1. PREPARATION OF CRUDE DRUGS FROM MEDICINAL PLANTS BY
ERHIRHIE EARNEST O.

2. OUTLINE Introduction Basic principles of extraction
Choice and quality of extraction solvents
Collection of plant materials
Preservation of plant materials
Grinding/size reduction of plant materials
Common methods of plant extraction
Filtration of macerate
Common methods of concentrating filtrate to dryness
Calculation of percentage yield
By Erhirhie Earnest O.

3. GRAPHICAL OUTLINE
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4. INTRODUCTION
The principle objective of this work is to enlighten researchers on the basic principles of extraction of active ingredients from medicinal plants for research purposes.
Extraction: This is the separation of medicinally active portions of plant from the inactive components by using selective solvents in standard extraction procedures.
Extract: This is a preparation of crude drug which contains all the constituents which are soluble in the solvent used in making the extract.
By Erhirhie Earnest O.

5. INTRODUCTION
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6. BASIC PRINCIPLE IN EXTRACTION
Plant constituents are usually contained inside the cells. Therefore, The solvent used for extraction must diffuse into the cell to dissolve the desired compounds.
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7. CHOICE AND QUALITY OF EXTRCTION SOLVENT
The ideal solvent for a certain pharmacologically active constituent should:
Dissolve the substance to be extracted, yet it must be only sparingly soluble in the solvent from which the desired substance is to be extracted.
Extract only the desired substance or as small an amount as possible of any other substance present.
Not react chemically with the solute in an undesirable way,
Be easily separated from the desired solute after extraction.
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8. QUALITY AND CHOICE OF EXTRCTION SOLVENT
Ethyl alcohol is the solvent of choice for obtaining classic extracts such as tinctures and fluid, soft and dry extracts. The ethyl alcohol is usually mixed with water to induce swelling of the plant particles and to increase the porosity of the cell walls which facilitates the diffusion of extracted substances from inside the cells to the surrounding solvent.
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9. Collection of plant materials
Suitable time for collection
The amount of a constituent is usually not constant throughout the life of a plant.
Roots and rhizomes should be collected in the raining season . In most cases they must be washed free of adhering soil and sand.
Bark should be collected in the dry season.
Leaves should be collected at the flowering stage.
Flowers should be collected when fully developed and also in the morning after the morning dew had evaporated.
Fruits and seeds should be collected when fully ripe.
Whole plant should be collected during flowering stage.
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10. Preservation of plant materials
After collection, the plant material must first be preserved so that the active compounds will remain unchanged during transport and storage.
The most common method for preserving plant material is drying.
Living plant materials have a high water content:
leaves may contain 60-90% water,
roots and rhizomes 70-85% water
wood 40-50%.
Seed contains 5-10% water

11. Preservation of plant materials
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12. Grinding/size reduction of plant materials
The first operation that must be performed after drying is grinding of the plant material to a powder of suitable particle size.
Large particles take a longer time for complete extraction than small ones and large differences in particle size thus slow down the extraction process.
The purpose for powdering the plant material is to rupture its tissue and cell structures so that its medicinal ingredients are exposed to the extraction solvent.
Furthermore, size reduction maximizes the surface area, which in turn enhances the mass transfer of active principle from plant material to the solvent.
Machines are available for grinding crude drugs:
Hammer mill
Knife mill;
Tooth mill;
Blender
Morter and pestle
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13. Machines are available for grinding crude drugs
Electrical blender
Hammer mill, Knife mill
Morter and pestle
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14. SAMPLES OF POWDERED PLANT MATERIALS
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15. COMMON METHODS OF PLANT EXTRACTION
Infusion
Decoction
Maceration
Percolation
Digestion
Continuous hot extraction
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16. METHODS OF PLANT EXTRACTION
Infusion:
In this method,
the plant material (herbal tea) is placed in a pot and wetted with cold water.
boiling water is poured over it, then left to stand.
It is then covered with a lid, for about fifteen minutes after which the tea is poured off.
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17. COMMON METHODS OF PLANT EXTRACTION
Decoction:
In this process, the crude drug is boiled in a specified volume of water for a defined time.
It is then cooled and filtered. This procedure is suitable for extracting water-soluble, heat-stable plant constituents.
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18. COMMON METHODS OF PLANT EXTRACTION
Maceration:
Whole or coarsely powdered plant material is placed in closed container with the extracting solvent and allowed to stand at room temperature for a period of time with frequent agitation until the soluble matter is dissolved.
The mixture then is filtered, the marc (the damp solid material) is pressed.
The combined liquids are clarified by filtration or decantation .
By Erhirhie Earnest O.

