Pharmacognosy Past Paper PDF 2025-2024

# Pharmacognosy ## **Course Description:** * **Course Name:** Pharmacognosy * **Department:** Pharmacy * **Instructor:** Dr. Essam Ali Hassan Farag * **Semester:** Fall 2025-2024 ## **Definition** Pharmacognosy comes from the Greek words: - **Pharmakon:** meaning drug, or medicine. - **Gignosco:** meaning to acquire knowledge. Pharmacognosy is the study of drugs derived from natural sources. The study focuses on: - **Plants** - **Animals** - **Microorganisms** - **Minerals** Pharmacognosy consists of the study of the physical, chemical, biochemical, and biological properties. This also includes the search for new drugs from natural sources. - **Pharmacognosy does not include the study of synthetic drugs.** - **Pharmacognosy is not identical to Medicinal Chemistry or Pharmacology but utilizes their methods.** ### **Pharmacognosy is closely related to:** - Botany - Ethnobotany - Marine biology - Herbal medicine - Chemistry (Phytochemistry) - Pharmacology - Pharmaceutics ## **Crude drugs** - The term crude drug generally applies to products from plants, animals, and minerals found in a raw form. These are used to treat various disorders and ailments in human beings. - The most important natural sources of drugs are: * Higher Plants * Microbes * Animals * Marine Organisms - Some useful products are obtained from minerals that are both organic and inorganic in nature. ### **Classifying crude drugs:** * **Purpose:** For the systemic and scientific study of crude drugs, it is essential to classify them in the proper form. A method of classification should be simple, easy to use, and free from confusion. * **Different Ways of Classifying the Crude Drugs:** 1. Alphabetical classification 2. Taxonomical classification 3. Morphological classification 4. Pharmacological classification 5. Chemical classification 6. Chemotaxonomical classification ### **1. Alphabetical classification:** - In this classification, crude 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 - **This method of classification is adopted by several books and Pharmacopoeias.** * Indian Pharmacopoeia * British Pharmacopoeia * British Herbal Pharmacopoeia * United States Pharmacopoeia and National Formulary * British Pharmaceutical Codex. * European Pharmacopoeia - **Merits:** * It is easy and quick to use. * There is no repetition of entries and is devoid of confusion. * Location, tracing, and addition of drug entries is easy. - **Demerits:** * It does not help distinguish the source of drug whether from plant, animal, or mineral origin. ### **2. Taxonomical classification:** - This system is purely botanical classification based on phylogenetic similarities in plants. - Crude drugs are arranged in groups according to their division, class, family genus, and species. - **Merits:** Taxonomical classification is helpful for studying evolutionary developments. - **Demerits:** This system does not correlate the chemical constituents and biological activity of the drugs. ### **3. Morphological classification:** - Drugs are arranged in various groups according to the parts used as drugs. - This system of classification categorizes drugs into two classes. | Type | Examples | |-----|-----| | **Organized drugs** | Characterized by the presence of a cellular structure. Leaves, flowers, fruits, barks, seeds, roots, rhizomes, bulbs, corms. | | **Unorganized drugs** | Do not represent any cellular structure Juices, Latex, Resins, Fixed oils, waxes, Gums and mucilages | - **Merits:** * Morphological classification is more helpful to identify and detect adulteration. * This system of classification is more convenient for practical study, especially when the chemical nature of the drug is not clearly understood. - **Demerits:** * The main drawback of morphological classification is that there is no co-relation of chemical constituents with the therapeutic actions. ### **4. Pharmacological classification:** - In this classification, crude drugs are arranged according to their pharmacological action or therapeutic use. - This classification is the most relevant and followed method. - Drugs having similar action are kept together. - **Example:** Drugs like digitalis, squill, and strophanthus having cardiotonic action are grouped together. ### **5. Chemical Classification:** - In this system of classification, crude drugs are classified into different groups according to the chemical nature of their most important constituent. - The pharmacological activity and therapeutic significance of crude drugs depend on the nature of their chemical constituents. - **The chemical classification of drugs is dependent upon the grouping of drugs with identical constituents.