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Food Chem. 2019 Mar 15;276:745-753. doi: 10.1016/j.foodchem.2018.10.067. Epub 2018 Oct 13.

Monitoring of the dopamine D2 receptor agonists hordenine and N-methyltyramine during the brewing process and in commercial beer samples.

Author information

1
Food Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany; Computer Chemistry Center, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstr. 25, 91052 Erlangen, Germany. Electronic address: thomas.sommer@fau.de.
2
Food Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany; Institute of Psychology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstr. 49 b, 91052 Erlangen, Germany. Electronic address: gelena.dlugash@fau.de.
3
Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany. Electronic address: harald.huebner@fau.de.
4
Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany. Electronic address: peter.gmeiner@fau.de.
5
Food Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany. Electronic address: monika.pischetsrieder@fau.de.

Abstract

The phenethylamine alkaloid hordenine, present in germinated barley, was identified recently as a functionally selective dopamine D2 receptor agonist contributing potentially to the rewarding effects of drinking beer. Here, it was shown that the hordenine precursor N-methyltyramine binds with a similar affinity to the dopamine D2 receptor as hordenine (Ki 31.3 µM) showing also selectivity towards the G protein-mediated pathway over the β-arrestin pathway. Using a newly developed UHPLC-ESI-MS/MS method to monitor beer production, we demonstrated that hordenine and N-methyltyramine were released continuously from barley malt during mashing and were stable during fermentation and conditioning. The amounts released from different base malt types were in a similar range but tended to be higher from caramel malts. Hordenine and N-methyltyramine concentrations in 24 types of beer varied between 1.05-6.32 and 0.59-4.61 mg/L, respectively. Thus, the human uptake of the alkaloids during beer consumption is in the low milligram range.

KEYWORDS:

Beer; Brewing; Dopamine D2 receptor agonist; Fermentation; Hordenine; Mashing; N-Methyltyramine

PMID:
30409657
DOI:
10.1016/j.foodchem.2018.10.067
[Indexed for MEDLINE]

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