Uniquely identifiable characteristics
Distinguishing Feature : With so many identifying features (see photo annotations) this St John's Wort is easily differentiated from the rest.
The books say that this Slender St John's Wort avoids lime, for it is a calcifuge, which is at variance with the photographs above, which was found growing in Gait Barrows, a limestone area containing clints and grykes (many of which have previously been bulldozed flat for use as ornamental stones in gardens and on the sea-front at Morecambe). However, it is possible that sufficient peat had gathered where this particular lone specimen had established itself to create an acidic micro-habitat.
The stems yield a brown-red dye when alum is used as the mordant. The flowers, on the other hand, yield a yellow dye when alum is used as the mordant and an orange-red dye when tin is used instead.
Hypericin, together with
Hyperfolin, are major constituents of St John's Wort plants, and both owe their names to the scientific name for St John's Worts.
Hypericin is a red-orange coloured naphthodianthrone, an anthraquinone derivative, and acts as an antibiotic if consumed. It is also fluorescent. Being a chromophore the molecule can cause photo-sensitization, which has been observed in animals which happen to eat any St John's Wort. Once an animal has become photo-sensitized to Hypericum, the sensitization will remain for the rest of its life, when further exposure of the skin to the sun results in skin lesions which develop 1-2 weeks after exposure. Subsequent exposure of the skin to UV light from the sun will result in increasingly severe symptoms.
Hypericin preferentially accumulates in cancerous tissues and has found use as an indicator of cancerous cells. By way of its photo-activation properties, it may also find use as a means of treating cancerous tissue which would then be activated when the tissue is illuminated by a strong source of light. It also exhibits photo-activated activity against various virii. It has (a much reduced) activity against viruses when in the dark, which may be mediated by a differing mechanism.
PseudoHypericin being the cause of the colour in St John's-Worts, is concentrated mostly in the parts of the plant which are orange-red, being the flowers. Other coloured compounds called flavonoids also contribute to the yellow colour. One, Hyperoside (aka Hyperin), which is concentrated mainly in the flowers, is the 3-O-galactoside of Quercetin. Hyperoside is also present in Selfheal (Prunella vulgaris), Sheep's Sorrel (Rumex acetosella) and Round-Leaved Sundew (Drosera rotundifolia).
PRENYLATED PHLOROGLUCINOL DERIVATIVES
Hyperforin is a
prenylated derivative of PhloroGlucinol which is found in the fruits and oil-glands of St John's-wort plants and is thought to be part of the plants defence mechanism against herbivores. It is also thought to be a neuro-transmitter re-uptake inhibitor, acting on
glutamate. Hyperfolin is a prenylated Phloroglucinol derivative and believed to be the primary active constituent in St John's Wort extracts responsible for its anti-depressant and anxiolytic properties. Hyperforin is also an antibiotic active against MRSA. It is a bicyclic molecule with one 2-methylpropanoyl, one 4-methylpent-3-enyl and three 3-methylbut-2-enyl groups attached to the central fused rings.
AdHyperforin is also present, the only addition being a slight extension of the moiety on the extreme right of the diagram. Strangely, both of these two Hyperforins are drawn with one CH3 moiety missing on some drawings to be found on the internet, some with captions swapped - that is Hyperforin is drawn as AdHyperforin, and vice versa!
There are many other acylphloroglucinols in the Dryopteris genus of Ferns, such as are detailed in Male-Fern (Dryopteris felix-mas).