Phytochemistry (PPC 303) Lecture (1) 2024-2025 PDF

Phytochemistry (PPC 303) Prof. Hala M. Hammoda Professor of Pharmacognosy and Vice Dean for Graduate Studies and Research Faculty of Pharmacy – Alexandria University Lecture (1) 1...

Phytochemistry (PPC 303) Prof. Hala M. Hammoda Professor of Pharmacognosy and Vice Dean for Graduate Studies and Research Faculty of Pharmacy – Alexandria University Lecture (1) 1 "Volatile Oils" "Essential Oils" sandalwood "Ethereal Oils" 2 2 1  Definition: The volatile oil is obtained by the steam distillation of plants or by other means then by direct steam distillation. All volatile oils are obtained from plant source except oil of Musk, from Male deer and Ambergris (Anber), from whale. http://upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Moschustier.jpg/220px-Moschustier.jpg 3 3 Occurrence of V.O. in plant tissues 1- In all tissues of the plant (Pinaceae) (‫(الصنوبر‬ 2- Localized in one or more organ of the plant, e.g.  - Petals of flowers (Rose)  - Barks and leaves (Cinnamon)  - Pericarp of fruits (Umbelliferous fruits)  - Stems and leaves glandular hair (Mentha)  - Petals and rind of fruits and leaves (Orange) 4 4 2  Forms & Combination of Volatile Oils in the plants Free form. Volatile oils may combine with a sugar part to form a glycoside (prepared by enzymatic hydrolysis). Volatile oils may also combine with: Gums ……. Oleo-gums Resins ……. Oleo-resins Both ……. Oleo-gum resins 5 5 Medicinal, pharmaceutical and commercial uses of V.O.  Therapeutic uses (Aromatherapy): External application and internal application.  Perfume industries, Cosmetics and Soap manufacture.  Spices and Condiments with preservative action.  Flavoring agents for pharmaceutical industries. 6 6 3  Therapeutic uses of V.O. A- External application:  Because of the lipoid solubility of V.O., they are easily resorbed through the skin and mucosa. (1) Hyperaemic effect:  V.O. cause a better local blood circulation on the applied area and may influence the inner organs. 7 7 Depending on the degree of skin-irritation: - Rubefacients cause only an increased blood circulation so increase nutrients and oxygen. - Vesicants cause stronger skin irritation and may even cause blisters. 8 8 4  Benefits of Hypaeramic effect: 1) Cardiac ointments for relief of pain in some cases of angina pectoris. 2) Relieve various skeletal muscles pains. ex. Eucalyptus oil, gaultheria oil and camphor oil. In form of: liniments, tinctures, extracts, oils for bath, ointments and gels. 9 9 3) Improve hair growth and re-growth by improving blood flow and strengthening blood vessels. Clove bud oil, Rosemary oil can nourish hair follicles, as well as help you relax, calm down and lower the risks or hair loss caused by stress. Therefore, the recommendation is massaging your scalp with 3-4 drops of clove bud oil before washing your hair with your usual shampoo. 10 10 5  (2) Anti-inflammatory effect: There are many reasons for this effect of essential oils, the antimicrobial action of essential oils is also an important aspect of their anti-inflammatory effect. ex.  Chamomile oil.  Arnica flower oil. 11 (3) Antiseptic effect:  Mechanism of action of V.O. as antiseptic: V.O. have lipoid solubility and it can dissolve the fats on cell wall of bacteria. Phenol coefficient: Expressing the bactericidal activity of a compound in relation to phenol (=1). 12 12 6  The higher the phenol coefficient value, the more effective the disinfectant. Value greater than 1 means that the disinfectant is more effective than phenol. Examples: Thyme oil ⎯→ phenol coeff. = 13.2 Thymol ⎯→ phenol coeff. = 20.6 Chlorothymol (synthetic) ⎯→ phenol coeff. = 75 13 13 Insecticide and insect repellent effect: Citronella oil (Lemon grass) is used as mosquito repellent. 14 14 7  B-Internal applications:  Essential oils are usually getting quicker into the blood-circulation by inhalation than by oral application. (1) Expectorating effect: is mainly caused by: a- Secretolytic effect (lysis of secretion). b- Secretomotor effect (moving the secretion).  Volatile oil has a little broncho- spasmolytic effect (relief broncospam).  Example: Peppermint, Anise, Thyme oils. 15 15 (2) Stimulation of secretions of digestive glands: Essential oils are used because of their appetite stimulation, this is done by stimulating the secretion of saliva and gastric enzymes and stimulating the secretion of bile (choleretic effect). 16 16 8  (3) Carminative effect: Anise fruits oil, basil, fennel, chamomile, coriander, caraway fruits, and peppermint oil. (4) Spasmolytic effect: It is observed as relief of spasms of smooth muscles of intestines and gall bladder. ex. Chamomile, caraway, fennel, orange and peppermint oil. 17 17 (5) Circulation stimulating effects: Some V.O. has stimulating effect on the respiration and circulation centers. ex: Camphor, rosemary, lavender and peppermint oils. 18 18 9  1- Allergic effect: V.O. have no allergic effect but upon storage, terpene hydrocarbons (contain double bonds) (have no allergic effect) will be converted into terpene hydroperoxides (have allergic effect). 