Peppermint, flavor compounds

The odor of a freshly crushed mint leaf, like many plant odors, is due to the presence in the plant of volatile C10 and Ci5 compounds, which are called terpenes. Isolation of these substances from the various parts of plants, even from the wood in some cases, by steam distillation or ether extraction gives what are known as essential oils. These are widely used in perfumery, as food flavorings and medicines, and as solvents. Among the typical essential oils are those obtained from cloves, roses, lavender, citronella, eucalyptus, peppermint, camphor, sandalwood, cedar, and turpentine. Such substances are of interest to us here because, as was pointed out by Wallach in 1887 and reemphasized by Ruzicka in 1935, the components of the essential oils can be regarded as derived from isoprene ... 

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)... 

D-Limonene is a compound found in many natural oils, including orange, lemon, grapefruit, berry, leaf, caraway, dill, bergamot, peppermint, and spearmint, and is used as a flavor additive in some foods, beverages, and chewing gum. 

Extraction of Essential Oils from Plants. Essential oils are aromatic substances widely used in the perfume industry, the pharmaceutical sector, and the food and human nutrition field. They are mixtures of more than 200 compounds that can be grouped basically into two fractions a volatile fraction, which constitutes 90-95% of the whole oil, and a nonvolatile residue, which constitutes the remaining 5-10%. The isolation, concentration, and purification of essential oils have been important processes for many years, as a consequence of the widespread use of these compounds. The common methods used are mainly based on solvent extraction and steam distillation. SFE has been used for the extraction of essential oils from plants, in an attempt to avoid the drawbacks linked to conventional techniques (57). Such is the case with the extraction of flavor and fragrance compounds, such as those from rose (58), rosemary (59), peppermint (60), eucalyptus (61), and guajava (62). The on-line coupling of the extraction and separation ietermi-nation steps (by SFE-GC-FID) has been proposed successfully for the analysis of herbs (63) and for vetiver essential oil (64). 

Professor Rufus T. Firefly of Fredonia State University wanted to stump his ace chemistry student. Sea Water (C-H2O, alias formaldehyde). The professor asked Sea Water to deduce the structure of menthol, the principal flavoring constituent of peppermint, on the basis of the following data the molecular formula of menthol is C10H20O when heated in the presence of sulfuric acid, a dehydration reaction ensues to form compound A ozonolysis of compound A followed by a reductive workup yields 3,7-dimethyl-6-oxo-octanal menthol also reacts with nitric acid and vanadium oxide, when heated, to form 2-isopropyl-5-methyl-hexanedioic acid. 

C, IH, gO, Mr 164.25. a pale yellow oil with a jasmin(e) odor resembling that of celery. Bp. 134-135 °C (1.6 kPa), LD50 (rat p. o.) 5 g/kg, soluble in alcohol and other organic solvents, practically insoluble in water. Occurrence With ca. 3% content in jasmin(e) absolute J. is one of the decisive compounds for jasmin(e) odor and is also contained, among others, in orange flower absolute, peppermint oils, and tea flavor. For synthesis, see LiV. ... 

IR-l-0cten-3-ol (Matsutake alcohol). CgH, 0, Mr 128.21, bp. 175 °C, [alg -20.2° LDjo (rat p.o.) 340 mg/kg. A typical mushrooms aroma constituent (olfactory threshold 1 ppb ) with an earthy-fungal odor impact compound in mushroom and Camem-bert flavor (see cheese flavor), but also occurring in many essential oils and flavors, e.g., in lavender, peppermint, rosemary, and thyme oil, as well as seafood flavors. Only the (/ )-enantiomer occurring in 90-97% enantiomeric excess possesses the pure fungus odor, the (S)-compound has a more vegetable-like odor. 

CHAiUNCt Natural (—)-menthol, the volatile oil primarily responsible for the flavor and aroma of peppermint, is the li ,25,5i -stereoisomer. (a) Identify (-)-menthol from the structures you drew for Problem 50, part (b). (b) Another of the naturally occurring diastereomers of menthol is (+)-isomenthol, the 15,2i ,5i -stereoisomer. Identify (+ )-isomenthol among your structures, (c) A third is (+)-neomenthol, the 15,25,5/f-compound. Find (+)-neomenthol among your structures, (d) Based on your understanding of the conformations of substituted cyclohexanes (Section 4-4), what is the stability order (from most stable to least) for the three diastereomers, menthol, isomenthol, and neomenthol ... 

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