Introduction to Pharmacognosy M.S.Abubakar Ph.D

Introduction to Pharmacognosy Course outlines01. Course outlines for Introduction to Pharmacognosy (10 hrs)1. Definition, subject coverage and area of application, relationship with other subjects (1hr).

2. Aims of study and definition of terms; drug, true drug, natural drug, synthetic and semi synthetic drug; organized and unorganised drug (1hr)

3. Classification of vegetable drugs alphabetical, taxonomical, morphological, pharmacological/therapeutical and chemical (2hrs)

4. Collection and preparation of natural drugs (time, location importance); drying of drugs (air drying, sundrying, oven drying), storage of crude drugs (control of moisture content and of appropriate storage material) (1 hr).

5. Adulteration of crude drugs a) Definition of adulteration,b) Causes of adulterationc) Detection of adulteration (1hr).

6. Evaluation of crude drugsa) Definition of evaluationb) Different types of evaluation i) Organoleptic methods ii) Microscopical evaluation iii) Chemical evaluation iv) Biological evaluation v) Physical evaluation (2hrs)

Various publications on Pharmacognosy - pharmacopoeia, text books, flora: these are classified under certain arrangements e.g. alphabetical system is used by the Pharmacopoeia (mention of different Pharmacopoeia and their use); taxonomical system is used by some text books e.g. Pharmacognosy by Trease and Evans, morphological system is used in certain books e.g. Pharmacognosy by Wallis and yet in other text books is used Pharmacological systems: e.g Pharmacognosy by Pratt Yung Ken and finally mention of other text books used chemical system of classification e.g. Pharmacognosy by Claus, Taylor and Brady. The Flora used the taxonomical systems e.g. The medicinal plants of Tropical West Africa by Dalziel (2hrs)

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Introduction to Pharmacognosy M.S.Abubakar Ph.D

Definition of Pharmacognosy

The Word "Pharmacognosy" is derived from two Greek words, "pharmakon" or drug, and "gnosis or gignosco" or knowledge. Like many contemporary fields of science, Pharmacognosy has undergone significant change in recent years and today represents a highly interdisciplinary science which is one of five major areas of pharmaceutical education. Its scope includes the study of the physical, chemical, biochemical and biological properties of drugs, drug substances, or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources.

History of the Development of Pharmacognosy

The history of Pharmacognosy is synonymous to the history of medicine, Papyrus Ebers is an old document written in 1500B.C which described the use of medicinal plants, animal and human anatomy by the ancient Egyptians. The greek physician Hippocratus: father of medicine (460-370 B.C) described human anatomy and physiology. Aristotle, a renowned philosopher and a student of Pluto (384-287 B.C) is known for his studies of Animal Kingdom. Theoprastus (370-287 B.C) who is a student of Aristotle is well known for the study of plant kingdom. A Greek physician Dioscorides (78 A.D.) described (78 A.D) described thousands of medicinal plants and their properties in “De Materia Medica”. Natural history was compiled by Plini (23-70 A.D) in 37 volumes. The great Greek pharmacist Galen (131- 200 A.D) described various methods of preparation containing active constituents from plant and animal sources and it is known as galenical pharmacy. Later on all the detailed information’s were compiled to form Materia Medica that was that was utilised by physicians. Naturally occurring drugs may be obtained from plants, animals and minerals. A German scienticist Sydler introduced the term Pharmacognosy in 1815 in his work “Analecta pharmacognostica”.

The Scope of Pharmacognosy

Research areas in pharmacognosy include studies in the areas of

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Introduction to Pharmacognosy M.S.Abubakar Ph.D

Phytochemistry microbial chemistry biosynthesis, biotransformation, chemotaxonomy, Other biological and chemical sciences.

Pharmacognosy is one of the five major divisions of the pharmaceutical curriculum, represents the oldest branch of the profession of pharmacy. In a restricted sense, the definition of pharmacognosy implies a particular knowledge of methods of identification and evaluation of drugs. In a broad sense, pharmacognosy embraces knowledge of the history, distribution, cultivation, collection, selection, preparation, commerce, identification, evaluation, preservation, and use of drugs and economic substances affecting the health of man and other animals. Such economic substances extend beyond the category of crude drugs and their derivatives and include a variety of commercial products: allergens, allergenic extracts, antibiotics, immunizing biologicals, flavoring agents, condiments, beverages, insecticides, rodenticides, and herbicides. As a part of the pharmacy curriculum pharmacognosy plays an important role as liaison agent between pharmacology and pharmaceutical chemistry on one hand and between pharmacy and pharmacy administration on the other. Pharmacology, like pharmacognosy, is an outgrowth of the old-time materia medica; it is easy to see the correlation of these two sciences concerning drugs of biological origin. The pharmacology student has a more complete understanding of the action of belladonna leaf if he is aware of the physical nature of the drug and its chemical constituents. Some of the laboratory procedures in pharmaceutical chemistry have miniature counterparts in the extractions and microchemical tests essential for the identification and evaluation of certain drugs.

