Curare, alkaloids pharmacological action

Such compounds often exhibit chemical and spectral behaviour which is specifically characteristic of the dimeric structure. Also of paramount interest are the specific pharmacological properties of certain of these alkaloids, such as the muscle relaxation action of the curare alkaloids and the anti-leukemia activity of the Vinca alkaloids leurocristine and vinblastine. Such aspects will be discussed in the last two sections of the review. 

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. 

Many Erythrina alkaloids possess curare-like action. Alkaloidal extracts from different parts of Erythrina species have been used in indigenous medicine, particularly in India (176). Many pharmacological effects, including astringent, sedative, hypotensive, neuromuscular blocking, CNS depressant, laxative, and diuretic properties, have been recorded for total alkaloid extracts, although not all these properties can be associated with the ery-thrinane structure alone (38, 177, 178). 

Pharmacology of Calabash-curare.f —Paralytic Activity. A number of Strychnos alkaloids have considerably greater paralytic action than any previously known natural or synthetic neuromuscular blocking agent. Unfortunately, frogs are not suitable for the evaluation of curare effects because they show sea-... 

---