St. John’s wort (Hypericum perforatum), also known as goat weed or enola weed, it’s a perennial flowering herb belonging to the Clusiaceae family. The name of the specie, “perforatum”, refers to small translucent spots that are evident when the leaves are held up to the light.
It has been used since Ancient Greece both externally as a macerated oil to treat wounds, burns, bruises, cuts, and pain and internally in infusion against stomach ulcers, neuralgia, anxiety, and insomnia.
The herb produces golden yellow flowers that, according to the traditional recipe, must be left to macerate for 40 days in olive oil and exposed to direct sunlight. Legend has it that the oil is more effective if flowers are collected on Saint John’s Day (June 24) and left to macerate until the day of the Saint’s beheading (August 29). The resulting oil is red, which is also associated with the color of St. John’s blood.
The red color of the oil is due to the presence of hypericin, an anthraquinone-derived pigment, belonging to the naphthodianthrones chemical family. Due to its chemical structure, with two oxygen atoms very close to each other sharing a mobile hydrogen atom, hypericin is very reactive to light.
The macerated oil contains other naphthodianthrones such as pseudohypericin, isophypericin, and protohypericin, together with other lipophilic compounds such as hyperforin (another photoreactive compound), adhyperforin and furohyperforin.
Hypericin and hyperforin are antioxidant and anti-inflammatory. Hyperforin stimulates the growth and differentiation of keratinocytes. St. John’s wort extract enhances collagen production and activates the fibroblasts that is responsible for wound closure.
Hyperforin has been shown to inhibit the growth of certain bacteria and viruses.
St. John’s wort extracts and macerated oils are used in skin care products to;
- Prevent fine lines
- Treat acne
- Soothe reddened, burnt, or sunburned skin
- Reduce itching, irritation, eczema, and inflammation
- Treat psoriasis or dermatitis
- Regenerate the skin in case of minor wounds, bruises, and dry skin
- Promote recovery after a tattoo
Due to the high photoreactivity of hypericin and hyperforin, St. John’s wort extracts and macerated oils are mildly phototoxic. Phototoxicity is a chemically induced skin irritation that takes place when the skin is exposed to the sun. It is advised not to expose the skin to the sun after using skin care products containing St. John’s wort extracts or macerated oils and apply them preferably at night.