Some basic terminologies use in Pharmacognosy

Drug: This is anything that is used in modifying conditions of animals and human in disease conditions drugs can be from natural, semi synthetic and synthetic origin. In real sence drugs can be referred to as true drugs or crude drugs

Crude Drugs: These are drugs that are derived from natural forms; from plants, animals and minerals. Crude drugs can be divided into organized and unorganised drug. Most crude drugs are derived from plant origin and are thus referred to as vegetable drugs.

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Introduction to Pharmacognosy M.S.Abubakar Ph.D

Organised (cellular) drugs: these are crude drugs that characteristically contained cellular structures. Examples includes Digitalis, Cinchona, clove, jalap, cochineal etc

Un-organised (acellular) drugs: These are crude drugs that do not contain cellular structures. Examples includes Aloe, Agar, colophony, bees-wax, castor oil, opium etcVegetable drugs: these are crude drugs derived from plants. Plants are the most important source of drugs and must research and a study of crude drugs is on vegetable drugs.

Non-vegetable drugs: these are drugs derived from sources other than plants and can be referred to as animal derived if they are from animal sources or mineral derived if they are from mineral sources

Difference between organised drugs and un-organised crude drugs

Organised crude drugs Un-organised crude drugsThese consists of organs of plants and animals and are made up of cells or definite structure. These drugs are named as flowers, seeds, insects, seeds barks etc

These are derived from parts of plants or animals by some process of extraction and/or purification e.g extracts, resins, juices, exudates etc.

They are solid in nature They are solid, semi-solid or liquids in nature

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They can be described based on their origin/sources. Botanical or zoological terminology can be used to describe the drugs

The origin may not be sufficient to describe them complete description may require the use of their physical characters

Microscopical examination is the most important criteria for their identification

Chemical test is the most important criteria for their identification

Classification of crude drugs

Crude drugs are derived from natural sources and are classified by the following methods

1. Alphabetical classification;

In this classification crude drugs are arranged alphabetically either in latin name or English name. This method of classification is adopted bya. British Pharmacopoeia (BP): English titlesb. British Pharmaceutical codex (BPC): English titlesc. British Herbal Pharmacopoeia: English titlesd. European Pharmacopoeia (EP): English titlese. African Pharmacopoeia (AP): English titlesf. Pharmacopoeia internationalis: Latin titlesg. Nigerian Pharmacopoeia : English titles. This will be out soon.Drugs are easily traced in these literitures but the classification does not help in distinguishing their source or if they are organised or un-organised drugs.

2. Taxonomic(Biological) classification

This is the botanical/zoological classification of drugs. It is the phylogenic classification according to their division, class, order, family, genus and species. This system gives the details and idea about the source. The crude plant drugs are classified based on accepted botanical classification, while animal derived drugs are classified based on established zoological classification. A large number of plant species have distinguishing characteristics that permit crude drugs from families to be studied, in most cases only part of the plant source is used as drugs. In most cases the whole plant source is rarely used as drugs. Example include Cascara bark, Nux-vomica seeds, Digitalis leaves, Quassia wood, pyrethrum flower etc. in case of animals, all terrestrial and marine animals are grouped according to their phylogenic relationships.Example of some few crude drugs classification

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Phyllum…………SpermatophytaDivision…………AngiospermaeClass…………….DicotyledonsOrder……………RosalesFamily……..……LeguminosaeSubfamily…….…PapilionaceaeGenus…..………Glycerrhiza, Astragalus, IndigoferaSpecies………….. Glycerrhiza glabra, Astragalus gummifer, Indigofera tictoriaIIPhyllum…………SpermatophytaDivision…………AngiospermaeClass…………….DicotyledonsSub-class……….. SympetalaeOrder……………TubifloraeFamily……..……SolanaceaeSubfamily…….…PapilionaceaeGenus…..………Atropa, Hyoscyamus, DaturaSpecies………….. Atropa beladonna, Hyoscyamus niger, Datura stramoniumPhyllum…………ThallophytaClass …………AscomycetesOrder……………ClavicipitalesFamily……..…… ClavicipitalceaeGenus…..………ClavicepsSpecies………….. Claviceps purpurea

