Components of Essential Oils

Most spices contain an essential or volatile oil (Table 22.2), which can be isolated by steam distillation. The main oil constituents are either 

Number Common name Latin name Class/order family (bot) Cultivation region 

1 Pepper, black Piper nigrum Piperaceae Tropical and subtropical regions 

2 Vanilla Vanilla planifolia Orchidaceae Madagascar, Comore Island, 

3 Allspice Vanilla fragans Vanilla tahitensis Vanilla pompona Pimenta dioica Myrtaceae Mexico, Uganda Caribbean Islands, Central America 

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The function of the essential oil in the plant is not fully understood. Microscopic examination of plant parts that contain the oil sacs readily shows their presence. The odors of flowers are said to act as attractants for insects involved in pollination and thus may aid in preservation and natural selection. Essential oils are almost always bacteriostats and often bacteriocides. Many components of essential oils are chemically active and thus could participate readily in metaboHc reactions. They are sources of plant metaboHc energy, although some chemists have referred to them as waste products of plant metaboHsm. Exudates, which contain essential oils, eg, balsams and resins, act as protective seals against disease or parasites, prevent loss of sap, and are formed readily when the tree tmnks are damaged. 

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. 

The enantiomeric distribution of the components of essential oils can provide information on the authenticity and quality of the oil, on the geographical origin and on their biogenesis (2). 

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. 

Compound identification. Determination of major components of essential oil was realized on the basis of use of standard compounds (/-/-a-bisabolol, chamazu-lene, cis-/trans-en-in-dicycloether and /-/-a-bisabololoxide A and B). Qualitative identification of selected components was carried out by the comparison the retention times of all detected components with retention time of standard compounds. 

Karasawa D, Shimizu S, Mentha candicans, a new chemical strain of section Spi-catae, containing tntwr-sabinene hydrate as the principal component of essential oil, Agric Biol Chem 42 433 37, 1978. 

Higher plants produce a great variety of terpenoids (78) but only a few of these have been implicated in allelopathy. The monoterpenoids are the major components of essential oils of plants and they are the predominant terpenoid inhibitors that have been identified from higher plants. Many fungi (82) and algae (83) produce terpenoid allelochemicals also. 

The volatile components of essential oils, for the most part, are made up of relatively low molecular weight (< 300-350) organic molecules of... 

Ksseutial oils, which are composed of mixtures of different substances, have no fixed boiling K>int, lmt boil between certain limiting temperatures-, often widely separated these limits lie between about 120 and 300° Fractional distillation serves cither to separate the various components of essential oils or to detect fraudulent practices. For instance, it is easy by distillation to detect addition ol. alcohol or petroleum ether, which boil below too . Addition of oil itf turpentine may atso, in many cases, lx- discovered by fractional distillation (mt later paragraph 12). 

Fig. 17.1. Components of essential oil from star anise (/. verum).

Note A classification of aromatic components of essential oils and perfumes. Top notes are sharp, penetrating and highly volatile (e.g. citrus oils, peppermint). Middle note characteristics are used to give body to blends (e.g. geranium, lavender). Base notes are the least volatile and used as fixatives to give more permanence (e.g. sandalwood, vetivert). 

Terpenoids Components of essential oils based on the hydrocarbon skeleton of terpene plus a functional group such as an aldehyde, alcohol or ketone. 

Oregano Origanum virens L. is an perennial herb with 40-70 cm high and very aromatic. This plant grows in open and dry countries, at altitudes lower than 500-700 m. The major components of essential oil from Origanum virens L. are terpineol, a-pinene, camphor, thymol, carvacrol and cineole. Compounds such as alcohols and dipentene are also present. 

Enantiomeric Mannich bases may be obtained either by using optically active starting materials or by optical resolution of racemic derivatives. In the former case, the reactants are mostly provided by natural products, such as components of essential oils (e.g., camphor ), hormones, nucleic acids, employed as substrates, or a-amino acids - mainly used as amine reagents, etc. A list of optically active reactants reported in the literature is summarized in Table 12. 

A greater understanding of the capabilities of biocatalysts will allow for an upgrading and increased commercial exploitation of many unutilized biological substances such as certain components of essential oils. 

Figure 3.4 Oxygenated components of essential oils extracted from Artemisia afra by hydrodistillation and microwave extraction.

ABSTRACT Monoterpenoids are the components of essential oils, which are produced and accumulated, in large amounts by plants from certain families, including Labiatae, Pinaceae, Cupressaceae, Umbelliferae and Rutaceae. They are of special interest because of their industrial applications and on account of their chemical properties and biological activity. Monoterpenic composition can be useful in genetic and chemotaxonomic studies of coniferous species. 

Oxygenated monoterpenoids (alcohols, aldehydes, ketones and other oxygen-containing compounds) are flavour determining components of essential oils and more important from practical aspects than monoterpenic hydrocarbons. 

The application of multidimensional gas chromatography (MDGC) to essential oil analysis is a great development in the determination of such complex samples. This is an appropriate approach when there are zones on the chromatogram where the peaks are not well resolved, which is a common situation in natural samples. The fractions corresponding to the zones with unresolved peaks are transferred to a second column containing a different stationary phase, where they are separated and completely resolved. Therefore MDGC permits the separation of poorly resolved peaks and increases resolution, with the final result of an improvement in both identification and quantification of components of essential oils. 

What r m trying to say is that people have been constantly proving and disproving the components of essential oils to this very day. And in all of the recent articles on sassafras oil I have found absolutely no detection of eugenol except in trace amounts. Interesting ... 

All flavouring and fragrance materials which are comparatively volatile are easily soluble (1-10% by weight), e.g. monoterpenes, phenylpropane derivatives and sesquiterpenes not only the hydrocarbons but also the oxygenated molecules like ethers, esters, ketones, lactones and alcohols. Ah of which are typical components of essential oils. 

Hendriks H, Bos R, Allersma DP, Malingre TM, Koster AS. Pharmacological screening of valerenal and some other components of essential oil of Valeriana officinalis. Planta Med 1981 42 62-8. 

Influence of Individual Components of Essential Oils and Flavorings on Citral Oxidation... 

Each essential oil is a multi component system, having certain red-ox potential, which determines it s AO activity. That is why it is of interest to turn out the role of individual components of essential oils in inhibition of oxidation process. 

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