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PubMed2005

[Enhancement of hypericin production and cell growth of Hypericum perforatum L. suspension cultures by nitric oxide].

Nitric oxide has emerged as a key signaling molecule in plants recently. The role of nitric oxide in elicitor-induced defense responses of plants has been extensively investigated. In this work, sodium nitroprusside was utilized as the donor of nitric oxide to investigate the effects of exogenous nitric oxide on hypericin production and cell growth of suspension cell cultures of Hypericum perforatum L.. Compared with the untreated Hypericum perforatum L. suspension cells, external application of 0.5 and 15.0 mmol/L sodium nitroprusside induced 1.4 and 0.5-fold dry cell weight, and 0.9 and 2.1-fold hypericin content respectively. The results showed that low concentration of sodium nitroprusside promoted the growth of Hypericum perforatum L. suspension cells, while high concentration of sodium nitroprusside enhanced hypericin biosynthesis in Hypericum perforatum L. suspension cells. The maximum hypericin production was achieved by adding 0.5 mmol/L and 15.0 mmol/L sodium nitroprusside to the culture at day 0 and day 14 respectively, increasing the total hypericin yield by nearly 3.2-fold. The effects of sodium nitroprusside on hypericin content and growth of Hypericum perforatum L. suspension cells were abolished by nitric oxide specific scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, which indicated that the effects of the application of sodium nitroprusside were caused by nitric oxide released from sodium nitroprusside rather than sodium nitroprusside itself. The results also showed that 15.0 mmol/L sodium nitroprusside stimulated the activities of phenylalanine ammonia-lyase (PAL), one of the key enzymes of phenylpropanoid pathway, in suspension cells of Hypericum perforatum L., which suggested that the synthetic pathway of hypericin might be activated by NO through triggering the defense responses of Hypericum perforatum L. suspension cells.

Anthracenes↗
PubMedDate not supplied

Efficacy and tolerability of Hypericum extract STW 3-VI in patients with moderate depression: a double-blind, randomized, placebo-controlled clinical trial.

In this double-blind, randomized, placebo-controlled, prospective study, the clinical efficacy and tolerability of oral Hypericum extract STW 3-VI (Laif) 900 mg once daily was compared with that of placebo. A total of 140 outpatients (94 women; 46 men) with moderate depressive disorders and a 17-item Hamilton Depression Scale (HAMD-17) score of 20 to 24 were enrolled in this study. Following a single-blind placebo run-in period of 7 days, the patients were randomized to Hypericum extract 900 mg or placebo for the 6-week treatment period. Nineteen patients have been excluded from the per protocol collective because of violations of protocol regarding the scheduling of study visits and intake of study medication. The primary endpoint for treatment efficacy was the change in total HAMD-17 score at the end of the 6-week treatment period. The HAMD-17 total score decreased significantly from baseline by approximately 11.1 +/- 4.5 points (from 22.8 +/- 1.1 to 11.8 +/- 4.4) in the Hypericum group and by approximately 3.4 +/- 3.9 points (from 22.6 +/- 1.2 to 19.2 +/- 3.8) in the placebo group (P < .001). Comparable group differences in favor of Hypericum were revealed by an additional responder analysis, the von Zerssen's Adjective Mood Scale, the Clinical Global Impressions scale, and a global efficacy assessment. Tolerability was very good in both groups; neither serious adverse events nor clinically relevant changes in safety parameters were observed, and only 2 cases demonstrated a possible connection between an adverse event and the study medication. The final safety assessment showed no differences between the Hypericum extract and placebo groups. The study provided evidence that Hypericum extract STW 3-VI in a once-daily dosing regimen may be an effective and well-tolerated option for patients with moderate depressive disorders.

Administration, Oral↗
PubMed2004

Safety of Hypericum extract in mildly to moderately depressed outpatients: a review based on data from three randomized, placebo-controlled trials.

