Oils essential

Essential oils are volatile substances and chemically different from the fatty oils. Their characteristic compounds are monoterpenes and esters with short-chain fatty acids. There are about 2500 essential oils but only about 100 are used. The essential oils are used especially in the perfume industry and for cosmetic articles in the food industry for creating aromatic essences in plastics, artificial leather, rubber, floor wax, household sprays and in pharmaceutical preparations because of their pharmaceutical effects, their antiseptic properties, and to improve taste. 

Resins are used for perfumery and in pharmaceuticals. Although synthetic resins are often used today, natural resins are also important for particular purposes. Most resins are obtained from tree species and, in some species, the resin formation is sufficiently abundant for its collection to be economically viable. The volatile aromatic compounds of many resins are separated by distillation. 

The production and utilisation of only those species that are already penetrating the market as new species for aromatic substances (Guenther, 1948-52 Howard, 1974) will be described. 

Aniba rosaedora (family Lauraceae) Mostly distributed in South America. Rosewood is a wild evergreen tree in Brazil and Peru. The oil is used for artificial flavours, in the perfume and soap industries. 

Acacia dealbata (family Leguminosae Mimosoideae) Native to Australasia, this is widely grown in the tropics and subtropics. Flowers are used for the processing of perfume. The tree produces gum similar to gum arabica. 

Essential oils are odorous principles stored in special plant cells— glands, glandular hairs, oil ducts or resin ducts—situated in any part of a plant or its exudations. These oils are responsible for the distinctive aromas associated with individual plant species. They are soluble in alcohol and fats, but only slightly soluble in water. Most essential oils are colourless, apart from azulene, which is blue. On exposure to light and air they readily oxidise and resinify. They are also called volatile oils, since they evaporate when subjected to heat. 

Steam and steam/water distillation are the predominant extraction methods used. Other methods include solvent extraction, cold pressing, infusion, effleurage and water distillation. Distillation is a method that involves the evaporation and subsequent condensation of liquids in order to produce, refine and concentrate essential oils. High quality oils are distilled once only, while some commercial oils are purified by double or triple distillation methods. 

This is the structure that is responsible for our sense of smell. The olfactory nerves connect directly to the limbic system in the brain, and thereby influence sensory functions such as hunger, sex and emotions. Smelling involves the inhalation of microscopic chemicals such as those contained in essential oils which flow through our nostrils into the nasal cavity. Here they pass over moist bony structures called turbinates to reach the olfactory receptor cells, where 

Essential oil composition can vary according to geographic and genetic factors, even though the same botanic species is involved—a phenomenon known as chemical polymorphism. When this occurs a terminology can be used where the Latin name is followed by the name of the chemical component most characteristic for that particular race of the plant, that is, its chemotype, for example Thymus vulgaris linalol. Thymus vulgaris thymol. Seven chemo types of thyme are known in the western Mediterranean area alone (Bruneton 1995). 

These are constructed from a series of isoprene units Unked together in head to tail fashion, as described in Chapter 5. 

Essential oils, known also as Ethereal oils, Volatile oils, or Essences, are products of more or less complex composition, consisting mostly of mixtures of substances with widely varying chemical functions of these substances the principal are as follows  

Hydrocarbons, rarely of the fatty series (heptane, myrcene and various paraffins), more often of the aromatic series, such as styrene and cymene, but usually terpenes, e.g. pinene, camphene, fenchene, limonene, dipentene, sylvestrene and phellandrene. 

Alcohols, such as linalool (licareol, coriandrol), geraniol (lemonol, rhodinol, r6uniol), citronellol (the rhodinol or rduniol of some authors), tcrpineol, bomeol and menthol. The alcohols occur in these oils both in the free state and also in combination with acids as esters (see later). 

Aldehydes, the most important being benzaldehyde, dnnamaldehyde, salicylaldehyde, citral and citronellal. 

