Pharmacognosy - Introduction & Definitions

# **Pharmacognosy** ## **Introduction** * **Course:** Pharmacognosy * **Department:** Pharmacy * **Professor:** A.D. Essam Ali Hassan Faraj * **Semester:** Fall 2024-2025 ## **Definition** * **Pharmacognosy:** The study of drugs derived from natural sources. * **Definition:** The word "Pharmaco...

# **Pharmacognosy** ## **Introduction** * **Course:** Pharmacognosy * **Department:** Pharmacy * **Professor:** A.D. Essam Ali Hassan Faraj * **Semester:** Fall 2024-2025 ## **Definition** * **Pharmacognosy:** The study of drugs derived from natural sources. * **Definition:** The word "Pharmacognosy" is derived from the Greek word "pharmakon" which means "drug or medicine" and "gignosco" which means to acquire knowledge. * **Sources:** Plants, Animals, Microorganisms, Minerals **Pharmacognosy** is the study of the physical, chemical, biochemical, and biological properties of drugs and drug substances of natural origin as well as the search for new drugs from natural sources. * **Note:** Pharmacognosy **does not** include the study of synthetic drugs. * **Relationship to other fields:** Pharmacognosy is **NOT** identical to medicinal chemistry and/or pharmacology but utilizes their methods. * **Close Relationship to:** Botany, ethnobotany, marine biology, herbal medicine, chemistry (phytochemistry), pharmacology, pharmaceutics ## **Crude drugs** * **Definition**:Crude drug refers to the products from plants, animal and mineral origins found in their raw form. They are used in the treatment of various disorders and ailments of human beings. * **Main sources:** Higher plants, microbes, animals and marine organisms. Some useful products obtained from minerals that are both organic and inorganic in nature. ### **Classification of crude drugs** * **Purpose:** For the systemic and scientific study of crude drugs, it is essential to classify them in the proper form. * **Criteria:** * **Simple** * **Easy to use** * **Free from confusion** #### **Methods of classifying crude drugs:** 1. **Alphabetical classification:** * Drugs are arranged in alphabetical order of their Latin and English names (common names). * **Examples:** Acacia, Benzoin, Cinchona, Dill, Ergot, Fennel, Gentian, Hyoscyamus, Ipecacuanha, Jalap, Kurchi, Liquorice, Mints, Nuxvomica, Opium, Podophyllum, Quassia, Rauwolfia, Senna, Vasaka, Wool fat, Yellow bees wax, Zeodary. * **Adopted by:** Indian Pharmacopoeia, British Pharmacopoeia, British Herbal Pharmacopoeia, United States Pharmacopoeia and National Formulary, British Pharmaceutical Codex, European Pharmacopoeia. * **Merits:** * **Easy and quick to use** * **No repetition of entries** * **Free from confusion** * **Easy to locate, trace and add drug entries** * **Demerits:** * **Does not help in distinguishing the source (plant, animal or mineral)** 2. **Taxonomical classification:** * **Based on:** Phylogenetic similarities in plants * **Arrangement**: Drugs are arranged in groups according to their division, class, family, genus and species. * **Examples:** * **Thallophyta:** Alage-e.g. Gelatin, Fungi-e.g. Yeast, Ergot * **Pteridophyta:** e.g. Dropteris (Male fern) * **Gymnosperm:** e.g. Pinus species, Resins, oil of terpentine * **Angiosperm:** (Moncot) Dicot * **Merits:** Helps in studying **evolutionary developments** * **Demerits:** Does **not** correlate the **chemical constituents** and **biological activity** of the drugs. 3. **Morphological classification:** * **Arrangement:** Drugs are arranged in different groups based on the part of the plant that is used as a drug (leaf, stem, root, bark, flower, fruit, seed). * **Categorization:** * **Organized drugs:** Characterized by the presence of a cellular structure (Overground organ: leaves, flowers, fruits, barks, seeds; Underground organ: roots, rhizomes, bulbs, corms) * **Unorganized drugs:** Does not represent any cellular structure (Juices, latex, resins, fixed oil, waxes, gums & mucilage). * **Merits:** * **More helpful to identify and detect adulteration** * **More convenient for practical study** * **Demerits:** There is **no correlation** of chemical constituents with the therapeutic actions. 