Methyllycaconitine

Methyllycaconitine (MLA) is a diterpenoid alkaloid found in many species of Delphinium (larkspurs). In common with many other diterpenoid alkaloids, it is toxic to animals, although the acute toxicity varies with species. Early research was focused on identifying, and characterizing the properties of methyllycaconitine as one of the principal toxins in larkspurs responsible for livestock poisoning in the mountain rangelands of North America. Methyllycaconitine has been explored as a possible therapeutic agent for the treatment of spastic paralyses in man, and it has been shown to have insecticidal properties. Most recently, it has become an important molecular probe for studying the pharmacology of the nicotinic acetylcholine receptor. Methyllycaconitine (MLA) is a diterpenoid alkaloid found in many species of Delphinium (larkspurs). In common with many other diterpenoid alkaloids, it is toxic to animals, although the acute toxicity varies with species. Early research was focused on identifying, and characterizing the properties of methyllycaconitine as one of the principal toxins in larkspurs responsible for livestock poisoning in the mountain rangelands of North America. Methyllycaconitine has been explored as a possible therapeutic agent for the treatment of spastic paralyses in man, and it has been shown to have insecticidal properties. Most recently, it has become an important molecular probe for studying the pharmacology of the nicotinic acetylcholine receptor. The first isolation of MLA, from Delphinium brownii, Rydb., was probably made by Richard Manske at the National Research Laboratories in Ottawa, Canada, in 1938. Presumably because he did not obtain the compound in sufficiently pure form, Manske declined to give it a name. The name 'methyl-lycaconitine' was assigned by John Goodson, working at the Wellcome Chemical Research Laboratories in London, England, when he isolated the alkaloid, in purer form, from seeds of Delphinium elatum, L. in 1943.A more modern isolation procedure is described by Pelletier and his co-workers, who used seeds of the 'garden larkspur', Consolida ambigua (also referred to as Delphinium ajacis) as their plant source. The complete molecular structure for MLA, correct in all but one detail, was first published by Kuzovkov and Platonova in 1959. This structure, supported in part by X-ray crystallography (considered usually to be a 'definitive' analytical technique) of a chemical derivative of MLA performed by Maria Przybylska, was accepted as correct until the early 1980s. At that time, the research groups of Pelletier and of Edwards and Przybylska independently corrected the stereochemistry of the methoxy group at C-1 from the β- to α- configuration. Thus any drawing of MLA appearing before Pelletier's 1981 paper will show the structure with the incorrect stereochemistry at C-1.