Phytochemistry I Lecture 2 PDF

Phytochemistry I Lecture 2 V.O. - Methods of preparation 1  Distillation Methods of Preparation of Volatile Oils 4....

Phytochemistry I Lecture 2 V.O. - Methods of preparation 1  Distillation Methods of Preparation of Volatile Oils 4. Enzymatic 1. Hydrolysis Distillation 3. Extraction 2. Scarification and Expression 2  1. Distillation method This depends on Dalton’s law of partial pressure which states that “when two immiscible liquids are heated together, they will boil at a temperature below the boiling point of either one”. A-Simple steam distillation or B-Saturated steam distillation Water distillation 1-Direct steam 2-Water and distillation steam distillation 3 A- Water distillation apparatus 4 Apparatus consists of: 1- Vessel for plant and water (=Still) 2-Condenser to cool and condense the vapor 3- Receiver to collect the volatile oil Cohobation: The return of the aromatic water (water saturated with volatile oil) to the body of the still to be redistilled in order to improve the yield of oil. 5 B- Saturated steam distillation 1-Direct steam apparatus 6 This process is adopted to: 1-Shorten the duration of distillation. It is suitable for heat sensitive materials 2-Limit the alteration of the constituents. 3-Conserve energy. 7 2-Water and steam apparatus 8 9 Precautions in handling the plant: 1.Comminution just before distillation. 2.Wetting of dry material. 3.Even packing or charging to facilitate hydrodiffusion. Hydrodiffusion is the process by which water penetrates the plant tissue. The highest the rate of hydrodiffusion the lowest is the hydrolysis and decomposition of the constituents. So, coarse comminution and even charging are recommended. 10 Distilled oil may be considered as artifacts due to: Insufficient distillation time may result into fractionation of the oil. High boiling point constituents may not be carried with steam. Volatile impurities such as amines may contaminate the final product. Sensitive constituents could be affected by boiling water. 11 At high temperatures: A. Esters are hydrolyzed. B. Tertiary alcohols are dehydrated to hydrocarbons. C. Unsaturated terpenes are polymerized. Purification of oils prepared by distillation 1- Removal of bad smelling or colored impurities: a- Re-distillation in steam. b- Dry distillation under reduced pressure. 2- Removal of water and moisture is done by filtration over anhydrous sodium sulphate. 12  Distillation Methods Water distillation Water and stem Direct steam distillation distillation Plant material 1. Dried e.g. Dried &fresh leaves Fresh plant powders and herbs containing sufficient 2. Petals moisture Mode of charging Material is covered Water in the still Water is absent and with water but the steam only the steam is forced is in contact with through the plant. the material. Hydrodiffusion Better when the Better when the Better when the material moves material is coarsely charging is even. freely in water comminuted, and the charging is even. Steam pressure About atmospheric About atmospheric Can be modified 13  Water distillation Water and stem Direct steam distillation distillation Temperature About 100◦C About 100◦C Can be modified Rate of distillation Relatively low Fairly good High Commercial 1. Turpentine oil 1. Clove oil Peppermint oil preparation 2. Rose oil 2. Cinnamon oil Advantage 1. Low price No hydrolysis 1. Suitable for large 2. No transportation scale production. 2. Suitable for oil rich in esters Disadvantage 1. Burning of the plant Hydrodiffusion Powders couldn’t be 2. Not used for oils could be affected by used. rich in saponifiable, fine comminution, water soluble or high uneven charging or boiling point excessive wetting constituents (low yield) 14  2. Scarification & Expression C. Expression A. Sponge B. Ecuelle a D. Machine of Rasping method piquer process process 15  2. Scarification & Expression Methods Principle Mechanical procedures carried at room temperature & based on puncturing & squeezing of the plant material to liberate the oil, which is collected. Applications Preparation of heat sensitive oils, present in large amounts in outer peels of fruits e.g. Citrus fruits (Rutaceae) as orange, lemon & bergamot 16 A- Sponge Method Based on squeezing the removed peels e.g. orange 1. Fruits washed, cut into halves & fleshy parts removed. 2. Peels soaked in water, turned inside out then pressed between a convex projection & a sponge. 