ISOLATION, PURIFICATIONAND SCREENING OF PLANT CONSTITUENT S DR.U.SRINIVASA. M.Pharm,Ph.D
INTRODUCTION The use of plant-derived medicinal dates back many centuries although it is still under estimation in modern medicine. Plants remain the most important source of natural drugs. More than 30% of prescription drugs are natural products. More than 60% of anticancer and anti-infective drugs are natural products.
SOURCES OF DRUGS1.Natural substances: From plants, microorganisms, animals etc. (totally obtained from nature).2. Semi synthetic substances: These are drugs that are manufactured by partial synthesis.3. Synthetic substances: These are drugs which are manufactured by total synthesis (i.e. complete synthetic process or processes)
MEDICINAL PLANTS INFORMATIONSOURCES : Information, however can be obtained from one or more of the following sources: 1- Herbals 2- Medical botany 3 - Ethnobotany 4 - Herbaria (herbarium) 5 - Field exploration 6 - Phytopharmacological surveys
PHYTOCHEMICAL SCREENING –To carry phytochemical screening the following pointsmust be fulfilled:1- Selection of promising plant materials.2- Proper collection of selected plants.3- Authentication of plant material.4- Drying of plant materials.5- Grinding of the dried plants.6 - Garbling of the dried plants7 - Packing, storage and preservation8 - Extraction and fractionation of constituents.9 - Methods of separation and purification.10 - Methods of identification of isolated compounds(Structure elucidation e.g. UV, IR, MS, H-NMR and C-NMR)
SELECTION OF PROMISING PLANTMATERIALS: Before investing time, effort and money in phytochemical screening it is very important to select a promising plant. The choice of promising plant depends upon the following:1- A plant which have a biological activity.2- A plant used in folk medicine.3- A plant which show a particular toxicities
IDENTIT Y Identity can be achieved by macro- and microscopical examinations. Voucher specimens are reliable reference sources. Outbreaks of diseases among plants may result in changes to the physical appearance of the plant and lead to incorrect identification. At times an incorrect botanical quality with respect to the labeling can be a problem.
PROPER COLLECTION OF SELECTED PLANTS Drug may be collected from: 1 - Wild plants. 2 -Cultivated plants. Wild plant Cultivated plant Disadvantage Advantage Scattered in large or Present in limited area unlimited area Difficult to reach Easy to reach The collector must be The collector must not be highly skilled botanists skillful person Deficiency may occur due Continuous supply to continuous collection
The following precautions should be considered during stage of collection : 1 .The proper time of the day, time of the year and maturity stage of collection is particularly important because the nature and quantity of constituents may vary greatly in some species according to the season and time of collection 2.The collected plant should be free from any contamination. 3.Collecting plants which are free from diseases (i.e. which are not affected by viral, bacterial, fungal infection).
Authentication of plant material : Thismay be confirmed by:1. Establishing the identity by a taxonomy experts.2.Collection of a common species in their expectedhabitat by a field botanist.3. By comparing the collecting plant with a voucherspecimen ( herbarium sheet).
Drying of plant materials Aim of drying:1. Ease of transport.2. Ease of grinding3. Inhibit the growth of microorganisms.4. Preservative of active constituents.Drying is done in:Shade and in sunlight (Natural drying).Hot air drying or by freeze-drying (Artificial drying).
Extraction and fractionation of constituents :There is no general (universal) method for the extraction of plant materials.The precise mode of extraction depends on:1- The texture of the plant material.2- The water content of the plant material.3- The type of substances to be extracted or nature of active constituents.
EXTRACTION: Is the separation of medicinally active portion ofplants or animal tissues through the use ofselective solvent and suitable methods extraction.The principal methods of extraction are:1 - Macération2 - Percolation3 - Infusion4 - Decoction5 - Digestion
MACERATION : 1.In maceration powdered drug is soaked inorganic solvent and kept for about 24 hrs ,sometimes 3-4 days also, depending upon thepart of the plant to be extracted. 2.The solvent is decanted, filtered andconcentrated.
PERCOLATION :In percolation special types of percolators are used.These are funnel shaped. The solvent continuouslypercolates through , the coarse particles of thedrug. Solvent is collected, filtered andconcentrated.
DECOCTION :In case of decoction , the powdered plant materialis boiled with the solvents .It is collected andfiltered. Filtered solvent is concentrated.Eg. Preparation of tea.
Continuous hot extraction technique (Soxhletextraction procèss )
Successive solvent extraction :Petroleum ether (60-80)BenzeneChloroformAcetoneEthanol (95%)Chloroform water