Written by Karen Pilkington, Edzard Ernst and the CAM-Cancer Consortium.
Updated September 21, 2016

St. John's wort (Hypericum perforatum)

What is it ?

Scientific name

Hypericum perforatum L. (Guttiferae/Clusiaceae).
Synonym(s): Hypericum, Hypericum veronese Schrank, H., Hypericum noeanum Boiss., Millepertus 1, Hyperici herba 2-3.


Extracts contain naphthodianthrone (=hypericin/pseudohypericin), phloroglycinderivatives (=hyperforin/adhyperforin) flavonoids, tannins, volatile oils, xanthones and many other ingredients. The major known constituents considered to be responsible for the antidepressant activity are hypericin and hyperforin 4-6. Extracts to study the anticancer activities have been mostly characterised by these two ingredients.

Application and dosage

Usually, St. John’s wort is taken orally. The dosage of commercial preparations varies according to the specifics of each product. Typical doses are as follows:
Dried herb: 2-4g as an infusion three times daily.
Liquid extract: 2-4 ml (1:1 in 25% alcohol) three times daily.
Standardised dried extracts applied in clinical trials: 240-1800 mg daily (equivalent to varying concentrations of hypericin and hyperforin), typically applied for 4 to 6 weeks.

According to the British and European Pharmacopoeias, St. John`s wort herb should contain not less than 0.08% of total hypericins, expressed as hypericin, calculated with reference to the dried drug 2-3.


St. John’s wort has been used medicinally for millennia. Today herbalists, naturopaths, and in some countries, doctors might prescribe or recommend St. John’s wort preparations. However, most of its usage is based on self-prescription as products are available in pharmacies and health food shops.

Claims of efficacy

Traditionally, St. John’s wort was employed for pain control, wound healing, melancholy, insanity and many other ailments 4. Today it is mainly used as an anti-depressive agent, and there is good evidence that it is effective for that purpose 7.

Mechanism of action

The anti-depressive effects of St. John’s wort seem to rely on the inhibition of the re-uptake of serotonin, noradrenalin, glutamate and dopamine in the central nervous system 5-6. Other known mechanisms of action include the modulation of interleukin-6 activity and gamma-aminobutyric acid receptor binding and antioxidant effects 4,8-9. There is preliminary evidence from in-vitro studies to suggest that constituents of St. John's wort have anti-cancer effects 33-35. A range of mechanisms have been proposed based on results of pre-clinical studies, e.g. cytotoxic, apoptosis-inducing and anti-angiogenic effects.

St. John’s wort extracts exhibit cytotoxic and apoptosis-inducing effects in neoplastic cell lines 11,33-35. They thus inhibit the growth of leukaemia and glioblastoma prostate cancer cells in vitro 12-13. Ex-vivo experiments have demonstrated anti-angiogenic activity 14 which theoretically could contribute to anticancer effects 15-16. These effects may not be linked purely to hypericin but also to other ingredients of St. John’s wort 17.

Animal experiments have shown that St. John’s wort inhibits pro-inflammatory cytokines 18. Hypericin also has phototoxic effects, and St. John’s wort could thus have potential as a photodynamic agent for some types of skin cancer 19. Collectively the evidence indicates that the threshold for phototoxicity of hypericin is between 100 and 1000 ng/ml 20. Since serum and skin concentrations of hypericin after oral administration of recommended doses are below 100 ng/ml, photosensitivity is unlikely 1. Nevertheless, it was reported that 3 µM of activated hypericin induced a necrotic mode of cell death in pigmented melanoma cells and melanocytes and an apoptotic mode of cell death in non-pigmented cells and keratinocytes 21.

Alleged indications

The claim is that St. John’s wort may exert direct effects on cancer cells (see below) and thus influence the natural history of the disease.

Prevalence of use

In most countries, St. John’s wort is a popular anti-depressant. Many cancer patients might thus try it to improve their mood by using this herbal extract. One survey suggested that 5% of lymphoma patients do so 10. There are only scarce data to show how many cancer patients might take St. John’s wort to treat their malignancy. One study suggested that 2-5% of US lung/colorectal cancer patients took St. John's wort supplements. These data, however, do not imply that they took it for treating cancer 24.

Legal issues

In most countries, St. John’s wort is available as a food supplement. In other countries (e.g. Germany), full licences have been issued for St. John’s wort as an anti-depressant. St. John’s wort is listed by the Council of Europe as a natural source of food flavouring.

Cost and expenditure

The cost of one week’s supply varies considerably from ~€15 to €25. High quality preparations tend to be at the higher end of this range.

Citation Karen Pilkington, Edzard Ernst, CAM-Cancer Consortium. St. John's wort (Hypericum perforatum) [online document]. http://ws.cam-cancer.org/The-Summaries/Herbal-products/St.-John-s-wort-Hypericum-perforatum. September 21, 2016.


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