Hypericum perforatum

Hypericum perforatum, commonly known as St. John's wort, is a flowering plant in the family Hypericaceae. It is a hairless, perennial herb with woody roots, yellow flowers marked by black glands, and leaves that appear perforated due to translucent glands, producing thousands of seeds per plant.
H. perforatum is the type species of its genus, known for its historical use in folklore and traditional medicine. Probably a hybrid between the closely related H. attenuatum and H. maculatum that originated in Siberia, the species has spread worldwide. It can further hybridize with related species due to its allopolyploid nature. It is native to much of Europe, West and Central Asia, and parts of Africa and China and has been widely introduced elsewhere, thriving in well-drained, temperate habitats such as meadows, hillsides, and open woods with moderate rainfall and mild temperatures. It is a resilient, toxic, and invasive plant that reproduces sexually and vegetatively, supports specialized insect herbivores, suffers from plant diseases, and poses ecological and agricultural threats in many parts of the world.
H. perforatum has been used for centuries in traditional medicine, especially for treating wounds and depression. To prepare it for use, the oil from its glands can be extracted or its above-ground parts can be dried and ground into a powder called herba hyperici. H. perforatum exhibits antidepressant effects comparable to drugs with fewer side effects for mild to moderate depression ; however, it may interact with various medications by accelerating their metabolism.

Description

Hypericum perforatum is an herbaceous perennial plant with hairless stems and leaves. The root of each plant is slender and woody with many small, fibrous small side roots and also extensive, creeping rhizomes. The central root grows to a depth of into the soil depending on conditions. The crown of the root is woody.
Its stems are erect and branched in the upper section, and usually range from 0.3 metres to 1 metre in height. The stems are woody near their base and look like they have segmented joints from the scars left behind after the leaves fall off. The stems of H. perforatum are rusty-yellow to rosy in color with two distinct edges and usually have bark that sheds near the base. The stems persist through the winter and sprout new growth with flower buds in the following year; first year growth does not produce flowers.
It has leaves that attach on opposite sides of the stems without a stalk. The leaves vary in shape from being very narrow and almost grass-like, to a rounded oval slightly wider at the base with a rounded tip or not much of a tip, or even narrow with the widest portion towards the end of the leaf like a reversed lance point, but still long and narrow. The principle leaves range in length from 0.8 to 3.5 centimetres and 0.31–1.6 centimetres in width. Leaves borne on the branches subtend the shortened branchlets. The leaves are yellow-green in color, with scattered translucent dots of glandular tissue. The dots are clearly visible when held up to the light, giving the leaves a perforated appearance. The edges of the leaves usually have scattered black dots, often called dark glands, though sometimes they will appear away from the edges. The odor of the plant is faint, but aromatic, resembling that of resins like balsam. The taste of the plant is bitter and acrid.

Flowering characteristics

The flowers are conspicuous and showy, measuring about across, and are bright yellow with black dots along the edges of the petals. Each of the flowers normally has five large petals and five smaller leaf-like sepals below them. The sepals are about in length, green in color, are shaped like the head of a spear with a pointed tip, and the same clear and black glands as the leaves. The petals are significantly longer, in length, and have an oblong shape. They completely hide the sepals from the front side of the flower. The many bright yellow stamens are united at the base into three bundles. The stalk portion of the stamens, the filaments, vary in length and stick out in every direction from the center of the flower. The pollen grains are pale brown to orange in color. Each flowering stem bears many flowers, between 25 and 100, and also is quite leafy.
The fruit of Hypericum perforatum is a capsule in length containing the seeds in three valved chambers. Seeds that are separated from the capsules have a much higher germination rate due to an inhibiting factor in the capsule itself. The black and lustrous seeds are rough, netted with coarse grooves. Each seed is about in size. Each plant may produce an average of 15,000 to 34,000 seeds.

Similar species

Hypericum maculatum is visually similar to Hypericum perforatum; however, its stems have four ridges instead of two and are also hollow. In addition, its leaves have fewer translucent glands and more dark glands. H. maculatum is native to the Old World but has also been introduced to North America.
In North America several native species may be confused with Hypericum perforatum. Hypericum anagalloides is a low-growing creeping plant with rounder leaves and fewer stamens. Hypericum boreale is a smaller plant with more delicate flowers. Hypericum canadense has smaller flowers with sepals that show between the petals. Hypericum concinnum has flowers with petals that bend backward at the tip and also has much narrower, gray-green leaves. Growing in riparian areas along rivers, Hypericum ellipticum has wider leaves with a more elliptic shape. Hypericum scouleri has leaves that are broader at the base and also thicker. All except for H. concinnum grow in environments that are generally more moist than where H. perforatum is found.

