EVALUATION OF A CRUDE DRUG

EVALUATION OF CRUDE DRUGs

Introduction

Evaluation of a crude drug means confirmation of its identity and determination of its quality and purity and detection of nature of adulteration. The evaluation of crude drugs is necessary because of 1. Biochemical variation 2. Deterioration due to treatment and storage 3. Substitution and adulteration.The crude drugs can be identified on the basis of their morphological histological, chemical, physical and biological studies.

General Methods of Drug Evaluation: 1. Organoleptic Evaluation: Colour, Smell, Taste and Consistence (Touch and Texture).

2. Morphological Evaluation: Leaves, Barks, Roots, Fruits and Stems.

3. Microscopic Evaluation: Palisade Ratio, Trichomes, Stomata, Phloem, Calcium Oxalate Cystals and Stone cells.Lycopodium Spores method is used for Quantitative Analysis.

4. Chemical Tests: Test of Anthrequinone, Test for Mucilage and Tests for other chemical constituents.

5. Physical Evaluation (Physical Constant):Refractive index, Sp. Gravity, Optical Rotation, Moisture Content, Density, Melting Points, Viscosity, Solubility, Ash Content, Extractives, Solubility in

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EVALUATION OF A CRUDE DRUG

various solvents. Free Fatty Acids, Ester values, Iodine Values, Saponification Values, Acid Values, Unsaponifiable Matter.

6. Chemical Method of Evaluation:Free Fatty Acids, Ester values, Iodine Values, Saponification Values, Acid Values, Unsaponifiable Matter Gravimetric, Volumetric, Colorimetric, Fluorimetric, Photometric, Spectroscopic and Chromatographic.

7. Biological methods: Hepatoprotective activity, Hypoglycaemic activity, Anti fertility activity, Anti inflammatory activity, Neuropharmacological activity and Anti ulcers activity.

8. Microbiological assays: Effect on living Micro-organisms, Cylindrical Plate method, Turbidimetric Method.

1. MORPHOLOGICAL OR ORGANOLEPTIC EVALUTION

Evaluation of drugs by Colour, Smell, Taste and Consistence (Touch and Texture) etc. It is the technique of qualitative evaluation means conclusion drawn from studies resulted due to impression on organs of senses.

2. MICROSCOPICAL EVALUATIONThis method allows more detailed examination of a drug and it can be used to indentify the organized drugs by their known histological characters. It is mostly used for qualitative evalution of orgainsed cruds in entire and powered forms.For the effective results, various reagents or stains can be used to distinguish cellular structure. Microscopic evaluation covers study of constituent by application of chemical methods to small quantities of drugs in powder form or to histological section of drug. Example- a drop of phloroglucinol and conc. HCL gives red stain with lignin.

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EVALUATION OF A CRUDE DRUG

Histological studies are made from very thick sections of drugs. The characteristics of cell walls, starch grains, calcium oxalate crystals, trichomes, phloems, stomata etc can be studied in details. The quantitative microscopy is used for the study of various parameters like stomatal number and index, palisade ratio, vein islet no., length of fibers etc.

1. Leaf constant: - Palisade ratio, Vein islet number, Vein termination, Stomatal number, and Stomatal index.

2. Palisade ratio: - is defined as average no of palassade cells beneath each epidermal cell it can be determined with powder drugs.3. Vein islet number: - is defined as no of Vein islet per square mm of leaf surface midway between midrib and the margin.4. Vein termination number: - is defined as no of veinlets terminations per per square mm of leaf surface midway betweeen midrib and the margin.5. Stomatal number: - is defined as average no. of stomata per sq mm of epidermis of the leaf 6. Stomatal index: - is the percentage which the no. of stomata form to the total no of epidermal cells, each stoma being counted as one cell.Stomata:- Trichome:-

3. CHEMICAL EVALUATIONIt comprises of different chemical tests and chemical assays. Quantitative chemical test such as acid value, saponification value, ester value etc. covered under this technique.

ACID VALUEDefinition: It is defined as the number which expresses in mg the amount of Potassium Hydroxide (KOH) necessary to neutralise the free acids presents in the 1g of the sample.

