Table 1.
The main constituents of St John's wort.
| Constituent | Percentage of composition | Possible contribution to mode of action |
|---|---|---|
| Phenylpropanes | Not reported | – |
| Flavonol glycosides (including hyperoside) | 2–4% | Inhibition of MAO-A |
| Biflavones | Not reported | Weak affinity for the benzodiazepine receptor |
| Tannins and proanthocyanidins | 15% | – |
| Xanthones | Very low concentrations | Inhibition of MAO-A |
| Phloroglucinols (hyperforin) | 4% of the buds and flowers | Affinity for GABA receptors |
| Essential oils | Not reported | – |
| Amino acids | Not reported | – |
| Naphthodianthrones (including hypericin) | Not reported | – |