Lecture 3: Pharmacognosy I (PHCG 111) PDF

For First year Pharmacy Students By 1  Bleaching e.g white bees-wax is produced by bleaching 2 B- DRYING OF CRUDE DRUGS Fresh organs, when collected are either used as such (fresh) and used instantaneously or dried to be...

For First year Pharmacy Students By 1  Bleaching e.g white bees-wax is produced by bleaching 2 B- DRYING OF CRUDE DRUGS Fresh organs, when collected are either used as such (fresh) and used instantaneously or dried to be used later. ▪ Objectives of Drying: 1. To aid their preservation. 2. Fix constituents to stop enzymatic action that may destroy active constituents. 3. Prevent growth of microorganisms (bacteria and fungi) 4. To facilitate powdering (comminution) of the plant. 5. To decrease size and weight of the plant. This facilitates packing, transport and storage. 3 Drying is best accomplished by the proper regulation of temperature and humidity of air. ▪ Fresh organs usually contain high percentage of moisture (80-90%). ▪ Drying must be carried out as rapidly as possible. ▪ Insufficient drying favors spoilage by moulds, bacteria and enzymatic action. ▪ The drying process should reduce the moisture content of the drug below this critical threshold level (the moisture requirements for moulds and bacteria growth) 4 The methods for drying may be classified as natural or as artificial. A- Natural drying ▪ The drug is dried by exposure to direct sun, or spreading in the shade. ▪ Shade drying: employed when it is desirable to retain natural color of the drug and preserve its sensitive active constituents. ▪ Sun drying: adopted to those items which are not affected by direct action of sunlight. 5 B- Artificial drying ▪ Artificial method may be: ❖ physical, that is, involve the use of elevated temperature and/ or decreased pressure (vacuum) or the use of radiation of infra-red or micro wave ovens. ❖ chemical, which is to involve use of desiccants. ▪ Drying with artificial heat is generally the most acceptable method when skillfully operated. The heat should be such as to maintain an efficient temperature for vaporizing the moisture but not high enough to affect the constituents of the drug. 6 ▪ Artificial drying has the distinct advantage over air drying (natural drying) in that: a. It immediately stops enzymatic action e.g. in Digitalis If the leaves are allowed to dry naturally, a very rapid hydrolysis of cardiac glycosides occur. b. Artificial drying is a rapid method, usually done at a well controlled temperature. Rapid drying not only prevents the decomposition of active principles but also retains the colour of the drug. 7 Artificial heat may be applied by: 1. Direct fire: Drugs are placed on a wire net over burning coal or wood. Excessive heat produces gelatinization of starch resulting in very hard drugs, as well as the undesirable odor of drug. 2. Use of heated stones: In which stones are used instead of wire 3. Use of stoves: These must be done carefully to prevent the damage produced to drugs when dried e.g. scorching or burning. 8 4. Drying sheds or chambers: ▪ The process is controlled completely and un-affected by difficulties arising from changes in weather. ▪ The chamber is provided with thermostat (to control the drying temperature) and a thermometer to indicate the temperature. 5. Drying tunnels: ▪ Drugs can be run on wheels moving on rails, heat is drawn or forced over the shelves from back to front of the chamber by means of fan and drying is quickly effected. ▪ Drying chambers and tunnels are used for large quantities of drugs. 9 6. Drying ovens: ▪ Theyare small cabinets heated electrically, supplied by a fan for circulating air, thermostat and thermometer. Sometimes it is evacuated (vacuum oven) which is rapidly and efficiently drying at lower temperature. 7. Pneumatic high speed drying: ▪ Is applied for sensitive drugs e.g. Digitalis. The drug dried by exposure to high temperature (800°C) for fraction of a second under reduced pressure. 10 8. Freeze Drying (Lyophilization): ▪ It is an extreme form of vacuum drying, in which liquid is frozen then subjected to high vacuum and drying takes place by subliming the solidified ice-phase. Very low temperature and high vacuum are used. ▪ This method is used usually for highly sensitive drugs, biological fluids (such as blood plasma), royal jelly, enzymes and hormone extracts (such as insulin). 9. Chemical drying: ▪ This method is done at room temperature where the drug is placed in a closed vessel called desiccators over a dehydrating agent or desiccants (anhydrous CaCl2, Conc. H2SO4 or Silica gel). ▪ This is used for small quantities of drugs for research and for storing pure natural products. 11 ▪ "An Absolutely dried drug" is that completely freed from water. When exposed to air, it absorbs 8 to 10% of moisture and is called "Air - dry drug". ❑ Changes in Drugs during Drying: 1. Size and weight; due to loss of water where drugs get smaller in size and they lose 80 to 90% of their original weight. 2. Shape and appearance; Some drugs shrivel and shrink when dried, and the surface gets wrinkled or reticulated. Examples:  Black Pepper  The petiole of Datura stramonium leaves becomes hooked on drying. 12 3.Color; generally on drying, the drug becomes darker in color, but in certain cases, a total change may occur. Examples:  Tea leaves change from green to dark brown, almost black.  Vanilla changes from yellow to dark brown. ▪ The green color of certain drugs change to brown on drying due to decomposition of chlorophyll. ▪ Flowers may lose their color especially when red or blue due to the destruction of the anthocyanin pigments producing these colors. 13 4. Odor; In certain drugs, drying changes odor. Examples: ▪ Digitalis and Hyoscyamus lose their bad odours when dried;. ▪ Orris, changes, its disagreeable odour when fresh into a pleasant odor when it is dried. ▪ Vanilla pods odourless, when fresh, and on drying acquire a fragrant, pleasant, aromatic odour due to the liberation of vanillin which has a nice aroma. 5. Taste; of the drug may be altered eg. Gentian very bitter when fresh, and becoming pleasant on drying. 6. Constituents; of some drugs may change due to drying 14 Examples: ▪ Fresh Vanilla On drying, hydrolysis and oxidation occur to produce vanillin. REMARK ▪ One should always notice if these changes, occurring on drugs are required or are objectionable to control the drying process accordingly. ▪ If these are required, drying is done slowly and the temperature controlled. If the changes are objectionable, drying must be carried out as rapidly as possible and controlling the temperature so as not allow these changes to occur. 15 C. PACKING OF DRUGS ▪ Packing may be loose or by use of considerable pressure. ▪ Packing will provide protection to the drugs as well as economy of space. ▪ Wooden or paper boxes and barrels are also common shipping and storage containers. ▪ Drugs likely to deteriorate from absorbed moisture (e.g. Digitalis, Ergot) are packed in moisture-proof cans. Effect of packing on Appearance: ▪ e.g. Indian Senna leaves are packed into large bales, using hydraulic pressure resulting in the leaves being flatter and showing faint oblique or transverse markings. Packing gives Indication for Geographical source: ▪ e.g. Aloes. ▪ Another example is opium