The ergot alkaloids constitute the largest known group of nitrogenous fungal metabolites and over 80 alkaloids have been isolated from diverse natural material. The common part of chemical structure of the most ergot alkaloids is a tetra-cyclic ergoline ring system (Figure 1), which is biosynthe-sized from tryptophan (Taber and Vining 1959), and mevalonic acid (Groger et al. 1961). The ergot alkaloids

Figure 1 Structure of ergoline.

can be separated into three main structural groups: (a) clavine alkaloids, (b) simple lysergic and paspalic acid derivatives, and (c) peptide alkaloids (ergopeptines). The clavine alkaloids are tricyclic (secoergolines) or tetracyclic (ergo-lines) compounds usually substituted with methyl, hydroxyl or hydroxymethyl group in position C-8 and in many cases have a double bond in positions 8,9 (D8,9-ergolenes) or 9,10 (D9,10-ergolenes) of the ergoline skeleton (Figure 2). The important feature of all D9,10-ergolenes (including simple derivatives of lysergic acid and ergopeptines) is an easy isomerization on C(8) resulting in formation of two isomers. Clavine alkaloids represent the largest group of ergot alkaloids due to the action of various enzymes, which direct agroclavine and/or elymoclavine from the main biosynthetic route agroclavine-elymoclavine-paspalic acid-lysergic acid. Such type of shunt activity is particularly evident in microorganisms that lack the complete pathway and are unable to synthesize substituted lysergic acid (Vining 1980).

The simple derivatives of paspalic and lysergic acid (Figure 3) are mostly amides, in which the amide part is either small peptide or a simple alkylamide. Amides of lysergic and paspalic acids found in ergot are ergometrine, lysergic acid 2-hydroxyethylamide, lysergic acid amide (ergine), paspalic acid, and 10-hydroxy-paspalamide (Flieger et al. 1993). Ergopeptines are derivatives of lysergic acid and are the only natural substances having the unique structure called cyclol (Figure 4) that consists of three aminoacids. The ergopeptines are further divided to (a) ergotamine, (b) ergoxine, (c) ergotoxine, and (d) b-ergoannine group (Flieger et al. 1997).

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