Mentha arvensis menthol from

The inexpensive natural alcohol ( )-menthol is obtained from the natural souree, Mentha arvensis, or from myreene via a homogenously eatalysed route (Takasago process) in multi-tonne quantities (Scheme 2.8). 

Artificial materials include aUphatic, aromatic, and terpene compounds that are made synthetically as opposed to those isolated from natural sources. As an example, ben2aldehyde may be made synthetically or obtained from oil of bitter almond (51) and t-menthol may be made synthetically or isolated from oil of Mentha arvensis var. to give Bra2iUan mint oil or com mint oil. 

Natural menthol is obtained by freezing the essential oU, eg, Mentha arvensis and the menthol crystals ate separated by centrifuging the supernatant hquid away from the crystals. The supernatant oU is then caUed dementholized cornmint oU. Impurities in the crystals come from the essential oU and usuaUy give a slight peppermint aroma to the crystallized menthol. The cornmint oU, rich in (—)-menthone (- 28%) and (—)-menthol (- 32%), can be further processed to give additional natural menthol. 

Menthol is the isomer that occurs most widely in nature. It is the main component of peppermint and cornmint oils obtained from the Mentha piperita and Mentha arvensis species. Esterified menthol also occurs in these oils (e.g., as the acetate and iso valerate). Other menthol stereoisomers may be present in these oils as well. 

Menthol from Cornmint Oil. Mentha arvensis oils, which may contain 70-80% free (—)-menthol, are cooled and the crystals separated by centrifugation. Since the crystalline product contains traces of cornmint oil, this menthol has a slightly herbaceous-minty note. Pure (—)-menthol is obtained by recrystallization from solvents with low boiling points. 

Most menthol is isolated from peppermint oils, especially from crude oil from Mentha arvensis from India. But menthol can also be prepared by chemical synthesis. There are two important commercial processes for the synthesis of menthol. One is based on a renewable resource, /1-pinene from turpentine, and the other on m-cresol from petrochemical origin (Scheme 13.3). 

Mentha Arvensis Oil, Partially Dementholized, occurs as a colorless to yellow liquid with a characteristic minty odor. It is the portion of oil remaining after the partial removal of menthol, by freezing operations only, from the oil of Mentha arvensis var. piperascens Holmes (forma piperascens Malin-vaud) (Fam. Lamiaceae). It is soluble in most fixed oils, in mineral oil, and in propylene glycol. It is insoluble in glycerin. 

Menthol is a white, waxy crystalline compound having a strong odor of peppermint. Its main source is oil of peppermint from the plant, Mentha arvensis. It is an ingredient of decongestant ointments and nasal sprays and is also used to flavour toothpaste and cigarettes. 

Production. Several processes exist for the industrial production of (-(-menthol [77a]. Currently, only the routes starting from myrcene or thymol are of commercial importance. The major portion of the world-wide annual demand of about 15,000 t is obtained from Mentha arvensis oil (see p. 216). In detail, the processes are the following ... 

Menthol can be extracted from various species of mint. Commint (Mentha arvensis) contains the highest levels of 1-menthol and therefore is the major variety cultivated for menthol production. Mint is grown in China, India, Brazil and the United States. Because of the vagaries of climate and competition for land from other agricultural products, the supply of natural menthol is not stable. Price and availability fluctuate and these movements have a major impact on the economics of the various synthetic processes for 1-menthol. When natural menthol is scarce, the synthetic materials command a high price and marginal processes become economically attractive. When the natural material is in abundant supply, only the more efficient of the synthetic processes will compete. The most competitive synthetic processes are those of Symrise and Takasago hence their market domination. 

Menthol is the principal component of Japanese peppermint oil. In Japan it has been obtained since the 17th century from corn mint (Mentha arvensis L.) (Fig. 3.25). Important areas of cultivation are at present in India, China, Japan,... 

Menthol from natural sources is obtained predominantly from the essential oil of corn mint Mentha arvensis), which is produced by steam distillation or a distdlation/extraction procedure using supercritical carbon dioxide cf. section 5.11 Caffeine). The menthol is frozen out and the crystalline mass centrifuged. Traces of impurities confer a slightly minty aroma to natural menthol. 

Definition Essential oil obtained by steam distillation of the fresh, owering aerial parts, recently gathered from Mentha canadensis L. [syn. Mentha arvensis L. var. glabrata (Benth) Fern., Mentha arvensis var. piperascens Malinv. ex Holmes], followed by partial separation of menthol by crystallization. 

Menthol is a major component of various mint oils. The plant oil, often referred to as peppermint oil (from Mentha piperita) or cornmint oil (from Mentha arvensis), is readily extracted from the plant by steam distillation (Wichtel, 2002). It has a pleasant typical minty odor and taste, and is widely... 

Worldwide, 12 000 tonnes of (—)-menthol are produced per year (1998). The majority is natural menthol from Mentha arvensis or Mentha piperita and only a quarter is produced synthetically. Nevertheless, the synthetic route is important as the price from natural resources fluctuates if the availability is limited due to bad... 

Many monoterpenes have found application in perfumery, aromatherapy, as cosmetics and insecticides. Menthol, a constituent of essential oils from Mentha species, is the most widely used monoterpene. It is contained in pharmaceuticals, oral health care products, chewing gums, and tobacco products (Croteau et al., 2005). More than 7,000 t of menthol are produced every year either by total synthesis or from the steam-distilled essential oil of corn-mint Mentha arvensis var. piperascens). The cooling sensation stimulated by menthol is caused by excitation of cation channels that serve as thermal receptors (Jordt et al, 2003). 

Cornmint oil is obtained from flowering tops and leaves of Mentha canadensis L. (M. arvensis L., Japanese mint, Lamiaceae), yield of 0.5-2%. The content of menthol achieved 90% of the oil. Menthol is partly separated by crystallization and the remaining oil has appearance and odor resembling peppermint oil. The oil is used as a cheap alternative to peppermint oil, but easily recognized organoleptically because of its harsh flavor. Commint oil can be used in herbal blends and liquor flavors. Menthol obtained from the oil is mainly used in dmg and cigarette production. 

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