Кастореум

Both beaver sexes have a pair of castor sacs and a pair of anal glands, located in two cavities under the skin between the pelvis and the base of the tail. The castor sacs are not true glands, endocrine or exocrine, on a cellular level, so the names preputial glands, castor glands and scent glands are misnomers. The castor sacs secrete castoreum, a liquid substance used mainly for marking territory. Beavers mark their territories by constructing scent mounds made of mud and vegetation, scented with castoreum. Scent marking increases in spring, during the dispersal of yearlings, to deter interlopers. Anal glands produce an oily substance which the beaver uses as a waterproof ointment for its coat. There are two extant species of beaver: the North American beaver (Castor canadensis) and the Eurasian beaver (C. fiber).

Canadian pouches are wrinkled, pear-shaped, almost flat, from 6 to 15 cm long and 4 to 8 cm wide. Siberian pouches are ovoid and smooth, slightly larger in size, but valued less commercially.

Chemical composition

At least 24 compounds are known constituents of beaver castoreum. Several of these have pheromonal activity, of which the phenols 4-ethylphenol and catechol and the ketones acetophenone and 3-hydroxyacetophenone are strongest. Five additional compounds elicit a weaker response: 4-methylcatechol, 4-methoxyacetophenone, 5-methoxysalicylic acid, salicylaldehyde and 3-hydroxybenzoic acid. There are also oxygen-containing monoterpenes such as isopinocamphone, pinocamphone, and two linalool oxides and their acetates. Other compounds are benzoic acid, benzyl alcohol, borneol, o-cresol, 4-(4'-hydroxyphenyl)-2-butanone, hydroquinone and phenol. Those compounds are gathered from plant food. Castoreum also contains nupharamine alkaloids, castoramine and cis-cyclohexane-1,2-diol.

A resinous and crystalline material (1 to 2%) has been identified in castoreum, together with a butter-like portion containing albumins, fats, urates, salts and probably cholesterols. Castoreum contains castorin (0.33 to 2.5%), volatile oil (1 to 2%), benzoic acid, salicylic acid and cinnamic acid, among other constituents. The intense, leathery odour of castoreum obtained from Siberian beavers is caused largely by phenolic compounds, such as 4-alkylphenols and catechol derivatives, which the beavers take in with their food and excrete into their abdominal pouches.

One minor component, 5-(3'-furyl)-8-methylindolizidine, is a nupharamine that makes up less than 0.0002% of castoreum. It has an indolizidine skeleton, a ring system made of one six-membered and two five-membered rings. Researchers at the University of Mainz in Germany determined the stereochemistry of this component by total synthesis, and the all-cis form proved identical to the natural product.

Food regulation and other uses

In the United States, the Food and Drug Administration lists castoreum extract as a generally recognized as safe (GRAS) food additive. In 1965, castoreum extract and castoreum liquid were added to the GRAS program (FEMA 2261 and 2262). Castoreum extract is rarely used as a food additive. Castoreum was also considered as an ingredient to flavour and scent cigarettes.

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