4. **Pharmacological classification:** * **Arrangement:** Drugs are arranged according to their pharmacological action or therapeutic use. * **Merits:** * **Mostly followed method** * **More relevant** * **Example:** Drugs like digitalis, squill and strophanthus (having cardiotonic action) are grouped together. * **Table:** * **Pharmacological Action**: Anticancer, Anti-inflammatory, Antiamoebic, Antiasthaustic, Anthelminthic, Antispasmodic, Astringent, Analgesic, Bitter tonic, Carminatives, Purgatives, Expectorat, Cardiotonic, Tranquilizern * **Drugs:** Vioca, Podophyllum, Tams, Colchicum, Tormeric, Ipecac soot, Karchi bark, Ephedra, Lobelia, Male fern, Quassia wood, Danna, Hyoscyаци, Catechu, Opium, poppy, Quassia wood, Nox-vomica, Gentian, Coriander, fennel, clove, peppermint, Senna, Rhubarb, Tulsi, Balsam of Toki, Vasaka, Digitalis, Squill, Stropahanthan, Rauvolfia Roots * **Demerits:** Drugs having different action on the body can be classified separately in more than one group causing ambiguity and confusion. 5. **Chemical classification:** * **Arrangement:** Drugs are classified into different groups based on the chemical nature of their most important constituent. * **Basis:** Pharmacological activity and therapeutic significance of crude drugs * **Grouping:** Drugs with identical constituents (i.e., the same active compound). * **Examples:** * **Carbohydrates:** Polyhydroxy aldehydes or ketones containing an unbroken chain of carbon atoms. * **Gums:** Acacia, Tragacanth, Guargum * **Mucilages:** Plantago seed * **Others:** Starch, Honey, Agar, Pectin, Cotton * **Glycosides:** Compounds which upon hydrolysis give rise to one or more sugars (glycone) and non-sugar (aglycone). * **Anthraquinone Glycosides:** Aloe, Cascara, Rhubarb, Senna * **Cardiac Glycosides:** Digitalis, Strophantus, Squill. * **Saponins Glycosides:** Quillaia, Arjuna, Glycyrrhiza * **Tannins:** Complex organic, non-nitrogenous derivatives of polyhydroxy benzoic acids. * **Examples:** Pale catechu, Black catechu, Ashoka bark, Galls, Myrobalan, Bahera, Amla. * **Alkaloids:** Nitrogenous substance of plant origin. * **Tropane:** Coca, Belladonna, Datura, Stramonium, Hyoscyamus * **Quinoline:** Cinchona * **Isoquinoline:** Opium, Ipecac, Calumba * **Indole:** Ergot, Rauwolfia * **Amines:** Ephedra * **Purine:** Tea, coffee * **Merits:** A popular approach for phyto-chemical studies. * **Demerits:** Difficult to place drugs containing two different types of chemical constituents. (e.g., Cinchona contains both alkaloids and glycosides). 6. **Chemotaxonomical classification:** * **Arrangement:** Relies on the chemical similarity of a taxon i.e. it is based on the existence of relationships between constituents in various plants. * **Underlying principle:** There are certain types of chemical constituents that characterize certain classes of plants. This gives birth to entirely new concept of chemotaxonomy that utilizes chemical facts/characters for understanding the taxonomical status, relationships and the evolution of the plants. * **Example:** Tropane alkaloids generally occur among the members of Solanaceae thereby, serving as a chemotaxonomic marker ## **Cultivation, Collection, Drying and Storage** ### **Cultivation** * **Wild Source:** * **Opium:** Only official growers may legally produce herbs. * **Advantages:** * **Often cheaper** * **May be more potent** * **Disadvantages:** * **Potentially difficult to transport** herb to area of processing. * **Difficult access (e.g. Forests, Mountains etc.,)** * **Collector ignorance** * **Admixture