A number of proposed mechanisms exist for St. John's
wort's antidepressant effects, involving several neurotransmitters and hormones. The
major pharmacological effects of the plant are attributed to the hypericin and
hyperforin components of the
plant. These constituents are believed to act through a variety of mechanisms, including
the inhibition of cortisol secretion, the blockade of catabolic hormones such as
IL-6, an increase in concentrations of CNS neurotransmitters (including
serotonin), and the inhibition
of monoamine oxidases (although this is not thought to be its major mechanism). In addition, hypericum
extracts contain at least 10 constituents or groups of components that may
contribute to its pharmacological and adverse effects. The following are
their proposed activities:
| Constituents |
Proposed Activities |
| Dianthrone derivatives |
photodynamic, antidepressant,
antiviral |
| Flavanols |
anti-inflammatory, astringent |
| Flavinoids |
diuretic, sedative, tumor
inhibition, anti-diarrheal |
| Xanthones |
MAO inhibition, anti-inflammatory,
diuretic |
| Phloroglucinol derivatives |
anti-bacterial |
| Essential oils |
anti-fungal |
| n-Alkaloids |
metabolic stimulants |
| Carotenoids |
burn healing activity |
|