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EVALUATION OF A CRUDE DRUG

PROCEDUREWeight accurately 10g of sample and dissolve it in 50ml of a mixture of Ethanol 95% (25 ML) and Ether (25 ML) previously neutralized with 0.1M Potassium Hydroxide to Phenolphthalein solution. If required dissolve the sample by heating slowly and using reflex condense. To the above sample solution add 1ml of Phenolphthalein indicator and titrate with 0.1M Potassium Hydroxide solution up to the end point pink after shaking for half minute.Acid value = 5.61n/wWhere n – ml of 0.1 M Potassium Hydroxide solution required.w – Weight of sample in g.

DETERMINATION OF ESTER VALUE:Definition: It is defined as the number of milligrams of Potassium Hydroxide required to saponify the Esters in the 1g of sample substance. It is calculated by subtracting the Saponification value from the Acid value of sample substance.

DETERMINATION OF SAPONIFICATION VALUE:Definition:It is defined as the number of milligrams of Potassium Hydroxide required for neutralization of free acid and to saponify the esters present of 1g of sample.

PROCEDUREWeight accurately 2g of sample and add it to 200ml glass flask fitted with reflex condenser. Add 25ml of 0.5 M Ethanolic potassium hydroxide and small quantity of pumice powder and boil for 30 min on water bath under reflux. Add 1ml Phenolphthalein solution and titrate immediately with 0.5 M hydrochloric acid (x). Take the blank reading by repeating the same procedure (y). Calculate the saponification values as: Saponification value = 28.05 (y-x) / w

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EVALUATION OF A CRUDE DRUG

Where, w - Weight of substance in g.

DETERMINATION OF IODINE VALUES:Definition: Iodine value is defined as the number which expresses in grams the quantity of halogen, calculated as iodine, which is absorbed by 100g of the substance under the described condition.PROCEDUREAdd accurately weighed quantity of sample in dry 500ml Iodine flask, add 10ml of carbon tetrachloride and dissolve. Add 20 ml of Iodine Monochloride solution fix the stopper and allow it to stand for 30 minute between temperatures 15 to 25°C in dark place. Add 15ml of Potassium Iodide solution in cup top and carefully remove the stopper, rinse the stopper and side of the flask with 100ml of water, mix by shaking and titrate with 0.1 M sodium Thiosulphate solution using Starch solution as indicator towards the end of titration. Note the Burette reading (x) and repeat the same procedure for blank titration and record the Burette reading (y).

Iodine Value = 1.269 (y-x) / wWhere, w is weight of sample in g.Preliminary Phytochemical screening is part of chemical evaluation This is useful in detection of adulteration. Ex. Testof anthraquinone, test for mucilage, test of glycosides, test of flavonoids etc.

4. PHYSICAL EVALUATION These are rarely constant for crude drugs but may help in evaluation, specifically with reference to Refractive index, Sp. Gravity, Optical Rotation, Moisture Content, Density, Melting Points, Viscosity, Solubility, Ash Content, Extractive value.

MOISTURE CONTENT:-

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EVALUATION OF A CRUDE DRUG

The % of active chemical constituent in crude drugs is mentioned on air dried basis. Hence, the moisture content of the drug should be determined and should be minimized to prevent decomposition of crude drugs either due to chemical changes or microbial contamination. The moisture content can be determined by heating the drug in oven at 105°C to a constant weight. Toluene Distillation method is used for determining the Moisture content of drug those contains Volatile active constituents.Ex. aloes moisture content not more than 10%w/w

VISCOSITY:-

Viscosity of liquid is constant at a given temp. and is an index of composition. Hence it can be used as a means of standerdising liquid drugs.Procedure:Fill the Viscometer, Previously washed with chromic acid E and five times with distilled water with the liquid being examined through tube L to slightly above the mark G, using a long pipette to minimize wetting the tube above the mark. Place the tube vertically in water bath which temperature is maintained at the temperature at which viscosity is to be measured. When the temperature of liquid in tube attends, adjust the volume of liquid so that the bottom of the meniscus set at the mark G. Attach the rubber tube to E end of the tube and suck the liquid 5mm above the point E.After releasing the suction, Measure the time required for the bottom of the meniscus to fall from the top edge of mark E to the top edge of mark F.Kinematic Viscosity = Kt. (Unit is Sq.mm per second)Dynamic Viscosity = KPt (Unit is Millipascal second Symbol – mPa S.)Where, K is constant of instrument, which P determined by using Liquid of known viscosity.t is time in second for the meniscus to fall from E to F.P is weight per Ml of liquid in g/Cubic cm.

