Phenols carvacrol

Carveol (5) is one of the minor components responsible for the odour of spearmint, and is easily prepared by reduction of carvone. Isopulegol (6) is prepared from citronellal, as discussed in the section on menthol below, and is a precursor to other materials in the group. The phenols carvacrol (7) and thymol (8) are important in some herbal odour types, but the major use for thymol is as a precursor for menthol q.v. Piperitone (9) and pulegone (10) are strong minty odorants, the latter being the major component of pennyroyal oil. 1,8-Cineole (11) is the major component of such eucalyptus oils as Eucalyptus globulus. These oils are inexpensive and so there is no need to prepare cineole synthetically. Menthofuran (12) is an important minor component of mint oils and can be prepared from pulegone. 

The oil contains very little menthol, but a considerable amount of pulegone, with a small amount of a phenol (carvacrol ). 

The oil contains about 3 per cent, of geranyl acetate, pinene, cymene, free geraniol, eucalyptol, traces of phenol (carvacrol ), and an aldehyde which is probably ouminic aldehyde. 

The oil CQuialna abont 70 to dO pec cent, of phenols, of which a small portion consists of carvacrol aod the remainder of thymol, the rest of the oil being chiefly cymene, which bolls at 17o to 176 U., whilst thymol boils at 232 C. 

The od is soluble iu 3 volumes of 70 per cent, alcohols, The phenols consist almost entirely of carvacrol, and there are also preaeut cymene and terpenes. 

Carvacrol, Cj Hj O, is a phenol isomeric with thymol, with which it is frequently found associated, especially in certain types of thyme and origanum oils. 

At higher concentrations, the antioxidant activities of thymol and carvacrol were close to that of a-tocopherol and were in fact responsible for the antioxidant activity of many EOs which contain them [12, 17, 139, 153, 163, 164, 168, 170-174]. The high potential of phenolic components to scavenge radicals might be explained by their ability to donate a hydrogen atom from their phenolic hydroxyl groups [175]. 

Phenols, such as anethole, eugenol, safrole, thymol, carvacrol and chavicol. 

Determination of the phenols is of special importance in the analysis of hop (carvacrol), thyme, ajOwan (thymol), aniseed, badiana, fennel (anethole), clove bud and stem (eugenol) and sassafras oils (safrole). 

Phenols appear superficially similar to alcohols, possessing an -OH group, but in practice they are very different. The names of phenols also end in -ol, e.g. carvacrol. 

In aromatherapy the family of phenols are called substituted phenols, as one or more of the five remaining available hydrogen atoms of the ring is replaced by another group of atoms. Examples are carvacrol, thymol and eugenol (Fig. 3.6). 

Carvacrol (5-isopropyl-2-methylphenol) Found in essential oils of thyme, sage and oregano. Phenolic, spicy odour. 

Eugenol (4-allyl-2-methoxyphenol) Eugenol is not actually derived from a terpene molecule (as opposed to carvacrol and thymol) but it is a phenol and is found in essential oils of clove, cinnamon leaf, pimento, ylang ylang and rose. It has a spicy, pungent odour typical of clove. 

Thyme oil contains thymol and carvacrol (phenols p. 59), which are also dermal irritants, but with linalool and other noncyclic alcohols the risks are significantly reduced. 

The GC analysis (Fig. 7.7) shows a commercial white thyme with a high percentage of the phenols thymol (55.8%) and carvacrol (2.07%). This contrasts with that of sweet thyme (Fig. 7.8) with no phenolic compounds present and alcohols terpineol-4 (13%), a-terpineol (12.37%) and bomeol (5.95%) making up a total of 31.34% for this particular sample. 

Phenol(s) Aromatic molecules in which one or more hydroxyl groups (-OH) are directly attached to a benzene ring. Phenols are powerful antibacterial compounds and essential oils containing phenols need to be used with caution. Examples of phenols in essential oils include thymol, carvacrol and eugenol. Phenol is the name for the parent compound, the simplest of the phenols (C6H5OH). 

Phenylpropane derivatives The name given to compounds of phenol that have a three-carbon-atom (propyl) chain attached those most commonly found in essential oils are thymol, carvacrol, chavicol (see Phenols). 

Identification The infrared absorption spectmm of the sample exhibits relative maxima at the same wavelengths as those of a typical spectrum as shown in the section on Infrared Spectra, using the same test conditions as specified therein. Assay Not less than 20.0% and not more than 57.0% of phenols as carvacrol (C H O). 

Aromatic versions of cyclohexane monoterpenes (benzenoid menthanes or cymenes) are also found in nature and are constituents of some plants frequently used as spices. The hydrocarbon p-cymene (E19) has been found to occur in the oils of cinnamon (Cinnamonum zeylanicum), cypress, eucalyptus, thyme, and turpentine, whereas m-cymene (E20) is a constituent of the oil of blackcurrant Rites nigrum, Saxifragaceae). The corresponding phenols, thymol (p-cymen-3-ol) (E21) and carvacrol... 

---