RATIONALE: Hypericum extracts have been regarded as antidepressant drugs without specific side effects by patients, medical professionals and researchers alike. Recently there has been discussion about potential interactions between St. John's wort and other drugs. OBJECTIVES: To investigate the tolerability of Hypericum extract by comparing adverse event rates observed during clinical trials with the herbal drug to those observed under placebo and synthetic antidepressants. METHODS: A data review was performed based on the original data of three double-blind, randomised multicenter trials, during which 594 out-patients suffering from mild to moderate depression according to DSM-IV criteria received 3 x 300 mg/day Hypericum extract (WS 5570, WS 5572, WS 5573) or placebo over a double-blind treatment period of 6 weeks. For the polled data from the three trials, the risk ratios and risk differences versus placebo for single and grouped adverse events were determined along with their 95% confidence intervals. The data were inspected for relevant differences between Hypericum extract and placebo and were compared to trials involving the administration of several synthetic antidepressants. RESULTS: For the polled data of the three trials, the percentage of patients with any adverse events under Hypericum extract exposition was comparable to placebo. The drug was also found to be devoid of effects of sedation, anticholinergic reactions, gastrointestinal disturbances and sexual dysfunction often found in patients treated with tricyclic antidepressants or selective serotonin reuptake inhibitors. CONCLUSION: The analysis did not reveal any specific effects of Hypericum extract.

Antidepressive Agents↗
PubMed2000

Comparison of an extract of hypericum (LI 160) and sertraline in the treatment of depression: a double-blind, randomized pilot study.

BACKGROUND: Hypericum (St. John's wort) has been shown to be as efficacious and well tolerated as standard antidepressants in the treatment of depression but has not been compared with selective serotonin reuptake inhibitors (SSRIs). OBJECTIVE: This study compared hypericum and the SSRI sertraline in the treatment of depression. METHODS: In a double-blind, randomized study conducted in a community hospital, 30 male and female outpatients (19 women, 11 men; mean age, 45.5 years) with mild to moderate depression received 600 mg/d of a standardized extract of hypericum (LI 160) or 50 mg/d sertraline for I week, followed by hypericum 900 mg/d or sertraline 75 mg/d for 6 weeks. RESULTS: The severity of symptoms, as assessed by scores on the Hamilton Rating Scale for Depression (HAM-D) and the Clinical Global Impression scale, was significantly reduced in both treatment groups (P < 0.01). Clinical response (defined as a > or =50% reduction in HAM-D scores) was noted in 47% of patients receiving hypericum and 40% of those receiving sertraline. The difference was not statistically significant. Both agents were well tolerated. A post hoc power analysis indicated that failure to reach statistical significance between treatments resulted primarily from an absence of clinical differences rather than the small sample size. CONCLUSION: The hypericum extract was at least as effective as sertraline in the treatment of mild to moderate depression in a small group of outpatients.

Adolescent↗
PubMed2001

Biochemical mechanisms of action of Hypericum LI 160 in glial and neuronal cells: inhibition of neurotransmitter uptake and stimulation of extracellular signal regulated protein kinase.

We have investigated biochemical mechanisms that may underlie the antidepressant effects of Hypericum LI 160. We found that LI 160 inhibits uptake of serotonin and norepinephrine in cultures of rat cortical astrocytes. Observed differences in the kinetic parameters Km and Vmax as well as in the recovery of uptake after removal of Hypericum indicates that LI 160 does not affect serotonin and norepinephrine transport in the same manner. This suggests that multiple components of the extract can mediate inhibition of these neurotransmitter transporters. Hypericum LI 160 also inhibits serotonin uptake in neuronal cultures from serotonergic-rich raphe nuclei; concentration-response studies indicate LI 160 is 25 times more potent in terms of inhibition of serotonin uptake in neurons than in astrocytes. In addition, Hypericum LI 160 inhibits norepinephrine uptake in SK-N-SH cells, a human neuroblastoma cell line enriched in norepinephrine transporters. A chemical constituent of LI 160, hyperforin, is about 10 to 20 times more potent than LI 160 in inhibiting neurotransmitter uptake in astrocytes and neuronal cells; this finding is consistent with the observation that hyperforin comprises 5% of LI 160 extracts. As several weeks are needed to achieve a clinical response with antidepressants, we have also investigated whether Hypericum LI 160 affects biochemical mechanisms that underlie long-term changes such as gene expression. We found that LI 160 stimulates a sustained activation of extracellular signal regulated protein kinase (ERK), a key component of a signal transduction pathway involved in gene expression. Taken together, our findings suggest that Hypericum LI 160 can affect rapidly-acting as well as slower-developing, long-term biochemical mechanisms related to depressive disorders.

