Alkaloids colour reactions

As regards general methods for distinguishing between the alkaloids of opium, mention may be made of the following Kofler and Kofler s study of the micro-sublimation of these alkaloids and the characters of the micro-sublimates the comparison by Maplethorpe and Evers of the picrates of a series of opium bases, comparison of the colour reactions of a series of opium alkaloids, and their behaviour with specific reagents and precipitants. ... 

Tuduranine, CjgHjgOgN. This member of the aporphine group (p. 306) is the most recent addition to Sinomenium alkaloids and was isolated by Goto from the mother liquors of sinomenine. It is crystalline, has m.p. 125° (with softening at 105°), and yields a sparingly soluble hydrochloride, m.p. 286° (dec.), [a] f — 148° (dilute MeOH), is freely soluble in alkali, and gives feeble ferric chloride and diazo-colour reactions and a fuchsin-red colour with formaldehyde and sulphuric acid. It behaves as a secondary base and yields a diacetyl derivative, m.p. 170°, [a] / — 321-71° (MeOH), which does not form a methiodide, but can be hydrolysed to A -acetyl-tuduranine, m.p. 277°, — 395-24°, and this can be methylated to... 

Alkaloids of Pot Curare. This variety of curare is a dark brown, comparatively dry extract. According to Boehm, it contains protocurine, colourless hair-like needles, m.p. 306° (dec.), a base of low toxicity and yielding crystalline salts. A second alkaloid of similar type is protocuridine prisms, m.p. 274-6°, sparingly soluble in all ordinary solvents. The poisonous constituent is protocurarine, a red powder, easily soluble in water, and giving characteristic colour reactions with nitric acid and with oxidising agents in sulphuric acid, this latter reaction indicating a Strychnos spp. as a possible botanical source. 

As these substances are difficult to isolate and to distinguish, particular importance attaches to their colour reactions and to their relative paralysing potencies these and other data for the ten alkaloids are summarised in the table (p. 384), the paralysing potencies being given in micro-grammes (y) per frog. 

Karrer and Schmid have noted that the dimeride of C-curarine I does not give the characteristic colour reactions of this alkaloid with acids, but still gives that with ceric sulphate and potassium dichromate (p. 384). 

Alkaloid A. This forms a chloride, [CjoHjaONjJ+Cl", HjO, isomeric with the chlorides of toxiferine, C-eurarine I and C-curarine III the picrate has m.p. 269° (dec.). The chloride differs from the isomerides named, in potency, colour reactions and ultra-violet absorption spectrum. The chloride in 2N-sulphuric acid gives a carmine-red colour with potassium dichromate. 

EtOH). No methoxyl is present. It forms a series of crystalline double chlorides with cadmium, zinc or copper, does not give the thalleioquin reaction, and solutions of its sulphate are not fluorescent. It is diacidie and forms two series of salts of which the nitrate, B. HNOj, crystallises in minute prisms, m.p. 196°, insoluble in water. Cinchonamine hydrochloride, B. HCl, laminae or B. HCl. HjO, cubical crystals, has been suggested for use in the estimation of nitrates. When warmed with strong nitric acid the alkaloid furnishes dinitrocinchonamine. It gives an amorphous, monoacetyl derivative, and forms a methiodide, m.p. 208 , which with silver oxide yields an amorphous methylcinchonamine. Raymond-Hamet found that cinchonamine ves typical indole colour reactions and is probably an indole alkaloid. This seems to have been... 

The free 2-position in the pyrrole ring (B) explains the indole colour reactions given by these acids and the parent alkaloids. 

Strychnicine. This alkaloid, isolated from nux-vomica leaves grown in. lava, forms needles, m.p. 240° dec.), and is characterised by the following colour reaction. When sodium hydroxide solution is added drop by drop to a solution of a salt of the alkaloid in water, the precipitate formed dissolves on addition of more alkali, forming an orange-coloured liquid which develops a violet colour on addition of hydrochloric acid. Strychnicine is scarcely poisonous, but is said to produce tetanus in frogs. 

The names, extended linear formulas, yields and typical colour reaction of the nine alkaloids are given in the table on p. 761. 

Rauwolscine gives colour reactions like those of yohimbine and the absorption curves of the hydrochlorides of the two alkaloids are very similar. Heated to 300°/5 mm. rauwolscinic acid forms barman (p. 490) and 3-ethylindole and on fusion with potassium hydroxide decomposes into indole-2-carboxylic acid, isophthalic acid, barman and an unidentified indole derivative. Rauwolscine itself on distillation with zinc dust produces barman, 2-methylindole (scatole) and tsoquinoline. It is suggested that the alkaloid has the skeletal strueture suggested by Seholz (formula XIV, p. 508) for yohimbine, the positions of the hydroxyl and earbomethoxy grouf s being still imdetermined. 

Methods for the isolation and estimation of the alkaloids of the root are described. The seeds of the plant contain alkaloids giving colour reactions different from those of the root alkaloids. 

A phytochemical investigation of taxine in the yew has been conducted by Kuhn and Schafer, who have devised special methods for the detection, estimation and purification of the alkaloid. Masson states that Taxus canadensis contains an alkaloid giving the colour reactions of taxine but different from it in being crystalline and having m.p. 238-9° no ephedrine was present. 

Leptactina senegambica (Rubiaceas). The root-bark contains about 1 per cent, of alkaloids, including leptactinine, m.p. 264f-6°, which forms a picrate, m.p. 258° (dec.), picrolonate, m.p. 196°, and styphnate, m.p. 240-2°. The colour reactions with numerous alkaloidal reagents are recorded, some of which indicate that an indole nucleus is present. Pharmacological effects of an extract of the root bark are described (Paris and Bouquet, Ann. pharm. franc., 1946, 4, 233). 

N ic opine was first isolated by Dobbie and Lauder from the last mother liquors from the processing of the opium alkaloids after all other bases had been eliminated [1], This remains the only source of the base. The method of isolation has since been improved and the alkaloid can ho separated from codeine through the sulphates [2], The base was first allotted the formula C18H2404N and the name hydroxycodeine it was shown to contain one —OMe, one —NMe, and to be a tertiary base. Its colour reactions and ultra-violet absorption spectrum are practically idontical with those of codeine [1]. 

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