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Musk
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Musk is the name originally given to a substance with a penetrating odor obtained from a gland of the male musk deer, which is situated between its stomach and genitals. The substance has been used as a popular perfume fixative since ancient times and is one of the most expensive animal products in the world.
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Musk is the name originally given to a substance with a penetrating odor obtained from a gland of the male musk deer, which is situated between its stomach and genitals. The substance has been used as a popular perfume fixative since ancient times and is one of the most expensive animal products in the world. The name, originated from Sanskrit meaning "testicle," has come to encompass a wide variety of substances with somewhat similar odors although many of them are quite different in their chemical structures. They include glandular secretions from animals other than the musk deer, numerous plants emitting similar fragrances, and artificial substances with similar odors.
Until the late 19th century, the natural musk were used extensively in perfumery until economic and ethical motives led to the adoption of synthetic musk, which are used almost exclusively. The organic compound primarily responsible for the characteristic odor of musk is muscone.
Modern use of natural musk pods is limited to Traditional Chinese medicine.
Natural sources
Musk deer
Musk was unknown in classical antiquity and reference to it does not appear until the 5th century when it is mentioned in the Talmud (Brachot 43.)as a animal based fragrance. The 6th century Greek explorer Cosmas Indicopleustes mentioned it as a product obtained from India. Soon afterwards Arab and Byzantine perfume makers began to use it, and it acquired a reputation as an aphrodisiac. Under the Abbasid Empire of Arabs it was highly regarded, and the caliphs of Baghdad used it lavishly. In the early 9th century, Al-Kindi included it in a large number of his perfume recipes and it became one of the important luxury items brought by Arabian ships from the East. The etymology of the name musk, originating from Sanskrit via Middle Persian , Late Greek (moschos), Late Latin muscus, Middle French musc and Middle English muske, hints at its trade route.
The musk deer belongs to the family Moschidae and lives in Pakistan, India, Tibet, China, Siberia and Mongolia. To obtain the musk, the deer is killed and its gland, also called "musk pod", is removed. It is dried either in the sun, on a hot stone, or by immersion in hot oil. Upon drying, the reddish-brown paste turns into a black granular material called "musk grain", which is used for alcoholic solutions. The aroma of the tincture becomes more intense during storage and gives a pleasant odor only after it is considerably diluted. No other natural substance has such a complex aroma associated with so many contradictory descriptions; however, it is usually described abstractly as animalic, earthy and woody or something akin to the odor of baby's skin.
Good musk is of a dark purplish color, dry, smooth and unctuous to the touch, and bitter in taste. It dissolves in boiling water to the extent of about one-half; alcohol takes up one-third of the substance, and ether and chloroform dissolve still less. The grain of musk will distinctly scent millions of cubic feet of air without any appreciable loss of weight, and its scent is not only more penetrating but more persistent than that of any other known substance. In addition to its odoriferous principle, it contains ammonia, cholesterol, fatty matter, a bitter resinous substance, and other animal principles.
The best quality is Tonkin musk from Tibet and China, followed by Assam and Nepal musk, while Carbadine musk from Russian and Chinese Himalayan regions are considered inferior. Obtaining one kilogram (2.2 lb) of musk grains requires between thirty and fifty deer, making musk tinctures highly expensive. At the beginning of the 19th century, Tonkin musk grains cost about twice their weight in gold.
Musk has been a key constituent in many perfumes since its discovery, being held to give a perfume long-lasting power as a fixative. Despite its high price, musk tinctures were used in perfumery until 1979, when musk deers were protected as an endangered species by the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES). Today the trade quantity of the natural musk is controlled by CITES but illegal poaching and trading continues. An illegal shipment of of Chinese musk from the musk deer was seized in Japan in 1987, an amount corresponding to approximately 100,000 deer killed.
Other animals
Muskrat (Ondatra zibethicus), a rodent native to North America, has been known since the 17th century to secrete a glandular substance with a musky odor. A chemical means of extracting it was discovered in the 1940s, but it did not prove commercially worthwhile.
Glandular substances with musk-like odor are also obtained from the Musk Duck (Biziura lobata) of southern Australia, the musk shrew, the musk beetle (Aromia moschata), the musk turtle, the alligator of Central America, and from several other animals.
In crocodiles, there are two pairs of musk glands, one pair situated at the corner of the jaw and the other pair in the cloaca. Musk glands are also found in snakes.