of other plants** * **Collection of undesired plant parts** * **Harvesting at the wrong stage of development** * **Harvesting during an incorrect season** (can lead to loss of medicinal activity). * **Damage to natural environment (leading to extinction of a species)** * **Cultivation:** * **Advantages:** * **Only desired species are collected → uniform quality** * **Improved collection, transport & access to processing facilities ** * **Better control of soil quality, pests & plant disease** * **Constant and Regular supply (Controlled)** * **Trained herb collectors** ### **Factors Affecting cultivation of drugs** * **Altitude:** * **Very important factor in cultivation of medicinal plants** * **Examples:** * **Tea, cinchona and eucalyptus:** cultivated favorably at an altitude of 1000-2000 meters. * **Cinnamon and cardamom:** grown at a height of 500-1000 meters. * **Senna:** can be cultivated at sea level. * **Temperature:** * **Excessive temperatures:** adversely affect the quality of medicinal plants * **Frost can also negatively impact some plants** * **Examples:** * **Comphor and coffee:** cannot withstand frost. * **Saffron:** needs only cold climate for cultivation. * **Pyrethrum:** Requires dry weather for cultivation.. * **Rainfall:** * **Most plants need either proper irrigation or sufficient rainfall for favorable development.** * **Exception:** Xerophytic plants (aloe, acacia, and a few others) * **Soil and soil fertility:** * **Most important natural resource** as it supports the growth of all plants. * **Provides:** mechanical anchorage, water, and essential plant food elements for plant growth. * **Soil fertility:** The capacity of soil to supply plant nutrient quantities and proportion required to provide a suitable medium for plant growth. * **Components of Soil:** * **Mineral matter** * **Organic matter** * **Soil air** * **Soil water** * **Soil organisms** * **Described as poor:** Less than 0.5% of organic matter is present * **Described as rich:** More than 1.5% to 5% of organic matter is present. * **pH:** * **Influences plant growth and the presence of microorganisms.** * **Optimal pH range:** Between 6.5 to 7.5. * **Examples:** * **Ground nut, sunflower seeds, cotton and rice:** grow better in alkaline soils only. * **Tobacco, cinchona, tea, and potato:** grow well only in acidic soils. * **Fertilizers:** * **Nutrients that are necessary for development & growth of the plant** * **Examples:** * **Vegetative growth:** plants need carbon dioxide, sunlight, water and mineral matter. * **Plant also need:** 16 nutrient elements for synthesizing various compounds. * **Primary nutrients:** Nitrogen, phosphorus and potassium * **Secondary nutrients:** Magnesium, calcium and sulfur * **Trace elements:** Copper, manganese, iron, boron, molybdenum and zinc * **Other elements:** Carbon, oxygen, hydrogen and chlorine, are obtained from water and air. ### **Plant growth regulators (Plant hormones)** * **Definition**: Organic compounds that affect the morphological structure or physiological processes of plants in low concentrations.. * **Groups:** * **Natural:** Found naturally in plants * **Synthetic:** Human-made * **Influence:** Both groups regulate or influence: * **Cell division** * **Cell differentiation** * **Root and shoot growth** * **Senescence (Plant aging)** #### **Major classes of plant growth regulators (Plant hormones):** 1. **Auxins:** * **Promote elongation:** of coleoptile tissues. * **Examples:** Internodes elongation, leaf growth, fruit growth, apical dominance. * **Types:** * **Natural:** Indole acetic acid (IAA) * **Synthetic:** Indole butyric acid (IBA), a-napthyl acetic acid (NAA) 2. **Gibberellins (GA):** * **Natural plant growth regulator:** Stimulates stem growth through cell division and cell elongation. * **Commercial sources:** Obtained from the fungus _Gibberella fujikuroi._ * **Uses:** Promoting vegetative and fruit growth, flower initiation and induction of parthenocarpy. 