Phytochemistry

The most common active chemicals in Hypericum perforatum are hypericin and pseudohypericin, and hyperforin. The species contains a host of essential oils, the bulk of which are sesquiterpenes. In the wild, the concentrations of any active chemicals can vary widely among individual plants and populations.

Acronym/Symbol	Meaning
MW	Molecular weight in g•mol⁻¹.
PGP	P-glycoprotein
t_1/2	Elimination half-life in hours
T_max	Time to peak plasma concentration in hours
C_max	Peak plasma concentration in mM
C_SS	Steady state plasma concentration in mM
	Partition coefficient.
PSA	Polar surface area of the molecule in question in square angstroms. Obtained from PubChem
Conc.	These values pertain to the approximation concentration of the constituents in the fresh plant material
–	Indicates inhibition of the enzyme in question.
+	Indicates an inductive effect on the enzyme in question.
0	No effect on the enzyme in question.
5-HT	5-hydroxytryptamine – synonym for serotonin.
DA	Dopamine
NE	Norepinephrine
GABA	γ-aminobutyric acid
Glu	Glutamate
Gly	Glycine
Ch	Choline
^a	?
^b	?
^c	?

'''Notes:'''

Taxonomy

Hypericum perforatum was selected to be the type species around which the genus Hypericum is based because of its wide cosmopolitan distribution; it is the most common species of the genus in many of the areas it is found, and is one of the most widely known plants among the St John's worts in folklore and medicine. The current accepted placement of H. perforatum within its genus can be summarized as follows:
''Hypericum''

Phylogeny

Hypericum perforatum has a chromosome count of 2n = 32. The likely reason for this is that the species is a hybrid between the very closely related H. maculatum subsp. immaculatum and H. attenuatum, which means it inherited sets of chromosomes from both parents and is allopolyploid. The two species almost certainly hybridized within Siberia, Russia. The equation for this hybridization is:
Because of its hybrid origins, Hypericum perforatum is one of the few species within its genus that is able to further hybridize with other species, specifically those within H. ser. Hypericum. The hybrids that are descended from H. perforatum can be triploid to hexaploid, depending on the chromosome count of the second parent species and the ploidy of the specific H. perforatum gamete that is fertilized or is fertilizing. The triploid offspring exhibit and a mix of traits from the two parents and pass them on to their offspring; the tetraploids also have a mix of traits, but often do not pass on the traits of both parents; the pentaploids are rarely distinguishable from H. perforatum. Because of this, after many generations of hybridization a wide range of traits on a spectrum between the two hybridizing species can be observed in the wild.

Etymology and common names

The genus name Hypericum is possibly derived from the Greek words hyper and eikon, in reference to the tradition of hanging the plant over religious icons in the home. The specific epithet perforatum is Latin and refers to the perforated appearance of the plant's leaves.
The common name St John's wort comes from the fact that its flowers and buds were commonly harvested at the time of the Midsummer festival, which was later Christianized as St John's Feast Day on 24 June. It was believed that harvesting the flower at this time made its healing and magical powers more potent. The herb would be hung on house and stall doors on St John's Feast Day to ward off evil spirits and to safeguard against harm and sickness to people and livestock. In other traditions it was burned in bonfires for the protection of crops along with other herbs believed to be magical. Because of its supposed potency in warding off spirits, the plant was also known as fuga daemonum. Many other similarly fanciful names have been used for it including devil's scourge, Lord God's wonder plant, and witch's herb. In medieval Kent it was called herbe Ion as recorded in the poem The Feate of Gardening. Other local names for Hypericum perforatum include balm of the warrior's wound in Somerset, penny John in Norfolk, rosin rose in Yorkshire, and touch-and-heal in Northern Ireland. Locally in the United States, it may also be referred to as Tipton-weed, goatweed, or Klamath weed.
In the 21st century, any species of the genus Hypericum can be referred to as St John's wort. Therefore, it is more accurate to call Hypericum perforatum the common St John's wort or perforate St John's wort.