Ergot Alkaloids

Introduction

Ergot is the name given to the sclerotium of the fungus Claviceps purpurea and some other Claviceps species that infect many wild grasses and cereals. These hard black tuber-like bodies consist of a compact mass of hyphae and are the resting stage of the fungus. These ergots produce a range of up to 40 different alkaloids that can lead to the formation of lysergic acid if the ergot ferments. Lysergic acid causes hallucinations, agitation and other symptoms. Ergot in rye consumed by the population was the main cause of Holy fire, ‘ignis sacer’, or St. Anthony’s fire in the 8^th to 16^th centuries in Europe, and the effects included gangrenous ergotism, burning sensations and hallucinations. Occasional outbreaks have continued to occur, usually associated with humid summers. Instances occurring in the last 30 year include outbreaks in Ethiopia and India. Ergot was first recognised as a fungus in the 18th century and was known as a source of drugs (‘a treasure house’ of pharmacologically active compounds) by the beginning of the 19th century. The main ergot alkaloids are ergotamine, ergocornine, ergocristine, ergocryptine, ergometrine and agroclavine.

Chemical and Physical Properties

Most alkaloids form colourless crystals that are readily soluble in many organic solvents but insoluble or only slightly soluble in water. Most melt with decomposition over a range of temperature.

Physical and chemical properties of selected ergot alkaloids

	Molecular formula	Molecular weight	Melting point (Deg C)
ergotamine	C33H35O5N5	581.6	212-214 (dec)
ergocornine	C31H39O5N5	561.7	182-184 (dec)
ergocristine	C35H39O5N5	609.7	165-170 (dec)
ergocryptine	C32H41O5N5	575.7	173 (dec)
agroclavine	C16H18N2	238.2	210-212 (dec)
ergometrine	C19H23O2N3	325.4	175-180 (dec)

* dec=decomposition

Toxicity and Importance

Ergotism in man is now relatively uncommon but it can affect livestock from time to time. The general effects on livestock have been categorized as follows: behavioural effects, convulsions, incoordination, lameness, difficulty in breathing, excessive salivation, diarrhoea, and dry gangrene of the extremities. Reproductive effects including abortion, high neonatal mortality, reduced lactation, reduced feed intake and weight gain. These effects are not seen in all types of livestock but are fairly species specific and are modified by the ergot source, amount consumed, period of exposure, and age and stage of production of the animal. Two characteristic effects of ergotism are convulsions and gangrene.

Cattle may exhibit both convulsive and gangrenous ergotism. Gangrene of the ear tips and tail may occur, but generally the feet are affected and signs include tenderness of the hind feet. There is little affect on reproduction or occurrence of abortion. Sheep that consume ergot exhibit difficulty in breathing, excessive salivation, diarrhoea, and internal bleeding within the digestive tract. Sheep tend not to graze on grass flowers, and therefore, are less affected than cattle due to the difference in grazing behaviour. Horses grazing grasses infected with ergot may develop symptoms of convulsion. Swine are less sensitive than other livestock to ergot. Abortions may occur, and newborn pigs have a high rate of mortality due to depressed lactation by affected sows. Poultry develop comb necrosis, while ergotism in chicks is characterized by depressed growth, poor feathering, nervousness, incoordination, and an inability to stand, and the beaks, toenails, and toes become dark and necrotic.

Products affected and Natural Occurrence

All the common cereals including rye, wheat, barley, triticale, oats, millet, sorghum and maize can be infected with ergot, although rye is the most susceptible. In Europe, rye bread has often been linked to outbreaks of ergotism. Ergot alkaloids are not transferred to the milk of cows consuming ergot.

Sampling and Analysis

Sclerotia of Claviceps species are unique in containing a rich triglyceride fraction in which ricinoleic acid is the principal component. The presence of this acid in a foodstuff known to be free from other sources of ricinoleic acid, such as castor oil is diagnostic for the presence of C. purpurea sclerotia. If the free fatty acids released are methylated with diazomethane, methyl esters can be analysed using gas-liquid chromatography that enables as little as 0.3% ergot in 1-2 g foodstuff to be detected by this procedure.

All the common analytical techniques such as TLC, HPLC, GLC and GC/MS have been used for the determination of ergot alkaloids. Methods have been reported for cereals, cereal products and milk and for human and animal blood plasma. A commercially available immunoaffinity extraction column has been reported for the analysis of lysergic acid diethylamide (LSD) in urine and hair.

Ergot contamination of pearl millet, due to infection by C. fusiformis, is characterized by the presence of another group of alkaloids, the clavine alkaloids. A procedure for its determination has been developed using thin-layer chromatographic separation and spectrophotometric detection following colour reaction using Van Urk's reagent. The procedure includes de-fatting of the grain sample, mixing of the defatted material with ammonium hydroxide, extraction with diethyl-ether, followed by extraction of the diethyl-ether phase with 0.1 N sulphuric acid. The extract is made alkaline and extracted with chloroform, followed by thin-layer chromatographic separation.

Stability and Persistence

Sclerotia can be removed from grain by standard seed-cleaning techniques but the screenings from ergot-containing grain should not be used in feeds. It is fortunate that the pharmacologically active ergot alkaloids are not very heat stable and are substantially reduced on baking bread, as, in contrast, the non-active isomeric forms are much more stable and survive processing. Only low levels of the active alkaloids thus remain in prepared foods as cleaning and milling remove the sclerotia and baking or other heat processing destroys most alkaloids.

Legislation and Control

There is no legislation for the ergot alkaloids but many countries have recommended, or compulsory, maximum limits for the % or ergots allowed in cereals. The tolerance level for ergot in grain in the U.S. is 0.3% crude ergot alkaloid. Levels of 0.1% ergot in complete feeds may have adverse effects on livestock performance. In the UK the UKASTA standards for ergot are 0.001% ergot by weight for feed grain, and a zero tolerance for all other grain.

When necessary the effects of ergot can be prevented by careful crop management. Thus in areas where ergot is a problem it may be advisable to grow ergot-resistant grains such as wheat, barley, or oats, rather than rye or triticale. Animals should be removed from ergot-infected pastures, and contaminated grain should not be used for feed. The use of clean seed, crop rotation, and deep cultivation assist in minimising Ergot infestation of grain. UK higher voluntary seed standards demand no ergots for basic seed and no more than one ergot in a 1 kg sample of wheat, barley or oats. Ergots survive only one season in soil so a break from cereals should provide good control.