Strychnos toxifera

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. 

The material first used by Wieland et al. was gourd curare from the middle Orinoco district, near Urbana, in Bolivar State, Venezuela, but in the fomth paper (1941) results are recorded for curares from Colombia and Venezuela, for which more precise details of origin are not available and there is considerable difference in the nature and quantity of the alkaloids in the various samples used. An examination has also been made of the bark of Strychnos toxifera, and one of the alkaloids (toxiferine II) it contains has been found in some of the curares examined. In all, ten alkaloids have been obtained and characterised and, with the exception of curine, they are all of quaternary type. They are named toxiferine, dihydrotoxiferine, or calabash-curarine (shortened to C-curarine in practice) according to type, and the variants within the type are distinguished by numbers, or numbers and letters, e.g., toxiferine I, toxiferine Ilb. 

Calabash-curarine I. This alkaloid was first named toxiferine (1937), as it was expected to be found in Strychnos toxifera bark when this bark yielded a different alkaloid, for which the name toxiferine was more appropriate, the name of the curare alkaloid was changed. Crystalline salts have been prepared of which the chloride, CjoHjaONjCI or HjO,... 

Alkaloids of Strychnos toxifera. The following alkaloids were obtained from the bark of this species —... 

ANTAGONIZING ACETYLCHOLINE Curare, found in a resinous extract of the plants Chondrodendrott tomentosum and Strychnos toxifera from the Orinoco and Amazon basins in South America, is an antagonist at nicotinic acetylcholine receptors. Curare does not cross the blood—brain barrier, and therefore its actions are expressed only outside of the brain at the neuromuscular junction where neurons control muscles. Curare is extremely lethal for one simple reason—it blocks the nicotinic receptors located on the diaphragm therefore, death from curare results from asphyxiation. Imagine you ve been shot by a curare-tipped arrow you d be awake, fully aware of having been shot, yet completely unable to move, speak, or, ultimately, breathe. 

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). 

Notmacusine-B was first obtained by the thermal decomposition of its quaternary methochloride, macusine-B, which was isolated from Strychnos toxifera It was found to be identical with 10-deoxysarpagine (CCCXX) and its IVa-methyldihydro derivative was identical with deoxyisoajmalol-B (CCCXXIII) (172, 173), thus establishing its structure and absolute stereochemistry (177, see Chapter 22). Subsequently, normacusine-B has been found in Diplorrhyncus mossambicensis (named tombozine, 116, 121, 122) and in Aspidosperma polyneuron (165). 

Chemical/Pharmaceutical/Other Class Toxic alkaloid (o-tubocurare) found in South American woody vines including Strychnos toxifera, S. castelnaei, S. crevauxii, and Chondodendron tom-entosum... 

Curares from the upper Amazon (Brazil and Peru) seem to be mainly Meni-spermaceous in origin, while those from British Guiana, Venezuela and Colombia owe much of their activity to species of the genus Strychnos (family Lopfaniaceae), especially Strychnos toxifera, S. castelnaeana and S. uianensis. 

All dimeric curare alkaloids are derived from the monomeric units Wieland-Gumlich aldehyde (32) and 18-desoxy-Wieland-Gumlich aldehyde (34) or their respective iV(j,)-metho-salts (33) and (35). The key substance for the synthesis of the dimeric calabash alkaloids is therefore Wieland-Gumlich aldehyde (32). Under the name caracurine VII it has been isolated from the South American Strychnos toxifera F. Schomb. and S. subcordata Spruce in the form of its V(j,)-metho-salt (= alkaloid 8 = hemitoxiferine = caracurine VII metho-salt). 

Principal paralytic alkaloids present in an alternative form of curare, calabash curare, prepared from the bark of Strychnos toxifera. Used to be packed in calabashes or gourds, hence the C (for calabash) in the name. Used as an arrow poison. Actions similar to tubocurarine. 

In the early 1960s Battersby and Yeowell (196) isolated two quaternary alkaloids from Strychnos toxifera. These they called macusine A and macusine C, which they claimed to be epimeric compounds and for which they presented structures 66 and 67, respectively (Fig. 2). A little later Orazi et... 

Aspidosperma peroba) Pleiocarpa tubicina (= Pleiocarpa pycnantha var. tubicina) Strychnos amazonica Strychnos decussata Strychnos ignatii Strychnos toxifera Strychnos usambarensis... 

Strychnine ip (strychnan, dimer ) Strychnos toxifera Skeletal muscle relaxant... 

The paralyzing activity in frogs was determined for the alkaloids isolated by Wieland (61-66) and by Karrer and Schmid (67-71) from the calabash curare. These alkaloids are named with the prefix C-, as, for example, C-curarine I. The alkaloids isolated by King (72) from Strychnos toxifera are named as toxiferines (toxiferine I, toxiferine II, etc.). The prefix has been dropped from C-toxiferme I and C-toxiferine. II, which Avere first isolated from calabash curare, as they are identical Avith toxiferine I and toxiferine II from Strychnos toxifera. 

Stephania harnandifolica Tridisia subcordata Strychnos toxifera Papaver somniferum... 

Alexander von Humboldt (1769-1859) was the first to report that Strychnos toxifera Isa source of curare. Information about a South American vine, Chondro-dendron tomentosum, as another source had come from Hippolyto Ruiz and Joseph Pavonin 1794. 

For centuries, the native Indians in Ecuador and Colombia used besides curare [546] from Strychnos toxifera and Chondrodendron tomentosum also the skin secretion of several dart-poison frogs of the genus PhyUobates and Dendrobates to tip the darts of their blowpipes for hunting (Fig. 5.212). 

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