Essential oils phenols

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. 

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

While present in only a relatively few aromatic herbs, phenolic volatile oils are among the most potent and potentially irritant compounds found in essential oils. Phenols are represented in both major classes of aromatic compounds—the monoterpenes and phenylpropanoids. The major monoterpene phenols, thymol and carvacrol, are found in thyme. Thymus spp., and oregano. Origanum vulgare (Lamiaceae). 

Keywords Phytochemicals Food preservatives Food spoilage bacteria Essential oils Phenolic compounds... 

This phenolic compound, CjjHjgOj, exists in the essential oil of Ev torium triplinerve, and in arnica root oil. It is an oil having the following characters —... 

This phenolic ether, CgH3(OH)(OCH3)2, has been identified in the essential oil of an Algerian plant, whose botanical source is not identified. It is a crystalline body melting at 51°, and yields a benzoyl derivative melting at 107° to 108°. 

The methyl ether of eugenol, CjjHj 02, is found in calamus oil, cassie oU, betel oil, bay oil, and various other essential oils. It can be prepared artificially by the action of methyl iodide on eugenol sodium. Its constitution is identical with that of eugenol, except that the phenolic group, OH, has been replaced by the methoxy group, O. CHg. 

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. 

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. 

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). 

Other phenolic compounds of commercial importance include the terpenoids, including mono, di, tri, and sesquiterpenes. While most of these are used as essential oils, fragrances, and flavors in various products, they are toxins in certain species. For example the sesquiterpene lactones of the Centaurea species cause an irreversible Parkinson s-like condition in horses called nigro-pallidal encephalomalacia. This is a lethal condition and the prognosis for recovery is grave in most cases, affected horses should be euthanized before reaching the terminal stages. 

In the last years, the use of comprehensive liquid chromatography has been greatly increased and it has been widely used to separate and characterize various complex samples, such as biomolecules [10-15], polymers [16,17], lipids [18-21], essential oils [22], acidic and phenolic compounds [23-28], pharmaceuticals and traditional medicines [29-31], etc. Comprehensive LC has been reviewed by several authors [32-37]. 

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. 

Moree- Testa, P., M. Donzel, M. H. Bergerol, and M. M. Luzinier. Determination of pyridinic and pyrazinic compounds in tobacco and cigarette smoke. Ann Tab Sect 1974 1(12) 27. Richter, M. Composition of essential oils in tobacco. III. Analysis of phenolic fraction. Ber Inst Tabakforsch (Dresden) 1974 21 52. 

Of the phenols and phenyl ethers used as fragrance and flavor substances, 4-allyl-(9, R = H) and 4-propenylphenols (10 and 11, R = H) and their methyl ethers (9-11, R = CH3) occur particularly frequently in essential oils. 

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 ... 

Laggera alata (D. Don) Schultz-Bip ex Oliver Lu Er Jin (whole plant) Flavonoid glycoside, phenols, amino acid, essential oil.56 Detoxicant, relieve swelling, treat fever, cough, hepatitis. 

Rhododendron mucronatum G. Don Bai Du Juan Hua (white azalea) (flower) Essential oil, germacrone, farreol, grayanotoxin, gossypetin, azaleatin, 5-methyl kaempferol, 5-methyl myricetin, syringic acid, dihydroquercetin, coumarins, phenolic acid, p-hydroxybenzoic acid, protocatechuic acid, vanillic acid.48 Treat cough, asthma, headache, respiratory infection. 

Numerous papers have relied on only UV-visible spectra for their identification of phenolics, but for positive identification purposes, HPLC-mass spectrometry (MS) is another detection mode that can provide detection of all phenolic compounds in foods. This technique involves a hyphenated instrument that uses a mass spectrometer as a detector for HPLC or uses HPLC as cleanup step for mass spectrometry. After preparative HPLC, the MS technique has frequently been employed for structural identification of phenolics in many foods and essential oils because of its sensitivity and selectivity and its ability to provide structural information. 

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