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

Importance of the Topic

Pyrrolizidine alkaloids (PAs) are secondary metabolites present in various plant families, notable for their hepatotoxic and carcinogenic properties. Regular consumption of contaminated teas and herbal products poses significant health risks. Monitoring PAs in these matrices is crucial for ensuring consumer safety and regulatory compliance.

Objectives and Study Overview

This work aims to develop and validate a robust LC-MS/MS method to detect and quantify multiple pyrrolizidine alkaloids in teas and herbal infusions. The study evaluates sample preparation protocols, chromatographic separation strategies, and MS/MS detection parameters to address analytical challenges posed by PA isomers.

Methodology and Instrumentation

Sample preparation follows the German BfR protocol with two extraction options:

• Sulfuric acid extraction combined with C18-SPE for clean-up
• Hot water extraction mimicking consumer tea preparation

Chromatographic separation is performed on C18 columns with gradient elution. Critical isomer pairs are further resolved using a phenyl-hexyl column under the same conditions. Mass spectrometric detection employs optimized MS/MS transitions for target and additional isomeric alkaloids.

Used Instrumentation

• Shimadzu Nexera UHPLC system
• Shimadzu 8060 Triple Quadrupole Mass Spectrometer

Main Results and Discussion

Analyses of tea samples from 2016–2019 revealed distinct contamination patterns related to plant sources. Key findings include:

• Detection of PAs chiefly from Senecio species in rooibos and chamomile
• Summed PA levels in 2018/19 were notably lower than in 2016/17
• Comparable MS/MS response for certain isomeric pairs led to reporting them as sum parameters

These results demonstrate the method's capability to differentiate contamination profiles and monitor trends over time.

Benefits and Practical Applications

This validated LC-MS/MS approach offers:

• High sensitivity and selectivity for multiple PAs in diverse tea matrices
• Flexibility to use simplified extraction for routine tea analysis
• Reliable monitoring tool supporting food safety assessments and regulatory requirements

Future Trends and Potential Applications

Further developments may focus on:

• Advanced chromatographic materials or coupling with high-resolution mass spectrometry to resolve all isomers
• Expansion to other food and feed matrices
• Standardizing target analyte lists across laboratories
• Automation of sample preparation workflows

Conclusion

The presented LC-MS/MS method, grounded in established protocols and enhanced for isomeric separation, provides a robust platform for routine detection of pyrrolizidine alkaloids in teas and herbal infusions. It supports ongoing safety monitoring and contributes to improved consumer protection.

References

1. BfR protocol “Bestimmung von Pyrrolizidinalkaloiden in Pflanzenmaterial mittels SPE-LC-MS/MS Methodenbeschreibung, BfR-PA-Tee-2.0/2014”
2. Mulder PPJ et al., Occurrence of Pyrrolizidine Alkaloids in Food, EFSA Supporting Publication 2015; EN-859
3. Czerwenka C, Turkowitsch A, Pyrrolizidine alkaloid isomers: Analytical challenges and solutions, RAFA symposium poster, 2017