3. Morphological Classification4.The crude drugs are grouped according to the part of the plant or animal into organised or un-organised drugs. The organised vegetable drugs are for example classified into leaves, flowers, seeds, woods, barks, and subterranean parts like roots and rhizomes. The un-organised vegetable drugs are classified into drugs like latex, gums, extracts,etcExamples of drugs under this classificationSeeds: Nux-vomica, Strophanthus, castorLeaves: Digitalis, Senna, EucalyptusBarks: Cascara, Cinchona, CinnamonWoods: Quassia, Sassafras, SandalwoodRoots: Rauwolfia, Ipecacuanha, Aconite, JalapRhizomes: Turmeric, Ginger, PodophyllumFlowers: Clove, Pyrethrum, SaffronFruits: Fennel, Coriander, ColocynthEntire Drugs: Ephedra, Ergot, Cantharides, BelladonaDried Latices: Opium, Gutta-percha, Papain

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Resin and Resin combination: Balsam of tolu, Myrrh, Asafoetida, BenzoinDried Juices: Aloes, Kino, Red GumGums: tragacanth, Acacia, GuarDried Extract: Gelatin, Catechu, Agar This system of classification is more convenient for practical study especially when the chemical nature of the drug is not clearly understood.

5. Chemical Classification

The crude drugs are classified according to the chemical nature of their most important constituent. Since the pharmacological activity and therapeutic significance of crude drugs are based on the nature of their chemical constituents, it would appear that chemical classification of crude drugs is preferred. The crude drugs containing alkaloids are grouped together regardless of their morphology and taxonomic relationship.

Examples of Chemical classificationGlycosides: Digitalis, senna, cascara, liquoriceAlkaloids: Nux-vomica, Ergot, Cinchona, DaturaVolatile oils: peppermint, clove, eucalyptus, garlicLipids: Castor oil, Bees-wax, Lanolin, Cod-liver oil, cocoa-butterCarbohydrates and derived products: Acacia, agar, Guar, pectin, honey, ispangula Resin and Resin combinations: Colophony, Jalap, Balsam of Tolu,Vitamins and Hormones: Yeast, Shark liver oil, oxytocin, insulinProteins and enzymes: Casein, Gelatin, papain, trypsin

6. Pharmacological (therapeutic) classification

This system of classification involves the grouping of crude according to the pharmacological action of their chief active constituent or their therapeutic uses. Regardless of morphology, taxonomy, or chemical relationship, the drugs are grouped together, provided they exhibit similar pharmacological action. Thus cascara, castor oil and senna are classified as laxatives or purgatives because of their common pharmacological action. Similarly Gentian, Cinchona, Nux-vomica and Swertia are grouped as bitters. Drugs differing in mechanism of action but with the same pharmacological effect are grouped together; e.g bulk-purgative, irritant laxative and emollient purgative are classified together.Some examples of Pharmacological classification of drugs

Drugs acting on gastro-intestinal tract

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Bitters: Gentian, Quassia, CinchonaCarminatives: Dill, Mentha, cardamomEmetics: IpecacuanhaPurgatives: Senna, Castor oil

Drugs acting on cardio-vascular systemCardiotonics: Digitalis, squill, StrophanthusCardiac depressants: Cinchona, VeratrumVaso-constrictors: Ergot, EphedraAntihypertensives: Rauwolfia Drugs acting on the autonomic nervous systemAdrenergics: EphedraCholinergics: Physostigma, PilocarpusAnticholinergics: Belladona, DaturaAnti-cancerVinca, Podophyllum, Taxus, Camptotheca

7. Chemotaxonomic identification and classification

The recent advances in the knowledge of phytochemistry have revealed the existence of relationship between chemical constituents and taxonomic status. Chemotaxonomy establishes a relationship between the plant and the chemical facts for understanding the biological evolution and relationship. Plants are classified based on certain chemotaxonomic markers, especially as it relates to those that have pharmaceutical importance. The characters studied in chemotaxonomy are secondary metabolites; this knowledge can serve as a basis for classification of drugs. Usually the plants are classified based on the distribution of chemotaxonomic markers. Recently techniques of DNA hybridisation, amino acid sequencing in proteins and serotaxonomy could serve as tools in crude drugs identification and classification

Collection Processing and preparation of crude drugs

Crude drugs intended for commerce and development of drugs are collected and processed by standard techniques. They are processed in such a way to make them stable during transportation and storage and to ensure that they do not contain substitutes and foreign materials. Quality standards of crude drugs are specified in pharmacopoeias. Pharmacopoeia standard requirements include standards with respect to methods of collection, harvesting, drying, garbling, coating, bleaching, garbling etc.

Collection

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The time and method of collection determines the quality of active constituents of the crude drugs and this depends on the morphological form of the drug

Collection times and method for morphological forms of crude drugs

Leaves and flowering tops: these are collected before the plant reaches maturity (flowering stage). Examples are the leaves of digitalis, vinca and belladonna. However, the leaves of Aloe is best collected when they sufficiently thick

Flowers: they are best collected just before pollination or just before full expansion. Examples are the flowers of Saffron, clove buds, chamomile etc. flowers are best collected during morning hours.

