C. Ergine
Synonyms Lysergamide; Lysergic acid amide;
Biological Sources It is obtained from the immature seeds of Argyreja nervosa (Burm.) Bojer (Convolvulaceae) (Wood Rose, Silver Morning Glory); Beeds of Ipomea Violaceae L. (Convolulaceae) (Tlitliltzen, Ololiuqui); seeds of Rivea corymbosa Hall. F. (Convolvulaceae) (Snakeplant); and also from the seeds of Ipomea tricolor Cav (Convolvulaceae).
Chemical Structure
9, 10-Didehydro-6-methylergoline-8β-carboxamide; (C16H17N3O).
Isolation It is isolated from the seeds of Rivea corymbosa (L.) and from Ipomea tricolor Cav. By the method of Hofmann and Tscherter.*
Characteristic Features
1. It is obtained as prisms from methanol which get decomposed at 242°C.
2. It has a specific optical rotation of [α]205461 + 15° (C = 0.5 in pyridine).
Identification Tests The precipitation reactions and the colour tests are the same as described under ergonovine (Section A).
Ergine may also be identified by forming its derivative as stated below:
Ergine Methane Sulphonate (C16H17N3O.CH3SO3H) It is obtained as prisms from a mixture of methanol and acetone that get decomposed at 232°C.
Uses It has a pronounced depressant action.
Note: It is a controlled substance listed in the U.S. Code of Federal Regulations. Title 21 Part 1308, 13 (1995).
Biosynthesis of Ergotamine The various steps involved in the biosynthesis of ergotamine are as enumerated below:
1. Three amino acids, viz., L-alanine, L-phenylalanine, and L-proline in the presence of ATP and enzyme SH; or D-(+)-lysergic acid in the presence of ATP and enzyme SH undergo two steps: first-activation via AMP esters, and secondly-attachment to the respective enzymes, thereby giving rise to an intermediate. It is worthwhile to observe that the enzyme is comprised of two subunits that essentially bind the substrates as indicated in the biosynthetic pathway given below.
2. The comparatively more complex structures comprising of the peptide fragments, such as: ergotamine are eventually formed by sequential addition of amino acid residues to the thioesterbound lysergic acid, yielding a linear lysergyl-tripeptide covalently attached to the enzyme complex.
3. The resulting complex undergoes lactam formation followed by release from enzyme. In other words, the cyclized tripetide residue is rationalized instantly by the formation of a lactam (amide) that releases ultimately the product from the enzyme.
4. This resulting product first affords hydroxylation then followed by generation of a hemeketallike linkage to give rise to the formation of ergotamine.
All these aforesaid steps (1) through (4) have been duly depicted in the following biosynthetic pathway.
Peptide Alkaloids in Ergot Interestingly, it has been observed critically that three amino acids, namely: alamine, phenylatine and proline, actually from the basis for the various structures which are encountered in the domain of the ‘ergot alkaloids’. Therefore, these known and established structures may be subdivided into three major groups which are: ergotamine group, ergoxine group, and ergotoxine group.
The various alkaloids having the peptide linkages found in ‘ergot’ are depicted as under.
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* Hofmann and Tscherter, Experientia, 16, 414 (1964).
