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.
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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