3. **Cytokinins:** * **Promote cell division and delay leaf aging.** * **Used as:** Growth promoter in tissue culture techniques. * **Slow down senescence:** By preventing the breakdown of chlorophyll in the leaf. 4. **Ethylene:** * **Volatile gas** * **Found in:** Ripening fruits, flowers, stems, roots, tubers and seeds. 5. **Abscisic acid (ABA):** * **Natural plant growth inhibitor:** Present in different organs such as leaves, stems, flowers and fruits. ## **Collection of medicinal plants** * **Sources:** Wild or cultivated plants * **Importance of timing:** Active constituents of medicinal plants are affected by many factors and may vary during the course of plant growth. * **Obtain a drug of good quality:** Proper time of collection is critical. ### **Factors Affecting Collection:** 1. **Time of the year:** * **Example:** Rhubarb contains no anthraquinone in winter, instead it contains anthranols, which in summer, are oxidized to anthraquinones. * **Example:** Colchicum corm is free from bitterness and is devoid of the alkaloid colchicine in autumn, hence is used in Austria as a food, instead of potatoes. Bitterness starts to appear in spring and early summer when it is used as a drug. 2. **Time of the day:** * **Some drugs, like Digitalis, contain different amounts of active constituents in different times of the day.** Being highest in the afternoon. 3. **Stage of maturity and age:** * **The value and content of active constituents of many drugs depends on the stage of maturity and age.** * **Examples:** * **Conium fruits:** Contain coniin when fruits are mature and unripe. * **Santonica Flowers:** Rich in santonin, when unexpanded, when it starts to open, the santonin content decreases. ### **Rules for general for collection:** * **Assumption:** The material is best collected when the organ in question has reached its optimal state of development. * **Roots and rhizomes:** Collected at the end of the vegetation period (usually in the autumn). * **Wash roots and rhizomes:** Free of adhering soil and sand. * **Bark:** Collected in the spring. * **Leaves and herbs:** Collected at the flowering stage * **Flowers:** Usually gathered when fully developed. * **Fruits and seeds:** Collected when fully ripe. ### **Methods of collection:** * **Medicinal plants:** Largely collected by hand (Especially true in the case of wild plants) * **Large scale cultivation:** Modern agricultural harvesters may be used. ## **Drying of crude drugs** * **Purpose:** To preserve plant material. * **Water content of living plants:** * **Leaves:** 60-90% water * **Roots and rhizomes:** 70-85% water * **Wood:** 40-50% water * **Seeds:** The lowest percentage, often no more than 5-10% water. ### **Reasons for drying:** 1. **Preservation:** To help in their preservation. 2. **Fixing constituents:** To fix their constituents, by preventing reactions that may occur in presence of water. 3. **Prevent microorganisms:** To prevent the growth of micro-organisms such as bacteria and fungi. 4. **Facilitate grinding:** To facilitate their grinding. 5. **Reduce size and weight:** To reduce their size and weight. 6. **Prevent spoilage:** Insufficient drying favors spoilage by micro-organisms and makes it possible for enzymatic destruction. ### **Methods of drying:** 1. **Natural drying:** * **Accomplished by:** Natural air in sun or shade. 2. **Artificial drying:** * **Rapid method:** Done at well-controlled temperature (accomplished by): * **Direct fire** * **Use of heated stones** * **Use of stoves** 3. **Lyophilization (Freeze drying):** * **Process:** Frozen material is placed in an evacuated apparatus which has a cold surface maintained at -60 to -80 °C. Water vapor from the frozen material passes rapidly to the cold surface. * **Uses:** Drying heat-sensitive substances (e.g., antibiotics and proteins.) 