Hypericum perforatum

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"St John's wort" redirects here. For other uses, see St John's wort (disambiguation).
Hypericum perforatum
Saint johns wart flowers.jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Malpighiales
Family: Hypericaceae
Genus: Hypericum
Species: H. perforatum
Binomial name
Hypericum perforatum
L.

Hypericum perforatum, known as Perforate St John's-wort,[1] Common Saint John's wort and St John's wort, [note 1] is a flowering plant of the genus Hypericum and a medicinal herb with antidepressant activity and potent anti-inflammatory properties as an arachidonate 5-lipoxygenase inhibitor and COX-1 inhibitor.[3][4][5] In common speech, the term "St John's wort" may be used to refer to any species of the genus Hypericum. Therefore, Hypericum perforatum is sometimes called "Common St John's wort" or "Perforate St John's wort" in order to differentiate it.

Studies have supported the use of St John's wort as a treatment for depression in humans.[5][6] A 2008 Cochrane review of 29 clinical trials concluded that it was superior to placebo in patients with major depression, as effective as standard antidepressants and had fewer side-effects.[7] According to the National Center for Complementary and Integrative Health (NCCIH) of the National Institutes of Health, it "may help some types of depression, though the evidence is not definitive," can limit the efficacy of prescription medicines, and psychosis can occur as a rare side effect. The NCCIH notes that combining St John's wort with certain prescription antidepressants can lead to a "potentially life-threatening increase of serotonin," a brain chemical targeted by antidepressants.[8] In horses, sheep and cattle, the plant can be toxic when ingested in large quantities.[9]

Hypericum perforatum is indigenous to Europe but has spread worldwide as an invasive species, including to temperate and subtropical regions of Turkey, Ukraine, Russia, the Middle East, India, Canada, the United States and China.

Botanical description[edit]

Translucent dots on the leaves

Hypericum perforatum is a yellow-flowering, stoloniferous or sarmentose, perennial herb indigenous to Europe. It has been introduced to many temperate areas of the world and grows wild in many meadows. The herb's common name comes from its traditional flowering and harvesting on St John's day, 24 June. The genus name Hypericum is derived from the Greek words hyper (above) and eikon (picture), in reference to the plant's traditional use in warding off evil by hanging plants over a religious icon in the house during St John's day. The species name perforatum refers to the presence of small oil glands in the leaves that look like windows, which can be seen when they are held against the light.[2]

St John's wort is a perennial plant with extensive, creeping rhizomes. Its stems are erect, branched in the upper section, and can grow to 1 m high. It has opposing, stalkless, narrow, oblong leaves that are 12 mm long or slightly larger. The leaves are yellow-green in color, with transparent dots throughout the tissue and occasionally with a few black dots on the lower surface.[2] Leaves exhibit obvious translucent dots when held up to the light, giving them a 'perforated' appearance, hence the plant's Latin name.

Its flowers measure up to 2.5 cm across, have five petals, and are colored bright yellow with conspicuous black dots. The flowers appear in broad cymes at the ends of the upper branches, between late spring and early to mid summer. The sepals are pointed, with glandular dots in the tissue. There are many stamens, which are united at the base into three bundles. The pollen grains are ellipsoidal.[2]

When flower buds (not the flowers themselves) or seed pods are crushed, a reddish/purple liquid is produced.

Ecology[edit]

St John's wort reproduces both vegetatively and sexually. It thrives in areas with either a winter- or summer-dominant rainfall pattern; however, distribution is restricted by temperatures too low for seed germination or seedling survival. Altitudes greater than 1500 m, rainfall less than 500 mm, and a daily mean January (in Southern hemisphere) temperature greater than 24 degrees C are considered limiting thresholds. Depending on environmental and climatic conditions, and rosette age, St John's wort will alter growth form and habit to promote survival. Summer rains are particularly effective in allowing the plant to grow vegetatively, following defoliation by insects or grazing.

The seeds can persist for decades in the soil seed bank, germinating following disturbance.[10]

Invasive species[edit]

Although Hypericum perforatum is grown commercially in some regions of south east Europe, it is listed as a noxious weed in more than twenty countries and has introduced populations in South and North America, India, New Zealand, Australia, and South Africa.[10] In pastures, St John's wort acts as both a toxic and invasive weed.[9] It replaces native plant communities and forage vegetation to the dominating extent of making productive land nonviable[citation needed] or becoming an invasive species in natural habitats and ecosystems. Ingestion by livestock can cause photosensitization, central nervous system depression, spontaneous abortion, and can lead to death. Effective herbicides for control of Hypericum include 2,4-D, picloram, and glyphosate. In western North America three beetles Chrysolina quadrigemina, Chrysolina hyperici and Agrilus hyperici have been introduced as biocontrol agents.