Ketones, such as camphor, methylheptenone, carvone, fenchone, thujone or tanacetone, pulegone and menthone. 

Essential (volatile) oils are obtained preferentially by steam distillation of plants (whole or parts) such as clove buds, nutmeg (mace), lemon, caraway, fennel, and cardamon fruits (cf. 22.1.1.1). After steam distillation, the essential oil is separated from the water layer, clarified and stored. The pressure and temperature used in the process are selected to incur the least possible loss of aroma substances by thermal decomposition, oxidation or hydrolysis. 

Many essential oils, such as those of citrus fruits, contain terpene hydrocarbons which contribute little to aroma but are readily au-tooxidized and pol)merized ( resin formation ). These undesirable oil constituents (for instance, limonene from orange oil) can be removed by fractional distillation. Fractional distillation is also used to enrich or isolate a single aroma compound. Usually, this compound is the dominant constituent of the essential oU. Examples of single aroma confounds isolated as the main constituent of an essential oil are 1,8-cineole from eucalyptus, 1(—)-menthol from peppermint, anethole from anise seed, eugenol from clove, or citral (mixture of geranial and neral, the pleasant odorous 

Various oils present in natural extracts have been classified as fixed oils or high boiling oils and essential or volatile oils. Very popular fixed oils are neem oils (nonedible), coconut, ground nut, soya, Sunflower, mustard etc. oils (edible). Some of the popular essential oils are rose oil, eucalyptus, lemon grass, jasmine, etc. oils of fragrance grade and cumin, coriander, cardamom, clove etc. of flavor grades. 

Essential oils or volatile oils are useful for their fixative properties as well as their odor. Among the fixative essential oils are clary, sage, ventiver. Patchouli orris, and sandalwood, etc. Usually, they have low boiling points not more than 285-290°C. 

Many of the naturally derived essential oils have been used in aromatherapy and in the manufacture of health products, cosmetics, and perfumes. Just as natural essential oils. 

Many components of natural essential oils are cresols or allied products. Some of these essentials oils giving their therapeutic actions and principal constituents are outlined here vide Table 10.1. Most of these oils are produced commercially although some of them are little known. Attempts have been also made by the global key players to produce matching synthetic blends from components made by organic chemical synthesis. Needless to emphasize that synthetically made essential oils are much cheaper than those obtained from natural sources. 

There are more than 150 natural essential oils and natural extracts from which a large number of important flne chemicals in the field of flavor and fragrances have been extracted, isolated, and sold as blends in predetermined quantities. Table 10.1 gives some details of only those natural substances containing cresols, precmsors such as cymenes, derivatives such as thymol, menthol, and other allied products. 

Purpose. In this exercise you will extract oil of cinnamon from a native plant source, such as Cinnamomum zeylanicum, and then purify the principal flavor and odor component of the oil, cinnamaldehyde. The experiment demonstrates the importance of steam distillation techniques (at the semimicro level) iHlwww] to the collection of essential oils. 

Technique 2 Simple Distillation at the Semimicroscale Level (pp. 61-64) Technique 3 Steam Distillation Technique 4 Solvent Extraction 

Let us begin by defining what we mean by the term metabolite. The metabolism of an organism is composed of the biochemical reactions and pathways in that living system. The products (most of them organic molecules) derived from this array of molecular transformations are the metabolites. This vast collection of substances that are generally referred to as natural products are, in fact, the metabolites of the natural living world. 

You may have had the opportunity to become acquainted with secondary metabolites in Experiments [llA] and [IIB]. In Experiment [llA] an aceto-genin (this term refers to the biochemical origin of this material from eight acetic acid residues), usnic acid, was isolated from a lichen where it can occur in dramatically high concentrations. Only recently has the role of usnic add as a defense mechanism come to be fully appreciated. 