Barks: they are best collected during spring time or early summer when the cambium is active. Sometimes they are collected in autumn (Wild cherry) or during rainy season (Cinnamon). Three different method for collecting barks are (i) coppicing when the barks are allowed to grow for a definite period after which the bark is cut-off from a specific distance from the soil. The stump that remains is allowed to send shoots which develops to yield aerial part. This method is very economical and less time consuming when compared to other methods. (ii) Felling when the tree is cut at the base and the bark is peeled off (iii) Uprooting when the root is dug out and the bark is stripped off from the roots.

Fruits: they are collected when they are fully grown, ripe or half ripe. Example cardamon fruits are collected just before they dehisce, tamarind when it reaches full maturity, fennel and coriander when they are fully ripe etc

Roots: they are collected in spring before vegetative process stops. The roots are sliced transversely or longitudinally to facilitate drying.

Rhizomes: they are collected when the storage food reserve materials and constituents are maximum

Un-organised Drugs. Example Resins, gums, lattices, are collected as soon as they ooze out of the plant. Acacia gum is collected 2-3 weeks after making incisions on the bark of the tree and when it is sufficiently hard. Opium and papaya lattices are collected after coagulation of the latex. Turpentine ole-resins and balsam of Peru are collected when the plant is about 8-10 years old.

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Harvesting

Harvesting is an important operation of cultivation, it reflects on the economic aspect of the crude drugs. Harvesting can be efficiently done by skilled workers. Selectivity is important in harvesting to allow only the desired drug to be collected while those not desired are rejected.Examples of Harvesting techniques used

Under-ground drugs: example like roots, rhizomes, tubers, bulbs, corms is harvested by mechanical devices like hoes, diggers, lifters etc. they are thoroughly washed in water to get rid of sand and earth.

Over –ground (aerial) drugs: aerial parts may be harvested using binders. Flowers, seeds and small fruits are hand-picked but many a times they are harvested using special devices known as strippers. Cloves are collected by beating the plant with bamboo sticks. Peppermint and spearmint are harvested by normal method using mowers, whereas fennel, coriander and caraway plants are uprooted and dried. After drying they are thrashed and the fruit separated by winnowing. Sometimes reaping machines are used for harvesting some over ground derived drugs.

Drying

Drying is the process of removing sufficient quantity of moisture content of crude drugs, it is done to prevent moulding, action of bacteria, enzymatic reaction, chemical and any other possible changes in the quality of the drugs. Drying facilitate pulverisation, grinding and milling of the crude drug. Control of temperature and maintenance of air-flow are the main principle involved in drying. Slow drying at a moderate temperature is essential. There are two process of drying

Natural drying: There are two processes involved in natural drying(a) Direct sun drying(b) Shade dryingWhen the content of the drugs are not affected by temperature and sunlight, they are dried directly under the sun light e.g. Acacia, fruits, seeds etc. for maintaining natural colour and the retention of volatile principles of a drug shade drying is preferred.

Artificial drying: Trays, stove, oven, hot water pipes, spray and vacuum dryers are the main devices used for artificial drying. Leaves and aerial parts are

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dried by tray method at temperatures between 40-60oC. Barks and roots are dried between temperatures of 35-60oC e.g. Cinchona bark, Belladonna roots, Tea and Raspberry leaves. Drugs that require high drying temperatures but with sensitive constituents are dried by vacuum drying which uses the principle of reduced temperatures at increased pressures e.g. Digitalis leaves and tannic acid. Drugs that are sensitive to temperatures are dried by spray drying method e.g. Papaya latex, pectin, milk, tannin etc. Rapid drying and prevention of enzymatic reactions are the main advantages of artificial drying. Flowers and leaves are dried in such a way that they their retain colour and oduour, this is done by rapid drying.

Garbling

This is the step of removal of foreign materials e.g. dirt, sand, debris, organic matter and other parts of the plant. Garbling is the preparation step that usually follows drying. Foreign materials are removed by several methods e.g. excess stems are removed from the leaves of Lobelia and Stramonium by hand picking, in rhizomes roots and rootlets are removed by hand picking, dirt and sand are removed from roots and rhizomes by washing thoroughly with water followed by passing air-current. Iron dusts are removed from castor seeds by the aid of magnet.

Packing/Packaging

Morphological conditions, storage, climatic conditions, chemical nature, transportation and ultimate use of the drug by manufacturer are important factors taking into consideration in packing crude drugs. Packaging is done in such a way to save space during transportation, storage and provide sufficient protection for the drugs. Leaves and herbs are put in solid compact mass (bales) with pressure balers at pressures. Drugs that usually deteriorate in moisture are put in moisture proof containers. Gums, resins, and extracts are packed in barrels, boxes or casks while vanilla beans are packed in tin lined boxes. Aloe is packed in goatskin and in 55 gallon steel drums. Balsam of Tolu and balsam of Peru are packed in kerosene cans. Roots and seeds are packed in bags internally coated with polythene.