4. **Chemical drying using desiccators:** * **An absolutely dried drug** is that completely freed from water, when exposed to air it absorbs 8-10% of moisture (is called air-dry drug). ## **Storage of crude drugs:** * **Essential:** Store them in a dry condition in carefully closed containers. * **Deterioration:** Drugs usually deteriorate over time, especially if not stored properly. * **Causes:** Improper methods of storing and inadequate protection during storage. ### **Reasons for deterioration:** * **Physiochemical:** * **Moisture** * **Heat** * **Air** * **Light** * **Biological:** * **Fungi** * **Bacteria** * **Insects and Rodents** ## **Pharmacognostic Evaluation of Medicinal Plants** ### **Preparation of crude drugs:** * **Extracts:** Preparations of crude drugs which contain all the constituents which are soluble in the solvent used in making the extract. * **Tinctures:** Prepared by extraction of the crude drug with five to ten parts of ethanol of varying concentration, without concentration of the final product. ### **Choice of solvent** The ideal solvent for a certain pharmacologically active constituent should: 1. **Selectivity:** Be highly selective for the compound to be extracted. 2. **No interaction:** Not react with the extracted compound or with other compounds in the plant material. 3. **Low price:** Have a low price. 4. **Harmless:** Be harmless to man and to the environment. 5. **Volatile:** Be completely volatile. * **According to the pharmacopoeias, _ethyl alcohol_ is the solvent of choice for obtaining classic extracts such as tinctures** ### **Mixing ethanol with water:** 1. **Induce swelling:** To induce swelling of the plant particles. 2. **Increase porosity:** To increase the porosity of the cell walls which facilitates the diffusion of extracted substances from inside the cells to the surrounding solvent. * **Recommended ratio:** * **For extraction of barks, roots, woody parts and seeds:** The ideal alcohol/water ratio is about 7:3 or 8:2. * **For leaves or aerial green parts:** The ratio 1:1 is usually preferred in order to avoid extraction of chlorophyll. ### **Methods of Extraction** 1. **Infusion** 2. **Maceration** 3. **Percolation** 4. **Digestion** 5. **Decoction** 6. **Continuous hot extraction** 7. **Solvent-solvent precipitation** 8. **Liquid-liquid extraction** 9. **Distillation** 10. **Specific procedures** ## **Cell Content** * **All cell is a living organism as it requires energy to survive:** This energy is derived from various metabolic processes within the cell. * **Metabolism requires:** Nutrients (which need to be taken up by the cell) and various enzymes (catalysts) that actually digest the nutrients. * **Enzymes are produced:** Within the cell itself from cell organelles, and the waste products after the digestion are then removed by the cell membrane. ### **Cell Content:** * **Living protoplasts:** * Examples: * Nucleus * Cytoplasm * Vacuoles * Mitochondria * Plastids * **Not diagnostically useful** * **Non-protoplasmic components:** * **Classified as 'ergastic' substances:** * **Starch** * **Crystals** * **Alkaloids** * **Oil** * **Proteins** * **Tannins** * **Very useful for identification** ## **Volatile oils** * **Definition:** Odorous principles found in plants that evaporate when exposed to air at ordinary temperature. * **Location:** Pre-exist in plant in particular secretory parts such as: * Glandular hairs, * parenchyma cells, * vittae or oil tubes, * epidermal tissues of lemon and orange * In lysigenous or schizogenous passages. * **Main component:** Derivatives of terpenes (C5H8). * **Properties:** * **High refractive indices** * **Generally optically active** * **Immiscible with water** * **Freely soluble in organic solvent:** alcohol, ether, chloroform, acetone