Livestock[edit]

Poisoning[edit]

In large doses, St John's wort is poisonous to grazing livestock (cattle, sheep, goats, horses).[9] Behavioural signs of poisoning are general restlessness and skin irritation. Restlessness is often indicated by pawing of the ground, headshaking, head rubbing, and occasional hindlimb weakness with knuckling over, panting, confusion, and depression. Mania and hyperactivity may also result, including running in circles until exhausted. Observations of thick wort infestations by Australian graziers include the appearance of circular patches giving hillsides a 'crop circle' appearance, it is presumed, from this phenomenon. Animals typically seek shade and have reduced appetite. Hypersensitivity to water has been noted, and convulsions may occur following a knock to the head. Although general aversion to water is noted, some may seek water for relief.

Severe skin irritation is physically apparent, with reddening of non-pigmented and unprotected areas. This subsequently leads to itch and rubbing, followed by further inflammation, exudation, and scab formation. Lesions and inflammation that occur are said to resemble the conditions seen in foot and mouth disease. Sheep have been observed to have face swelling, dermatitis, and wool falling off due to rubbing. Lactating animals may cease or have reduced milk production; pregnant animals may abort. Lesions on udders are often apparent. Horses may show signs of anorexia, depression (with a comatose state), dilated pupils, and injected conjunctiva.

Diagnosis[edit]

Increased respiration and heart rate is typically observed while one of the early signs of St John's wort poisoning is an abnormal increase in body temperature. Affected animals will lose weight, or fail to gain weight; young animals are more affected than old animals. In severe cases death may occur, as a direct result of starvation, or because of secondary disease or septicaemia of lesions. Some affected animals may accidentally drown. Poor performance of suckling lambs (pigmented and non-pigmented) has been noted, suggesting a reduction in the milk production, or the transmission of a toxin in the milk.

Photosensitisation[edit]

Most clinical signs in animals are caused by photosensitisation.[11] Plants may induce either primary or secondary photosensitisation:

  • primary photosensitisation directly from chemicals contained in ingested plants
  • secondary photosensitisation from plant-associated damage to the liver.

Araya and Ford (1981) explored changes in liver function and concluded there was no evidence of Hypericum-related effect on the excretory capacity of the liver, or any interference was minimal and temporary. However, evidence of liver damage in blood plasma has been found at high and long rates of dosage.

Photosensitisation causes skin inflammation by a mechanism involving a pigment or photodynamic compound, which when activated by a certain wavelength of light leads to oxidation reactions in vivo. This leads to lesions of tissue, particularly noticeable on and around parts of skin exposed to light. Lightly covered or poorly pigmented areas are most conspicuous. Removal of affected animals from sunlight results in reduced symptoms of poisoning.

Medical uses[edit]

Major depressive disorder[edit]

St John's wort is widely known as a herbal treatment for depression. In Germany, it is sometimes prescribed for mild to moderate depression, especially in children and adolescents.[12][13] It is proposed that the mechanism of action of St. John's wort is due to the inhibition of reuptake of certain neurotransmitters.[2] The best studied chemical components of the plant are hypericin and pseudohypericin.[citation needed]

An analysis of twenty-nine clinical trials with more than five thousand patients was conducted by the Cochrane Collaboration. The review concluded that extracts of St John's wort were superior to placebo in patients with major depression. St John's wort had similar efficacy to standard antidepressants. Trials from German-speaking countries displayed findings that were more favorable to St. John's wort. The rate of patient drop-outs due to adverse effects was half that of newer SSRI antidepressants and one-fourth that of older tricyclic antidepressants.[7] The report[7] from the Cochrane Review states:

The available evidence suggests that the Hypericum extracts tested in the included trials a) are superior to placebo in patients with major depression; b) are similarly effective as standard antidepressants; and c) have fewer side-effects than standard antidepressants. The association of country of origin and precision with effects sizes complicates the interpretation.