Animals↗
PubMed1997

Effects of long-term administration of hypericum extracts on the affinity and density of the central serotonergic 5-HT1 A and 5-HT2 A receptors.

Extracts of St. John's wort, Hypericum perforatum L. (Hypericaceae), are used as a phytotherapeutic antidepressant. A number of clinical studies demonstrate that their antidepressive potency is comparable to tricyclic antidepressants (TCA). Although the therapeutic effect of hypericum extracts is well documented, very little is known about the molecular mode of action. As the improvement of the depressive symptoms with both TCA and hypericum extracts only occurs significantly after a lag phase of 10 to 14 days, it is assumed that the medication causes long-term adaptations within the central nervous system. In this context, serotonergic (5-HT) receptors are of special interest. Therefore, we investigated possible alterations in affinity and density of 5-HT1 A and 5-HT2 A receptors caused by long-term treatment of rats with St. John's wort. The brain without cerebellum and brain stem of rats, treated daily for 26 weeks with a commercially available hypericum extract (2700 mg/kg LI 160) were used for membrane preparations. Affinity (KD) and amount (Bmax) of serotonergic receptors were determined by employing receptor binding assays using 3 H-8-OH-DPAT and 3H-Ketanserin as selective radioligands for the 5-HT1 A and the 5-HT2 A receptors, respectively. We found that in hypericum-treated rats the number of both 5-HT1 A and 5-HT2 A receptors were significantly increased by 50% compared to controls, whereas the affinity of both serotonergic receptors remained unaltered. The data suggest an upregulation of 5-HT1 A and 5-HT2 A receptors due to prolonged administration of hypericum extracts. These results are consistent with a modification of the expression levels of serotonergic receptors caused by synthetic antidepressants.

Animals↗
PubMed2000

An open-label trial of St. John's Wort (Hypericum perforatum) in obsessive-compulsive disorder.

BACKGROUND: Recent interest in and evidence for the efficacy of St. John's wort (Hypericum perforatum) for the treatment of mild-to-moderate depression has led to speculation about its efficacy in other disorders. Hypericum's mechanism of action is postulated to be via inhibition of the synaptosomal uptake of serotonin. As such, there is a suggestion that Hypericum may be effective for obsessive-compulsive disorder (OCD). METHOD: Twelve subjects were evaluated with a primary DSM-IV diagnosis of OCD of at least 12 months' duration. Treatment lasted for 12 weeks, with a fixed dose of 450 mg of 0.3% hypericin (a psychoactive compound in Hypericum) twice daily (extended-release formulation). Weekly evaluations were conducted with the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the Patient Global Impressions of Improvement Scale, and the Clinical Global Impressions of Improvement scale (CGI) and monthly evaluation with the Hamilton Rating Scale for Depression. RESULTS: A significant change from baseline to endpoint was found, with a mean Y-BOCS change of 7.4 points (p = .001). Significant change occurred at 1 week (p = .020) and continued to increase throughout the trial. At endpoint, 5 (42%) of 12 were rated "much" or "very much improved" on the clinician-rated CGI, 6 (50%) were "minimally improved," and 1 (8%) had "no change." The most common side effects reported were diarrhea (N = 3) and restless sleep (N = 2). CONCLUSION: Significant improvement was found with Hypericum, with a drop-in Y-BOCS score similar to that found in clinical trials. The fact that a significant change was found as early as 1 week into treatment suggests a possible initial placebo response, although improvement grew larger over time. Results warrant a placebo-controlled study of Hypericum in OCD.

