Ergot

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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Alkaloids

Ergot is the dried sclerotium of a fungus, Claviceps purpurea Tulasne, belonging to family Clavicipitaceae, developing in the ovary of rye plant, Secale cereale (Family Poaceae). Ergot should yield about 0.15% of the total alkaloids calculated as ergotoxine and water-soluble alkaloids equivalent to about 0.01% of ergonovine.


ERGOT

 

 

Synonyms

 

Ergot; Rye Ergot; Secale cornutum; Spurred rye; Ergot of rye; Ergota.

 

Biological Source

 

Ergot is the dried sclerotium of a fungus, Claviceps purpurea Tulasne, belonging to family Clavicipitaceae, developing in the ovary of rye plant, Secale cereale (Family Poaceae).

 

Ergot should yield about 0.15% of the total alkaloids cal-culated as ergotoxine and water-soluble alkaloids equivalent to about 0.01% of ergonovine.

 

Geographical Source

 

It is mainly found in Czechoslovakia, Hungary, Switzerland, Germany, France, Yugoslavia, Spain, Russia and India. In India Ergot is cultivated at Kodaikanal (T.N.).

 

Cultivation and Collection

 

The life cycle of the fungus, Claviceps purpurea, which is a parasite, passes through the following characteristic stages:

 

1)    Sphacelia or honeydew or asexual stage

 

2)    Sclerotium or ascigerous or sexual stage and

 

3)    Ascospore stage.


1. Sphacelia or honeydew or asexual stage

 

The rye plant becomes infected by the spores of the fungus in the spring session when flowers bloom for about one week. The spores are carried by the wind or by insects to the flowers and collected at the base of the young ovary where moisture is present. There germination of the spores takes place. A filamentous hyphae is formed which enters into the wall of the ovary by enzymatic action. A soft, white mass over the surface of ovary is formed, which is known as Sphacelia. A sweet viscous yellowish liquid, known as honeydew, is secreted during the Sphacelia stage which contains reducing sugars (reduce Fehling solution). From the ends of some hyphae small oval conidiospores (asexual spore/s) are abstricted which remain suspended on honeydew. The sweet taste of honeydew attracts some insects like ants and weevils. Insects suck the sweet liquid and carry the conidiospores to the plants and spread the fungal infection in the rye plants. Cultured conidiospores are used for the inoculum. Strains capable of producing about 0.35% of selected alkaloids, mainly ergotamine, are now utilized.

 

2. Sclerotium or ascigerous or sexual stage

 

During the Sphacelia stage the hyphae enter only the outer wall of the ovary. On further development they penetrate into deeper parts, feed on the ovarian tissues and replace it by a compact, dark purple hard tissue known as pseudoparenchyma. It forms the sclerotium or resting state of the fungus. During summer the sclerotium or ergot increases in size and projects on the rye, showing sphacelial remains at its apex. It is collected at this stage by hands or machine and used as a drug. Ergot is then dried to remove moisture. About 6 weeks after inoculation, the mature sclerotia are harvested. They may be picked up by hand or collected by machine. The number and size of the ergots produced on each spike of cereal by C. purpurea varies, rye usually bears sclerotia, while wheat bears very few.

 

3. Ascospore stage

 

If Ergot is not collected, it falls on the ground. In the next spring session they produce stalked projections known as stromata which have globular heads. In the inner surface of the heads there are many flask-shaped pockets known as perithecia. Each of these perithecia contains many sacs (asci) which possesses eight of the thread-like ascospores. These ascospores are carried out by insects or wind to the flowers of the rye as described in the first stage. In this way life cycle of Ergot is completed.

 

The ascospores may be germinated on a nutritive medium to get conidiospore bearing cultures. The suspension of these conidiospores is usually used as a spray to infect rye plants for commercial production of Ergot.

 

Ergot is collected from fields of rye when the sclerotia are fully developed and projecting from the spike, or they are removed from the grain by shifting. The size of the crop varies according to weather conditions. The vegeta-tive phase of the fungus can, like that of other moulds, be cultivated artificially. Under such conditions the typical sclerotia do not develop.


Characteristics

 

The size of sclerotium (Ergot) is about 1–4 cm long, 2–7 mm broad. Shape is fusiform, slightly curved, sub-cylindrical, tapering at both ends. The outer surface is dark or violet-black in colour, has longitudinal furrows and sometimes small transverse cracks. The fractured surface shows thin, dark outer layer, a whitish or pinkish-white central zone of pseudoparenchyma in which darker lines radiate from the centre. Odour is characteristic and taste is unpleasant.

 


                        Claviceps purpurea



Microscopy

 

Ergot shows an outer zone of purplish-brown, obliterated rectangular cells. The pseudoparenchyma consists of oval or rounded cells containing fixed oil and protein, and with highly refractive walls which give a reaction for chitin. Cellulose and lignin are absent.

 

Chemical Constituents

 

A large number of alkaloids have been isolated from the Ergot. The most important alkaloids are ergonovine and ergotamine. On the basis of solubility in water the alkaloids are divided into two groups: water-soluble ergometrine (or ergonovine) group or water-insoluble (ergotamine and ergotoxine) groups as given hereunder:

 


 

Only the first group, ergometrine group, belongs to water-soluble compounds. Alkaloids of Group II and III are polypeptides in which lysergic acid or isolysergic acid is linked to amino acids. Alkaloids obtained from lysergic acid are physiologically active compounds. In the first group, for example, ergometrine alkaloids, lysergic acid or its isomer is linked to an amino alcohol.


 


 

The ergot alkaloids (ergolines) can also be divided into two classes (1) the clavine-type alkaloids, which are derivatives of 6,8-dimethyl-ergoline and (2) the lysergic acid derivatives, which are peptide alkaloids and contains the pharmacologically active alkaloids that characterize the ergot sclerotium (ergot). Each active alkaloid occurs with an inactive isomer involving isolysergic acid.

 

Chemical Tests

 

1. Ergot under UV light shows a red-coloured fluores-cence.

 

2. Ergot powder is extracted with a mixture of CHCl3 and sodium carbonate. The CHCl3 layer is separated and a mixture of p-dimethylaminobenzaldehyde (0.1 g), H2SO4 (35%, v/v, 100 ml) and 5% ferric chloride (1.5 ml) is added. A deep blue colour is produced.

 

Uses

 

Ergot is oxytocic, vasoconstrictor and abortifacient and used to assist delivery and to reduce post-partum haemorrhage. Lysergic acid diethylamide (LSD-25), obtained by partial synthesis from lysergic acid, is a potent specific psychoto-mimetic. Ergometrine is oxytocic and used in delivery. It stimulates the tone of uterine muscles and prevents post-partum haemorrhage.

 

Only ergometrine produces an oxytocic effect, ergot-oxine and ergotamine having quite a different action. Ergometrine is soluble in water or in dilute alcohol. It is known as ergonovine. Ergotamine and the semisynthetic dihydroergotamine salts are used as specific analgesics for the treatment of migraine. Lysergic acid diethylamide (LSD-25), prepared by partial synthesis from lysergic acid, is a potent specific psychotomimetic.

 

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