19. COMMON METHODS OF PLANT EXTRACTION
Percolation:
In this method, the plant material is subjected to a slow flow of fresh solvent at intervals until sufficient active ingredient is extracted.
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20. COMMON METHODS OF PLANT EXTRACTION
Digestion:
Digestion is also considered as maceration but, at a relatively elevated temperature.
This method is suitable for hard barks or woods which are difficult for water to penetrate.
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21. COMMON METHODS OF PLANT EXTRACTION
Continuous hot extraction method:
This is the most common method used for the extraction of organic constituents from dried plant tissue.
It can be used both on laboratory and industrial scales.
In the lab, the powdered material is continuously extracted in a Soxhlet apparatus with a range of solvents of increasing polarity.
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22. FILTRATION OF MACERATES
The extract so obtained is separated out from the marc (exhausted plant material) by allowing it to drip/drop into a beaker or a reservoir.
The marc is retained at the false bottom, and the extract is received in the holding tank.
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23. CONCENTRATION OF FILTRATE TO DRYNESS
The filtered plant part (liquid portion) must be reduced to paste-like, cakey, and finally powdered form through standard techniques.
The essence of concentrating filtrate to dryness is to;
Calculate the active ingredient present after the extraction by calculation of percentage yield.
To obtain dose of plant extract in milligram or gram that can be further constituted in a known volume of vehicle for experimental animals dosing.

24. COMMON METHODS OF CONCENTRATING FILTRATE TO DRYNESS
Heating mantle
Rotatory evaporator
Freeze dryer (Lyophilizer)
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25. CONCENTRATION OF FILTRATE TO DRYNESS
The enriched extract from maceration or extractors, is;
fed into a water bath, oven, hot plate, heating mantle, etc to produce a thick concentrated extract free from solvent.
Or the concentration could be done using rotary evaporator in order to remove excess solvents from samples by applying heat to a rotating vessel at a reduced pressure.
A freeze dryer or lyophilizer can also be used to concentrate and dry the filtrate extract (only aqueous) at reduced temperature (eg -20 to -500C).
By Erhirhie Earnest O.

26. Calculation of percentage yield
Percentage yield is the amount of product captured by the extraction. This will provide the extraction yield.
Percentage yield = x
For example:
If 400g of powdered leaf was soaked in 1200ml (1.2litres) of ethanol and after concentration to dryness the final weight recovered was 40g, the percentage yield can be calculated as follows;
Percentage yield =   X = 10%w/w

27. CONCLUSION AND RECOMMENDATIONS
Plant extracting is necessary for scientific purpose. The intending plant meant for research purpose should be carefully identified, collected at the right time, preserved, grinded, and extracted in other to avoid errors in research.
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28. CONCLUSION
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29. REFERENCES
Agrawal, S.S. Paridhavi, M.H. Herbal drug technology pg no: , 3.
EMEA, 2006, Guideline on Quality of Herbal Medicinal Products/Traditional Herbal.
Harborne, J.B. Phytochemical methods- a guide to modern techniques of plant analysis pg no:5-15.
Medicinal Products, EMEA/CVMP/814/00 Rev 1, European Medicines Agency, London, U.K., p
Renu, S. and Badri P. N. (2012). New methods for extracting phytoconstituents from plants. International Journal of Biomedical and Advance Research. 03(10)
Stefani D. H. and Susanne V. From plant to drugs. Center for Toxicology. The University of Arizona.
WHO, 2003, WHO Monographs on Selected Medicinal Plants, Vol. III, World Health. Organization, Geneva.
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