Phenol-containing essential oils

Phenol-containing essential oils reacted rapidly with zinc, whereas oils containing monoterpenes have been reported to react strongly with aluminum. It is recommended not to use aluminum for long storage of essential oils. 

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). 

Since the ancient times, spices have been added to different types of food to improve their flavor and to enhance their storage stability. The intake of herbs and spices is regulated by themselves by means of the flavor intensity of the essential oil. However, antioxidant extracts with high contents of phenolic diterpenes do not necessarily contain essential oils. Particularly, plant material from essential oil production for cosmetic or pharmaceutical products is an interesting side product to be used for the preparation of antioxidative extracts. However, data published by Richheimer et al. (1996) indicated that the deoiled biomass contains markedly less camosic acid than the dried, nondeoiled plant material. 

Phytochemistry Most species contain essential oils, volatile organic compounds, flavonol glycosides, phenols, vitamins, ascorbic acid, mineral salts and microelements (Khalmatov 1964), as well as steroidal saponins and sapogenins (Mimaki et al. 1999). 

Phytochemistry Aboveground parts contain essential oil, phenols, ketones, flavonoids, alkaloids, and coumarins (Plant Resources of the USSR 1993). 

Phytochemistry The herb contains essential oil (with phenols such as thymol and isomers of carvacrol), bi and tricyclic sesquiterpenes, free alcohols, tannins, ascorbic acids, and flavonoids (Akopov 1990 Sivropoulou et al. 1996). A total 62 constituents were identified from the essential oil of Origanum vulgare ssp. vulgare, with the main constituents being caryophyllene, spathulenol, germacrene-D, and terpineol (Sahin et al. 2004). 

Phytochemistry The fruits contain vitamins (ascorbic acid, B, and carotene), sugars, organic adds (citric and malic), pectins, anthocyanin compounds (cyanidin and delphinindin) and their glycosides, as well as quercetin and isoquercetin. Buds contain essential oil with d-pinene, 1- and d-sabinene, d-caryophyllene, alcohol, and phenols. The leaves contain essential oil and ascorbic acid (Akopov 1990 Knox et al. 2001). 

Wood flour, fibrous in structure, contains about 15% protein and has -OH functional group with variable chemical formula. Typical particle size ranges from 10 to 100 pm. The sources of wood flours are soft woods, hard woods, bark, sawdust, etc. Wood, containing essential oils such as cedar, is not suitable. Wood fibers are obtained through defibration treatment of wood chips [ 127,128]. Wood flour may absorb some resins and gums when mixed with some plastics. Phenolic resins have been mixed with wood flour as an additive since as early 1907. 

Essential oils are known to have detrimental effects on plants. The inhibitory components have not been identified, but both alde-hydic (benzol-, citrol-, cinnamal-aldehyde) and phenolic (thymol, carvacol, apiol, safrol) constituents are suspected. Muller et al. (104) demonstrated that volatile toxic materials localized in the leaves of Salvia leucophylla, Salvia apiana, and Arthemisia californica inhibited the root growth of cucumber and oat seedlings. They speculated that in the field, toxic substances from the leaves of these plants might be deposited in dew droplets on adjacent annual plants. In a subsequent paper, Muller and Muller (105) reported that the leaves of S. leucophylla contained several volatile terpenes, and growth inhibition was attributed to camphor and cineole. 

It is not only lipids but also essential oils which are sensitive to oxidative changes on storage. Sometimes stabilised by synthetic or natural antioxidants, they usually contain substances showing moderate antioxidant activity, but these may be lost by evaporation or oxidised by air oxygen unless more powerful phenolic antioxidants are added. 

Terpenes are polymers of the 5-carbon compound isoprene (Figure 1.12) and, as such, generally display properties similar to those of hydrocarbons. Terpenoids are substituted terpenes (i.e. contain additional chemical groups, such as an alcohol, phenols, aldehydes, ketones, etc.). Only a few such substances could be regarded as true drugs. Terpenes, such as limonene, menthol and camphor, form components of various essential oils with pseudo-pharmaceutical uses. A number of these molecules, however, exhibit anti-tumour activity, of which taxol is by far the most important. 

Ginger oleoresin is prepared by extracting ginger rhizomes with acetone or alcohol. The product contains the essential oil along with the substances responsible for the pungency of ginger. These compounds are substituted phenols of the following structure ... 

The composition of the volatile oil, which determines the odour and flavour characters, has been of particular interest to chemists. Ajowan oil is composed of phenols, terpenes and p-cymene. The essential oil contains more than 27 compounds, of which thymol (61%) is the major one, the others being paracymene (15.6%), y-terpinene (11.9%), (3-pinene (4-5%), dipen-tene (4-6%), camphene and myrcene. The essential oil composition of ajowan seed is given in Table 16.3. 

Tanacetum species contain mainly sesquiterpenoids and flavonoids, whereas the other terpenoids and phenolic compounds are rarely found. Sesquiterpenoids which are the main constituents of the genus, supposed to be bioactive principles of the plants. Flavonoids and essential oils are also pointed out as active substances in some species. On the other hand, there is a confusion on the systematic position and classification of several species of Asteraceae, therefore chemotaxonomy of the species will help the systematic studies. 

Certain phenols and their ethers are isolated from the essential oils of various plants (so called because they contain the essence—odor or flavor—of the plants). A few of these are ... 

Main components 1.5-4% essential oil, which contains linalool, bomeol, terpinene -ol, a-terpineol, the methyl ethers of thymol, carvacrol and eugenol, cuparophenol (a phenolic sesquiterpene), sesquiterpene hydrocarbons, cascarilladiene, cascarillone [45, 46] and cascarillic acid ]47], Moreover, cascarilline (bitter constituent), cascaril-line A, vanillic aldehyde, resin, tannins, fat and starch are present. 

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