Storage and Preservation of DrugsPrior to use drugs are stored, appropriate storing conditions are necessary. Drugs are usually stored in light proof, moisture proof, air-tight closed containers (covered by metal bins), sometimes amber glass containers are used. Drugs should not be stored in wooden

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boxes or in drawers and never in paper bags because they will deteriorate with moisture and may be attacked by insects and rodents. Few drops of chloroform and carbon tetrachloride are added at interval, this may useful in preventing insect attack. Digitalis and Ergot needs low moisture content and are kept with calcium oxide which is a non-liquefying, inert dehydrating substance. Drugs containing volatile oils are stored in well closed, air-tight, dark coloured containers in a cool place. In some drugs sterilisation is important before storage to prevent microbial contamination. Ware-houses for drug storage should be cool, dark, well ventilated, fire proof, moisture proof, steel or brick constructed.

Adulteration and Evaluation of drugs

Adulteration of crude drugs

Adulteration is act of incorporation of impurities in genuine or standard drugs; this may be accidental or deliberate. In few cases dealers mix the substandard and spoiled drug with genuine ones due to scarcity or high price of the commodity. Adulteration may occur due to improper collection, drying, preparation, and storage of crude drugs. In this way the crude drugs are of inferior quality containing fewer amounts of bioactive compounds and more of foreign matter. There are various methods in which drugs are adulterated.

1. Substitution with exhausted drugsThis type of adulteration normally takes place with costly drugs. Many drugs are extracted on a large scale to isolate their active constituents. These exhausted materials are used entirely or partly as substitute for the standard drugs. Example Tea leaves are collected, dried and mixed with genuine tea leaves and sent to the market

2. Adulteration by artificial substituteArtificial substitute are prepared for some drugs which resemble genuine drugs in form and appearance and are sold as the genuine drugs. Example paraffin wax is yellow in colour and is substituted for yellow Bees-wax.

3. Adulteration due to common vernacular namesThis type of adulteration is caused by common vernacular names used for different plants. Several plants have same common names but are of different family example Both Steganataenia araliacea (Apiaceae) and Boswellia dalzielli (Burseraceae) are known as Hanno in Hausa

4. Subsitution by different plant materialSome substituted plant materials are sold in the market which resembles standard ones. Example Ashoka bark is obtained from Saraca indica and is substituted with Blume bark obtained from Trema orientalis. Senna leaves is obtained from Cassia acutifolia and

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Cassia angustifolia but these leaves are substituted with Cassia auriculata.

5. Subsitution with other materialsIn this type of adulteration standard crude drugs are partially mixed with other plant materials such as black Catechu with Aloe, black pepper with papaya seeds.

6. Adulteration from faulty collectionThe optimum amount of active constituent is present in a crude drug at a particular season, time and age of the plant. When the drugs are not collected during the specific collection season, the quality and quantity of active constituent is likely to be reduced. When these drugs are mixed with standard drug they cause adulteration. Example Coriander fruits and Linseed are collected when the plant is 3-4 years old, sometimes they are mixed with samples collected before the plant is fully developed. Sometimes less valuable part of the plant is collected and adulterated with genuine drug.

7. Adulteration due to imperfect storageA number of drugs are spoiled due to imperfect storage or sometimes are destroyed by enzymes, microbes, moisture, light and temperature. These drugs become useless and are unfit for human consumption. These drugs are sometimes used to adulterate genuine drugs. Example if cod-liver oil is improperly protected from light, there is decomposition of vitamin A; Fatty acids become rancid with bad storage and are unfit for human consumption.

Evaluation of crude drugsEvaluation is the determination of quality and purity of drugs. Important terminologies in evaluation areIdentity: This refers to exact biological source of drugsQuality: which refers to the concentration of biologically active constituents?Purity: which refers to the absence of both organic and inorganic foreign material?There are different methods for evaluation of crude drugs

Organoleptic EvaluationDrugs are evaluated by means of their organoleptic characteristics with the aid of the sense organs. The parameters used include morphology and sensory characters which include colour, odour, taste and texture of crude drugs.

a) Morphological characters of crude drugs:Morphological characters are very useful in identification of crude drugs. They can give an idea of presence of adulterants in the drugs. Organised vegetable drugs are classified on the basis of the part used

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Barks: barks are the external tissues present in woody roots and stems, they are the tissues outside the inner fascicular cambium. Example includes Cinchona, Quillaia, and Cascara etc.

Underground Structures: they include roots, rhizomes, bulbs, corms, tubers and are often swollen due to the presence of carbohydrate and other chemicals. Official drugs include Rawolfia roots, Ginger rhizomes, Dioscorea tubers, liquorice roots etc.

