Volatile Oils Introduction 2024 PDF

VOLATILE OILS  Definition: Complex liquid mixtures of odoriferous principals of varying chemical composition, which easily evaporate when exposed to air at ordinary temperature they are also named as ethereal oils or essential oils used as therapeutic, flavoring or perfumin...

VOLATILE OILS  Definition: Complex liquid mixtures of odoriferous principals of varying chemical composition, which easily evaporate when exposed to air at ordinary temperature they are also named as ethereal oils or essential oils used as therapeutic, flavoring or perfuming agents, as well as, starting materials for semi- synthesis of other compounds They may be present in combination with: Sugars forming the aglycone part of certain glycosides, or Gums, resins or both to form oleo-gums, oleoresins or oleo-gum-resins.  Physical properties volatile liquids. pleasant smell. steam distilled (c.f. fixed oils). immiscible with water, but sufficiently soluble to impart a distinct fragrance to water (aromatic waters). soluble in common organic solvents and lipids (liposoluble). They may darken in color when exposed to light (due to oxidation and resinification).  Chemical composition complex mixtures of constituents: - hydrocarbons - oxygenated compounds e.g. alcohols, ketones, aldehydes, ethers, oxides, phenols and esters. - Few oils may consist of one main component such as the volatile oil of mustard (93% allylisothiocyanate) and oil of clove (85% eugenol).  Methods of preparation of Volatile Oils Factor affecting selection of the suitable method: 1- The condition of the plant material (moisture content i.e. dry or fresh ) 2- the degree of comminution i.e. intact, crushed or powdered), 3- The localization of the oil in the plant (superficial or deep). 4- The amount of the oil. 5- The nature of its constituents Methods of preparation of Volatile Oils: 1. Distillation. 2. Expression. 3. Extraction. 4. Enzymatic hydrolysis.  I- Distillation methods: Types of distillation: Water-distillation method Water and steam distillation Direct steam distillation  Water-distillation method : The dry plant material is in direct contact with boiling water. Used for stable oil as turpentine oil Water and steam distillation: The plant material [either dry or fresh] is supported on a perforated screen, where water is contained on the lower part of the still to a level below the screen, the material is in contact with the steam only. Applied for cinnamon and clove. Direct steam distillation: No water is kept in the bottom of the still , steam is introduced through steam coil. Applied for fresh drugs. e.g. peppermint and spearmint.  Precautions in handling the plant material Crushing should be carried just before distillation to prevent loss by volatilization. Dried plant material if subjected to saturated steam distillation should be wet before packing. Packing or charging should be even in order to facilitate "hydro diffusion". Iron should not be used specially for oxygenated compounds, stainless steal is preferred.  Water distillation water Water & steam Direct steam distillation distillation steam water Different types of distillation apparatus II- Expression Methods Principle These are mechanical procedures carried at room temperature. Applications preparation of heat sensitive oils which are present in large amounts in outer peels of fruits,e.g. epicarp of Citrus Fruits (Rutaceae) E.g. orange and lemon. 1- Sponge Method: This is based on squeezing the removed peels between projection and a sponge which serves to collect the oil and filtration of the product 2- Expression of rasping: This is based on removing the outer layer of the peel with a grater, collecting the rasping in special bags (horsehair bags) followed by strong pressing, followed by decantation 3- Scarification method [Ecuelle-à-piquer ] This is based on puncturing (scarifying) the surface of whole fruits and thus allowing exudation of the oil from the outer colored zone of their peels. The method is applied, in France, for preparation of lemon bowl with numerous oil. pins  4- Machine processes New machine techniques based on the same principle have been designed to replace the three previous old traditional methods. For example, whole fruits are charged into machines in which the peels are removed, sprayed with water, squeezed or pressed and a centrifuge may be used to separate the oil.  III- Extraction methods Applied for preparation of delicate flowers oils, such as jasmine, violet, Narcissus, etc… which contain either: Small amounts of oils, easily lost in the large volume of distillation water. Oils, which decompose by the action of, heat (thermolabile constituents). According to the nature of the solvent used, they are sub classified into: 1- Non-volatile solvent extraction methods. 2- Volatile solvent extraction methods.  1- Non-volatile solvent extraction for preparation of natural flower oils producing the finest perfumes. They are based on the liposolubility of the fragrant components of plants. Lipids of high degree of purity are used. ***Lipid selection - Fats such as lard and tallow, a mixture of 2: 1 is used to avoid melting during extraction (tallow is harder and of higher m.p. than lard). Lard 2 Tallow - Fixed oils such as olive oil. 1  1-a-“Enfleurage” process applied in the South of France, for the preparation of oil of jasmine. The equipment consists of a number of glass plates closely arranged in wooden frames (or chassis). 