** | Chemical Constituent | Example | |-----|-----| | Carbohydrates | Acacia, Tragacanth, Guargum, Plantago seed, Starch, Honey, Agar, Pectin, Cotton | | Glycosides | Aloe, Cascara, Rhubarb, Senna, Digitalis, Strophantus, Squill, Quillaia, Arjuna, Glycyrrhiza | | Tannins | Pale catechu, Black catechu, Ashoka bark, Galls, Myrobalan, Bahera, Amla.| | Alkaloids | Coca, Belladonna, Datura, Stramonium, Hyoscyamus, Cinchona, Opium, Ipecac, Calumba, Ergot, Rauwolfia, Ephedra, Tea, coffee. | - **Merits:** It is a popular approach for phytochemical studies. - **Demerits:** It is difficult to place the drug containing two different types of chemical constituents. - **Example:** Cinchona contains both alkaloids and glycosides. ### **6. Chemotaxonomical classification:** - This system of classification relies on the chemical similarity of a taxon. - It is based on the existence of a relationship between constituents in various plants. - There are certain types of chemical constituents that characterize certain classes of plants. - This gives birth to the concept of chemotaxonomy, utilizing chemical facts/characters to understand the taxonomical status, relationships, and the evolution of plants. - **For example:** Tropane alkaloids generally occur among the members of Solanaceae, serving as a chemotaxonomic marker. ## **Cultivation, Collection, Drying, Storage, and Preparation of Crude Drugs** ### **1. Cultivation:** **Benefits of cultivating crude drugs:** - Only desired species are collected, resulting in uniform quality. - Collection, transport, and access to processing facilities are improved. - Better control of soil quality, pests, and plant disease. - Constant and regular (controlled) supply. - Trained herb collectors. **Disadvantages of wild drugs:** - Only official growers may legally produce certain herbs. - Potentially difficult to transport the herb to the area of processing. - Difficult access (e.g., forests, mountains, etc.). - Collector ignorance can lead to a mixture of other plants, collection of undesired plant parts, incorrect stages of development or incorrect seasons, resulting in a loss of medicinal activity. - Damage to natural environments can lead to extinction of a species. ### **Factors Affecting Cultivation of Drugs** - **Altitude:** - Altitude is a very important factor in cultivating medicinal plants. - Tea, cinchona, and eucalyptus are cultivated favorably at an altitude of 1000-2000 meters. - Cinnamon and cardamom are grown at a height of 500-1000 meters, while Senna can be cultivated at sea level. | Plant | Altitude (metres) | |------|----------------| | Tea | 1000-1500 | | Cinchona | 1000-2000 | | Cinnamon | 250-1000 | | Clove | Upto 900 | | Saffron | Upto 1250 | | Cardamom | 600-1600 | - **Temperature:** - Excessive temperature and frost affect the quality of medicinal plants. - Comphor and coffee cannot withstand frost, whereas saffron needs only a cold climate, and pyrethrum requires dry weather for cultivation. - **Rainfall:** - Most plants require either proper arrangements for irrigation or sufficient rainfall for their favorable development. - Xerophytic plants like aloe and acacia have different needs. - **Soil and Soil Fertility:** - Soil is the most important natural resource, as it supports the growth of all plants. - Soil provides mechanical anchorage, water, and essential plant food elements for plant growth. - The capacity of soil to supply plant nutrients and provide a suitable medium for plant growth is known as soil fertility. - **Soil is made up of five components:** * Mineral matter * Organic matter * Soil air * Soil water * Soil organisms - Soil containing less than 0.5% of organic matter is described as poor. - Soil with more than 1.5% to 5% of organic matter is described as rich soil. - The pH of soil affects favorable growth of plants and the presence of microorganisms. - The maximum availability of plant nutrients is between the pH range of 6.5 to 7.5. - 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:** - Fertilizers are nutrients essential for the development and growth of the plant. - Every element performs a specific function in plant growth and development. - For vegetative growth, plants