19 19 2- Phototoxic and photosensitizing effect: Some V.O. containing furanocoumarins (are used in the treatment of vitiligo) can after an initial photosensitizing effect. Ammi majus 20 20 10  They give phototoxic reactions which can be observed as erythema (Redness of the skin, caused by hyperemia, increase of blood flow) and formation of blisters. 21 21 3- Abortion provoking effect: The uterus stimulating effect of some essential oils has been and is still misused for abortion. Essential oils cause distinct filling of blood vessels of the pelvis and strong contraction of the uterus. This misuse of essential oils may be fatal. 22 22 11  ex. High doses of thujone containing essential oils as junipers )‫(العرعر‬, chenopodium oil and parsley fruit (‫ (البقدونس‬oil. 23 23 4- Carcinogenic effect: β - asarone has a chromosome - damaging effect on human lymphocytes (white blood cells). Carcinogenic activity (liver carcinoma) may also be caused by safrole (the main component of sassafras oil, used as spice it has lemon odor). In some countries safrole is not permitted in food. 24 24 12  Estragole (methyl chavicol) is the main constituents of one of the varieties of fennel oil known as bitter fennel oil. Estragole has carcinogenic and mutagenic effect. It is important to avoid the use of estragole - rich chemotypes of fennel particularly for small children. 25 25 Methods of preparation of V.O. 1. Hydrodistillation. 2. Scarification and expression. 3. Extraction with solvents. 4. Enzymatic hydrolysis. 5. Supercritical method. 26 26 13  1. Hydrodistillation method This method is based on the fact that a mixture of water and immiscible liquid (V.O.) boils at a temperature lower than water. ex. The boiling point of turpentine oil is about 160°C, but on mixing with water and heating, the mixture boils at about 95.6°C. 27 27 Before distillation the plant material must be subjected to size reduction in order to expose a great number of oil glands and Facilitate handling of plant material. This process termed "Comminution". 28 28 14  Oil Separator (Oil Trap) 29 29 Disadvantages of the distillation The high temperature in the presence of water during distillation induce: Hydrolysis of esters and Removal of water from tertiary alcohols. Volatile amines and volatile degradation products of carbohydrates (furfural) pass over during distillation and contaminate the V.O. 30 15  Loss of water-soluble components of V.O. The distilled water contains small amounts of dissolved volatile oil and is often returned to the distillation still in order to recover the dissolved oil. This process is called Cohobation (Redistillation of distilled water collected in the separator). 31 31 2. Scarification and expression method Used for volatile oils: ❑ Cannot be distilled without decomposition (sensitive to heat, thermolabile). ❑ Found in large amount in oil - glands in the outer surface in the peel (rind). Generally, they are obtained by expressing the rind of the fresh fruit. ex. oil of orange and lemon. 32 32 16  3. Extraction with solvent Used for volatile oils: ❑ Containing thermo-labile constituents (sensitive to heat). ❑ Present in extremely small quantities ex. in the flowers of jasmine, violet, roses (Perfumes). 33 33 a- Using volatile solvent: Usually, light petroleum is used by percolation (continuous). 34 34 17  b- Using non- volatile solvent: i. Enfleurage method (Extraction with cold fat): The principles of enfleurage: Certain flowers continue the physiological activities of developing and giving off perfume even after picking. ex. Jasmine flowers. Fat possesses a high power of absorption of the perfume emitted. 35 35 - In the enfleurage process, A fat base (lard) “Corps” is spread in a thin layer on both sides of a glass plate supported on a rectangular wooden frame "Chassis". Batches of fresh flowers are lightly layered over the fat base. Several chassis are placed one above the other so that the flowers get sandwiched between two layers of fat which absorbs the perfume as it is given off. 36 36 18  Exhausted flowers are removed "De flèurage" and replaced by the fresh flowers until the fat is relatively saturated with flower oil. The perfumed (scented) fat must then be removed from the glass plates and called "Pomade". 37 37 The most highly saturated pomade being "Pomade 36" means the fat has been treated with fresh flowers 36 times during the whole process of enfleurage. The pomade is then extracted three times with alcohol 95% "Triple extraction", the obtained solution known as "extracts". The extract is concentrated at low temperature till free from alcohol, the concentrated flower oil is called "Absolute of enfleurage", "Absolute of pomade" or "Liquid concretes". 38 38 19  ii. Extraction with hot fat: The physiological activities of some flowers, ex. roses, are stopped by picking. So, the flowers are extracted by immersion in hot fat (their cell membranes ruptured then the hot oil absorbs the essence). The same batch of hot fat is treated with several batches of fresh flowers until the fat becomes quite saturated. 