Caraway odour, -carvone

Monoterpenic ketones are frequently very important aromatic substances of many food raw materials, spices and medicinal herbs. Monocyclic ketone (-F)-carvone (8-50) is a key component of caraway and diU oils, where it is accompanied by (-F)-( )-dihydrocarvone, that is (lS,4S)-dihydrocarvone (8-50) that also possesses caraway odour. (-)-Carvone (8-50) is a typical component of spearmint essential oil, where it is accompanied by (-)-( )-dihydrocarvone, (lE,4E)-dihydrocarvone, which has the same odour (see Table 8.32). Isomeric ( )-menthone (8-50) and its precursor (-F)-pulegone (8-50) occur in the essential oils of the European pennyroyal Menthaptdegium, Lamiaceae), a traditional culinary herb and folk remedy, and other Mentha species (such as M. longifolia), as well as in marjoram essential oil. In the essential oil of mint, (-)-menthone is accompanied by (-F)-isomenthone (8-50) and other terpenoids. 

The major constituent of caraway oil is (+)-carvone, and the typical caraway odour is mainly due to this component. On the other hand, the typical minty smell of spearmint oil is due to its major component, (—)-carvone. These enantiomers are unusual in having quite different smells, i.e. they interact with nasal receptors quite differently. The two enantiomeric forms are shown here in their half-chair conformations. 

At the beginning of the 1970s there appeared works in Science and Nature concerning the relationships between odours and chirality. The authors have stated that the experimental evidence is in favour of the claim that the optical isomers of carvone have characteristically different odours, (-)-carvone resembling spearmint oil and (+)-carvone, caraway oil... 

The constituents recognised in caraway Oil are carvone. (i-limonene, dihvdrocarvom-, oai veol, and dibydrocurVcol, and Sp base having a nainoiic odour which hn.s not been investigated. 

Carvone (94) occurs as (+)-carvone, (-)-carvone or racemic carvone. (S)-(+)-Carvone is the main component of caraway oil (ca 60%) and dill oil and has a herbaceous odour reminiscent of caraway and dill seeds. (R)-(-)-Carvone occurs in spearmint oil at a concentration of 70-80% and has a herbaceous odour similar to spearmint [26]. (S)-(+)-Carvone (94) was used as substrate for bioconversions by selected microorganisms five... 

The importance of the scent molecule linking to a specific receptor in the nose is thought to be related to the shape of the molecule. The optical isomers d- and /-carvone are mirror images of each other, with different 3D molecular arrangements (Fig 5.10). This means that the d- and /-forms do not fit the same receptor sites and are responsible for different aromas. The c/-carvone smells of caraway, while the /-form has a minty odour. 

The difference between the odours of two optical isomers of carvone has been characterised by various authors. Russell and Hills have described that 4S-carvone has the odour of caraway and 4R-carvone has the odour of spearmint. They have stated that these observations lend a definite support to stereochemical considerations of odour pereeption... 

The chief constituent of dill oil is carvone (Gladstone, J. Chem. Soc. 1872, 25, 1), which is also the chief constituent of oil of caraway. There is, indeed, very little difference in the composition of these two oils both owe their odour in the main to the presence of this ketone, but, in the case of caraway oil, traces of sweet-smelling substances are present which give to the oil a secondary strawberry-like odour. 

Q8. (-)-Carvone (73) occurs in spearmint and its enantiomer (+)-carvone (74) is found in caraway seed. To the human sense of smell, these two enantiomers have different odours. Where is the stereogenic centre in 73 and in 74 What conclusions can be drawn about the human olfactory receptor site ... 

Carvone is the principal odour component of spearmint oil. Both the oil and synthetic 1-carvone are used as ingredients in mint flavours. The synthetic material is made from d-limonene, which is the major component of orange oil and therefore is available as a by-product of orange juice production. Quest International is the world s major producer of 1-carvone. The classical chemistry used to produce 1-carvone is shown in Figure 4.19. The chirality of the carvone is crucial to the odour, since the enantiomeric d-carvone has an odour reminiscent of dill or caraway rather than spearmint. It is therefore important that any... 

Another complication is that most of our descriptions are of complex mixtures and individual chemical signals are not always additive in a simple predictable arithmetic way. For example, it is known that the odours of the enantiomers of carvone are different. 1-Carvone (13.2) smells of spearmint whilst d-carvone (13.3) smells of caraway. Less well known is the fact that addition of nonanol (13.4), an alcohol with an oily smell reminiscent of unperfumed washing up liquid, to 1-carvone, will create an odour impression very similar to that of d-carvone. This... 

Numerous aldehydes and ketones, like the terpene alcohols, possess a characteristic odour. Some are easily accessible synthetically and are often used in the perfume industry. Commonly known examples are cinnamaldehyde with the typical smell of cinnamon vanillin with the vanilla odour and carvone smelling of caraway seed. 

The odour of oil No. 2 hardly i-esembled that of caraway seeds, nor did it contain either limonene or carvone, the characteristic constituents of caraway oil, in any perceptible quantity. The small sample was just sufficient for ascertaining the boiling-point it began to boil at 195 C., the thermometer then rapidly rose to 230 C., and between 230 and 270 about 65 to 70 per cent, distilled over the residue was resinified. 

The constituents recognised in caraway oil are carvone, d-limonene, dihydrocarvone, carveol, and dihydrocarveol, and a base having a nai-cotic odour which has not been investigated. 

The odour is distinctly sweeter than the normal cummin oil and a. little more reminiscent of caraway, although, from the figures above indicated, it does not seem to contain a higher percentage of cumic aldehyde. Carvone does not appear to be present. ... 

Other monoterpenes of note include hmonene (Section 7.4.5, Figure 7.29) which is the precursor of carvone (+)-carvone provides the characteristic odour of caraway while... 

In spite of tbe difference in odour between this and caraway oilSp the composition of the two is almcet identical, both consisting nearly entirely of limonene and carvone. Dill oil, however, contains less car-vone than caraway oil, Hence tbe tests given under caraway oil apply here, and screjss should he laid on Ihss sfM cific gravity, optical rotation, and fractionation. Not move than 15 per ctint. should distil below 185", and not less than 40 per cent, above English distilled oils usually... 

---