require carbon dioxide, sunlight, water, and mineral matter. - Plants 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. * Carbon, oxygen, hydrogen, and chlorine are provided to plants from water and air. - **Plant Growth Regulators (Plant Hormones):** - Plant growth regulators are organic compounds that affect the morphological structure or physiological processes of plants in low concentrations. | Type | Examples | |------|-----| | Natural | Found naturally in the plant. | | Synthetic | Human-made. | - Both natural and synthetic plant growth regulators influence: * Cell division * Cell differentiation * Root and shoot growth * Senescence (plant aging) - **Major classes of plant growth regulators (plant hormones):** * Auxins: Promote elongation of coleoptile tissues, internodes elongation, leaf growth, fruit growth, apical dominance. * **Examples:** * Natural: Indole acetic acid (IAA) * Synthetic: Indole butyric acid (IBA), α-napthyl acetic acid (NAA) * Gibberellins (GA): Stimulates stem growth through cell division and cell elongation. * **Examples:** Gibberellins are obtained from the fungus Gibberella fujikuroi and are used to promote vegetative and fruit growth, flower initiation, and induction of parthenocarpy. * Cytokinins: Promote cell division and delay leaf aging, used as growth promoters in tissue culture techniques to slow the process of senescence by preventing the breakdown of chlorophyll in the leaf. * **Examples:** * Natural: Zeatin * Synthetic: Kinetin * Ethylene: Present in the form of a volatile gas, present in ripening fruits, flowers, stems, roots, tubers, and seeds. * Abscisic Acid (ABA): A natural plant growth inhibitor, present in different organs such as leaves, stems, flowers, and fruits. ### **2. Collection of Medicinal Plants** - Drugs can be collected from wild or cultivated plants. - The active constituents of medicinal plants are affected by many factors and may vary during the plant growth. - Proper time of collection is essential to obtain a drug of good quality. **Factors Affecting Collection:** - **Time of the year:** * The plant may contain a substance in winter that is not present in summer, or the amount varies. * **Example:** Rhubarb contains no anthraquinone in winter but contains anthranols, which are oxidized to anthraquinones in summer. * 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. The bitterness appears in spring and early summer when it is used as a drug. - **Time of the Day:** * Some drugs like digitalis contain different amounts of active constituents at different times of the day, with the highest content in the afternoon. - **Stage of maturity and age:** * The value and content of active constituents in many drugs depend on the stage of maturity and age. * **Example:** * Conium fruits contain coniin when fruits are mature and unripe. * Santonica flowers are rich in santonin when unexpanded, but as they open, the santonin content decreases. **Rules for Collection:** - The following general rules assume that the material is best collected when the organ in question has reached its optimal stage of development. 1. **Roots and rhizomes** are collected at the end of the vegetation period, usually in the autumn. They should be washed free of adhering soil and sand. 2. **Bark** is collected in the spring. 3. **Leaves and herbs** are collected at the flowering stage. 4. **Flowers** are usually gathered when fully developed. 5. **Fruits and seeds** are collected when fully ripe. - **Methods of Collection:** * Medicinal plants are generally collected by hand, especially true in the case of wild plants. * With cultivation on a large scale, modern agricultural harvesters may be used. ### **3. Drying of Crude Drugs** - The most common method for preserving plant material is drying. - Living plant material has a high water content: * Leaves may contain 60-90% water. * Roots and rhizomes 70-85%. * Wood 40-50%. * The lowest percentage, often no more than 5-10%, is found in seeds. **Reasons for Drying:** * **To help in preservation:** By preventing reactions that may occur in the presence of water. * **To fix their constituents:** Preventing reactions that occur in the presence of water. * **To prevent the growth of microorganisms:** Such as bacteria and fungi. * **To facilitate grinding:** Making the material easier to grind. * **To reduce their size and weight:** Making the material easier to store and transport. * **To prevent spoilage:** Insufficient