016/17 revealed distinct PA contamination patterns linked to specific weeds, such as Senecio angustifolia in rooibos and region-specific Senecio jacobaea in chamomile. Quantitative data show that cumulative PA concentrations measured in 2018/19 were lower than in 2016/17, indicating improved raw material quality or processing controls. Remaining analytical challenges include partial co-elution of stereoisomers and similar fragmentation behavior, addressed by dual-column strategies and reporting sum parameters.

Benefits and Practical Applications of the Method

The validated LC-MS/MS workflow delivers sensitive, reproducible quantification of a broad spectrum of pyrrolizidine alkaloids. It supports routine quality control in laboratories testing teas, herbal products, and other food matrices. The option of hot-water extraction simplifies sample preparation for tea leaves and aligns with consumer preparation methods.

Future Trends and Potential Applications

Advances in high-resolution mass spectrometry and ion mobility separation promise enhanced isomer resolution. Expanded analyte libraries and harmonized regulatory target lists will improve comparability across studies. Automation of sample processing and data interpretation, coupled with machine-learning algorithms, will streamline large-scale monitoring programs.

Conclusion

This study demonstrates an effective LC-MS/MS approach for detecting pyrrolizidine alkaloids in teas and herbal infusions. Adoption of standardized protocols and ongoing method refinement are essential to safeguard consumer health and ensure compliance with evolving regulatory standards.

References

• German Federal Institute for Risk Assessment (BfR) protocol for PA determination in plant material by SPE-LC-MS/MS, BfR-PA-Tee-2.0/2014.
• Mulder P. P. J. et al., Occurrence of Pyrrolizidine Alkaloids in Food, EFSA Supporting Publication 2015: EN-859.
• Czerwenka C., Turkowitsch A., Pyrrolizidine alkaloid isomers: Analytical challenges and solutions, RAFA Symposium poster, 2017.