How St John’s wort benefits were found?
Ancient Greeks had used St. John’s wort to treat many internal and external diseases. Hypericum perforatum is the botanical name of this herb found throughout temperate regions, including European, American and Asian countries. Since ancient time, this herb is effective to treat different mental conditions like anxiety, depression, burns, and cuts. Later researchers discovered this herb has potent neuroprotective, antioxidant, anti-inflammatory and antimicrobial properties.
After discovering these therapeutic benefits, many European pharmaceutical companies started to prepare St. John’s wort containing herbal formulation and earn several billion dollars. The efficacy of this herb is tested through both animal and human trials and also identify the possible mechanism of action of this herbal medicine. 
What are the phytochemicals present in St John’s wort?
There are a wide variety of phytochemicals present in St. John’s wort. Hypericin and hyperforin have great medicinal properties. St. John’s wort also contains flavonoids, quercetin, rutin, and kaempferol, which also add medicinal benefits.
The detail chemical analysis of St. John’s wort reported that seven groups of medicinally active compounds present in St. John’s wort. Flavonoids like biflavones, flavonol glycosides, and phenylpropanes, certain essential oils, naphthodianthrones, and phloroglucinols are some recently identified phytochemicals present in St. John’s wort herb. Among the wide variety of phytochemicals present in St. John’s wort herb, 20% are biologically active. 
What is the mode of action of St John’s wort benefits?
St. John’s wort containing hypericin has the main antidepressant property which stimulates capillary blood flow. An animal study reported that this active phytochemical has MAO A and MAO B inhibitory effect. This active constituent facilitates neurotransmission activity by preventing the degradation of amine neurotransmitters. St. John’s wort treatment also enhances dopamine activity by binding with sigma receptors.
Hyperforin is another phytochemical present in St. John’s wort, which acts as a serotonin uptake inhibitor. Treatment with this antidepressant increases the concentration of both Na+ and Ca2+ ions. 
St. John’s wort has a growth inhibitory effect against a wide variety of disease-causing germs. Hyperforin is active against MRSA (Methicillin-resistant Staphylococcus aureus ) and PRSA (penicillin-resistant Staphylococcus aureus). These gram-negative bacteria have often developed resistance against conventional antibiotics.
Flavonoid and catechin-containing active ingredients of St. John’s wort effective against viral infections. Hypericin interferes with viral cell cycle and provides an antiviral effect. 
Hyperforin and hypericin, both of these active ingredients have anticancer properties. They induce apoptosis and inhibit tumor growth. Hypericin acts as a powerful natural photosensitizer and has potent antioxidant property. The mechanism involves in anticancer activity includes prolonging cell growth inhibitory effect, induces apoptosis and reduces phototoxicity. 
The anti-inflammatory and gastroprotective activity exerted by St. John’s wort obtained due to inhibition of pro-inflammatory genes expressions like cyclooxygenase-2, interleukin 6, and inducible nitric oxide synthase (iNOS). This herb also reduces prostaglandin E2 production. 
St. John’s wort extract enhances the collagen production and activates fibroblast cells to accelerate the wound healing process.
St. John’s wort herb can activate the opioid receptors without causing withdrawal symptom. 
What are the different forms of St John’s wort?
Different dosage forms of St. John’s wort herb is available in the market. The herbal preparations of St. John’s wort herb may contain flowering tops to prepare tablets, capsule, teas, tincture, liquid extract and skin lotions for external application to accelerate wound healing. Most of these herbal preparations contain 0.3% hypericin.
St. John’s wort herbal preparations usually recommended for adults, however, a pediatric study also reported this relatively safe to use for children having mild to moderate depression problem.
Tablet and capsules containing dry herb are recommended for mood disorder or mild depression. The recommended adult dosage is 300mg thrice daily with meals. Sustainable release St. John’s wort herbal capsules also available in the market.
St. John’s wort herbal tea and liquid extract are also available. It is advised to take experts opinion for dose determination. Usually 3 to 6 weeks treatment period require to check the efficacy of St. John’s wort herbal preparation. Experts also recommended not to stop the drug suddenly, as it may cause a side effect. Gradually lower the dose before complete stopping of the medicine.