39 39 4. Enzymatic hydrolysis The volatile oil may find in the plant in a glycosidal form, the odoriferous substance is released only by hydrolysis: Bitter almond oil (Glycoside) (Volatile genin) 40 40 20  Winter green oil (Glycoside) (Volatile genin) 41 41 Black mustard oil N C S N S -glu + H2O OSO3 -K+ Allyl isothiocyanate Sinigrin (Volatile genin) (Glycoside) 42 42 21  5. Supercritical method Supercritical fluid extraction (SFE) Effective methods for the isolation of high- quality essential oils. High pressure extraction is more effective and an efficient way to extract valuable constituents from botanicals. 43 43 In this method the plant material is placed in a pressure vessel and pump a particular liquefied gas such as carbon dioxide through it at a specific pressure and temperature simultaneously above its critical point. Gas ------ High penetration power Liquid ---- High solubilizing power 44 44 22  Separating any essential oil from the matrix using supercritical fluid as extracting solvent, ex. SC CO2. 45 45 Physical methods of examination of V.O. Most oils are colorless when pure and fresh. Upon exposure to the air they acquire various colors. Volatile oils can be made colorless by re-distillation (Rectification). The blue color of oil of chamomile is an inherent property of the oil even when freshly distilled and said to be due to the highly unsaturated hydrocarbon called Chamazulene. 46 46 23  Variable 47 47 Specific gravity Gives an indication on composition of the volatile oil: 1- Oils lighter than water, ex: caraway, coriander, orange, lemon, and turpentine oils, are usually rich in hydrocarbons (aliphatic), alcohols, esters and ketones. 48 48 24  2- Oils heavier than water ex: anise, cinnamon and clove, usually contain chiefly aldehydes, phenols (aromatic), phenolic derivatives or certain esters. 49 49 Optical activity The rotatory power serves as a valuable means of detecting adulteration of volatile oil. ex. lemon oil (+ 57º to + 65.6º) adulterated with turpentine oil (about + 25° to - 40°). 50 50 25  Refractive index A property of a material that changes the speed of light, computed as the ratio of the speed of light in a vacuum to the speed of light through the material. This determination may serve for the detection of extraneous matter. 51 51 Congealing point The congealing point of a liquid the temperature at which it solidifies upon cooling. This determination is carried out with oils, ex. anise oil and eucalyptus, which contain large amounts of the readily crystallizable constituents as anethole and eucalyptol. 52 52 26  An abnormally low congealing temperature of V.O. indicates partial removal of the characteristic constituent for which the oil valued or the addition of extraneous matter, such as alcohol. 53 53 Chemistry of volatile oils Volatile oils constituents may be classified broadly into: i) Terpenes, related to isoprene or isopentene unit (C5H8) and their oxygenated derivatives. ii) Aromatic compounds, (Phenyl propanoid derivatives, (C6 – C3)). iii) Nitrogen, sulphur and lactone containing volatile oils. 54 54 27  Terpenes can be built up by the union of two or more isoprene (isopentene) units. Terpenes and terpenoids can be built up by the union of two or more isoprene (isopentene) residues (C5 units). Isoprene units: - Branched chain, 5 carbon atoms containing 2 double bonds. 1 4 3 2 55 5 55 How is the isoprenoid compounds are synthesized inside the plant? The biogenesis of terpens occurs via Mevalonic acid pathway (Formation of isoprene units). Then, oxygenation of the terpene hydrocarbons would naturally account for the presence of alcohols, aldehydes, ketones, esters and oxides. 56 56 28  Just reading Isoprene unit 57 57 THE ISOPRENE RULE The carbon skeletons of terpenes can be built up by the union of two or more isoprene (isopentene) residues. These units are usually united in a head-to-tail manner. 1 Tail Head 2 l 4 1 Tai 5 4 3 2 d 3 Isoprene Hea Isoprene C5H8 5 C5H8 58 58 29  The main classification of terpenes is on the basis of the number of isoprene units in the molecule, a single "terpene unit" being equal to two isoprene units: Isoprene Cn Group units 2 C10 Monoterpene 3 C15 Sesquiterpene 4 C20 Diterpene 6 C30 Triterpene 8 C40 Tetraterpene >8 C>40 PoIyterpene 59 59 The terpenes found most often in volatile oils are monoterpenes and sesquiterpens. They either occur in Acyclic OR cyclic (monocyclic, bicyclic or tricyclic). As hydrocarbons OR As oxygenated derivatives, such as: alcohols, aldehydes, ketones, phenols, oxides, peroxides and esters. 60 60 30  How is the phenyl propanoid compounds are synthesized inside the plant? They are synthesized via the Shikimic acid pathway. The principal precursors for compounds (C6 - C3) as cinnamic acid and p-hydroxycinnamic acid. These compounds arise from the aromatic amino acids phenylalanine and tyrosine respectively, which in turn are synthesized via shikimic acid pathway. 61 61 These contains (C6) phenyl ring which is attached (C3) propane side chain. In some cases, the side chain has been abridged to produce C1 or C2 side chain, to give structure (C6 – C1) or (C6 - C2), respectively. ____________________ 62 62 31