Definition

Nicotine alkaloid (plural nicotine alkaloids)

1. 1.    (chemistry) any of a range of related alkaloids found in various species of the genus Nicotiana, especially Nicotiana tabacum which is cultivated for the manufacture of cigarettes

ALKALOIDS

Most organic alkaloids are well-defined crystalline substances which unite with acids to form salts. In the plant they may exist in the free state, as Salts or as N-oxides. In addition to the elements carbon, hydrogen and nitrogen, most alkaloids contain oxygen. A few, such as nicotine from tobacco, are oxygen-free and are liquids

Knowledge of the solubility of alkaloids and their salts is of considerable pharmaceutical importance. Not only are alkaloidal substances often administered in solution, but also the differences in solubility between alkaloids and their salts provide methods for the isolation of alkaloids from the plant and their separation from the non-alkaloidal substances that are also present. While the solubility’s of different Alkaloids and salts show considerable variation, as might be expected from their extremely varied structure, it is true to say that the free bases are frequently scarcely soluble in water but highly soluble in organic solvents; with salts the reverse is often the case, these being usually soluble in water but scarcely soluble in organic solvents.

EXTRACTION OF  NICOTINE ALKALOIDS

Extraction methods vary with the scale and purpose of the operation, and with the raw material. For many research purposes chromatography gives both speedy and accurate results. However, if an appreciable quantity of alkaloid is required, one of the following general methods will usually serve.

Process A

The material is moistened with water and mixed with lime which combines with acids, tannins and other phenolic substances and sets free the alkaloids (if they exist in the plant as salts). Extraction is then carried out with organic solvents such as ether or petroleum spirit. The concentrated organic liquid is then shaken with aqueous acid and allowed to separate. Alkaloid salts are now in the aqueous liquid, Volatile liquid alkaloids such as nicotine and coniine are most conveniently isolated by distillation. An aqueous extract is made alkaline with caustic soda or sodium carbonate and the alkaloid distilled off in steam. Leaving most of the impurities behind in the remaining organic liquid.

Process B

The material is extracted with water or aqueous alcohol containing dilute acid. Pigments and other unwanted materials are removed by shaking with chloroform or other organic solvents. The free alkaloids are then precipitated by the addition of excess sodium bicarbonate or ammonia and separated by filtration or by extraction with organic solvents.

Large-scale extractions based on the above principles are sometimes done in the field and the crude mixtures of alkaloids afterwards sent to a factory for separation and purification.

The separation and final purification of a mixture of alkaloids may sometimes be done by fractional precipitation or by fractional crystallization of salts such as oxalates, tartrates or picrates (salts). Chromatographic methods are particularly suitable if the mixture is a complex one and if small quantities of alkaloids will suffice.