Dihydro-P-erythroidine

The beanlike seeds of the trees and shrubs of the genus Erythrina, a member of the legume family, contain substances that possess curare-like activity. The plants are widely distributed in the tropical and subtropical areas of the American continent, Asia, Africa, and Australia, but apparently they are not used by the natives in the preparation of arrow poisons. Of 105 known species, the seeds from more than 50 have been tested, and all were found to contain alkaloids with curariform properties. Erythroidine, from E. americana, was the first crystalline alkaloid of the group to be isolated. It consists of at least two isomeric alkaloids, a and P-erythroidine both are dextrorotatory. Most experimental and clinical study has centered on the b form because it is more readily obtainable in pure state. P-Erythroidine is a tertiary nitrogenous base. Several hydrogenated derivatives of p-erythroidine have been prepared of these, dihydro-P-erythroidine has been studied most carefully and subjected to clinical trial. Conversion of P-erythroidine into the quaternary metho salt (p-erythroidine methiodide) does not enhance, but rather almost entirely, abolishes its curariform activity this constitutes a notable exception to the rule that conversion of many alkaloids into quaternary metho salts results in the appearance of curare-like action. 

The pharmacological properties of P-erythroidine and its dihydro derivative are very similar to those of d-tubocurarine and therefore need not be described in any detail. The two compounds differ from curare in three important respects, namely, less potent paralytic action on neuromuscular junctions, briefer duration of paralysis, and oral efficacy. Indeed, gastrointestinal absorption of the alkaloids is so rapid and complete that the difference between effective oral and subcutaneous doses is rather small. Dihydro-P-erythroidine is longer acting than P-erythroidine and about six times as active. Similar to curare, P-erythroidine and its dihydro derivative are antagonized at the neuromyal junction by anticholinesterases such as neostigmine. 

Keywords A-84543 A-85380 ABT-089 ABT-418 ABT-594 Aminoethoxypyridines Anabaseine Anabasine Chloronicotine, 6- Cotinine Cytisine Dihydro-P-erythroidine DMXB Epibatidine GTS-21 Isonicotine Lobelanidine Lobelanine Lobeline Metanicotine Myosmine Nicotine Nicotinoids Nornicotine SIB-1508Y SIB-1553A SIB-1765F Tetrahydropyrido[3,4-rf]azepines... 

Erythroidine behaves as a lactone and when one of its salts with an alkali or alkaline earth metal is catalytically hydrogenated under pressure, a mixture of dihydro-j3-erythroidines, with two tetrahydro- compounds is produced, from which dihydro- -erythroidine can be isolated as the hydrobromide. The dihydro- base has m.p. 85-6° (dec.), + 102-5° and... 

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