Leaves: they are the lateral outgrowth of stem or an appendage developing upon a node having a bud in its axil. Leaves are usually flattened and green and are the photosynthetic organs of the plant. Leave based drugs are identified on the basis of their shapes, size, margin, base, apex, venation etc. official leave drugs includes Senna leaves, digitalis leaves, etc.

Flowers: the flower is the reproductive organ of the plant. It is composed of four basic parts: corolla, calyx, androecium and gynoecium. The flowers help in the formation of fruits and seeds. Example of official flower drugs includes Pyrethrum and Saffron flowers.

Fruits: this is a ripened ovary and contains seeds example of official fruit crude drugs are Fennel, Almond, Cardamon etc.

Seeds: Seeds are developed from the ovules in the carpels of the flower and are characterised by the present of hilum, the microphyle and sometimes the raphe. Example Ispangula, Nux-vomica etc.

Herbs: herbs are small soft textured plants. They contain little woody tissues. They may be annual, biennial, perennial. Sometimes the whole aerial part of the plant is used as drug.

b) Sensory characters Sensory characters include colour, odour,taste and texture. They are important factors used for evaluation of crude drugs. Properly dried drugs have characteristic colour while volatile oil containing drugs have characteristic odour (aroma). There are various terms used for describing the sensory characters of a drug and this depends on the morphological form.

Microscopic EvaluationMicroscopic evaluations of drugs are very useful in the identification of different varieties of drugs and adulterants. The drug is examined under the microscope. Microscopic examination is usually done on powder, thin section (LS/TS) and macerated sample of the crude drug. After the preparation staining reagents are used to distinguish

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arrangement and cellular structures of the crude drug. Microscopical examination can also be used for studying the chemical constituent of a crude drug. The basic arrangement of tissues in stems, roots, leaves, bark, seeds etc is fairly constant. There may be considerable variation due to climatic condition, extent of lignification etc. fibers, sclereids, tracheids, calcium oxalate etc. are not affected by drying. The characteristic cell wall, cell content, fibers, trichomes, sclerieds, vessels etc are essential for identification of crude drug sample. During microscopic examination drawings are essential especially with the aid of camera lucida; however with the advent of digital technology representation of microscopic image is simple and accurate. Microscopic evaluation can be quantitative when the evaluation involves counting and measurements or qualitative when it involves the determination of constituent and component of the sample.

Physical EvaluationIt is essential for the determination of quality and purity of drugs. This evaluation involves the measurement of the drug’s physical constants and extractive values, solubility, refractive index, freezing point, boiling point, moisture content, spectroscopic analysis, ash-value etc.

a) Moisture content: The presence of excessive moisture in a drug will lead to deterioration in quality as a result of activation of enzymes and the growth of microbes. The moisture content of crude drugs is determined by the Karl-Fischer method. There are pharmacopoeia standards for moisture content of crude drugs.

Example of pharmacopoeia moisture content limit for some crude drugs

Crude Drugs Maximum Moisture content (% W/W)

Digitalis 5Balsam of Tolu 4Aloe 10Starch 15Acacia 15

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b) Melting Point: This is useful for determining the purity of some crude drugs. Pure constituent give sharp and constant melting points. This parameter is very important in evaluating solid fixed oils and fats.Example of pharmacopoeia melting point limit for some fats/fixed oils

Crude Drugs Melting point(OC)Cocoa-butter 30-33Bess-wax 62-65Wool fat 34-40

c) Refractive IndexThis is the ratio of the velocity of light in vacuum to the velocity in a substance in which the light passes through. The refractive index depends on the wavelength of the incident light, temperature and pressure. This physical constant is very useful in the evaluation of volatile oils and fixed oils

Refractive Index= Velocity of light in Vacuum

Velocity of the light in substance

d) Optical rotationOptical activity is the ability to rotate the direction of plane polarized light; many substances of biological origin are optically active. If light is rotated to the right the substance is said to be dextrorotatory (+) if it is towards left is called laevorotatory (-). Optical rotation is determined using polarimeters. Most volatile and fixed oils are optically active, and this parameter is important in their evaluation.Relative flow (RF) valuesThin layer and paper chromatography are important techniques in drug evaluation for qualitative and quantitative estimations. Relative flow (RF) is characteristic constant and is given as

RF= Distance covered by solute (drug) Distance covered by solvent (mobile Phase)

RF values of a compound are constant for a particular solvent system. The recent techniques used in evaluation of crude drugs are referred to as chromatographic finger-printing.

e) Foreign matterThis is the other part of the drug source other than the desired crude drugs. Since it is difficult to completely eliminate the presence of foreign matter in crude drugs, the official books have set standards for presence of foreign matter. The maximum limit of foreign matter is given in the monograph of the crude drugs in the various Pharmacopoeias.

