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Evaluation of crude drugs:

Naureen Shehzadi Department of Pharmaceutical Sciences, Faculty of Pharmacy, Superior University Evaluation of crude drugs


A natural substance is regarded as food if it is used for filling up the stomach daily without experiencing any deleterious effects. But, it may be referred to a drug if it results in changing a pathological/disease state of an individual or animal to a normal/physiological state without producing any side effects in a specific dose. introduction

Why needed?:

The evaluation of crude drug is necessary because of three reason; 1. Biochemical variations in the crude drug 2. Deterioration due to treatment and storage 3. Substitution and adulteration, as a result of carelessness, ignorance or fraud Why needed?

Drug evaluation:

Evaluation of crude drug ensures its identification and determination of its quality and purity. These are needed to establish whether or not a substance qualifies to be a drug or food or eliminated from general use. Drug evaluation


In every country, there is national herbarium where most of the native plants are preserved. Identification of the crude drug is usually done by; A qualified, specialized and experienced personnel (Botanist, Herbal specialist) Comparison with the standard/authenticated sample specimens Identification


It refers to intrinsic value of the crude drug i.e. nature and amount of active/medicinal principles. These active principles may be; Alkaloids Glycosides Carbohydrates Volatile oils Fixed oils Tannins etc. quality


To maintain quality of the crude drugs, it is necessary to; Select proper source of crude drugs (either wild or cultivated) Collect the crude drugs at appropriate time Collect the required parts of the plants Preparation of collected drugs by proper cleaning and drying Properly preserve the crude drugs in order to avoid contamination due to microbes and against moisture, heat, air and light. quality


Purity of the crude drug can be achieved by; Proper identification Quality assurance purity

Morphology and morphography:

The study of the form of crude drugs is called morphology and determination of the form of crude drugs is called morphography. Morphology and morphography

Types of drug evaluation:

Types of drug evaluation

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DEFINITION It refers to the evaluation of crude drugs using organs of sense. The study includes; Macroscopic or external appearance Color Odor Taste Sounds of its fractures etc….


characteristics The macroscopic features of the crude drugs include; Size Shape External color Odor Taste Fractures and internal color


size The size of crude drug encompasses measurements of; Length Breadth Diameter It may be measured in mm or cm.


shape The crude drug may be having different shapes e.g. Crude drugs Shape Sarsaparilla root Cylindrical Podophyllum Sub-cylindrical Aconite Conical Jalap Ovoid Calumba Disk

External color:

External color The crude drugs may acquire a variety of colors. The color of the crude drugs vary from white to yellowish gray, yellowish brown, reddish orange or brownish black. The fruits and seed crude drugs have different colors whilst barks posses brownish gray to brownish black color. The internal and external color of the barks varies; internal color is little lighter than the outer one.

Odor of crude drugs:

Odor of crude drugs The crude drugs may be odorless or pose an odor which may be; Distinct Indistinct General terms for describing odor are; Aromatic Balsamic Spicy Fruity Pungent etc….

TASTE of crude drugs:

TASTE of crude drugs The crude drugs may posses a characteristic taste or may be tasteless. The different terms used to define taste of a crude drug are; General terms used in describing taste are: 1- Acid (sour) 2- Saccharine ( sweet) 3- Saline (salty) 4- Alkaline 5- Bitter 6- Tasteless

TASTE of crude drugs:

TASTE of crude drugs Taste Examples Mucilaginous Starches Oily Linseed oil Astringent Pomegranate, catechu Pungent Ginger Acrid Coca Nauseous Ipeca

Fractures and internal color:

Fractures and internal color Fractures and internal color of crude drugs refer to the external markings that are characteristics of a particular drug and color after breaking the crude drug. Internal color of a crude drug is usually lighter compared to the external colour. Example is turmeric, ginger etc…..