Adult↗
PubMed1997

Inhibition of benzodiazepine binding in vitro by amentoflavone, a constituent of various species of Hypericum.

Flower extracts of Hypericum perforatum, Hypericum hirsutum, Hypericum patulum and Hypericum olympicum efficiently inhibited binding of [3H]flumazenil to rat brain benzodiazepine binding sites of the GABAA-receptor in vitro with IC50 values of 6.83, 6.97, 13.2 and 6.14 micrograms/ml, respectively. Single constituents of the extracts like hypericin, the flavones quercetin and luteolin, the glycosylated flavonoides rutin, hyperoside and quercitrin and the biflavone 13, II8-biapigenin did not inhibit binding up to concentrations of 1 microM. In contrast, amentoflavone revealed an IC50 = 14.9 +/- 1.9 nM on benzodiazepine binding in vitro. Comparative HPLC analyses of hypericin and amentoflavone in extracts of different Hypericum species revealed a possible correlation between the amentoflavone concentration and the inhibition of flumazenil binding. For hypericin no such correlation was observed. Our experimental data demonstrate that amentoflavone, in contrast to hypericin, presents a very active compound with regard to the inhibition of [3H]-flumazenil binding in vitro and thus might be involved in the antidepressant effects of Hypericum perforatum extracts.

Animals↗
PubMed1999

The experimental and clinical pharmacology of St John's Wort (Hypericum perforatum L.).

Hypericum (St John's Wort) is a plant that has been used for centuries as a medicinal herb. Pre-clinical animals studies suggest that hypericum is effective in three major biochemical systems relevant for antidepressant activity, namely the inhibition of the synaptic re-uptake system for serotonin (5-HT), noradrenaline (NA) and dopamine (DA). It is the only antidepressant capable of inhibiting the re-uptake of 5-HT, NA and DA with similar potencies. The potencies for monoamine re-inhibition and chronic changes in receptors are also consistent with changes seen with known antidepressants. Behavioral studies suggest that hypericum is active in pre-clinical animal models of depression with comparable effects to known antidepressants. Supporting the pre-clinical pharmacology and efficacy, many clinical studies have shown that hypericum has superior efficacy compared to placebo and comparable efficacy to standard antidepressants in the treatment of mild-to-moderate depression. The advantage of hypericum over other antidepressants may result from its favorable side-effect profile. Although pre-clinical and short-term clinical studies demonstrate antidepressant activity, the lack of long-term use and efficacy, and the heterogeneity of patients, interventions, extract preparations from previous clinical studies suggests that more careful and controlled studies are needed to determine the long-term efficacy of hypericum in mild-to-moderate depression.

Animals↗
PubMed2004

Effect of Hypericum perforatum on marble-burying by mice.

The effect of Hypericum perforatum extract (LI 160) at a dose that exerts an antidepressive-like effect was studied in mice in the marble-burying test. Acute Hypericum perforatum (150, 300 and 500 mg/kg, p.o.) reduced immobility time in the forced swimming test. The number of marbles buried, but not locomotor activity, was reduced by acute treatment with Hypericum perforatum (150 and 300 mg/kg, p.o.). However, this effect was not seen after chronic treatment (21 days) with Hypericum perforatum (300 mg/kg, p.o.). Thus, Hypericum perforatum extract, at antidepressant dose, exerts an acute anxiolytic drug effect on the marble-burying test, which could indicate a potential anti-obsessive effect, although the development of tolerance could be an important drawback.

Administration, Oral↗
PubMedDate not supplied

Hypericum perforatum versus fluoxetine in the treatment of mild to moderate depression.