In Experiment [IIB], the alkaloid caffeine was obtained from tea. This compound is a very unusual example of a purine ring system in a secondary metabolite. The ecological significance of the presence of caffeine in both tea and coffee seeds has been established and it has been shown that caffeine acts against both predators and competitors. 

FT-Raman spectroscopy could be also successfully applied to investigate the occurrence of curcumin, the valuable dyeing component of curcuma root Curcuma longa) with widespread use in the Asian cuisine. Most intense bands of curcumin occur at 1630 and 1601 cm , which are assigned to the benzene ring, 

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CioHi O. White leaflets, with a strong smell and sweet taste, m.p. 22 C, b.p. 235 C. The chief constituent of anise and fennel oils and other essential oils, from which it is manufactured. It can also be prepared from anisole (meihoxybenzene). It is widely used for flavouring pharmaceuticals and dentifrices, and in perfumery. 

The generic term azulene was first applied to the blue oils obtained by distillation, oxidation, or acid-treatment of many essential oils. These blue colours are usually due to the presence of either guaiazulene or velivazulene. The parent hydrocarbon is synthesized by dehydrogenation of a cyclopentanocycloheptanol or the condensation of cyclopentadiene with glutacondialdehyde anil. 

An acyclic monterpene, b.p. 166-168°C, found in many essential oils, e.g. in verbena oil and oil of hops. 

C10H13O. B.p. 225-226"C. A terpenic alcohol and a constituent of neroli, petit-grain and bergamot, and of many other essential oils. Nerol has a blander smell than its isomer, geraniol, and is more valuable as a constituent of perfumes. 

C, b.p. 156 C. The most important of the terpene hydrocarbons. It is found in most essential oils derived from the Coniferae, and is the main constituent of turpentine oil. Contains two asymmetric carbon atoms. The (- -)-form is easily obtained in a pure state by fractionation of Greek turpentine oil, of which it constitutes 95%. Pinene may be separated from turpentine oil in the form of its crystalline nitrosochloride, CioHigClNO, from which the ( + )-form may be recovered by boiling with aniline in alcoholic solution. When heated under pressure at 250-270 C, a-pinene is converted into dipentene. It can be reduced by hydrogen in the presence of a catalyst to form... 

Unsaturated dicyclic ketone found in the essential oil from the leaves of Umbellularia cali/ornica, with pungent mint-like smell. 

But, safrole is the major component of the essential oil of sassafras which is still quite legal to obtain. Sassafras oil has a strong licorice smell which is imparted to it from the safroie molecule. Commercially, there are two kinds of sassafras... 

According to the Merck, and "Essential Oils" by Guenther, Sassafras Oil is composed of the following ... 

You people won t believe the potential amphetamine precursors just sitting around in naturally occurring oils and essential oils [6, 7... 

OSMORHIZOLE Makes up 25% of the essential oil of chervil. Very hard to find this oil though. 

The synthesis of MMDA in Pihkal is one of the longest and most tedious in the book. If one is going the route via myristicin, the Sisifos work of isolating the tiny amount of essential oil present in nutmeg, followed by fractional distillation to purify the myristicin fraction is also added to the labor of the poor chemist. Therefore I propose a new route to this "essential amphetamine". 

Essential is also used as the adjective form of the noun essence The mixtures of substances that make up the fragrant material of plants are called essential oils because they contain the essence that is the odor of the plant The study of the composition of essential oils ranks as one of the oldest areas of organic chemical research Very often the principal volatile component of an essential oil belongs to a class of chemical sub stances called the terpenes... 

Essential oils (Section 26 7) Pleasant smelling oils of plants consisting of mixtures of terpenes esters alcohols and other volatile organic substances Ester (Sections 4 1 and 20 1) Compound of the type... 

Adams, F., Gijbels, R., and Van Grieken, K., Inorganic Mass Spectrometry, Wiley Interscience, New York, 1988. Adams, R.R, Identification of Essential Oils by Ion Trap Mass Spectrometry, Academic Press, San Diego, CA 1989. 

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