2 Extraction of crude drugs - Copy (3).pptx

Extraction of crude drugs

1. Extraction The need for extraction Crude drugs are not usually directly used as therapeutic agents because: Crude drugs are bulky Problems of administration Problems of transportation and storage Problems of formulation Safety problems Crude drugs contain heterogeneous mixture of compounds

2. Standardization of dose is a problem Due to biochemical variation Crude drugs are not suitable for research purpose as they are: The biological or therapeutic activity of a medicinal plant is closely related to the plant chemicals in it Therefore, the active principles are separated from crude drugs by various means and are employed in a more purified form The process of drug extraction is a generally accepted method of obtaining these active principles

3. Definition Extraction is the process of obtaining the desired constituent(s ) from crude drugs through the use of selected solvent (s) in which the desired constituents are soluble Since crude drugs contain a number of constituents that may be soluble in a given solvent (s), the products of extraction are called extractives or crude extracts

4. Crude extracts contain varying number of constituents, depending upon: the crude drug the solvent used the condition of extraction Plant materials are composed of heterogeneous mixture of constituents, some of which are pharmacologically active and therefore considered desirable and others are pharmacologically inactive and/or inert

5. If an inert substance interferes with the stability of either the active constituent or the final extractives (crude extract) steps would be taken either to prevent its extraction or to remove it from the extractive after its extraction The phytochemical constituents of plants can be classified into major groups of chemicals such as essential oils, alkaloids, acids, steroids, tannins, glycosides, saponins and so forth Each one of these classes of chemicals may have a preferred effective method of extraction which facilitates getting the chemicals out of the plant

6. In pharmacy the solvent or solvent-mixtures used for extraction is referred to as menstruum and the drug residue which is exhausted of active constituents is termed as the marc . Note:- the plant material should be properly authenticated or identified before extraction

7. Preparation of crude drugs for extraction Most drugs are dried soon after collection to:- Reduce any enzymatic activity that could result in destruction of the active constituents; Prevent the growth of bacteria, molds and yeast and; Facilitate pulverization, packaging, storage and shipping of the bulky material Fix the constituents

8. Before a plant drug is dried, the active constituents are generally present within the cells in aqueous solution or in colloidal suspension After drying, the active constituents occur with in the dried cells as crystalline or amorphous substances

9. The dried plant materials are generally ground or comminuted into powder to:- To break the majority of the cell walls and enhance solvent penetration To increase surface area If fresh plant material is to be used, it should be homogenized or cut into smaller pieces before extraction

10. Choice of suitable solvents Solvents differ widely from each other in boiling points , polarity and how they act or react with substances in which they come in contact When considering the suitability of a solvent for extraction, it should meet the following criteria It should be readily available and cheap It should have good solvent action for many plant constituents

11. It should be non-toxic, non-irritant and nonflammable It should be environmentally friendly It should be non-explosive It should not have any destructive effect on the constituent(s) to be extracted It should penetrate the plant material and reach where the plant constituent is found It should be easily evaporated at a low heat

12. The selection of the menstruum to use in extraction of crude drugs is based primarily upon the relative solubility of the active constituents and inactive and/or undesirable constituents in it Alcohol is a general solvent for many plant constituents because it will meet almost all of the above criteria 70% alcohol is used as a universal solvent for extraction

13. Water immiscible solvents are also widely used:- Light petroleum, benzene, and hexane for extraction of essential oils, fixed oils, and steroids Ether and chloroform for extraction of alkaloids and quinines, etc.

14. Methods of extraction An extraction method should be:- Preferably fast Efficient Economical Selective to the medicinally important plant components and Should preserve the plant constituents

15. Classification of extraction methods

16. Solvent extraction Solvent extraction is a method of extraction where the plant material is extracted with a solvent, which could be liquid, semisolid or supercritical fluid (CO 2 or N 2 ) Depending on the volatility of the solvent, one can have:- Volatile solvent extraction Non-volatile solvent extraction and Supercritical solvent extraction

17. Solvent extraction is mostly applied to obtain non-volatile plant constituents Extraction is effected mainly due to solubility and to some extent due to diffusion The choice of solvent depends on mainly the solubility of the plant constituents of interest. Remember that “like dissolves like”.

18. Preparation of plant material for volatile solvent extraction Plant material is collected and separated from unwanted materials such as unwanted parts of the plant, other plants, soil etc. The plant material is then dried. WHY???

19. Note that drying should be done as quickly as possible. Drying conditions: Temperature not more than 40 o C and under the shade (avoid direct sunlight). The plant material is grinded to appropriate size Grinding facilitates extraction by increasing surface area.

20. Solvent extraction methods The principal methods of drug extraction employed in pharmacy are:- Maceration Percolation Refluxing Soxhlet /continuous hot extraction

21. The choice of the extraction procedure generally depends on:- The nature of the crude drug The nature of the components to be isolated Purpose of extraction Degree of purity desired Availability of solvent and apparatus, etc .