Side effects[edit]

St John's wort is generally well tolerated, with an adverse effect profile similar to placebo.[14] Commonly reported adverse effects include gastrointestinal symptoms (nausea, abdominal pain, loss of appetite, and diarrhea), dizziness, confusion, fatigue, sedation, dry mouth, restlessness, and headache.[15][16][17] Reports of adverse drug reactions to St John's wort follow a very similar pattern to those in response to traditional SSRIs such as fluoxetine.[18] St John's wort also decreases the levels of estrogens, such as estradiol, by speeding up its metabolism, and should not be taken by women on contraceptive pills as it upregulates the CYP3A4 cytochrome of the P450 system in the liver.[19]

St John's wort may rarely cause photosensitivity. This can lead to visual sensitivity to light and to sunburns in situations that would not normally cause them.[14] Related to this, recent studies concluded that the extract reacts with light, both visible and ultraviolet, to produce free radicals, molecules that can damage the cells of the body. These can react with vital proteins in the eye that, if damaged, precipitate out, causing cataracts.[20] Another study found that in low concentrations, St. John's wort inhibits free radical production in both cell-free and human vascular tissue, revealing antioxidant properties of the compound. The same study found pro-oxidant activity at the highest concentration tested.[21]

St John's wort is associated with aggravating psychosis in people who have schizophrenia.[22]

Interactions[edit]

Consumption of St. John's wort is discouraged for those with bipolar disorder. There is concern that people with bipolar depression taking St. John's wort may be at a higher risk for mania.[23]

St. John's Wort has interactions with medications such as SSRI antidepressants, warfarin, and birth control. Combining both SJW and SSRI antidepressants could lead to increased serotonin levels causing serotonin syndrome.[24] Combining estrogen containing oral contraceptives with SJW can lead to decreased efficacy of the contraceptive and eventually unplanned pregnancies.[25] These are just a few of the drug interactions that SJW possesses. It is also known to decrease the efficacy of HIV medications, cholesterol medications, as well as transplant medications.[26] It should be noted, however, that traditional SSRI antidepressants such as fluvoxamine carry similar contraindications.

Pharmacokinetic interactions[edit]

St John's wort has been shown to cause multiple drug interactions through induction of the cytochrome P450 enzymes CYP3A4 and CYP2C9, and CYP1A2 (females only). This drug-metabolizing enzyme induction results in the increased metabolism of certain drugs, leading to decreased plasma concentration and potential clinical effect.[27] The principal constituents thought to be responsible are hyperforin and amentoflavone.

St John's wort has also been shown to cause drug interactions through the induction of the P-glycoprotein efflux transporter. Increased P-glycoprotein expression results in decreased absorption and increased clearance of certain drugs, leading to lower plasma concentration and potential clinical efficacy.[28]

Examples of drugs whose effectiveness may be reduced by St. John's wort
Class Drugs
Antiretrovirals Non-nucleoside reverse transcriptase inhibitors, protease inhibitors
Benzodiazepines Alprazolam, midazolam
Hormonal contraception Combined oral contraceptives
Immunosuppressants Calcineurin inhibitors, cyclosporine, tacrolimus
Antiarrhythmics Amiodarone, flecainide, mexiletine
Beta-blockers Metoprolol, carvedilol
Calcium channel blockers Verapamil, diltiazem, amlodipine
Statins (cholesterol-reducing medications) Lovastatin, simvastatin, atorvastatin
Others Digoxin, methadone, omeprazole, phenobarbital, theophylline, warfarin, levodopa, buprenorphine, irinotecan
Reference: Rossi, 2005; Micromedex

For a complete list, see CYP3A4 ligands and CYP2C9 ligands.

Pharmacodynamic interactions[edit]

In combination with other drugs that may elevate 5-HT (serotonin) levels in the central nervous system (CNS), St John's wort may contribute to serotonin syndrome, a potentially life-threatening adverse drug reaction.[29]

Drugs that may contribute to serotonin syndrome with St John's wort
Class Drugs
Antidepressants MAOIs, TCAs, SSRIs, SNRIs, mirtazapine
Opioids Tramadol, pethidine (meperidine), Levorphanol
CNS stimulants Phentermine, diethylpropion, amphetamines, sibutramine, cocaine
5-HT1 agonists Triptans
Psychedelic drugs Methylenedioxymethamphetamine (MDMA), LSD, Dimethyltryptamine (DMT), MDA, 6-APB
Others Selegiline, tryptophan, buspirone, lithium, linezolid, 5-HTP, dextromethorphan
Reference:[29]

