Menthol from peppermint oil

Monocyclic and bicyclic oxygenated terpenes include some familiar and interesting substances such as menthone and menthol from peppermint oil, 1,8-cineole from eucalyptus, and ascaridole, which is a naturally occurring peroxide from chenopodium oil ... 

Peppermint oil is the volatile oil extracted from the fresh leaves of the flowering plant of Mentha piperita via steam distillation. Peppermint oil contains not less than 44% menthol. American peppermint oil contains from 50 to 78% of free /-menthol (Fig. 13.12.1) and from 5 to 20% combined in various es-... 

Production. Many industrial processes exist for the production of menthols. For (—)-menthol, isolation from peppermint oil (see Mint Oils) competes with partial and total syntheses. When an optically active compound is used as a starting material, optical activity must be retained throughout the synthesis, which generally consists of several steps. Total syntheses or syntheses starting from optically inactive materials require either resolution of racemic mixtures or asymmetric synthesis of an intermediate. Recently used processes are the following ... 

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). 

PROBLEM 3.25 Menthol, a flavoring agent obtained from peppermint oil, contains carbon, hydrogen, and oxygen. On combustion analysis, 1.00 g of menthol yields 1.161 g of H20 and 2.818 g of C02. What is the empirical formula of menthol ... 

Oils may contain toxic compounds. For example, Myristicin is the compound that flavors nutmeg and mace it is also found in black pepper and carrot, parsley, and celery seeds. Used in culinary quantities, myristicin is only a flavoring. In massive doses, it causes hallucination. Thujone, the anise-flavored oil in wormwood, caused an epidemic of brain disease in drinkers addicted to the now-banned liquor absinthe. Sassafras contains a toxic oil similar to thujone, which is why it is no longer used to make root beer. Very high doses of menthol, from peppermint, may cause dangerous irregularities in the heart s rhythm (Weiss, 1997)... 

Menthol (Fig. 1.19) is a monoterpene natural product obtained from peppermint oil. Typical of terpenoids, menthol is only slightly soluble in water and is soluble in most organic solvents. The trans arrangement of the methyl and isopropyl substituents on the cyclohexane... 

Menthol is a compound that contains C, H and O. It is derived from peppermint oil and is used in cough drops and chest rubs. When 0.2393 g of menthol is subjected to carbon-hydrogen combustion analysis, 0.6735 g of C02 and 0.2760 g of H20 are obtained. 

Two-dimensional GC in the direct enantiomer separation of menthone, isomenthone and menthol with Ni(HFC)2 as the chiral main column has been reported by Bicchi et al. [92]. Werkhoff et al. [68] isolated these compounds from peppermint oils before stereoanalysis with permethylated p-cyclodextrin. 

Menthanes, which include menthol, menthonc, terpineol, and carvone, are some of the best known monoterpene-based chiral synthons in organic synthesis. They are all relatively inexpensive and are commercially available in bulk quantities. Menthols and their corresponding ketones, menthones. were first isolated from peppermint oils of various species of Mentha piperita L [30]. Menthones can exist in two diastereomeric forms, each with two enantiomers. The ones with the methyl and isopropyl groups in a Zrans-orientation are termed menthones, whereas those with the two in a cz.s-orientation are isomenthones. /-Menthone (22), also denoted as (7A,4S)-(-)-menthone. is the most abundant stereoisomer and is obtained by the dry distillation of the wood of Finns palustris Me II [31]. It can also be produced chemically by chromic acid oxidation of /-menthol (23) [32]. /-Menthone is commercially available in bulk quantities with optical purities of 90-98% ee [33]. 

Oil of Peppermint. Col perm in Mintec. Steam-distilled, volatile oil from fresh flowering plant Mentha piperita L, Labiatae. The Japanese oil, also known as oil of Poho, is the liq portion remaining after the separation of menthol from the oil of Mentha arvensts L., Labiatae. Constit Not less than 50% total menthol including 5 -9% esters ealed as menthyl acetate menthyl isovalerate, menthone, inactive pinene, /-limonene, cadinene, phellandrene, some acetaldehyde, isovaleric aldehyde, amyl alcohol, dimethyl sulfide. 

Rgure 24 HPTLC-FTIR Gram-Schmidt chromatogram from peppermint oil (A) and from a mixure of its ingredients (B) menthol 1.8 min. carvone 2.8 min, menthone 4.0 min, and menihylacetate 5.0 min. 

Many essential oils, such as those of citrus fruits, contain terpene hydrocarbons which contribute little to aroma but are readily au-tooxidized and pol)merized ( resin formation ). These undesirable oil constituents (for instance, limonene from orange oil) can be removed by fractional distillation. Fractional distillation is also used to enrich or isolate a single aroma compound. Usually, this compound is the dominant constituent of the essential oU. Examples of single aroma confounds isolated as the main constituent of an essential oil are 1,8-cineole from eucalyptus, 1(—)-menthol from peppermint, anethole from anise seed, eugenol from clove, or citral (mixture of geranial and neral, the pleasant odorous... 

GW 3.65 Menthol is a flavoring agent extracted from peppermint oil. It... 

Natural peppermint contains several components that, if ingested, lead to a cold sensation in the mouth. The best known and best understood is (-)-menthol (IV), which is the dominant component of the peppermint oil extracted from Mentha piperita and M. arvensia. 

Werkhoff P, Hopp R, Isolation and gas chromatographic separation of menthol and menthone enantiomers from natural peppermint oils, in Brunke EJ (ed.). Progress in Essential Oil Research, Walter de Gruyter, Berlin, Germany, pp. 529— 549, 1986. 

Natural menthol is obtained by freezing the essential oil, eg, Mentha arvensis, and the menthol crystals are separated by centrifuging the supernatant liquid away from the crystals. The supernatant oil is then called dementholized commint oil. Impurities in the crystals come from the essential oil and usually give a slight peppermint aroma to the crystallized menthol. The commint oil, rich in (—)-menthone ( 28%) and (—)-menthol ( - 32%), can be further... 

From Menthane.— Taking up these compounds in the same order in which we considered the terpenes themselves we have first the alcohols and ketones derived from menthane, the saturated mono-cyclic terpene. The more common alcohol is known as menthol, menthanol or terpanol and the corresponding ketone is named similarly menthone, menthanone or terpanone. Both of these compounds are present in Japanese, Russian and American peppermint oil the former occurring both as the free alcohol and as the acetic acid ester. Menthol is a crystalline solid, m.p. 42°, b.p. 213°. It has the characteristic peppermint odor and is used as a disinfectant and as a mild anesthetic for headache. Menthone is a liquid, b.p. 207°. The constitution of both compounds is proven by their relationship to thjrmol, i-methyl 3-... 

---