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EVALUATION OF A CRUDE DRUG

Viscosity can be measured by using other viscometers like Brookfield Viscometer, which is more accurate. Ex. Pyroxylin - Kinematic Viscosity, 1100 to 2450 centistokes

DETERMINATION OF MELTING POINT:-

Pure chemicals and Photochemical are having sharp melting points. Crude drugs from animal and plant origin contain the mixed chemicals; they are described with certain range of melting points.Ex. Colophony 75 to 80 0 C

SOLUBILITY:-The presence of adulterant in a drug could be indicated by solubility studies. Ex. Castor oil is soluble only in 3 volumes of 90% alcohol, while the adulterated form may show good solubility in alcohol.ASH VALUE:- is the residue remaning after incineration is theash contaent of the drug, which simply represents inorganic salts, naturally occurring in drug or adhering to it or delibaterly added to it, as a form of adu;teration.

PROCEDUREWeight accurately 2 to 3g of air dried crude drug in a treated silica dish and incinerate at a temperature not exceeding 450°C until free from carbon. Cool the Silica dish and weight. If a carbon free ash can not be obtained. Exhaust the charred mass with hot water. Collect the residue on an ash less filter paper, until the ash in white or nearly white, add the filtrate evaporate to dryness and ignite at a temperature not exceeding 450°C. Calculate the % of ash with reference to the air dried drug.

EXTRACTIVESExtract obtained by exhausting crude drugs are indicative of approximate measure of their chemical constituents. Taking in to consideration the diversity in chemical nature and properties of content of drugs, various solvents are used for determination of extractives

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EVALUATION OF A CRUDE DRUG

PROCEDURE

ALCOHOL SOLUBLE EXTRACTIVES:- Alcohol is an added solvent for extraction of various chemicals like tannin, resin etc therefore this method is frequently used to determine such content of drugs.PROCEDUREPrepare coarse powder of air dried drug. Take 100ml of Ethanol (Specified Strength) in conical flask. Macerate 5g of powdered drug in above conical flask, close and conical flask for 24 hours. Shake the flask frequently during first 6 hours; allow it to stand for 18 hours. Filter rapidly taking precaution against loss of ethanol evaporate 25ml of the filtrate to dryness in a tared flat bottomed shallow dish. Dry at 105°C and weight it. Calculate the % of Ethanol soluble extractive with reference to the air dried drug.

WATER SOLUBLE EXTRACTIVE:This method is applied to drugs which contain water soluble constituents of drug such as tannin, sugar, flavonoids.PROCEDUREFollow the procedure described under Ethanol Soluble Extractive. Use Chloroform water instead of ethanol.

VOLATILE OIL CONTENT Pharmaceutical significance of aromatic drugs is due to their odorous principles that are volatile oils. Such crude drugs are standerdised on the basis of their volatile oil content. Ex. Caraway volatile oil content NLT 2.5% w/w

FOREIGN ORGANIC MATTER The part of organ or organs other than those named in definition and description of drug are defined as foreign organic matter . the maximum limit

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EVALUATION OF A CRUDE DRUG

for FOREIGN ORGANIC MATTER is defined in monograph of crude drugs. If it exceeds the limits, deterioration in quality of drug takes place. The limit for FOREIGN ORGANIC MATTER is specially mentioned for natural drugs of vegetable origin in their respective monographs.

Chromatographic analysis of herbals can be done using TLC, HPLC, HPTLC, GC, UV, GC-MS, fluorimetry etc.

5. BIOLOGICAL EVALUATIONWhen estimation of potency of crude drugs or its preparations is done by means of its effect on living organisms like bacteria, fungal growth or animal tissue or entire animal is known as bioassay.Ex. Hepatoprotective activity, hypoglycemic activity, Anti fertility activity, Anti inflammatory activity, Neuropharmacological activity and Anti ulcers activity.

MICROBIAL ASSAYEffect on living Micro-organisms by Cylindrical Plate method, Turbidimetric Method.

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