In a randomized, controlled, double-blind trial, 70 patients (mean age, 49.7 years) suffering from mild to moderate depression received one tablet of either St. John's Wort (Hypericum perforatum) extract (Calmigen) or fluoxetine hydrochloride (Prozac) twice a day for 6 weeks. Efficacy was determined according to the 17-item Hamilton Rating Scale for Depression (HAMD), the von Zerssen depression scale (DS), Clinical Global Impression (CGI), and patients' overall evaluation. Significant decreases (P<.001) of 50% in the Hypericum group and 58% in the fluoxetine group in the HAMD score and of 42% and 52% on the DS spoke to the efficacy of both medications. The Hypericum extract achieved 83% of the efficacy of fluoxetine on the HAMD and 78% on the DS. Assessments by physicians (CGI) and patients indicated considerable improvement with no between-treatment differences. Of the 9 dropouts (13%), 2 in the Hypericum group and 2 in the fluoxetine group were due to adverse reactions. Safety evaluations demonstrated only minor changes. The Hypericum preparation tested in this study is therapeutically equivalent to fluoxetine and is therefore a rational alternative to synthetic antidepressants.

Adolescent↗
PubMed2002

Cluster analysis of symptoms during antidepressant treatment with Hypericum extract in mildly to moderately depressed out-patients. A meta-analysis of data from three randomized, placebo-controlled trials.

RATIONALE: Although extracts from Hypericum have long played a major role in the treatment of mild to moderate depression, information pertaining to the drug's therapeutic profile is sparse. OBJECTIVES: To investigate whether the administration of the Hypericum extract has a selective effect on particular signs and symptoms of depression as opposed to a more general acceleration of recovery. METHODS: A meta-analysis was performed on the original data of three double-blind, randomized multicenter trials, during which 544 out-patients suffering from mild to moderate depression according to DSM-IV criteria received 3x300 mg/day Hypericum extract (WS 5570 or WS 5572) or placebo over a double-blind treatment period of 6 weeks. The primary outcome measure for treatment efficacy in the original trials was the change in the total score of the Hamilton Rating Scale for Depression (HAMD, 17-item version) between baseline and treatment end. The relationship between the symptoms of depression represented by the items of the HAMD was assessed by means of cluster analysis and individual item analysis. RESULTS: Two clusters of items were identified which were stable in several independent subsets of the full data set. While cluster 1 (HAMD items 1, 2, 3, 7, 8, 12, 13, 14, 16) was interpreted to represent the core symptoms of depression (including somatic aspects), cluster 2 (items 4, 5, 6, 9, 10, 11, 15, 17) was primarily composed of items assessing depression-related anxiety and insomnia. In both clusters, Hypericum extract reduced the symptoms of depression more effectively than placebo. However, the herbal drug was particularly effective in the core symptoms of the disorder. CONCLUSIONS: The results indicate that Hypericum extract accelerated the recovery from depression in a rather general manner, by influencing all investigated signs and symptoms of the disease. The drug's therapeutic profile was thus found to be similar to the profile of selective serotonin reuptake inhibitors.

Antidepressive Agents↗
PubMed2004

Hypericum extract LI 160 and fluoxetine in mild to moderate depression: a randomized, placebo-controlled multi-center study in outpatients.

Efficacy and tolerability of Hypericum LI 160 was compared to fluoxetine and placebo in mild to moderate Major Depression (DSM-IV) in a 4-week randomized, double-blind trial. One hundred and sixty-three outpatients from 15 general practitioner centers received either 900 mg Hypericum LI 160, 20 mg fluoxetine, or placebo daily. Amelioration was measured by the Hamilton and the Montgomery-Asberg Depression scales. Response and remission rates and global ratings by investigators and patients were measured. Adverse event reports, laboratory screening, vital signs, physical exams and ECG were collected. No significant differences could be observed regarding efficacy measures except for remission rate (Hypericum 24%; fluoxetine 28%; placebo 7 %). Hypericum was significantly better tolerated than fluoxetine. Hypericum LI 160 or fluoxetine were not more effective in short-term treatment in mild to moderate depression than placebo.

Adult↗
PubMed2004

The antidepressant mechanism of Hypericum perforatum.

