Clinical Studies About Pharmacokinetics Of St Johns Wort Or Hypericum Extract
Some pharmacokinetic studies about st johns wort or Hypericum extract are discussed. They are about – the difference of hypericin and pseudohypericin, hypericin uptake as sensitizer in phtotherapy in cancer, MAO and COMT inhibitor fragments of hypericum extract and the effect of hypericum extract on serotonin receptors.
First study is about the difference between hypericin and pseudohypericin along several pharmacokinetic criteria like median plasma levels, elimination half time, lag time, steady state concentration.
Next study is about the pattern of uptake, biodistribution and elimination of hypericin in various tissues. This typical pattern tells more about late onset of antidepressant effect and its building up over time.
Hypericin, Xantholones and Flavolons are the phytochemicals found in Hypericum extract. The MAO and COMT inhibitory activity is seen in different grades in these three groups of phytochemicals.
How the SSRIs like effect is actually exerted by Hypericum extract is the topic of this study. It found that pharmacological drugs blocks the neurotransmitter, whereas hypericum extracts blocks the receptor of the neurotranmitter.
What Happens To Hypericin And Pseudohypericin After Oral Intake of St. John’s Wort Extract (1994):
Median maximal plasma levels of hypericin are 1.4, 4.1 and 14.2 ng/ml and for pseudohypericin are 2.7, 11.7 and 30.6 ng/ml for three doses.
Median elimination half life time was 24.8 to 26.5 hours for hypericin and it varied between 16.3 to 36 hours for pseudohyoericin.
Median lag time for absorption was 2 to 2.6 hour for hypericin and 0.3 to 1.1 hours for pseudohypericin.
During long term administration of doses, the steady state concentration is achieved in 4 days for hypericin.
Mean maximal plasma level during steady state concentration was 8.5 ng/ml for hypericin and 5.8ng/ml for pseudohypericin.
These findings suggest that despite similarities in chemistry of hypericin and pseudohypericin, there are substantial difference in pharmacokinetics of these two phytochemicals of st. john’s wort.
AU: Staffeldt-B; Kerb-R; Brockmoller-J; Ploch-M; Roots-I
AD: Institut fur Klinische Pharmakologie, Universitatsk-linikum Charite Berlin, Germany.
SO: J-Geriatr-Psychiatry-Neurol. 1994 Oct; 7 Suppl 1: S47-53
Hypericin Uptake In Rabbits And Mice – As A New Sensitizer In Phototherapy (1994):
Rabbits and mice were xenografted with P3 human squamous cell carcinoma so that the value of the dye can be assessed as in vivo sensitizer for laser photoactivation of human tumor. The uptake and biodistribution of hypericin were measured in xenografted cancer tissue.
Results of this study demonstrated that peak concentration of hypericin was reached after 4 hours of its administration and it had been present in the following order.
There is 35 times higher uptake of hypericin in lungs than brain tissue. The elimination of hypericin had been very good with only 10% residual after 7 days in most tissues except brain, gut and skin. This characteristic directly indicates that hypericin is accumulated in these tissues over time.
Many conclusions were drawn from this study – that hypericin can cross blood brain barrier and thus can reach brain. The antidepressant effect of st. john’s wort exhibits in same manner esp. with reference to time as it gradually builds up over time. There is further need to affirm these positive results.
AU: Chung-PS; Saxton-RE; Paiva-MB; Rhee-CK; Soudant-J; Mathey-A; Foote-C; Castro-DJ
AD: Department of Otolaryngology-Head and Neck Surgery, Dankook University, College of Medicine, Cheonan, Korea.
SO: Laryngoscope. 1994 Dec; 104(12): 1471-6
MAO And COMT Inhibition By Hypericin And Hypericum Extract (1994):
Serotonin and norepinephrine are broken down by MAO (Mono Amino Oxidase) and COMT (Catechol-O-methyl-transferase) enzymes. MAO and COMT inhibition is associated with antidepressant activity.
The effect of hypericin, full hypericum extract and hypericum fractions on the activity of MAO and COMT was investigated in this study. MAO and COMT enzymes were inhibited by hypericum extract. MAO inhibitory activity is found in hypericin and flavolons. COMT inhibitiory activity was found in flavolons and xantholones. But MAO inhibitory concentration of hypericin might not explain its antidepressant action.
AU: Thiede-HM; Walper-A
AD: AnalytiCon Gesellschaft fur Chemische Analytik und Consulting mbH, Berlin, Germany.
SO: J-Geriatr-Psychiatry-Neurol. 1994 Oct; 7 Suppl 1: S54-6
Hypericum Extract And Serotonin Receptors Expression (1994):
This study is related with the influence of hypericum extract on the expression of serotonin receptors in neuroblastoma cells. The effect of Cytokines like IL1 is also shown.
Hypericum extract reduced the expression of serotonin receptors. Addition of IL1 further reduces this expression. The reduced expression of serotonin receptors inhibits reuptake of serotonin into cells.
Modern pharmacological antidepressant drugs bind with neurotransmitter while hypericum blocks the receptor for the neurotransmitter that increases the concentration of neurotransmitter and this increased concentration is the cause for antidepressant action.
AD: Institute fur Physiologische Chemie der Johannes-Gutenberg-Universitat, Mainz, Germany.
SO: J-Geriatr-Psychiatry-Neurol. 1994 Oct; 7 Suppl 1: S63-4