Mechanism of action[edit]

St. John's wort (SJW), similarly to other herbs, contains a whole host of different chemical constituents that may be pertinent to its therapeutic effects.[30] Hyperforin and adhyperforin, two phloroglucinol constituents of SJW, are TRPC6 receptor agonist and, consequently, they induce noncompetitive reuptake inhibition of monoamines (specifically, dopamine, norepinephrine, and serotonin), GABA, and glutamate when they activate this receptor.[6][31][32] It inhibits reuptake of these neurotransmitters by increasing intracellular sodium ion concentrations.[6] Moreover, SJW is known to downregulate the β1 adrenoceptor and upregulate postsynaptic 5-HT1A and 5-HT2A receptors, both of which are a type of serotonin receptor.[6] Other compounds may also play a role in SJW's antidepressant effects such compounds include: oligomeric procyanidines, flavonoids (quercetin), hypericin, and pseudohypericin.[6][33][34][35]

In humans, the active ingredient hyperforin is a monoamine reuptake inhibitor which also acts as an inhibitor of PTGS1, arachidonate 5-lipoxygenase, SLCO1B1 and an inducer of cMOAT.[31][32][36] Hyperforin is also a anti-inflammatory compound with anti-angiogenic, antibiotic, and neurotrophic properties.[31][32][36] Hyperforin also has an antagonistic effect on NMDA receptors, a type of glutamate receptor.[32]

Chemistry[edit]

Detection in body fluids[edit]

Hypericin, pseudohypericin, and hyperforin may be quantitated in plasma as confirmation of usage and to estimate the dosage. These three active substituents have plasma elimination half-lives within a range of 15–60 hours in humans. None of the three has been detected in urine specimens.[86]

Chemical constituent[edit]

The plant contains the following:[30][38]

The naphthodianthrones hypericin and pseudohypericin along with the phloroglucinol derivative hyperforin are thought to be among the numerous active constituents.[2][87][88][89] It also contains essential oils composed mainly of sesquiterpenes.[2]

Research[edit]

St John's wort is being studied for effectiveness in the treatment of certain somatoform disorders. Results from the initial studies are mixed and still inconclusive; some research has found no effectiveness, other research has found a slight lightening of symptoms. Further study is needed and is being performed.

A major constituent chemical, hyperforin, may be useful for treatment of alcoholism, although dosage, safety and efficacy have not been studied.[90][91] Hyperforin has also displayed antibacterial properties against Gram-positive bacteria, although dosage, safety and efficacy has not been studied.[92] Herbal medicine has also employed lipophilic extracts from St John's wort as a topical remedy for wounds, abrasions, burns, and muscle pain.[91] The positive effects that have been observed are generally attributed to hyperforin due to its possible antibacterial and anti-inflammatory effects.[91] For this reason hyperforin may be useful in the treatment of infected wounds and inflammatory skin diseases.[91] In response to hyperforin's incorporation into a new bath oil, a study to assess potential skin irritation was conducted which found good skin tolerance of St John's wort.[91]

Hypericin and pseudohypericin have shown both antiviral and antibacterial activities. It is believed that these molecules bind non-specifically to viral and cellular membranes and can result in photo-oxidation of the pathogens to kill them.[2]

See also[edit]

Notes[edit]

  1. ^ Less common names and synonyms include Tipton's weed, rosin rose, goatweed, chase-devil, or Klamath weed.[2]

References[edit]

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  3. ^ "Enzymes". Hyperforin. Human Metabolome Database. 3.6. University of Alberta. 30 June 2013. Retrieved 12 December 2014. Hyperforin is found in alcoholic beverages. Hyperforin is a constituent of Hypericum perforatum (St John's Wort) Hyperforin is a phytochemical produced by some of the members of the plant genus Hypericum, notably Hypericum perforatum (St John's wort). The structure of hyperforin was elucidated by a research group from the Shemyakin Institute of Bio-organic Chemistry (USSR Academy of Sciences in Moscow) and published in 1975. Hyperforin is a prenylated phloroglucinol derivative. Total synthesis of hyperforin has not yet been accomplished, despite attempts by several research groups. Hyperforin has been shown to exhibit anti-inflammatory, anti-tumor, antibiotic and anti-depressant functions (PMID 17696442 , 21751836 , 12725578 , 12018529 )
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