Clinical data indicate that hydroalcoholic extracts of Hypericum perforatum might be as valuable as conventional antidepressants in mild-to-moderate depression, with fewer side effects. One clinical trial using two extracts with different hyperforin contents indicated it as the main active principle responsible for the antidepressant activity. Behavioural models in rodents confirm the antidepressant-like effect of Hypericum extracts and also of pure hyperforin and hypericin. A hydroalcoholic extract lacking hyperforin also lacks the antidepressant-like effect. According to pharmacokinetic data and binding studies, it appears that the antidepressant effect of Hypericum extract is unlikely be due to an interaction of hypericin with central neurotransmitter receptors. The main in vitro effects of hyperforin (at concentrations of 0.1-1 microM) are non-specific presynaptic effects, resulting in the non-selective inhibition of the uptake of many neurotransmitters, and the interaction with dopamine D1 and opioid receptors. However, it is still not clear whether these mechanisms can be activated in vivo, since after administration of Hypericum extract brain concentrations of hyperforin are well below those active in vitro. In the rat, Hypericum extract might indirectly activate sigma receptors in vivo (through the formation of an unknown metabolite or production of an endogenous ligand), suggesting a new target for its antidepressant effects.

Animals↗
PubMed1999

Hypericum LI 160 inhibits uptake of serotonin and norepinephrine in astrocytes.

Extracts of Hypericum perforatum, commonly known as St. John's wort, are frequently used in Germany and other European countries to treat mild to moderately severe depression, but the mechanism of antidepressant activity of Hypericum is not understood. Because known mechanisms of antidepressant activity include inhibition of serotonin and/or norepinephrine uptake, we investigated the effects of standardized extracts of Hypericum LI 160 on the transport of these monoamine neurotransmitters into astrocytes, cells which surround synaptic terminals and regulate neurotransmission by means of their uptake systems. We found that LI 160 inhibited both serotonin and norepinephrine uptake in a dose-dependent manner. The two monoamine transport systems were affected differently by LI 160: for serotonin, the main effect was a 50% decrease in the rate of maximal transport, whereas for norepinephrine, the main effect was a 4.5 fold reduction in the apparent affinity of norepinephrine for its uptake sites. Upon removal of LI 160, uptake was restored, thereby indicating that the inhibition was not due to a toxic effect of Hypericum on the cells. These findings suggest that the ability of LI 160 to inhibit serotonin and norepinephrine uptake may underlie the antidepressant activity of this Hypericum extract.

Animals↗
PubMed2004

Commercially available Hypericum perforatum extracts do not decrease immobility of rats in the forced swimming test.

There are controversial results of clinical trials on the antidepressant effects of Hypericum perforatum, while several preclinical studies describe antidepressant properties for Hypericum extracts. This study evaluates the antidepressant effect of two commercially available hydroalcoholic extracts of H. perforatum standardized to contain 0.3% hypericin in comparison to imipramine (IMI), in the forced swimming test (FST). Wistar rats were treated with different doses of two Hypericum extracts, of hypericin or of IMI and submitted to the FST. The experiments were videotape recorded to detail immobile and active behaviors of rats during the procedures. The imported extract tested and hypericin did not modify rats' behaviors in the test, while IMI, a classical antidepressant, significantly shortened immobility and prolonged climbing behavior during forced swimming. The locally produced Hypericum extract significantly increased immobility duration as compared to the controls at the same time as climbing efforts were decreased. Therefore, the two different commercially available Brazilian hydroalcoholic H. perforatum extracts did not show the expected effects in a screening test for antidepressant agents, on the contrary, one of the extracts promoted a depressant-like effect in rats. Therefore, these extracts available to the population differ from other Hypericum extracts. At which step of the production or commercialization chain these extracts probably lost their therapeutic potential remains to be evaluated.

Animals↗
PubMed1999

Pharmacokinetic interaction of digoxin with an herbal extract from St John's wort (Hypericum perforatum).

