Study 14
St. John's wort: In-vitro study about hypericum extract, hypericin and kampferol as antidepressants
Au: Müller W.E. and Schäfer C.S
Deutsche Apotheker Zeitung vol 136 Nr 13 1996 page 1015-1022
Description
In this study the reuptake of norepinephrine and serotonin in rat brains is studied. The methods are similar to Study 13 above.
The effect of these substances on the so-called imipramine receptor is also studied.
Results
They found that hypericum extract at a concentration of 15 microg/ml reduced the synaptosomal reuptake of both norepinephrine and serotonin by 50%. This result is not very far from the result in the previously mentioned study (6 microg/ml) that used a slightly different method. As comparison, a concentration 20 microg / ml only led to a MAO-inhibition of 20%.
Pure hypericin and pure Kampferol did not have as much effect as the full hypericum extract. It therefore seems obvious that these substances alone do not explain the effect of hypericum.
Researchers' comments
Because we do not know the therapeutic concentrations in the brain of the leading substances in hypericum extract and which substances make the effect, it is hard to conclude whether or not these results explain how hypericum works. More research is needed.
Our comments
It seems likely that hypericum works on both norepinephrine and serotonin reuptake. The 20% inhibition of MAO on a concentration of 20 microg/ml might not be able to explain hypericum's antidepressant effect by itself, but might contribute to the serotonin and norepinephrine reuptake inhibiting effect. Recent studies have confirmed that a combination of serotonin reuptake inhibitors and MAO-inhibitors can be very powerful, even at low concentrations.
Copyright © 1996 by Harold H. Bloomfield, M.D. and Peter McWilliams
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