3. Sponge (saturated with oil emulsion) periodically squeezed in a vessel The tissue of the sponge serves for: 1. Collection of the oil 2. Filtration of the product from any particles of the inner white zone of the peel. (e.g. orange oil in Sicily) 17 B- Ecuelle-à-piquer method Based on puncturing (scarifying) the surface of whole fruits (lemon), the oil exudes from the outer zone of the peels in the form of emulsion. The instrument is funnel-shaped, formed of a shallow bowl with a tubular project ion at the center. The bowl bears numerous pins which scarify the oil glands to release the oil. The tubular part serves as: 1. Handle to rotate the instrument. 2. Receiver to collect the oil. (e.g. lemon oil in France). 18 C- Expression of rasping process Based on removal of the outer layer of the peel with a grater, collecting the rasping in special bags then strong pressing. The oil emulsion is collected in large vessels II 19  3. Solvent Extraction A. Extraction B. Extraction C. Supercritical with volatile with non- fluid extraction solvent volatile solvent I. Enfleurage II. Pneumatic III. Maceration Method Method Method 20  3. Solvent extraction methods Principle Based on extraction of the volatile oil from the plant material with a suitable solvent Application Preparation of delicate flower oils e.g. as jasmine, violet, tuberose, narcissus which are 1. Present in very small amounts, (not easily obtained by distillation or expression) 2. Oils formed of thermolabile constituents (i.e. easily decomposed by heat) 21 According to the nature of the solvent used, three types are distinguished: 1. Non-volatile solvent extraction 2. Volatile solvent extraction 3. Supercritical fluid extraction A- Non-volatile solvent extraction: Solvent used may be: a. Fats such as lard and tallow (2:1). e.g. “Enfleurage method” The products are: “Enfleurage product” “Triple extract” “Absolute of enfleurage” or “volatile oil” b. Fixed oil such as olive oil. 22 “Enfleurage” Process Cold Enfleurage Hot Eufleurage 23  Enfleurage Process-Preparation of jasmine oil Equipment: Great number of glass plates closely arranged in wooden frames (orchassis). Procedure: 1. Spread the mixture of fat (lard/tallow2:1) on both surfaces of each glass plate. 2. Cover the top of each plate with flowers or petals, so that each layer of flowers is enclosed between 2 layers of fat. 3. Replace old flowers by fresh every 2-3 days 4. Repeat the process until the fat is saturated with the oil 5. Remove the last charge of flowers from the fat ("Defleurage") 6. Scrap & collect the fat layers, warm, filter through gauze & cool “Enfleurage product” or “Floral pomade” 24  Flower petals ↓ Fat mixture (lard + tallow 2:1) Enfleurge product (floral pomade) [fat saturated with oil] ↓ Successive extraction by Absolute alcohol & cooling to remove fats Triple extract [alcoholic solution of v.o. + pigment+ traces of fats] ↓ 1. Dilution with water + NaCl 2. Evaporation or fractional distillation Absolute of enfleurage Semi-solid, alcohol-free product Volatile oil 25 B- Volatile solvent extraction e.g. Preparation of “floral concrete” and “floral absolute”. ♠The absolutes are richer in oxygenated constituents which are in most cases responsible for the odor of the oil. ♠Thus, they can be used in much smaller concentrations than the corresponding concretes in perfume industry. C- Supercritical fluid extraction (Extraction by supercritical gas) 26  Methods of Preparation of Volatile Oils Process Application Advantage Disadvantage Distillation Suitable fresh and dried Cheapest commercial The use of high materials, rich in volatile technique temperature and water oil with constituents may affect the oil mostly unaffected with constituents. heat Scarification and Suitable for oils present 1.Carried at room High cost as it needs Expression in high amounts in the temp. high number of outer peels of fruits and 2.Yield oils with workers. rich in heat sensitive natural odours. constituents Extraction For fresh materials with 1.Carried at room High cost as it needs heat sensitive oils present temp. high number of in small amounts. 2.Yield oils with workers. natural odours 27  4. Preparation of volatile oils present in glycosidic combination The plant material is first hydrolyzed (by the aid of specific enzymes present in the same plant) to liberate the volatile constituents from the parent odorless glycoside. Then the plant material is subjected to either distillation or extraction. Purification of the products. 28  Storage of volatile oils Before storage the oil should be freed from any metallic impurities (that may act as a catalyst for decomposition reactions). Oils should be dried over anhydrous sodium sulphate to get rid of moisture. The containers should be dark colored, completely filled and tightly closed. The oils are kept away from light, at low temperature (if necessary under an atmosphere of CO2 or N2 gases). 29