Plants
Some plants such as Angelica archangelica or Abelmoschus moschatus produce musky smelling macrocyclic lactone compounds. These compounds are widely used in perfumery as substitutes for animal musk or to alter the smell of a mixture of other musks.
The plant sources include musk flower (Mimulus moschatus), the muskwood (Olearia argophylla) of the Guianas and West Indies, and the seeds of Abelmoschus moschatus (musk seeds).
Artificial compounds
Since obtaining the deer musk requires killing the endangered animal, nearly all musk fragrance used in perfumery today is synthesis, or called "white musk". They can be divided into three major classes — aromatic nitro musks, polycyclic musk compounds, and macrocyclic musk compounds. The first two groups have broad uses in industry ranging from cosmetics to detergents. However, the detection of the first two chemical groups in human and environmental samples as well as their carcinogenic properties initiated a public debate on the use of these compounds and a ban or reduction of their use in many regions of the world. Macrocyclic musk compounds are expected to replace them since these compounds appear to be safer.
Nitro-musks
An artificial musk was obtained by Albert Baur in 1888 by condensing toluene with isobutyl bromide in the presence of aluminium chloride, and nitrating the product. It was discovered accidentally as a result of Baur's attempts at producing a more effective form of trinitrotoluene. It appears that the odour depends upon the symmetry of the three nitro groups. Following the discovery of Musk Baur, the first nitro-musk, many similar preparations have been made. Notable nitro-musks include
- Musk Baur (Tonquinol)
- Musk Ketone
- Musk Xylene
- Musk Ambrette
- Moskene
Polycyclic musks
An artificial musk that contains more than one ring in its molecular structure. These musks became popular after World War II and slowly supplanted the nitro-musks in popularity due to the latter's toxicity and molecular instability.
The creation of this class of musks was largely prompted through the need for eliminating the nitro functional group from nitro-musks due to their photochemical reactivity and their instability in alkaline medium. This shown to be possible through the discovery of Ambral, a non-nitro aromatic musk, which promoted research in the development of nitro-free musks. This led to the eventual discovery of Phantolide, so named due to its commercialization by Givaudan without initial knowledge of it chemical structure (elucidated 4 years later). While poorer in smell strength, the performance and stability of this compound class in harsh detergents led to its common use, which spurred further development of other polycyclic musks including Galaxolide.
However it was discovered in the 1990s that polycyclic musks are also potentially harmful in that they can disrupt cellular metabolism. Many of these musks were used in large quantities to scent laundry detergents. Commonly used polycyclic musks include
- Galaxolide (HHCB)
- Tonalide (Musk Plus, AHTN)
- Phantolide
- Celestolide (Crysolide)
- Traesolide
Macrocyclic musks
A class of artificial musk consisting of a single ring composed of more than 6 carbons (often 10-15). Of all artificial musks, these most resemble the primary odoriferous compound from Tonkin musk in its "large ringed" structure. While the macrocyclic musks extracted from plants consists of large ringed lactones, all animal derived macrocyclic musks are ketones.
Although muscone, the primary macrocyclic compound of musk was long known, it was only in 1926 that Leopold Ruzicka was able to synthesize this compound in very small quantities. Despite this discovery and the discovery of other pathways for synthesis of macrocyclic musks, compound of this class were not commercially produced and commonly utilized until the late 1990s due to difficulties in their synthesis and consequently higher price.
About half the human population are anosmics (unable to smell) to macrocyclic musks, possibly due to its high molecular weight. Common macrocyclic musks include:
- Ethylene Brassilate
- Globalide (Habanolide)
- Ambrettolide
- Muscone
- Thibetolide (Exaltolide)
- Velvione
Alicyclic musks
Alicyclic musks, otherwise known as cycloakyl ester or linear musks, are relatively novel class of musk compounds. The first compound of this class was introduced 1975 with Cyclomusk, though similar structure were noted earlier in citronellyl oxalate and Rosamusk. Alicyclic musks are dramatically different in structure than previous musks (aromatic, polycyclic, macrocyclic) in that they are modified akyl esters. Although they were discovered more than 10 years before, it was only in 1990 with the discovery and introduction of Helvetolide at Firmenich that a compound of this class was produced at a commercial scale. Romandolide, a more ambrette and less fruity alicyclic musk compared to Helvetolide was introduced ten years later. Common musks of this class include:
- Cyclomusk
- Helvetolide
- Romandolide
See also
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