1- Spreading the pure mixture of fat (lard / tallow 2: 1) on each of the surface of the glass plates. 2- Covering the top of each plate with flowers or petals, so that each layer of plant material is enclosed between an upper and a lower layer of fat. 3- Replacing old flowers by fresh ones periodically, and repeating the process until the fat is saturated with the oil or until a certain concentration of the oil is reached. Enfleurage" process – Removing the last charge of flowers from the fat (or Defleurage) e.g. for jasmine after 70 days. – Scraping the oil-saturated fat layers, warming the combined fat and filtering through gauze followed by cooling to yield the "Enfleurage product", sometimes called "floral pomade“ – The "Enfleurage product" could be marketed as such or the oil could be extracted using absolute alcohol. 1-b- Maceration Method The flowers are soaked in hot oil to have their cell membranes ruptured when the hot oil then absorbs the essence. The oil-containing fat is cooled then successively extracted with alcohol to obtain the volatile oil. 2- Volatile solvent-extraction [Preparation of "concrete" & “absolute"] Solvent selection Selectivity: in order to dissolve the volatile oil with the least amount of impurities. Stability (or chemical inertness): i.e. it should not react with any of the oil constituents. Boiling point: this should be suitable, preferably as low as possible. Volatility: it should be completely volatile, i.e. leaving no residue on evaporation. Handling safety: preferably, it should be non- toxic and non-inflammable Soxhlet apparatus  Preparation of "floral concretes" 1. Extraction by percolation or maceration at room temperature, or by continuous hot extraction in a Soxhlet at a constant temperature not exceeding 50ºC. 2. Removal of the solvent by distillation under reduced pressure. 3. The "floral concrete" of jasmine obtained by this procedure is a semi-solid product with a yellowish-orange color. 4. The "floral concrete" consists of the fragrant constituents together with the liposoluble impurities e.g. fats, waxes, and pigments.  Preparation of "floral absolutes more expensive and purified products than the corresponding concretes, prepared as follows: 1. Repeated extraction with absolute alcohol, thus extracting most of the oxygenated constituents of the oil. 2. Chilling (strong cooling) followed by decantation after each extraction in order to remove waxes, and fat-soluble pigments. 3. The resulting "absolutes" are, therefore, richer in oxygenated constituents, which are in most cases responsible for the odor of the oil. used in much smaller concentrations than the corresponding concretes in the perfume industry. 4- Methods based on enzymatic hydrolysis of glycosides Many glycosides give a volatile aglycone upon hydrolysis. They exist in plants together with enzymes responsible for their hydrolysis. The aglycones belong to different classes.  Principle The process includes the following steps: 1. Subjecting the plant material to hydrolysis (generally enzymatic) to liberate the volatile constituents (aglycones) from the parent odorless glycosides. 2. Separation of the volatile aglycones by either distillation or extraction.  Plant Non-volatile Volatile aglycone Other hydrolytic Hydrolytic name Glycoside products enzyme Gaultheria Gaultherin Methyl salicylate Primeverose Gaultherase (Xylose+glucose) Black Sinigrin Allyl isothiocyanate Glucose +Potassium Myrosin Mustard acid sulfate seeds Vanilla Glucovanilln Vanillin Glucose -Glucosidase pods Seeds of Amygdalin Benzaldehyde Gentiobiose Emulsin Bitter (2 glucose units) almond +HCN Determination of the volatile oil Quantitative Qualitative V/Wt To evaluate the quality of the plant species as well as the raw material which will be used in commercial preparations To differentiate between genuine and adulterated oil Quantitative Analysis Clavenger’s apparatus Qualitative Analysis Physical examination of volatile oils Odor: abnormal odor indicates adulteration or deterioration Solubility: solubility in different alcohol strengths  Optical rotation: it is the property of rotating the plane of polarization of a polarized light to the right (d, dextrorotatory, (+)) or to the left (l, levorotatory, (-)) Most constituents of the volatile oil are optically active Apparatus: polarimeter  Chemistry of V.O. Single component e.g. oil of bitter almond (benzaldehyde), oil of winter green (methyl salicylate) Complex mixture of hydrocarbon (known as terpenes) and related oxygenated compounds Terpenes Definition: natural product whose formula is divided into units called isoprene units (C5) usually united in a “head to tail” manner (isoprene rule)  Tail Isoprene Head C5H8 isoprene Monoterpene (2 x C5) Terpene classes Class Cn Isoprene units Hemiterpene C5 1 Monoterpene C10 2 Sesquiterpene C15 3 Diterpene C20 4 Sesterterpene C25 5 Triterpene C30 6 Polystyrene n x C5 nx5