PowerPoint Presentation:

Determine basic shapes of a leaf. Determine internal and external color of 15 plant drugs. Key components in a national herbarium Write the characteristic odor of 10 crude drugs. Write taste of 5 animal drugs and 5 mineral drugs. CLASS ACTIVITY

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Physical evaluation:

Physical evaluation The physical evaluation of the crude drugs is accomplished by the determination of various physical characteristics/parameters by using various physico-chemical techniques. In crude plant evaluation, physical methods are used to determine; Solubility Specific gravity Optical rotation Viscosity

Physical evaluation:

Physical evaluation Refractive index Melting point Water content Degree of fiber elasticity Ash values Extractive values Foreign organic matter etc…….


solubility I n this evaluation, the specific behavior of the drugs towards solvents is taken into consideration. Crude drugs Characteristic solvents Colophony Light petroleum Peru B alsam Chloral hydrate Castor oil Light petroleum (half to the volume of castor oil) Alkaloidal bases Organic solvents Alkaloidal salts Polar solvents

Optical rotation:

Optical rotation Certain drug substances may have capability of rotating the plane polarized light to specific orientation (+, dextrorotatory and -, levorotatory). Substances that rotate the plane polarized light to the right/clockwise are dextrorotatory (d) or (+). Substances that rotate the plane polarized light to the left/anti-clockwise are levorotatory (l) or (-). Measuring optical rotation helps in determining; Whether a substance is optically active or not Purity Quality Strength Crude drugs Optical rotation Eucalyptus 0 ° – (+)10° Honey (+)3 ° - (-)15°

Refractive index:

Refractive index Refractive index is the property of a material that changes the speed of light, computed as the ratio of the speed of light in a vacuum to the speed of light through the material. n = c/v Where; n = Refractive index c = Speed of light in vacuum v = Speed of light in the substance Its measure gives an idea of; Identification of a substance Purity Concentration Crude drugs Refractive index Castor oil 1.4758-1.527 Clove oil 1.527-1.535

Specific gravity:

Specific gravity It is also referred to as the “relative density”. It is the ratio of the mass of a solid or liquid to the mass of an equal volume of distilled water at 4°C or of a gas to an equal volume of air or hydrogen under prescribed condition of temperature or pressure. Its measurement gives the idea of floatability of the drug. Specific gravity > 1: Substance sinks Specific gravity < 1: Substance floats Crude drugs Specific gravity Cottonseed oil 0.88-0.93 Coconut oil 0.925 Castor oil 0.95  


viscosity It refers to the resistance of a liquid to flow. This resistance acts against the motion of any solid object through the fluid and also against the motion of a fluid itself past stationary surfaces. It is a constant value.

Melting point:

Melting point It refers to a temperature at which it changes state from solid to liquid. Plant constituents have very sharp and constant melting points. Crude drugs Melting point (°C) Beeswax 62-65 Wool fat 34-44 Agar 85

Moisture content:

Moisture content The moisture content of a crude drug is responsible for decomposition of crude drug due to chemical change or microbial attack. It is necessary to determine and control the moisture content of the crude drug. It is determined by heating the drug at 105°C in an oven to a constant weight. Crude drugs Moisture content Digitalis Not more than 5% w/w Ergot Not more than 8% w/w

Ash values:

Ash values Determination of ash values is useful for detecting low-grade products, exhausted drugs and excess of sandy or earthy material. Different ash values are calculated for such purposes e.g. Total ash Acid-insoluble ash Water soluble ash Sulphated ash

Ash values:

Ash values Total ash It is useful for detection of the crude drug mixed with various minerals e.g. sand, soil, calcium oxalate, chalk powder or other drugs with different inorganic contents to improve their appearance. The maximum temperature used for total ash is not more than 450°C. It is because of the fact that at higher temperatures, volatile alkali chlorides may be lost.

Ash values:

Ash values Acid-insoluble ash Acid-insoluble ash means ash insoluble in dilute hydrochloric acid. Its value is higher than total ash. The majority of crude drugs contain calcium oxalate whose quantity varies frequently. Therefore, total ash of a crude drug vary within wide limits for specimen of genuine drug e.g . for Rhubarb, total ash ranges from 8-40% and in this case , determination of acid-insoluble content is more preferable.

