Volatile oil Essential oils

Volatile oils (essential oils) are very complex, pleasant smelling, volatile mixtures containing many different compounds. Most of the essential oils have a high refractive index and they are often optically active. These properties are used for their identification and quality control. Essential oils have low water solubility but are readily soluble in organic solvents. Chemically and biosynthetically they are a heterogenous group. 

Volatile oils (essential oils), complex mixtures of lipophilic mono-/sesquiterpenes and/or phenylpropanoids secreted in oil cells, secretion ducts/cavities or glandular hairs (constituents of Lamiaceae)... 

Essentia.1 Oils. Essential oils (qv) are extracted from the flower, leaf, bark, fmit peel, or root of a plant to produce flavors such as mint, lemon, orange, clove, cinnamon, and ginger. These volatile oils are removed from plants either via steam distillation, or using the cold press method, which avoids heat degradation. Additional processing is sometimes employed to remove the unwanted elements from the oils, such as the terpenes in citms oils which are vulnerable to oxidation (49,50). 

Exceptions to the simple definition of an essential oil are, for example, gadic oil, onion oil, mustard oil, or sweet birch oils, each of which requires enzymatic release of the volatile components before steam distillation. In addition, the physical process of expression, appHed mostly to citms fmits such as orange, lemon, and lime, yields oils that contain from 2—15% nonvolatile material. Some flowers or resinoids obtained by solvent extraction often contain only a small portion of volatile oil, but nevertheless are called essential oils. Several oils are dry-distiUed and also contain a limited amount of volatiles nonetheless they also are labeled essential oils, eg, labdanum oil and balsam oil Pern. The yield of essential oils from plants varies widely. Eor example, nutmegs yield 10—12 wt % of oil, whereas onions yield less than 0.1% after enzymatic development. 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

Nepeta (Lamiaceae) is a genus of perennial or annual herbs found in Asia, Europe and North Africa. About 250 species of Nepeta are reported of which, 67 species are present in Iran. Some species of this genus are important medicinal plants and their extracts have been used for medicinal purposes. Aerial parts of Nepeta sintenisii Bornm. was subjected to hydrodistillation and the chemical composition of isolated essential oil has been analyzed by GC/MS method for first time. Identification of components of the volatile oil was based on retention indices relative to n-alkanes and computer matching with the Wiley275.L library, as well as by comparison of the fragmentation patterns of the mass spectra with those reported in the literature. 

The essential oil from the leaves has been investigated by So Uchida. On distillation vitti steam the green leaves yielded 0 70 per cent, of volatile oil, which was brov.-Qisli.yellow in colour and had a fresh aromatic odour. It has the following characters ... 

An absolutely scientific definition of the term essential cr volatile oils is hardly possible, but for all practical purposes they may be defined as odoriferous bodies of an oily nature obtained almost exclusively from vegetable sources, generally liquid (sometimes semi-solid or solid) at ordinary temperatures, and volatile without decomposition. This definition must be accepted within the ordinary limitations which are laid down by the common acceptation of the words, which will make themselves apparent in the sequel, and show that no more restricted definition is either advantageous or possible. Many essential oils, for example, are partially decomposed when distilled by themselves, and some even when steam distilled. 

Essential oil (Chapter 6 Focus On) The volatile oil obtained by steam distillation of a plant extract. 

The volatile oil containing the essential flavor/aroma of the named plant, herb, root, bark, flower, etc. The volatile oil is obtained by distillation or expression, e.g. expressed Orange oil. 

Volatile compounds are often involved in long distance attraction and are especially important as attractants and repellents (as defined by Kogan, ). One major class of volatile materials, essential oils, is comprised of complex mixtures of terpenes, phenylpropanoid derived compounds and a number of esters, alcohols, aldehydes, ketones, acids, and hydrocarbons. The constituent compounds are mostly of low to medium molecular weight and generally not highly oxygenated. Some of the biological properties of these compounds have been reviewed (17,41,46,55,56). 

Essential oil, also defined as essence, volatile oil, etheric oil or aetheroleum, is a complex mixture of volatile constituents biosynthesised by living organisms. Essential oils can be liberated from their matrix by water, steam and dry distillation, or expression in the case of citrus fruits [1-5]. Their occurrence and function in nature is still a question and the subject of ongoing research. However, there is evidence that organisms produce essential oils for defence, signalling or as part of their secondary metabolism. As a consequence essential oils comprise an important bio resource for renewable natural products [1-25]. 

