Alkaloidal reagents

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). 

It yields salts with the usual alkaloidal reagents, such as platinum, gold, and mercuric chlorides. Its constitution is—... 

Scheme IS. Lounasmaa synthesis of 4-benzyltropane alkaloids. Reagents i, benzaldehyde, KOH ii, H2/Pd iii, LiAIH4 iv, RCOCI.

Scheme 46. Synthesis of 3-arylisoquinoline alkaloids. Reagents a, BrCN b, CH3NH2 c, 10% KOH, EtOH d, Pd, tetralin e, NaBH3CN f, T1(N03)3, MeOH g, 5% HC1 h, H2CrOA, H2SO i, CH2N2.

Scheme 94. Synthesis of chilenine (380) and its conversion to related alkaloids. Reagents a, aq NH3 b, py-HCl, py c, Zn, HCl-AcOH d, NaBH4 e, Mel, MeOH f, AcOH g, NaOH, aq MeOH h, CF3COOH.

Errera examined the distribution of alkaloids in plant tissues by histochemistry and found that alkaloids were present in active tissues near the vegetative points, ovule, epidermis and the layer just inside of it, hair, peripheral layers of fruits and seeds, vascular bundle, cork cambium, cork tissues, and latex tube (9). Molisch microscopically investigated 15 kinds of alkaloids as distinguishable crystal forms after treatment with acids or alkaloid reagents, and then histochem-ically examined them in plant tissue and cell sections following treatment with acids or alkaloid reagents (9). Tunmann and Rosenthaler observed histochemi-cally the distribution of alkaloids in tissues and cells of 36 families of plants 10). 

Alkaloids are invariably found in combination with acids forming salts which dissolve in water or alcohol. They are composed of carbon, hydrogen and nitrogen. Some contain oxygen. They are precipitated from saline solutions by the addition of alkalies. They are mostly colorless and crystallizable. They can be precipitated by one or more of the following alkaloidal reagents tannic acid, gold chloride, phospho-molybdic acid, picric acid and potassio-mercuric iodide. 

Homatropine Methylbromide, USP. Homatropini methylbromidc. 3a-hydroxy-8-methyl-1 aN.Sa/f-tropanium bromide mandelate (Novatropine, Mesopin), occurs as a bitter. white, odorless powder and is affected by light. Tbe compound is readily soluble in water and alcohol but insoluble in ether. The pH of a 1% solution is 5.9 and that of a 10% solution is 4.5. Although a solution of the compound yields a precipitate with alkaloidal reagents, such as mercuric potassium iodide test solution, addition of alkali hydroxides or carbonates does not cause the precipitate thil occurs with nonquatemary nitrogen salts (c.g.. atropine, homatropine). 

Codeine Sulfate, USP. Ctxleine sulfate is prepared by neutralizing an aqueous suspension of codeine with diluted sulfuric acid and then effecting crystallization. It cK Curs us white cry.stals. usually needle-like, or as a white cry.stalline powder. The salt is efflorescent and light sensitive. It is. soluble in water (1 30. 1 6.S at 80°). much less soluble in alcohol (1 1.280). and insoluble in ether or chloroform. This salt of codeine is prescribed frequently but is not as suitable os the pho.sphate for liquid preparations. Solutions of the sulfate and the phosphate are incompatible with alkaloidal reagents and alkaline sub.stances. 

Monohydrate, faintly bitter crystals producing transient numbness ol the tongue. Stable in air. When anhydr mp 190-192. One gram dissolves in 50 m] water. Freely so] in boiling water, alcohol, chloroform. Insol in ether. Incompatible with alkalies and their carbonates and the usual alkaloidal reagents. Aq solns are stable and are not dec by boiling. 

USE Removing green color from glass during its manuf alkaloidal reagent. 

In their behavior with alkaloidal reagents from those of neurin in forming no precipitate wth tannic acid, and in forming a voluminous white precipitate with phosphomolybdic acid, which becomes crystalline on-standing. 

III. The Ordinary Alkaloidal Reagents,—The reagents which precipitate alkaloids from their solutions react also with proteins. Among these may be mentioned phosphotungstic acid, phosphomolybdic acid, tannic acid, picric acid, potassium mercuric iodide, and potassium bismuth iodide. The alkaloidal reagents precipitate the majority of the proteins in acid solution only. 

Echinopsine is a weak base. Solutions of its salts, which exhibit no fluorescence, ve precipitates with the usual alkaloid reagents, although not at great dilution. The most senidtive reag ts are iodine and phosphomolybdic acid the former has been employed for investigating the distribution of the alkaloid in the tissues of Eehinopa (1). With ferric chloride, the alkaloid gives an intense blood-red coloration. 

The xanthines are alkaloids, but they do not react to the classical alkaloid reagents that are discussed in 3.3 Alkaloids. 

Detection, The alkaloid reagents (Nos. 98, 147, 245, for example) have been those principally used for detecting aminoalcohols and quaternary ammonium salts. The dipicrylamine reagent (No. 90) is... 

Willstatter expressed his mature conclusions at Cornell University in 1926, and in the same place on 29 April of that year, J. B. Sumner obtained from jack bean a new protein that crystallizes beautifully and whose solutions possess to an extraordinary degree the ability to decompose urea to ammonium carbonate. Sumner marshaled arguments that his octahedral crystals were practically uncontaminated with any other material. Solutions of the crystals exhibited greater urease activity per unit weight than any other preparation of the enzyme. Solvents that did not dissolve the crystals had little or no urease activity. The crystals were proteins by every test, and in solution urease activity behaved like a protein in its reactions with heavy metals, alkaloid reagents, alcohol, and acids. 

Thiamine gives a number of colour reactions. With diazotized sulfanihc acid and formaldehyde a pink colour is produced with diazotized />-amino-acetophenone a red-purple colour. Potassium bismuth iodide gives an orange-red precipitate. Coloured precipitates are also obtained with picrolonic acid, gold chloride, mercuric chloride and iodine. Thiamine is further precipitated by picric acid and a variety of alkaloidal reagents. 

Since alkaloids often occur in minute quantities, classification based upon color reactions with various alkaloidal reagents is generally used. The individual members may sometimes be detected by means of their typical physiological behaviors. 

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