OBJECTIVE: Extracts of St John's wort (Hypericum perforatum) are widely used in the treatment of depression, often as an over-the-counter drug. In contrast to its frequent use, knowledge about the pharmacokinetics of ingredients and drug interactions of St John's wort is poor. We studied the interaction between hypericum extract LI160 and digoxin. METHODS: The pharmacokinetics of digoxin were investigated in a single-blind, placebo-controlled parallel study. After the achievement of steady state for digoxin on day 5, healthy volunteers received digoxin (0.25 mg/d) either with placebo (n = 12) or with 900 mg/d LI160 (n = 13) for another 10 days. Digoxin concentration profiles on day 5 were compared with day 6 (single-dose interaction) and day 15 (tenth day of co-medication). RESULTS: There was a highly significant combined-day-and-group effect for digoxin area under the plasma concentration-time curve [AUC(0-24); P = .0001], peak concentration in plasma (Cmax; P = .0001), and plasma drug concentration at the end of a dosing interval (P = .0003) by two-way ANOVA. No statistically significant change was observed after the first dose of hypericum extract [AUC(0-24) at day 6 of 18.1+/-2.9 microg x h/L and 17.7+/-3.0 microg x h/L, mean +/- SD for placebo and hypericum group, respectively]. However, 10 days of treatment with hypericum extract resulted in a decrease of digoxin AUC(0-24) by 25% (day 15, 17.2+/-4.0 microg x h/L and 12.9+/-2.3 microg x h/L; P = .0035). Furthermore, comparison with the parallel placebo group after multiple dosing showed a reduction in trough concentrations and Cmax of 33% (P = .0023) and 26% (P = .0095), respectively. The effect became increasingly pronounced until the tenth day of co-medication. CONCLUSION: As with grapefruit juice, a food product, physicians should also be aware of potential drug-herb interactions. The interaction of St John's wort extract with digoxin kinetics was time dependent. The mechanism involved may be induction of the P-glycoprotein drug transporter.

Adult↗
PubMed2001

Acute and chronic actions of a dry methanolic extract of Hypericum perforatum and a hyperforin-rich extract on dopaminergic and serotonergic neurones in rat nucleus accumbens.

Dry hydroalcoholic extract of Hypericum perforatum L. is effective in the treatment of mild-to-moderate depression. Neither the mechanism of action nor the component or components of the extract responsible are known to date. In several in vitro and ex vivo models, the extract and hyperforin, one of its active components, cause changes similar to those of tricyclic antidepressants. Little is known about effects on a complex neuronal system relevant to antidepressant actions such as the mesolimbic system in the brain. In animal models of depression, the levels of dopamine were reduced in the nucleus accumbens, which is an important part of the mesolimbic system. These and other deficits were compensated by imipramine. We investigated the actions of the methanolic Hypericum extract LI 160 and a hyperforin-rich research extract in the shell region of the nucleus accumbens under in vivo conditions after acute administration, and after application repeated fourteen times. Both extracts induced an increase of dopamine (DA) and 5-hydroxytryptamine (5-HT) levels measured by in vivo microdialysis. The dose-response curve followed an inverse U-shape. Repeated application caused a rapid tolerance of DA but not of 5-HT neurones. Similar changes were observed after acute and repeated applications of imipramine. Several lines of evidence have suggested other active components in the Hypericum extract. The potency of hyperforin surpassed that of imipramine in the acute release of both DA and 5-HT by the nucleus accumbens. The effect of hyperforin correlated well with the inhibiting potency on high-affinity DA and 5-HT uptake. The missing effect of relatively high doses on DA and 5-HT levels as found in dose-response experiments may be explained by self-inhibition caused by the activation of autosomal receptors and by the inhibition by GABA. The inhibition of neuronal GABA transport occurs at somewhat higher concentrations of hyperforin. In conclusion, the findings demonstrate an imipramine-like effect of methanolic Hypericum extract LI 160 and of hyperforin on mesolimbic, dopaminergic and serotonergic neurones in acute and chronic experiments, which probably contributes to the antidepressant action of the medication. The methanolic Hypericum extract contains active compounds other than hyperforin.

Animals↗