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f) Ash valuesThis is determined by incinerating a known amount of crude drug in a crucible and the total ash is determined as a percent of the crude drug. The ash value will give an idea of the amount of foreign matter in crude drugs. The distinction between organic and inorganic foreign matter can be made by determination of ash extractive values (water or acid soluble or insoluble ash values). The pharmacopoeias have set standards for these values for various crude drugs.

g) Extractive ValueCrude drugs contain a large number of chemical constituents; extractive value is used for evaluation of crude drugs as this values a fairly constant for the drugs. The extracts are prepared in different solvents such as water, ethanol, ether, chloroform, etc by maceration, percolation, and soxhlet extraction The extractive value is given as percent of the crude drugs and is referred to as water, alcohol, chloroform and ether extractive value depending on the solvent used.

h) Spectroscopic analysisThis is an important parameter used in evaluation of drugs. The methods used include Ultraviolet light (UV), Infra red light (IR), Nuclear magnetic resonance (NMR) and Mass spectroscopy.

i) Microbial ContaminationSome drugs may be contaminated by microbes; the official books have set standards and limits for the presence of certain types and levels of microbes in the drugs. It is in this line that certain crude drugs need to be sterilised prior to storage.

Chemical evaluationThis is useful for determination of purity of crude drugs. Chemical evaluation includes the qualititative and quantitative chemical test for various constituents.

a. Quantitative chemical evaluations:This includes

acid value saponification value acetyl value peroxide value hydroxyl valuesetc.

b. Qualitiative chemical testsCrude drugs contain various chemical groups that can be identified by specific and non specific chemical tests. Example includes

Vitali morin reaction for tropane alkaloids lead acetate and lead sub-acetate precipitation methods

for gums Borntragger’s test for anthraquinones

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Introduction to Pharmacognosy M.S.Abubakar Ph.D

Keller-Killiani’s and Kedde’s test for cardiac glycosides (digitalis)

Murexide test for purine derivatives (Caffeine) Million’s, Ninhydrin and Biuret’s tests for proteins and

amino acids Molisch’s test for carbohydratesEtc.

Phytochemical screening is the technique used for identification of the various chemical groups in given crude vegetable drug. The technique usually involves successive extraction with different polarity of solvent like petroleum ether, chloroform, acetone, ethanol and water. The bioactive compounds are identified and estimated by chemical tests.

Biological evaluationThis is a technique used in evaluating some drugs by using whole animals or isolated biological tissues or organs. Such biological assay utilises the pharmacological/biological activity of the drug. Experimental animals includes rodents (mice, rats, guinea pigs, rabbits, hamsters etc), primates (monkeys, apes, baboons etc) while isolated tissues includes guinea pig ileum, rat uterus, rabbit duodenum, frog rectus abdominis muscle, rat phrenic nerve etc. other biological models includes bacterial cells (Gram positive and gram negative bacteria) and fungal cells, theses are particularly important for antibiotics. Biological evaluation is expensive, time consuming and require extensive skills.

Official books, text books and learning resources for Pharmacognosy

Official booksThe official books are the pharmacopoeias which contains monographs of drugs,

these includesI. British Pharmacopoeia (BP): this is a publication which establishes officially

recognized standards for the use of medicines. Both electronic and online copies are available

II. British Pharmaceutical codex (BPC) : this is a publication which establishes officially recognized standards for the use of  medicines. Both electronic and online copies are available

III. United states Pharmacopoeia (USP): : this is a publication which establishes officially recognized standards for the use of  medicines; also available online at US Pharmacopeias - http://www.usp.org/

IV. International Pharmacopoeia: this is an official book of WHO containing monographs of some drugs. Both electronic and online copies are available at http://www.who.int/

V. African Pharmacopoeia; this is an official publication of WHO an STRC on monographs of drugs and medicinal substances

VI. Nigerian Pharmacopoeia: this is under production; it is done in collaboration between the FMH, Nigeria and WHO. It contains monograph of common medicnal plants and herbs currently used in the country

VII. Martindale: the complete drug reference.  London : Pharmaceutical Press, 1999

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Introduction to Pharmacognosy M.S.Abubakar Ph.D

Text booksTextbook of Pharmacognosy 5th Edition, J&A Churchill Limited, London pp (by

Wallis, T.E ) The Practical Evaluation of Phytocharmaceuticals. Wright Scientechnica.

Bristol. (by Brain K.R. and Turner T.D. 1975. )Trease and Evans Pharmacognosy. Thirteenth Edition. English language Book

society/Baillere Tindall. London. (by Evans W.C. 1989.)CRC Handbook of Medicinal Herbs.  James A. Duke. Boca Raton, Fla. : CRC Press.  A Dictionary of Natural Products : Terms in the Field of Pharmacognosy Relating to

Natural Medicinal and Pharmaceutical Materials and the Plants, Animals, and Minerals from which they are Derived.  George Macdonald Hocking.  Medford, NJ : Plexus Pub., c1997. 