etc. * **Physical state:** Mostly volatile oils are liquid except menthol, thymol, anethol which are solids at 15.5 °C. ## **Tannins** * **Definition:** Complex organic, non nitrogenous derivatives of poly hydroxyl benzoic acids. * **Origin:** Derived from tan which means conversion of hides and skins to leather by forming insoluble compound with protein. * **Location:** Present in aerial parts (leaves, fruits, barks and stem); generally occur in immature fruits but disappears during ripening process. * **Types:** * **True tannins:** * **High molecular compounds** * **Show positive test with Goldbeaters skin test** * **Pseudo tannins:** * **Low molecular compounds** * **Show a negative reaction with Goldbeaters skin test** ### **Chemical test of Tannins:** * **Goldbeaters skin test:** A small piece of skin (membrane prepared from the intestine of an ox) is soaked in 2% HCl, washed with water, and then placed in a solution of tannins for 5 minutes. The skin is then washed again with water and kept in a solution of FeSO4. A brown or black color is produced on the skin due to the presence of tannins. * **Vanillin test:** Drug solution + Vanillin hydrochloride → Pink or red colour formed. * **Matchstick test:** A matchstick is dipped in the drug solution, dried near a burner, moistened with conc. HCl and then warmed near the burner. → Pink or red colour formed. ## **Alkaloids** * **Definition:** (Alkali-like) They are basic in nature. * **Origin:** Derived from amino acids present in plant sources. * **Presence:** Contain one or more nitrogen atoms (usually in a heterocyclic ring). * **Action** : Marked physiological action on humans or other animals. ### **Deviation from Definition:** * **Basicity:** Some alkaloids are not basic. (e.g., Colchicine, Piperine) * **Nitrogen:** The nitrogen in some alkaloids is not in a heterocyclic ring. (e.g., Ephedrine, Colchicine). ### **Types of Alkaloids:** 1. **True Alkaloids:** Nitrogen is part of a heterocyclic ring. Derived from amino acids. 2. **Proto Alkaloids:** Does not have a heterocyclic ring with nitrogen. 3. **Pseudo Alkaloids:** Nitrogen is part of a heterocyclic ring. Not derived from amino acids. ### **Examples of Alkaloids:** * **True Alkaloids:** Quinine, Colchicine, Tryptophan * **Proto Alkaloids:** Phenylalanine * **Pseudo Alkaloids:** Caffeine, Xanthine ## **Occurrence and Distribution of Alkaloids** * **PLANTS:** * **Rare:** In lower plants. * **Higher plants:** About 10 to 25% * **Dicots:** More rich in alkaloids than Monocots. * **Families rich in Alkaloids:**Apocynaceae, Loganiaceae, Liliaceae, Rubiaceae, Solanaceae and Papaveraceae. * **Families free from Alkaloids:** Rosaceae, Labiatac * **ANIMALS:** * **Ergot alkaloids:** Ergotamine and egrometrine from Ergot fungus. * **Muscopyridine:** From Musk deer. * **Lycopodine:** From Lycopodium spores. ### **Distribution in Plant:** * **All Parts:** Catharanthus * **Barks:** Cinchona * **Seeds:** Nux vomica * **Roots:** Aconite * **Rhizomes:** Rauwolfia * **Flowering tops:** Datura * **Fruits:** Black pepper * **Leaves:** Tobacco * **Latex:** Opium ## **Functions of Alkaloids in Plants:** * **Protective:** May act as protective against insects and herbivores due to their bitterness and toxicity. * **Source of nitrogen:** In case of nitrogen deficiency. * **Growth regulators:** Sometimes, act as growth regulators in certain metabolic systems. * **Source of energy:** May be utilized as a source of energy in case of deficiency in carbon dioxide assimilation ## **Qualitative Tests for Alkaloids:** * **Indicate the presence or absence of alkaloids:** * **Dragendorff's reagent (Potassium bismuth iodide):** Orange coloured ppt * **Mayer's reagent (Potassium Mercuric iodide):** Cream coloured ppt. * **Wagner's reagent (Iodine in potassium iodide):** Red brown coloured ppt. * **Hager's reagent (Picric acid):** Yellow ppt.