Date of Award

2014

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Dr. Ambrose Furey

Abstract

Pyrrolizidine Alkaloids (PAs) are known plant toxins which can cause hepatic veno-occlusive disease (HVOD) in both humans and livestock when ingested. Although PAs are primarily known for their hepatotoxicity they also induce genotoxicity, carcinogenicity and pneumotoxicity. PAs are consumed through plants as food, for medicinal purposes, or as contaminants of agricultural crops. Aside from ingesting the plants directly PA exposure may occur through the consumption of honey produced by bees that visit PA-containing plants or by drinking milk produced by animals that have consumed PA-containing plants. Possible PA contamination in our food chain is a potential health risk.

To assess the presence of PAs in the food chain 369 retail honeys from Ireland, 59 honeys from Australia, 48 milk samples, 72 cheese samples, 18 herbal teas and 54 Traditional Chinese Medicines (TCMs) were analysed using liquid chromatography coupled to mass spectrometry. The sample extraction and clean-up protocol was optimised to be robust, sensitive and applicable to a range of food matrices providing significant advantages over pre-existing protocols. LC-MS methods were optimised, developed and validated for both ion trap and triple quadrupole mass spectrometers whilst utilising software functionalities for data acquisition, integration and spectral library matching. The analytical methods were targeted but the most comprehensive to date, including all commercially available PA and PA N-oxide (PANO) reference standards.

The results were utilised in a dietary exposure assessment conducted for the Irish population based on the consumption of PAs in honey. The mean PA concentration in positive honey from Irish markets was 81 μg kg-1 (or 20 μg kg-1 for all 369 samples). The data was positively skewed meaning that the majority of results fell to the left of the mean. The mean results from the deterministic approach were exposure values of 0.0016, 0.0024 and 0.0022 μg kg-1 bw day-1 for children, teenagers and adults, respectively. This is based upon the overall mean PA concentration (20 μg kg-1) detected and utilising the mean honey consumption data. The results for the probabilistic mean exposure values were 0.0037, 0.0046 and 0.0046 μg kg-1 bw day-1 for children, teenagers and adults, respectively. However, using the 95th percentile exposure estimates resulted in values which far exceeded the recommended maximum daily intake of 0.007 μg kg-1 bw day-1 at 0.0157, 0.0213 and 0.0196 μg kg-1 bw day'' for children, teenagers and adults, respectively.

Comments

Under the supervision of:

Dr. Ambrose Furey (CIT)

and

Dr Martin Danaher (Teagasc Food Research Centre)

Access Level

info:eu-repo/semantics/openAccess

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