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Ergot alkaloids are constituents of various fungi, but especially from the ergot fungus (Claviceps purpurea (Fr.) Tul.). In the 20th century the poisoning of grain with ergot lead to mass extinction and a higher infant mortality.
In addition to the deposits in the ergot fungus, they are still synthesized in other fungal species. In particular, they can be in the fungi of the genera Aspergillus, Claviceps, Penicillium and Rhizopus. In addition to their occurrence in fungi, the ergot alkaloids found in a few plants.
The ergot alkaloids are characterized by their ergolin-like basic structure and an equal biosynthesis starting with tryptophan and dimethylallyl pyrophosphate. Overall, the group includes 80 individual compounds, which can be subdivided into the clavines and in the lysergic acids.
Ergot alkaloids are active ingredients. In particular, the amide derivatives of lysergic acid are highly active. Lysergic acid diethylamide, known as LSD, is a famous example.
The ergot fungus (Claviceps purpurea (Fr.) Tul.) lives parasitically on rye and grasses. Its preferred host is the rye, but also wheat, barley, oats and spelled are attacked by him. This fungus forms for wintering ergot, a sclerotium, which is elongated and similar to grain. The plants are infected by spores carried by the wind on the fields. After infection, a fungal mycelium and later the sclerotia is formed.
Claviceps purpurea from Köhlers Medizinal Pflanzen
The ergot contains up to 1% ergot alkaloids. Among them, the ergotamine, the ergosine, the ergocristine & the ergocryptine.
Ergot poisoning occur in two different forms. However, in both cases it comes to headaches, nausea and a tingling especially in the extremities. In the so-called gangrenous form it comes to circulatory disorders of the extremities, and in severe pain. In the other form, the convulsive, however, it comes to long seizures. Furthermore, it comes to long-term neurological damage.
Already 5-10 g of ergot can lead to dead for an adult human being. Responsible for this are the mix of different ergot alkaloids and their high concentration. On the other side, after the isolation of individual alkaloids such as ergonovine and ergotamine and their application in defined amounts, the alkaloids can be used for special treatments. Ergometrine can be used for example for obstetrics. Generally show the ergot alkaloids a ecbolic effect. Ergotamine, however, can be used against migraines and cluster headaches.
The lysergic acid is a well-known representative of the ergot alkaloids. In addition to the occurrence in ergot there is lysergic acid in wind plants (Convolvulaceae Juss.).
The lysergic acid is a tetracyclic system with two stereocenters. It is poorly soluble in water and in organic solvents. The acid group is able to form amides with amines. So tripeptides of lysergic acid can be formed.
The lysergic acid is synthesized from tryptophan and dimethylallyl pyrophosphate (see biosynthesis of terpenes). After the CC bond formation chanoclavine is formed by decarboxylation, cyclization and oxidation. After oxidation to the aldehyde, a cis-trans isomerization (not shown) is necessary to re-cyclise in the next step. The resulting elymoclavine is oxidized to delta-8,9-lysergic acid, which is isomerized to lysergic acid.
Other ergot alkaloids are synthesized according to a similar pattern. The development of further lysergic acids done by further derivatization. The synthesis of the clavines branches off before the formation of elymoclavine.
The ergot alkaloids are a popular research topic of pharmaceutical scientists because of their highly potent effects. Several drugs such as methylergometrine or lisuride are developed by the derivatization of the ergot alkaloids. In such researches the Swiss Albert Hofmann explore an artificial derviate of lysergic acid, lysergic acid diethylamide, the (LSD). The surprising thing of LSD is its highly-potent effect. Already 50-300 micrograms (ie 0.00005 - 0.00003 g) cause the effect.
LSD is an amide of lysergic acid. Lysergic acid can be converted to LSD by the reaction of a suitable coupling reagent with diethylamine. Current methods for the synthesis of derivates from ergot alkaloids are usually semi-synthetic. That means that the natural alkaloids derived from ergot are used for further derivatisation.
In addition to physical effects of LSD, such as dilation of the pupils and the increase in blood pressure, the psychological effects are in the foreground. Here especially perception changes in sense of time and at optical and acoustic stimuli occurs. In addition, hallucinations can happen. By reinforcing the perception and changes can occur even while mood-altering conditions such as happiness, satisfaction, but also anxiety. Due to this effect Hofmann held LSD to be suitable for use within a controlled psychotherapeutic frame. However, the use as a party drug and the subsequent repressive policy prevented such use.