jf6b05824_si_001.pdf (294.93 kB)
High-Throughput Quantitation of Proline Betaine in Foods and Suitability as a Valid Biomarker for Citrus Consumption
journal contribution
posted on 2017-02-03, 00:00 authored by Roman Lang, Tatjana Lang, Matthias Bader, Anja Beusch, Verena Schlagbauer, Thomas HofmannProline
betaine has been proposed as a candidate dietary biomarker
for citrus intake. To validate its suitability as a dietary biomarker
and to gain insight into the range of this per-methylated amino acid
in foods and beverages, a quick and accurate stable isotope dilution
assay was developed for quantitative high-throughput HILIC-MS/MS screening
of proline betaine in foods and urine after solvent-mediated matrix
precipitation. Quantitative analysis of a variety of foods confirmed
substantial amounts of proline betaine in citrus juices (140–1100
mg/L) and revealed high abundance in tubers of the vegetable Stachys affinis, also known as Chinese artichocke
(∼700 mg/kg). Seafood including clams, shrimp, and lobster
contained limited amounts (1–95 mg/kg), whereas only traces
were detected in fish, cuttlefish, fresh meat, dairy products, fresh
vegetable (<3 mg/kg), coffee, tea, beer, and wine (<7 mg/L).
The human excretion profiles of proline betaine in urine were comparable
when common portions of orange juice or fried Stachys tubers were consumed. Neither mussels nor beer provided enough proline
betaine to detect significant differences between morning urine samples
collected before and after consumption. As Stachys is a rather rare vegetable and not part of peoples’ daily
diet, the data reported here will help to monitor the subject’s
compliance in future nutritional human studies on citrus products
or the exclusion of citrus products in the wash-out phase of an intervention
study. Moreover, proline betaine measurement can contribute to the
establishment of a toolbox of valid dietary biomarkers reflecting
wider aspects of diet to assess metabolic profiles as measures of
dietary exposure and indicators of dietary patterns, dietary changes,
or effectiveness of dietary interventions.