Ash values:

Ash values Acid-insoluble ash The calcium oxide formed due to incinerated oxalate is soluble in hydrochloric acid. The insoluble as is then weighed. In this way, excessive earthy matter that is usually present in root, rhizome and leaves can be determined. Water-soluble ash It is used to detect the presence of material which is exhausted by water .

Ash values:

Ash values Sulphated ash This ash is produced after treating the drug with sulphuric acid to get sulphate salts. percentage ash is calculated with reference to air-dried sample. Temperature used for the procedure is more than 600°C. Crude drugs Ash values Ginger (acid-insoluble) 3% Ginger (total ash ) 16%

Extract values:

Extract values Extracts of crude drugs are obtained with different solvents. These extract give approximate measures of their chemical contents. Various solvents are used according to the type of constituents to be analyzed. Water soluble extracts are used for determination of crude drugs containing glycosides, tannins and mucilage and alcohol-soluble extracts are used for determination of resins, certain glycosides whilst ether-soluble extracts are used for drugs containg fats and volatile principles.

Foreign organic matter:

Foreign organic matter The parts of the organs or organs other than the required are called foreign organic matter. These may include; Insects Moulds Earthy material Animal excreta Each crude drug has its own limits for presence of foreign matter e.g . garlic and saffron should not contain more than 2%

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Chemical tests:

Chemical tests These are carried out using various chemical reagents to identify the nature and quantity of chemical constituents of crude drugs. Chemical tests may be; Qualitative Quantitative

Qualitative chemical tests:

Qualitative chemical tests Qualitative chemical tests involve identification tests for various phytochemical constituents e.g. alkaloids, glycosides, tannins etc. these tests provide information regarding nature of active principle. Examples include; Molisch's test for carbohydrate drugs e.g. Glucose, Sucrose etc. Iodine test for identification of starches Spot test for identification of fixed oils

Quantitative chemical tests:

Quantitative chemical tests These tests give the value or amount of active constituent in the crude drug. Examples include; Saponification values for lipids (number of milligrams of potassium hydroxide required to saponify 1g of fat under the conditions specified. It gives a measure of molecular weight of the crude drug.) Ester value for volatile oils (number of mg of potassium hydroxide required to saponify the esters in 1.0 g of the substance) Acid number for resins


CHEMICAL ASSAYS These tests give an approximate value of total phytochemical constituents in a crude drug. Examples include; Total alkaloid in belladonna leaf Total alkaloid in ipecacuanha Total resinous principle in jalap Total vitamins in cod liver oil

Instrumental techniques:

Instrumental techniques These techniques identify the chemical group in phytoconstituents using chromatography and spectroscopy techniques.

PowerPoint Presentation:

Write chemical assay method of any crude drug from official book Write down at least 2 identification tests for carbohydrates, alkaloids, glycosides, fixed oils and tannins Prepare a list of the approximate value of phytochemical constituents in 5 crude drugs e.g. turmeric, fennel, caraway, cardamom and cinnamon Write a method for quantification of active principle of crude drug using UV-visible spectrophotometer Class activity

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DEFINITION It refers to evaluation of therapeutic or pharmacological and toxicological activity of the whole crude drug or its active principle by using animals or microbes. Biological evaluation determines; Therapeutic activity of drug or active principle Potency Toxicity


importance There are several method by which the plant or extract can be evaluated for pharmacological activity. These are a method of choice when the drug cannot be assayed satisfactorily by chemical and physical methods. These are also necessary to carry out since the crude drug is considered important only if it exerts significant biological effects.




method These assays are conducted by determining the amount of drug of known potency required to produce a definite effect on suitable test animals or organs under standard conditions. Reference standards are used in procedures to minimize errors. Toxicity studies are performed in suitable animal models to decide the lethal dose and effective dose of crude drugs.

