Spearmint, odor

Colorless, yellow or greenish-yellow liq characteristic Spearmint odor and taste, djj 0.917-0.934, ajf —48 to -59 , njf 1,4820-1,4900. Very slightly sol in water sol in equal vol 80% alcohol. Keep welt closed, cool and protected from light. 

Terpenes are widely used as pharmaceutical excipients. The odor of some terpenes such as carvone, limonene, and menthol are stereospecifically different [21-23]. For example, S-(-l-) carvone has the odor of caraway, while the R enantiomer has a spearmint odor [20]. In the case of limonene, the R isomer has an orange odor, whereas its antipode has a lemon odor. 

The human body can distinguish between enantiomers. For example, consider the enantiomers of limonene. The R-(+) enantiomer has the odor of orange and the S-(-) enantiomer the odor of lemon. The designation (+) indicates that plane polarized light is rotated in the clockwise direction or that the compound is dextrorotatory and (-) indicates counterclockwise rotation, also known as levorotatory. R and S indicate the positioning of the substituents on the chiral carbon. Some R compounds are dextrorotatory and other R compounds are levorotatory. R-(-) carvone has a spearmint odor and S-(+) carvone has a caraway odor. R-(-) amphetamine has a musty odor and S-(+) a fecal odor. There are examples of other compounds where enantiomers do not have different odors, but there are several examples that prove that enantiomers can have different odors [30]. 

For instance, R- and S-carvone are enantiomers the i -isomer has a caraway odor whereas the S-isomer has a spearmint odor. 

Chiral compounds are frequently foimd among the flavor volatiles of fruits and, like many naturally occurring chiral compounds, one enantiomer usually exists with a greater preponderance when compared with its antipode. Chiral odor compounds may show qualitative and quantitative differences in their odor properties (7). For example, (/ )-(+)-limonene has an orange-like aroma while (5)-(-)-limonene is turpentine-like (5)-(+)-carvone is characteristic of caraway while its enantiomer has a spearmint odor (2). However, other chiral compounds, such as y 6-lactones, show very little enantioselectivity of odor perception (7). The occurrence of chiral flavor compounds in enantiomeric excess provides the analyst with a means of authenticating natural flavorings, essential oils, and other plant extracts. The advent of cyclodextrin-based gas chromatography stationary phases has resulted in considerable activity in the analysis of chiral compounds in flavor extracts of fruits, spices and other plants (i-7). 

Enantiomers can have striking differences however m properties that depend on the arrangement of atoms m space Take for example the enantiomeric forms of carvone (R) (—) Carvone is the principal component of spearmint oil Its enantiomer (5) (+) carvone is the principal component of caraway seed oil The two enantiomers do not smell the same each has its own characteristic odor... 

Limonene (+15) is an important raw material for producing (-)-carvone [6485-40-1]. The process uses nitrosyl chloride and proceeds via nitrosochloride and oxime (78,79). The (-)-carvone (40) is found as the main component of spearmint oil and the (+)-carvone produced from (—)-limonene has the characteristic odor of diU. 

Examine actual three-dimensional structures for the twc enantiomers of carvone. One occurs naturally in carawa> while the other is found in spearmint oil, and are responsible for the characteristic odors of these materials. Determine which form, R or S, is responsible for which odor. 

Linalol is found very widely distributed in essential oils. It forms the principal constituent, in the free state, of oil of linaloe, and the chief odorous constituent, in the form of esters, in bergamot and lavender oils. It is also found in ylang-ylang, rose, champaca leaf, cinnamon, petit-grain, spike, geranium, lemon, spearmint, and numerous. other essential oils. 

Carvone, a substance responsible for the odor of spearmint, has the following structure. Tell how many hydrogens are bonded to each carbon, and give the molecular formula of carvone. 

Carvone is an unsaturated ketone responsible for the odor of spearmint. If car-vone has M+ = 150 in its mass spectrum and contains three double bonds and one ring, what is its molecular formula ... 

Aldehydes occur naturally in essential oils and contribute to the flavors of fruits and the odors of plants. Benzaldehyde, C6H5CHO (8), contributes to the characteristic aroma of cherries and almonds. Cinnamaldehvde (9) is found in cinnamon, and vanilla extract contains vanillin (10), which is present in oil of vanilla. Ketones can also be fragrant. For example, carvone (Section 18.1) is the essential oil of spearmint. 

The mammalian olfactory system possesses enormous discriminatory power. It is claimed that humans can perceive many thousands of different odorous molecules, termed odorants. Even slight alterations in the structure of an odorant can lead to profound changes in perceived odor quality. One commonly cited example is carvone, whose L- and D-stereoisomers are perceived as spearmint and caraway, respectively. However, more subtle molecular alterations can also generate striking changes in perception. 

Spearmint oils are obtained by steam distillation of the flowering herbs of Mentha spicata L. (native spearmint) and Mentha cardiaca Ger. (Scotch spearmint). They are colorless to yellow-green liquids with a fresh, caraway-minty odor. 

Absorption, metabolism, and biological activities of organic compounds are influenced by molecular interactions with asymmetric biomolecules. These interactions, which involve hydrophobic, electrostatic, inductive, dipole-dipole, hydrogen bonding, van der Waals forces, steric hindrance, and inclusion complex formation give rise to enantioselective differentiation. Within a series of similar structures, substantial differences in biological effects, molecular mechanism of action, distribution, or metabolic events may be observed. For example, (f )-carvone (I) has the odor of spearmint whereas (.Sb-carvone (2) has the odor of caraway. 

For example, our ability to taste and smell is regulated by chiral molecules in our mouths and noses that act as receptors to sense foreign substances. We can anticipate, then, that enantiomers may interact differently with the receptor molecules and induce different sensations. This appears to be the case. The two enantiomers of the amino acid, leucine, for example, have different tastes—one is bitter, whereas the other is sweet. Enantiomers also can smell different, as is known from the odors of the two carvones. One has the odor of caraway and the other of spearmint. 

As another example of the effects of shape and molecular handedness, look at the substance called carvone. Left-handed carvone occurs in mint plants and has the characteristic odor of spearmint, while right-handed carvone occurs in several herbs and has the odor of caraway seeds. Again, the two structures are the same except for their shapes, yet they have entirely different odors. 

R)-Carvone and (S)-carvone are enantiomers and can be distinguished from each other by their optical rotations, by circular dichroism and by smell. Laevorotatory (R)-carvone has a spearmint smell (spearmint = Mentha spicata), whilst (S)-(+)-carvone has a caraway odor. 

Often the difference in odor between two such forms is surprisingly great. For example, dextro carvone is the main odor constituent of caraway oil, while its optical isomer levo carvone is typical of spearmint. Among other materials that occur in important dextro and levo forms are citronellol and rose oxide. 

Many other ketones and aldehydes are used as flavorings and additives to foods, drugs, and other products. For example, benzaldehyde is the primary component of almond extract, and (- )-carvone gives spearmint chewing gum its minty flavor. Table 18-4 lists some simple ketones and aldehydes with well-known odors and flavors. Pyrethrin, isolated frompyrethrum flowers, is commercially extracted for use as a natural insecticide. Natural or not, pyrethrin can cause severe allergic reactions, nausea, vomiting, and other toxic effects in animals. 

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