22. Maceration Maceration simply means cold soaking It is a process in which the properly powdered drug is allowed so soak in the menstruum until the cellular structure is softened and penetrated by the menstruum and the soluble constituents are dissolved Maceration is usually done at a temperature between 15 to 20°C for a period of usually 3 days according to USP

23. Procedure The drug to be extracted is placed in suitable container (beaker, flasks, bottle, etc.) The prescribed amount of menstruum is added The vessel is stoppered tightly and the contents are agitated or stirred occasionally The extract is filtered and the filtrate is concentrated/dried

24. Advantage : Simplicity Preserve thermolabile compounds Disadvantage : Consumes too much solvent Saturation is attained quickly Time taking

25. Percolation The term percolation comes from the Latin words per means through and colare mean to strain Percolation may be described generally as a process in which powdered drug is extracted by slow passage of a suitable solvent through a column of drug The powdered drug is packed in a special extraction apparatus termed percolator and the extractives collected are termed percolate

26. In the process of percolation the flow of solvent over the drug column is generally downward to the exit orifice, impelled by force of gravity as well as the weight of the column liquid

27. preparation of crude drugs for percolation powdering moistening to encourage swelling packing the percolator period of maceration percolation and collection of percolate Disadvantage : not suitable for unorganized drugs

28. Refluxing Refluxing means:- to boil a liquid in a vessel attached to a condenser so that the vapors continuously condense for re-boiling The purpose is to thermally accelerate the solubility of the components at an elevated temperature (i.e. the solvent’s boiling point .)

29. Fig. Refluxer

30. Procedure Powdered plant material is placed in a flask Sufficient amount of the menstruum is added The flask is connected to a condenser, such that any vapors given off are cooled back to liquid, and fall back into the flask The flask is then heated vigorously for the course of extraction (usually 48hrs) Cool the content of the container under running water and then filter Concentrate the filtrate

31. Advantage of this technique is: It can be left for a long period of time without the need to add more solvent or No fear of the flask content boiling dry as any vapour is immediately condensed in the condenser Moreover, as a given solvent will always boil at a certain temperature, one can be sure that the extraction will proceed at a constant temperature By careful choice of solvent, one can control the temperature within a very narrow range Disadvantage : It is not suitable for thermolabile plant constituents

32. Soxhlet (continuous hot extraction ) In the most commonly used semi-continuous method applied to extraction A soxhlet extractor was invented in 1879 by Franz von Soxhlet

33. Procedure The sample is dried, ground into small particles and placed in a porous cellulose thimble The thimble is placed in extraction chamber which is suspended above a flask containing the solvent and below a condenser The flask is heated and the solvent evaporates and moves up into the condenser where it is converted into a liquid that trickles into the extraction chamber containing the sample

34. The extraction chamber is designed so that when the solvent surrounding the sample exceeds a certain level it overflows and trickles back down into the boiling flask through a siphon arm This cycle may be allowed to repeat many times, over hours or days During each cycle, a portion of the non-volatile compound dissolves in the solvent After many cycles the desired compound is concentrated in the distillation flask

35. At the end of extraction process the flask containing the solvent and the soluble constituents is removed The solvent in the flask is then evaporated by means of a rotary evaporator and the mass of the remaining extract is measured The non-soluble portion of the extracted solid remains in the thimble, and is usually discarded

36. Advantages : Saves solvent Efficient Saturation is not a problem i.e. instead of many portions of warm solvent being passed through the sample, just one batch of solvent is recycled Disadvantages Not suitable for thermolabile components Expensive

37. video

38. Successive solvent extraction The air-dried powdered plant material is extracted in soxhlet assembly successively with petroleum ether, benzene, solvent ether, chloroform, acetone, ethanol and methanol Finally, the drug is macerated with chloroform water. Each time before extracting with the next solvent, the powdered material is dried in hot-air oven below 50˚C.

39. Each extract is concentrated by distilling off the solvent and the evaporating to dryness on water-bath. The extract obtained with each solvent is weighed and its percentage is calculated in terms of air-dried weight of plant material The extract with different solvents can also be prepared by successively macerating (cold extraction) the powdered drug in order of increasing polarity.

40. Distillation A process in which a liquid mixture is separated in to its components by vaporization and subsequent condensation It is a physical process. vapor evolved from a boiling liquid mixture Richer in the more volatile components than the liquid with which it is in equilibrium

41. 41 Applications Traditionally to produce beverage To extract volatile active principles from vegetable drugs To separate volatile substances from their less volatile impurities To recover volatile solvents ,notably alcohol for further use

42. 42 Types Simple distillation Fractional distillation Steam distillation

43. 43 1. Simple distillation A process of converting liquid in to its vapor, transferring the vapor to another place and recovering the liquid by condensing the vapor generally employed for the separation of liquids from non volatile solids preparation of distilled water in the recovery of alcohol during the preparation of dry extracts Apn : Liquids having minimum BP difference e.g chloroform benzene acetone…25c

44. Hydro distillation

45. Steam distillation Steam distillation brings steam in direct contact with the plant material in the retort from an outside source. A steam boiler is generally used, producing live steam, usually of a pressure higher than atmospheric. From here the steam is injected into the retort which may operated at or about atmospheric pressure, or may also run above or below atmospheric pressure.

46. Steam distillation is used for Termally responsive compds e.g bromobenzene the determination of volatile oils in drugs manufacture of essential oil The distillate separates in to two layers water & the other component: these are separated in separating funnel

47. Steam distillation