Compound Monograph
Hypericin
A red naphthodianthrone pigment from St. John's Wort, notable as a photosensitiser used to standardise the herb.
Classification
Hypericin is a naphthodianthrone (pigment), part of the phenolics class. Antioxidant compounds built around one or more phenol rings — the flavonoids, tannins, phenolic acids, coumarins, and pigments behind much of a plant's protective chemistry.
Where Does It Come From? (2)
Hypericin is a naturally occurring naphthodianthrone (pigment), found in St. John's Wort and 1 other source. It is flagged as moderately toxic.
Research & Evidence
Hypericin is a red naphthodianthrone pigment found in St. John’s Wort (Hypericum perforatum), concentrated in the dark glands of the flowers and leaves. It is often used, alongside hyperforin, as a marker to standardise St. John’s Wort extracts. Hypericin is a strong photosensitiser — it absorbs light and generates reactive oxygen species — a property that has been explored in photodynamic and antiviral research.
Toxicity & Safety
Because hypericin is a photosensitiser, high intakes of St. John’s Wort can increase sensitivity to sunlight, and photosensitisation (hypericism) is a well-documented problem in grazing livestock that eat the plant. Fair-skinned people taking St. John’s Wort, and anyone using light-based or photosensitising therapies, should be mindful of increased sun sensitivity. The broader cautions around St. John’s Wort, including its drug interactions, also apply to products containing hypericin.