Animal models:

Animal models Drugs Animal models Vaccines Mice Vasopressin injection Guinea pigs Oxytocin injection Domestic chickens Digitalis glycosides Pigeons Depressor activity and mydriatic drugs Cats Anthelmintic drugs Worms Eye preparations Rabbits GIT and cardiac drugs Dogs Next to the animal drugs, the studies are carried out in humans and it is not necessary that same results be expressed by the human beings.

Microbiological studies:

Microbiological studies Microbiological assays are carried out to determine anti-microbial activity of various drugs. Various methods include; Agar diffusion methods Turbidimetric methods Disc-diffusion methods Yeasts, moulds and living bacteria are used for assaying vitamins. Living bacterial strains are used for testing antimicrobials.

Agar diffusion method:

Agar diffusion method

Turbidimetric method:

Turbidimetric method

Disc-diffusion method:

Disc-diffusion method

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DEFINITION This evaluation is based on microscopic examination of whole, certain parts or powdered crude drug. Microscopy techniques may be simple or complex. The powdered crude material can be observed using only chloral hydrate (simple technique) but the presence of starch in that crude material is detected using iodine tincture. The starch will be stained blue and other components of the sample will not be stained.


importance Microscopic evaluation of the crude drug is indispensable in; Initial identification of herbs Identification of small fragments of crude or powdered drugs Detection of adulterants (insects, animal feacal matter, moulds, fungi) Identification of plant by its characteristic tissue features



Identification of crude drug using qualitative microscopy:

Identification of crude drug using qualitative microscopy Every plant possess a characteristic tissue structure that can be demonstrated through study of; Tissue arrangement Cell walls structure Cell contents (calcium oxalate crystals, fibers, parenchyma etc.) Configuration (when properly mounted on the slide) Reagents (Lignin stains red or pink with a drop of phloroglucinol and concentrated hydrochloric acid; Mucilage are stained pink with ruthenium red; Starches stained blue with iodine solutions) Media


example Surinam Quassia is recognized from the other herbs due to following characteristic features that are observed microscopically Absence of calcium oxalate crystals Presence of crystal fibres Presence of uniseriate medullary rays

Microscopic linear measurements:

Microscopic linear measurements T hese include identification of crude drug by measurements like; Size of starch grains (e.g. diameter of starch grain in cassia bark distinguishes from cinnamon) Size of the stomata Diameter of phloem fibers (e.g. detection of cassia in cinnamon) Width of the vessel (e.g. detection of clove stalks in powdered cloves) Length and width of fibres

Determination of leaf constants:

Determination of leaf constants

Stomatal index:

Stomatal index It is the percentage which the numbers of stomata form to the total number of epidermal cells (each stomata being counted as one cell). S Here; S = Number of stomata per unit area E = Number of epidermal cells in the same unit area.  

Vein-islet number:

Vein-islet number It is defined as the number of vein islets per square mm of leaf surface midway between the midrib and the margin. This value is constant for a given specie of a plant and used as a characteristic for the identification of allied specie.

Veinlet termination number:

Veinlet termination number It is defined as the number of veinlet termination per square mm of leaf surface midway between the midrib and the margin (unbroken leaf part is required). A vein termination is the ultimate free termination of the veinlet. Hall and Melville in 1951, determined veinlet termination number of Indian and Alexandrian Senna which was quite different for each other.

Palisade ratio:

Palisade ratio It is the average number of the palisade cells beneath each epidermal cell. This ratio can be determined with powdered drug.

Quantitative microscopy:

Quantitative microscopy This is an important technique employed in identification of crude drug when physicochemical methods are inapplicable. The powdered crude drugs with well-defined particles that can be counted or the objects with measurable diameter and thickness under suitable magnification are calculated using lycopodium spore method. Adulterated starchy drugs can be determined by counting the number of starch grains per mg and calculating the amount from the known umber of starch grains per mg of the pure starch/starchy material.


calculation Here; N = Number of characteristic structures (e.g. starch grains) in 25 fields W = Weight in mg of lycopodium taken S = Number of lycopodium spores in the same 25 fields M = Weight in mg of the same (calculated on the basis of sample dried at 105 degree centigrade P = Standard value of characteristic structure  

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