Plant Extracts and Herbal Preparations PDF

# Plant Extracts and Herbal Preparations ## Extraction procedures There are many procedures for obtaining extracts like: - Maceration - Infusion - Percolation - Digestion - Decoction - Continuous hot extraction - Solvent-solvent precipitation - Liquid-liquid extraction - Distillation - Specific...

# Plant Extracts and Herbal Preparations ## Extraction procedures There are many procedures for obtaining extracts like: - Maceration - Infusion - Percolation - Digestion - Decoction - Continuous hot extraction - Solvent-solvent precipitation - Liquid-liquid extraction - Distillation - Specific procedures ### 1. Maceration In this process, the whole or coarsely powdered crude drug is placed in a stoppered container with the solvent and allowed to stand at room temperature for a period of at least 3 days with frequent agitation until the soluble matter has dissolved. The mixture then is strained, the marc (the damp solid material) is pressed, and the combined liquids are clarified by filtration or decantation after standing. - The main advantage of this method is that no degradation of extracted products since no heat is used. - The disadvantage is that not all compounds could be extracted. ### 2. Infusions This is prepared by leaving the material to be extracted (plant material) to soak in a pre-heated (hot) solvent at room temperature for a short period of time, with or without intermitted stirring, followed by separation of the plant debris from the extracting solvent e.g tea. ### 3. Digestion This is a form of maceration in which gentle heat is used during the process of extraction. It is used when moderately elevated temperature is not objectionable. The solvent efficiency of the menstrum is thereby increased. ### 4. Decoction In this process, the crude drug is boiled in a specified volume of water for a defined time; it is then cooled and strained or filtered. This procedure is suitable for extracting water-soluble, heat stable constituents. ### 5. Percolation In this method the material to be extracted is packed in a column with a tap at the lower end and an intermediary filter to prevent escape of solid material. The tap is opened and the extraction solvent (at room temperature ) is poured in at the top and allowed to trickle through the plant material. ### Soxhlet extraction (Continuous hot extraction process) In this method of extraction which requires the use of the soxhlet apparatus, the plant material to be extracted is placed in a porous thimble made of tough filter paper or cellulose, which is placed in the extraction tube of the apparatus. The apparatus is fitted to a around bottom flask containing the solvent used for extraction and to a reflux condenser. The solvent is boiled gently, the vapor passes up through the bypass side arm, condensed by the condenser and the condensed solvent falls into the thumble and slowly fills the inner tube. When the solvent reaches the top, if the reflux side arm tube reaches a certain point, it siphons over into the flask, thus extracting the plant material. This process is repeated as many times as necessary. - The major disadvantage of this method is that degradation of extracted compounds due to the use of heat and as extraction continuous the solvent become more concentrated with substance extracted thus they lose their solubility in it and eventually precipitate. Where the advantage of this method lies in it's use for large scale and is also useful for extraction with solvents of increasing polarity. ## Steam distillation Steam distillation is a popular method for extraction of volatile oils from plants. This can be carried out in a number of ways mainly include: - **Distillation with water.** Where the plant material is mixed with water and heated to boiling. The emergent vapors are collected and allowed to condense, the oil extracted is then separated from the water. - **Direct steam distillation** In this method steam from a separate generator is passed directly through the plant material. However, steam distillation is a relatively simple method with no separation or filtration step is needed. ## Solvent-solvent precipitation - The extract dissolved in a suitable solvent, is mixed with a less polar but miscible solvent causing the selective precipitation of the less soluble plant constituent, e.g. the precipitation of triterpenoid saponins from the methanol extract of Phytolacca dodecandra by the addition of acetone and the precipitation of gum from aqueous extracts of Olibanum by addition of alcohol. - By the addition of the extract to a solvent in which the constituents is insoluble or very sparingly soluble e.g. precipitation of resins from the alcoholic extracts by the addition of distilled or acidulated water. ## 1- The Volatile oil - The volatile oil is obtained by the steam distillation of plants or by other means (pressing or solvent extraction). - All volatile oils are obtained from plant source except oil of Musk, from Male deer and Amber, from whale. ## Methods of preparation of V.O. - Hydrodistillation - Scarification and expression - Extraction with solvents - Enzymatic hydrolysis - Supercritical methods The choice of the method depends on: - The condition of the plant material - The location of the oil in the plant - The amount of the oil - The nature of the constituents of the oil ### 1. Hydrodistillation method This method is based on the fact that a mixture of water and immiscible liquid 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. The choice of the method depends on: - The condition of the plant material. - The location of the oil in the plant **There are three types of hydrodistillation:** The principle of these methods is that, the boiling water or steam penetrate the plant tissue and vaporizes all volatile substances. - Before distillation the plant material must be subjected to size reduction in order to expose a great number of oil glands. This process termed "Comminution". - Flowers, leaves and other thin and non-fibrous parts of the plant can be distilled without comminution. - Seeds and fruits must be crushed. - Roots, stalks and all woody materials should be cut into short length. - **a- Water distillation:** The plant material is mixed directly with water in a still pot. - **b- Water and steam distillation:** The plant material is supported on a perforated grid screen inserted some distance above the bottom of the still, prevent direct water contact with the plant material. - **c- Direct steam distillation:** No water is kept in the bottom of the still. ### Disadvantages of the distillation The high temperature in the presence of water during distillation induce: - Hydrolysis of esters - Removal of water from tertiary alcohols. - Loss of water soluble components of V.O. - Volatile amines and volatile degradation products of carbohydrates (furfural) pass over during distillation and contaminate the V.O. ## The oil separator The mixture of the oil and water is passed through condenser, then oil is separated from the aqueous layer and can be isolated, usually by use of a Florentine receiver. Receiver for oils lighter than water. Receiver for oils heavier than water. - The distillation 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 water). ## Defination ### 2- Alkaloids - (Alkali-like) they are basic in nature - Derived from amino acid present in plant sources - Contain one or more nitrogen atoms (usually in a heterocyclic ring) - Marked physiological action on man or other animals. ### Deviation from Definition - Some alkaloids are not basic. eg. Colchicine, Piperine - The nitrogen in some alkaloids is not in a heterocyclic ring eg. Ephedrine, Colchicine ### Types of Alkaloids - **True Alkaloids:** Nitrogen is part of a heterocyclic ring. Derived from Amino acid. - **Proto Alkaloids:** Does not have heterocyclic ring with nitrogen. - **Pseudo Alkaloids:** Nitrogen is part of a heterocyclic ring. Not derived from Amino acid. ## Occurrence and Distribution ### PLANTS - Rare in lower plants. - In higher plants - about 10 to 25% - Dicots are more rich in alkaloids than Monocots. - Families rich in Alkaloids: Apocynaceae, Loganiaceae, Liliaceae Rubiaceae, Solanaceae and Papaveraceae. - Families free from Alkaloids: Rosaceae, Labiatae ### ANIMALS - Ergot alkaloids: Ergotamine and egrometrine from Ergot fungus. - Muscopyridine from Musk deer and Lycopodine from Lycopodium spores. ### Distribution in Plant - All Parts e.g. Catharanthus - Barks e.g. Cinchona - Seeds e.g. Nux vomica - Roots e.g. Aconite - Rhizomes e.g. Rauwolfia - Flowering tops e.g. Datura - Fruits e.g. Black pepper - Leaves e.g. Tobacco - Latex e.g. Opium ### Function in Plants - They may act as protective against insects and herbivores due to their bitterness and toxicity. - Source of nitrogen in case of nitrogen deficiency. - They, sometimes, act as growth regulators in certain metabolic systems. - They may be utilized as a source of energy in case of deficiency in carbon dioxide assimilation. ## Definition ### 3- GLYCOSIDES - Glycosides are organic compounds hydrolysis with acid, alkali, or enzymes - A sugar part is called as Glycone (One or more sugar) - Normally aromatic in nature. - Known as the aromatic aglycone or genin portion ### Occurrence - Occur in higher plant tissues in very small amounts. - Also fungal and bacterial cells (exuded in medium) and animals. - Formed by a biochemical reaction that makes a water insoluble compound more polar than a water soluble molecule. - Hence can be removed from an organic system. - Man forms them in the liver as part of the process of detoxification and they are excreted via urine. - Mammalian glycosides are simple compounds whereas plant glycosides are much larger and chemically more complex. ### The function or the role of glycosides in the plant organism - Converting toxic materials to non or less toxic. - Transfer water insoluble substances by using monosaccharide. - Source of energy (sugar reservoir). - Storing harmful products such as phenol. - Regulation for certain functions (growth). - Some have beautiful colours (pollenation process). - Some glycosides have antibacterial activity, so they protect the plants from bacteria and diseases.