Supplement
Hordenine is a plant compound found in barley and beer, chemically related to tyramine, that can influence dopamine and noradrenaline signaling. In lab work it activated dopamine D2 receptors, but when four people drank beer, their blood levels stayed too low to reach those receptors and faded within about an hour. Overall the evidence is very limited, and most findings come from animal or lab studies, not human trials.
Sources: PMID 31984737; PMID 2570842
- Updated
- How we grade
- 3 studies cited
- Best evidence
- Grade D
- Conditions studied
- 1
- Outcomes
- 4
- Graded outcomes
- 0004
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Noradrenergic Activity In isolated rat vasa deferentia, hordenine (25 μM) potentiated contractile responses to submaximal noradrenaline and inhibited responses to tyramine, consistent with noradrenaline reuptake inhibition. Hordenine did not directly produce tissue contractions, suggesting indirect sympathomimetic activity rather than direct adrenergic agonism. | Improves (the measure goes up) | Small effect | 1 study | |||
Studies that measured noradrenergic activity | ||||||
General
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Dopamine D2 Receptor Activation Hordenine has been identified as a dopamine D2 receptor agonist in vitro. However, a human pharmacokinetic study (n=4) found that peak plasma concentrations after oral beer consumption (12.0–17.3 nM) were too low to provoke direct D2 receptor interaction relevant to food reward, with a short elimination half-life of 53–66 minutes. | Improves (the measure goes up) | Small effect | 1 study | 4 people | ||
Studies that measured dopamine d2 receptor activation | ||||||
| Blood-Brain Barrier Permeability An in vitro blood-brain barrier permeability assay classified hordenine as a BBB-permeable (BBB+) compound, suggesting potential for CNS activity. Hordenine was also detected at significant levels (up to 6,357 μg/g dry extract) in commercial Ginkgo biloba products as one of the most abundant tyramine derivatives. | Improves (the measure goes up) | Small effect | 1 study | |||
Studies that measured blood-brain barrier permeability | ||||||
| MAO-B Selective Metabolism In rat tissue, hordenine was shown to be a highly selective substrate for MAO-B and was not deaminated by MAO-A of intestinal epithelium. This selectivity distinguishes it from tyramine, which is a substrate for both MAO isoforms, and has implications for potential interactions with MAO inhibitor medications. | Improves (the measure goes up) | Small effect | 1 study | |||
Studies that measured mao-b selective metabolism | ||||||
Key findings
- Noradrenergic ActivityImproves (the measure goes up)
- Dopamine D2 Receptor ActivationImproves (the measure goes up)
- Blood-Brain Barrier PermeabilityImproves (the measure goes up)
Safety notes in the studies
- However, a human pharmacokinetic study (n=4) found that peak plasma concentrations after oral beer consumption (12.0–17.3 nM) were too low to provoke direct D2 receptor interaction relevant to food reward, with a short elimination half-life of 53–66 minutes.
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- Grade D
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Studies cited
3 studies from PubMed
- Absorption, Biokinetics, and Metabolism of the Dopamine D2 Receptor Agonist Hordenine (N,N-Dimethyltyramine) after Beer Consumption in Humans.
- Blood-brain barrier specific permeability assay reveals N-methylated tyramine derivatives in standardised leaf extracts and herbal products of Ginkgo biloba.
- Deamination of hordenine by monoamine oxidase and its action on vasa deferentia of the rat.