Herbal Drugs and Phytopharmaceuticals:  a Handbook for Practice on a Scientific Basis.  edited and translated from the second German edition by Norman Grainger Bisset ; with a foreword by J. David Phillipson ; German edition edited by Max Wichtl ; with contributions from F.-C. Czygan ... [et al.]. Stuttgart : Medpharm Scientific Publishers ; Boca Raton : CRC Press, 1994. 

Pharmacognosy, Phytochemistry, Medicinal plants.  Jean Bruneton ; preface by A. Cavé ; translated by Caroline K. Hatton.  Paris ; New York : Lavoisier ; Andover, England : Intercept, c1995. 

Some Pharmacognosy/Pharmacy Learning resources on the

Internet

History of Pharmacy/pharmacognosy

The Apothecary Shoppe - http://www.collectmedicalantiques.com/apothecary.html illustrates the spread of Pharmacy from the Middle East, plus snake oils and show globes History of Pharmacy - http://www.pharmacy.wsu.edu/History/index.html in 40 pictures taken from Great Moments in Pharmacy

Useful herbal Internet Sites

HerbWeb http://www.herbmed.org/HerbMed® - an interactive, electronic herbal database - provides hyperlinked access to the scientific data underlying the use of herbs for health.  It is an evidence-based information resource  for professionals, researchers, and general public.  HerbMed® is a project of the Alternative Medicine Foundation, Inc, provided as a freely available, public resource.

Martindale's Health Science Guide - The Virtual Pharmacy Center http://www.martindalecenter.com/Pharmacy.html

MedWebhttp://www.medweb.emory.edu/MedWeb/ This site is is collection of links to medical sites developed by the Robert W. Woodruff Health Sciences

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Introduction to Pharmacognosy M.S.Abubakar Ph.D

Library of Emory University.  To locate Pharmacy links, select "browse for keyword" and select the link "Pharmacy and Pharmacology".The American Herbal Pharmacopoeia™ - http://www.herbal-ahp.org/The American Society of Pharmacognosy - http://www.phcog.org/A Modern Herbal, by Mrs. M. Grieve, 1931 - http://www.botanical.com/botanical/mgmh/mgmh.htmlArchives of Phytopharmacognosy@jiscmail.ac.uk - http://www.jiscmail.ac.uk/lists/phytopharmacognosy.htmlAromatherapy Materia Medica - http://www.healthy.net/clinic/therapy/aroma/AromaMM.aspBotanical Medicine of Edgar Cayce - http://www.meridianinstitute.com/echerb/Files/classics/mausert/matmed1.htmlCulpeper, The Complete Herbal Online - http://www.bibliomania.com/2/1/66/113/frameset.htmlEclectic Materia Medica, Pharmacology and Therapeutics by Harvey Wickes Felter, M.D. (1922) - http://www.ibiblio.org/herbmed/eclectic/felter/main.htmlHealth World Online - Herbal Materia Medica - http://www.healthy.net/clinic/therapy/herbal/herbic/herbs/index.aspBy David Hoffmann, M.H.I.M.H.Medicinal Herbs Online - http://www.egregore.com/index.htmPhytochemical Society of Europe - http://www.dmu.ac.uk/ln/pse/Phytochemical Society of North America - http://www.ucalgary.ca/~dabird/psna/Phytomedicine - http://www.urbanfischer.de/journals/phytomed/Phytopharmacognosy - http://www.phytochemistry.freeserve.co.uk/Phytotherapies.org - http://www.phytotherapies.org/Planta Medica - http://www.thieme.de/plantamedica/Rocky Mountain Herbal Institute TCM HerbLibrary: introduction, theory, materia medica - http://www.rmhiherbal.org/ai/pharintro.htmlNewsReuters Health - http://www.reutershealth.com/ latest world-wide health news - also try CNN Health News : http://cnn.com/HEALTH/ BBC health news : http://news.bbc.co.uk/hi/english/health/ ABC Health Matters :http://www.abc.net.au/health/ WHO Guide to Good Prescribing: a Practical Manual - http://www.who.int/medicines/library/par/ggprescribing/begin.html covers the process of prescribing drugs, understanding standard treatment guidelines, suitability of drugs, writing prescriptions, basic pharmacology, essential references etc.Search EnginesGoogle - http://www.google.com/ simple, fast with excellent results. this I quick Meta search - http://www.ixquick.com/ gets selected results from 12 search engines simultaneously Searching the Internet - http://www.library.jcu.edu.au/Resources/Internet/searchtools.shtml check out some other good search engines (and how to use them)

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