Owing to their liquid nature at room temperature, essential oils are called as such. They should not be confused with fixed oils or fatty oils, which are composed of a naturally occurring mixture of lipids which may not necessarily be volatile. Therefore, essential oils differ entirely both in chemical and in physical properties from fatty oils. Essential oil evaporates completely when dropped on filter paper however, fixed oil leaves a permanent stain which does not evaporate even when heated. 

Monoterpenes, 10-carbon-containing terpenoids, are composed of two isoprene units, and found abundantly in plants, e.g. (+)-limonene from lemon oil, and (—)-linalool from rose oil. Many monoterpenes are the constituents of plant volatile oils or essential oils. These compounds are particularly important as flavouring agents in pharmaceutical, confectionery and perfume products. However, a number of monoterpenes show various types of bioactivity and are used in medicinal preparations. For example, camphor is used in liniments against rheumatic pain, menthol is used in ointments and liniments as a remedy against itching, bitter-orange peel is used as an aromatic bitter tonic and as a remedy for poor appetite and thymol and carvacrol are used in bactericidal preparations. 

Extraction of Simple Odors. —By Distillation.—This process is neoessary for the preparation of nearly all the essential or volatile oils, the fragrant waters, and mure particularly Cologne waters. The apparatus consists of a metallic still and ite appliances, for general purposes but in certain cases, such as the distillation of vinegars and other substances that might act upon metal, glass or stoneware retorts are the proper implements. Those latter, it should also be remembered, are better applicable for small and nice operations. 

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 ... 

Many essential oils contain esters (mostly acetates) of alcohols of the formulae C10HlsO (borneol, geraniol, terpineol, linalool), C H O (menthol, citronellol), C1SH240 (santalol). When boiled with alcoholic potash, these esters are hydrolysed (saponified) and yield the free alcohol and the potassium salt corresponding with the acid of the ester. Thus, the volatile oils containing esters have saponification numbers, which may be determined in a manner analogous to that used for fatty matters. 

Cedarwood Oil, Copaiba Balsam Oil and Gurjun Balsam Oil.—These volatile oils lend themselves readily to the adulteration of many essential oils, owing to their cheapness and slight odour. 

Turpentine is an oleo-resin exuded from the trunks of certain conifers (so-called Scio turpentine is obtained from one of the Terebinthaceae, Pistada terebinthus L.) and consists essentially of resin acids, neutral resins, volatile oil and small proportions of various other substances (succinic acid, bitter principles, colouring matters, water). Distillation of turpentine and rectification of the distillate gives oil oj turpentine, the residue being colophony. By dry distillation of the latter resin oils are obtained. The present chapter deals with the natural product, i.e. turpentine, and with the products obtained from it. 

Volatile or essential oils are usually obtained from the appropriate plant material by steam distillation, though if certain components are unstable at these temperatures, other less harsh techniques such as expression or solvent extraction may be employed. These oils, which typically contain a complex mixture of low boiling components, are widely used in flavouring, perfumery, and aromatherapy. Only a small number of oils have useful therapeutic properties, e.g. clove and dill, though a wide range of oils is now exploited for aromatherapy. Most of those employed in medicines are simply added for flavouring purposes. Some of the materials are commercially important as sources of chemicals used industrially, e.g. turpentine. 

The Latin name comes from the legend that Achilles cured wounds with yarrow during the Trojan War. It arrests internal and external bleeding. Chamazulene, found in yarrow s essential volatile oil, is an anti-inflammatory agent, an antiallergen, and an antispasmodic. 

Eugenol occurs in essential oils and is a major constituent of carnation, cinnamon, and clove oils. The substance is primarily is obtained from the clove oil isolated from trees indigenous to the Molluca Islands, and which are also cultivated in other parts of Indonesia, Zanzibar, Madagascar, and Ceylon. Clove is rich in volatile oil (16-19% by weight), which can be obtained by distillation. 

There are two main components of black and white pepper the volatile oil and pungent compounds. The volatile oil level in black pepper is usually higher than in white pepper. The hull of pepper contains fibre and some essential oil. Black pepper contains about 2.0-2.6% volatile oil and about 6-13% oleoresin. The nutritional composition of black pepper is given in Table 2.3. 

EFFECT OF y-IRRADIATION IN VOLATILE OIL COMPOSITION Currently, y-irradiation is used for the decontamination of spices but its effect on essential oil composition is controversial and contradictory in cardamom (Ljubica, 1983 Klaus and Wilhelm, 1990 Maija et al, 1990). 

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