Clinical Studies About Pharmacodynamics Of Hypericum Extract Or St. John’s Wort
St johns wort or Hypericum extract related various pharamacological studies are about the pharacodynamics this botanical. Finally the summary of assumptions or hypothesis regarding possible mechanism of action, whatever you may call them, is also presented.
First study is about the influence of Hypericum extract on CNS or central nervous system activity that included heart rate variability, cognitive functions and EEG.
Second study confirmed that the phototoxic dose of hypericum extract is 30-50 times higher than its normal therapeutic dosage.
Another study found hypericum extract effective in alcoholics with gastritis and peptic ulcer.
This study found that st johns wort didn’t have any side effects or interactions with alcohol.
Influence Of St. John’s Wort On Central Nervous System Activity (1992):
12 patients were taken in this study with hypericum dosage of 0.37 mg dosage thrice a day. This study compared the effects of multiple dosing with St John’s wort (Hypericum perforatum) extract and amitriptyline on heart rate variability, cognitive function and quantitative EEG (qEEG) with placebo in healthy humans.
The study was done with auditory and visually evoked potential and EEG related with cognitive and attention tests. Measurements of heart rate variability, psychometric tests and qEEG were performed before start of medication and repeatedly on the last treatment day.
Researchers concluded that hypericum had activating effect on cognitive tests (attention tests) and reaction time and don’t affect heart rate variability. Hypericum didn’t show any sedative effect. Amitryptiline, the standard antidepressant drug, caused a decrement in heart rate variability and sedation but no cognitive impairment.
AU: Johnsson-D, Siebenhuener-G, Hofer-E, Sauerwein-Giese-E, Frauendorf-A
SO: TW Neurologishe Psychiatrie 6, 436-444, juni 1992
Phototoxicity Of Hypericum Extract (1993):
Phototoxic effects of different extracts of hypericum was investigated in this study on human keratinocytes radiated with ultraviolet light. No phototoxic effect was seen on hypericum dosage that are used as antidepressant.
Hypericum dosage that are 30-50 times higher than antidepressant dosage had shown phototoxicity. People with light colored skin were more prone for phototoxic effects.
AU:Siegers-C-P, Biel-S, Wilhelm-K-P
So: Nervenheilkunde 12(1993) 320-322
St. John’s Infusion In Alcoholics With Peptic Ulcer & Chronic Gastritis (1993):
Hypericum was found to be effective in alcoholics with peptic ulcer and chronic gastritis. 57 outpatients were taken into this study of two months duration.
AU: Krylov-AA; Ibatov-AN
SO: Vrach-Delo. 1993 Feb-Mar (2-3): 146-8
Hypericum Extract And Its Interaction With Alcohol (1993):
32 healthy persons were taken into this double blind cross over study. One group was given hypericum (2.7 mg hypericin daily in three divided dosage) and then placebo for another week. The other group was given placebo in first week and hypericum in second week.
Researchers found no side effects or interaction with alcohol based on cognitive and motor tests.
AU: Scmidt-U, Harrer-G, Kuhn-K, Berger-Deinert-W, Luther-D
SO: Nervenheilkunde 12 (1993):6: 314-319
Summary Of Pharmacological Studies:
There is no clarity still about how many pharmacological drugs affect and interact with our body. In the same manner there are many assumptions or hypothesis about how hypericum affects our body and nervous system. Some of those mechanisms are:
- As MAO Inhibitor.
- As A Cortisol Secretion Inhibitor.
- Norepinephrine and Serotonin Reuptake Inhibitor (Müller et al).
- Hypericum acts on ACTH, CRH and Cortisol by by inhibiting the cytokine interleukin-6 and other cytokines excreted by cells of the immune-system.
- Some studies suggest hypericum’s effect on urinary secretion of catecholamine metabolites, light-induced and nocturnal secretion of melatonin and effects on benzodiazepine receptors.
- Other findings indicate toward dopamine- reuptake inhibiting and prolactin-inhibiting effects of hypericum extract (Winterhoff et al).
It is clear with this herb as well as other natural botanicals that the medicinal effect is not dependent on any single active principle or phytochemical. And their effect can’t be explained through single or simple physiological pathway. Various phytochemicals interact harmoniously to affect our body in diverse beneficial ways.