Phenols from essential oils

Essential oil preparations from a variety of plants have found industrial applications relating to taste (liqueurs and flavour additives) and odour (perfumes, liqueurs, agents for masking unpleasant odours and pleasant-smelling phenolic antiseptics). Many... 

ABSTRACT This study shows that, in spite of the great biological and cultural potential in Brazil, there is, even today, no phytomedicines originating from this flora, as an alternative to allopathic anxiolytics and hypnotics prescribed by psychiatry. Thirty-nine plants with potential anxiolytic effects and 28 hypnotics were indicated in the course of ethnopharmacological surveys carried out with Afro-Brazilians and/or Quilombolas, the Caboclo population (river-dwellers), and Indians in Brazil. Practically no pharmacological studies have been found in the scientific literature as evidence of their popular use. From the phytochemical point of view, it is of interest to observe that flavonoids, essential oils, phenolic acids, and alkaloids are the chemical constituents predominantly present in these species, both in those indicated as anxiolytic, and the hypnotic. 

Typically consisting of highly complex mixtures of mono- (Cjo), sesquiterpenes (C15), 49 d phenols that confer the scent of the plant from which they are derived, plant essential oils are obtained through steam distillation of plant material from a relatively select group of plants [5]. As a result, most essential oils come from highly aromatic species such as those in the Apiaceae (carrot), Lamiaceae (mint). 

Phytochemistry The herb contains flavonoids, phenolic compounds and small amounts of alkaloids (Khalmatov 1964 Bandyukova et al. 1969 Hosseinimehr et al. 2007). The main components of the essential oil isolated from plants in Iran, were piperitone and elemol (Esmaeili et al. 2005). 

Among the substances which are treated in this section, the methoxy-phenylpropane derivatives are of more interest in medicine and in the perfume industry than are the steam-volatile phenols. Compounds of this type occur in a number of plants or in the essential oils obtained from them cloves, pimento, anise, fennel, parsley, dill, calamus and sassafras may be mentioned. 

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. 

In a phenol, a hydroxyl group is attached directly to an aromatic ring. The parent compound, phenol itself, Cr,HsOH (4), is a white, crystalline, molecular solid. It was once obtained from the distillation of coal tar, but now it is mainly synthesized from benzene. Many substituted phenols occur naturally, some being responsible for the fragrances of plants. They are often components of essential oils, the oils that can be distilled from flowers and leaves. Thymol (5), for instance, is the active ingredient of oil of thyme, and eugenol (6) provides most of the scent and flavor of oil of cloves. 

Other assays have been used to evaluate the antioxidant activity against H202 of several plant-based products, namely, fruit juices from different cultivars of berries (Wang and Jiao 2000), fractions rich in phenolics isolated from the aqueous by-products obtained during the milling of oil palm fruits (Balasundram and others 2005), cherry laurel fruit and its concentrated juice (Liyana-Pathirana and others 2006), and strawberries and blackberries treated with methyl jasmonate, allyl isothiocyanate, essential oil of Melaleuca alternifolia, and ethanol (Chanjirakul and others 2007). 

Nutmeg and mace are the two major primary products of M. fragrans and are considered commercially as spices. The constituents of nutmeg can be classified broadly into terpenoids, fatty acids, phenolic acids, lig-nans, neolignans and miscellaneous compounds. The oil content ranges from 3.9 to 16.5% in nutmeg, whereas in mace it varies from 6.0 to 26.1%. The major constituents of the essential oil in nutmeg and mace are sabinene and pinenes. The chief... 

In summary, Foeniculum is stated to have three species, F. vulgare (fennel), F. azoricum Mill. (Florence fennel) and F. dulce (sweet fennel). Fennel is widely cultivated, both in its native habitat and elsewhere, for its edible, strongly flavoured leaves and seeds. The flavour is similar to, but milder than, that of anise and star anise. Anethole and fenchone are the major constituents of the solvent extract of seed phenols, free fatty acids, carbohydrates, proteins, vitamins and minerals have been reported in varying proportions. In the mature fruit, up to 95% of the essential oil is located in the fruit, greater amounts being found in the fully ripe fruit. Approximately 45 constituents have been determined from fennel seed oil, the main constituents being frans-anethole, fenchone, estragol (methyl chavicol), limonene, camphene, a-pinene and other monoterpenes, fenchyl alcohol and... 

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. 

Gerber has isolated (+ )-epicubenol (81) from a Streptomyces species. This compound is the enantiomer of that found in the essential oil of Cedrela toona Roxb. The syntheses of four naturally-occurring phenolic sesquiterpenoids obtained from the essential oil of elm wood have been reported, viz. (82 R = Me), (82 R = CHO), (83 R = Me), and (83 R = CHO). The known o-quinone, mansonone C (84), has also been isolated from elm wood. The structure (85) of sesquichamaenol, a minor component of the essential oil of Chamaecyparis forrnosensis, has been deduced on the basis of spectroscopic evidence and synthesis. Piers et al. have published complete details of their syntheses of a- and ) -cubebenes (86). 

There are a few minor wood-based chemical industries. After chestnut blight wiped out the American chestnut, U.S. tannin production essentially ceased. The main natural tannins, watde and quebracho, are now imported. High U.S. labor costs and the advent of synthetic tannins make re-establishment of a U.S. tannin industry unlikely. Tannins are used in oil-weU drilling muds. Tree exudates are a continuing wood-based chemical industry. Tree exudates include mbber, tme carbohydrate gums (eg, acacia gum), kinos (eg, the phenolic exudates from eucalyptus), balsams (eg, Storax from l iquidambar spp.), and many different types of oleoresins (mixtures of a soHd resin and a liquid essential oil). The most important oleoresin stiU collected in the United States is pine gum (rosin plus turpentine). 

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 ... 

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. 

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