Curare calabash

Gourd or Calabash Curare. This type, exported in small gourds, is said to be made from Strychnos toxifera Schomb., and this was confirmed by King, who isolated from botanically authenticated material collected in British Guiana, an amorphous, quaternary alkaloid indistinguishable from curarine prepared from gourd curare, and Wieland et al. have isolated from this species alkaloids which they have also found in this type of curare. Other Strychnos spp. from the same territory examined by King contained alkaloids, but not of the curarine type. 

Alkaloids of Goukd ok Calabash Curare. The toxic constituent of this form, as prepared by Boehm, was an amorphous curarine to which the formula C gHjgONj was assigned. Gourd curare has been investigated in recent years by Wieland et aZ. and by Schmid and Karrer. ... 

Calabash curare, probably from the middle Orinoco region, has also been investigated by Karrer and Schmid,who have isolated eight new alkaloids in addition to Wieland s C-curarine I. 

Karrer and Matter have confirmed the presence of succinic acid as recorded by Boehm, and of protoeatechuic acid as found by Wieland, Konz and Sonderhoff and have added thereto, mesaconic acid as a constituent of calabash curare. 

Cacalia hastata, 601 Cacotheline, 566 Cactaceae, 154 Cadaverine, 518 Calabar bean alkaloids, 539 Calabarine, 540 Calabash curare, 373 alkaloids, 380... 

Alkaloids of Curare Curine, Tubocurarine, Protocuridine, Calabash-curare I, etc., including Erythrina alkaloids Alkaloids of Ipecacuanha. ... 

The alkaloid content of curare is from 4% to 7%. The most important constituent in menispermaceous curare is the bis-benzyltetrahydroisoquinoline alkaloid (+)-tubocurarine (Figure 6.48). This is a monoquaternary ammonium salt, and is water soluble. Other main alkaloids include non-quaternary dimeric structures, e.g. isochondrodendrine and curine (bebeerine) (Figure 6.48), which appear to be derived from two molecules of (R)-N-methylcoclaurine, with the former also displaying a different coupling mode. The constituents in loganiaceous curare (from calabash curare, i.e. Strychnos toxifera) are even more complex, and a series of 12 quaternary dimeric strychnine-like alkaloids has been identified, e.g. C-toxiferine (toxiferine-1) (see page 359). 

Wieland and Neeb140 for the synthesis of some pentacyclic analogs (118) of calabash curare. 

Appendix. Alkaloids of Unknown Structure from Calabash Curare and... 

Calabash curare originates in the more northern parts of the subcontinent, particularly in the Amazon and Orinoco basins and surrounding regions. It is considerably more toxic than tube-curare and has presented much more formidable chemical problems with regard to both isolation and structural elucidation. 

Only a few of the quaternary alkaloids so far isolated have high curare-activity, and these are responsible for the toxicity of the curares and bark extracts the majority of the pure alkaloids are inactive or only weakly active. At present there is no evidence against the view that all the toxic alkaloids of calabash curare are derived from Strychnos species it is probable that the same also holds true for most of the nontoxic curare alkaloids. 

The first chemical work on calabash curare was carried out in 1897 by Boehm (8), who isolated a highly active amorphous material which was named curarine. This was soluble in water and insoluble in ether, so it is probable that Boehm was handling a mixture of crude quaternary alkaloids. Much later (1935), King described (9) the preparation of an equally active amorphous quaternary iodide from the bark of S. toxifera. However, the first isolation of well-characterized crystalline alkaloids was achieved by H. Wieland and his school (10-13). Calabash curares were extracted with methanol, and the water-soluble quaternary alkaloids in the extract were precipitated as the reineckate salts this mixture was then fractionated by adsorption chromatography on alumina. The various reineckate fractions so obtained were converted into the corresponding chlorides by successive treatment with equivalent quantities of silver sulfate and barium chloride some of the quaternary alkaloids then crystallized as the chlorides or as the picrates. C-Curarine1... 

For characterization purposes, the Rf values of the alkaloids are given as Rc values, which are displacements calculated with respect to C-curarine, the most abundant and one of the most stable of the calabash curare alkaloids. Thus ... 

Quite early in the chemical studies of Wieland and King, evidence accumulated that the calabash curare alkaloids are indole derivatives, and with present knowledge it is possible to correlate the UV-spectra of many of them with one or another of the following related chromo-phores formally derived from the indole nucleus by oxidation, reduction, and substitution, or combinations of these processes. They are the indoline (II), 2-hydroxyindoline and the derived ethers (III), iV-hydroxy-alkylindoline and its ethers (IV), 2-methyleneindoline or 1-vinylindoline (Va or Vb, respectively), indole (VI), oxindole or 1-acylindoline (Vila or Vllb, respectively), -indoxyl (VIII), and /J-carbolinium (IX) systems it is not possible to distinguish with certainty by spectroscopic methods between the chromophores III and IV, between Va and Vb, or between Vila and Vllb. 

C-Mavacurine was isolated by Wieland and Merz (17) from a calabash curare, and C-fluorocurine was crystallized, also from a calabash, by Schmid and Karrer (41) both alkaloids were subsequently found in... 

Venezuelan 8. toxifera bark (30), and they have been detected chromato-graphically in extracts from the barks of several Strychnos species (20, 25, 43-45). A study of these two alkaloids gave a first insight into the structures of alkaloids from calabash curare and commenced with a demonstration that they are interrelated. 

---