drying can favor spoilage by microorganisms and make it possible for enzymatic destruction. **Methods of Drying:** - **Natural drying:** Using natural air in the sun or shade. - **Artificial drying:** A rapid method done at a well-controlled temperature. It is often used to overcome limitations of natural drying in countries with wet climates or humid environments. * **Methods:** * Direct fire * Heated stones * Stoves - **Lyophilization (Freeze Drying):** Frozen material is placed in a vacuum apparatus with a cold surface maintained at -60 to -80 °C. Water vapor from the frozen material passes rapidly to the cold surface. This method is used for drying heat-sensitive substances such as antibiotics and proteins. - **Chemical Drying Using Desiccators:** A completely dried drug is one that is freed from water, but when exposed to air, it absorbs 8-10% of moisture and is called an air-dry drug. ### **4. Storage of Crude Drugs:** - It is essential to store crude drugs in a dry condition in carefully closed containers. - Storage is the last stage of preparing crude drugs. - Drugs typically deteriorate over time. - Improper storage methods can cause pronounced deterioration. #### **Two principal reasons for deterioration:** * **Physicochemical:** * Moisture * Heat * Air * Light * **Biological:** * Fungi * Bacteria * Insects and rodents ### **Pharmacognostic Evaluation of Medicinal Plants** #### **Preparation of Crude Drugs:** - **Extracts** are preparations of crude drugs containing all the constituents soluble in the solvent used in making the extract. - **Tinctures** are prepared by extracting the crude drug with 5-10 parts of ethanol of varying concentration but without concentrating the final product. #### **Choice of Solvent:** The ideal solvent for a certain pharmacologically active constituent should: * Be highly selective for the compound to be extracted. * Not react with the extracted compound or with other compounds in the plant material. * Be inexpensive. * Be harmless to humans and the environment. * Be completely volatile. - **Ethyl alcohol is the solvent of choice for obtaining classic extracts such as tinctures.** - **Ethanol is usually mixed with water:** 1. To induce swelling of plant particles. 2. To increase the porosity of cell walls, facilitating the diffusion of extracted substances from inside the cells to the surrounding solvent. - **Ideal alcohol/water ratio:** * Barks, roots, woody parts, and seeds: 7:3 or 8:2. * Leaves or aerial green parts: 1:1 to avoid chlorophyll extraction. #### **Methods of Extraction:** - There are many procedures for obtaining extracts: 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 cells are living organisms requiring energy to survive. This energy is derived from various metabolic processes within the cell. Metabolism requires nutrients, which are taken up by the cell, and various enzymes, which act as catalysts. * Enzymes are produced within the cell itself, from cell organelles. * After the digestion process, waste products are removed from the cell by the cell membrane. | Category | Description | |------|-----| | **Living protoplasts** | These include cell structures like the nucleus, cytoplasm, vacuoles, plastids, and mitochondria. **Not diagnostically useful.** | | **Non-protoplasmic components** | These are classified as "ergastic" substances. They are important for identification. * Starch * Crystals * Alkaloids * Oils * Proteins * Tannins | #### **Volatile Oils** - These are odorous principles found in plants and evaporate when exposed to air at ordinary temperatures. - They pre-exist in plants in particular secretory parts: * Parenchyma cells * Glandular hairs * Vittae or oil tubes * Lysogenous or schizogenous passages * Epidermal tissues (e.g., lemon and orange) - The main component of volatile oils are derivatives of terpenes (C5H8). - They have high refractive indices and are generally optically active. - They are immiscible with water and freely soluble in organic solvents like alcohol, ether, chloroform, acetone, etc. - Most volatile oils are liquid, with a few exceptions: menthol, thymol, and anethol are solids at 15.5 °C. #### **Tannins:** - Complex organic, non-nitrogenous derivatives of polyhydroxy benzoic acids. - The word "tannin" is derived from "tan" due to its use in the process of converting hides and skins to leather by forming insoluble compounds with protein. - Present in aerial parts (e.g., leaves, fruits, barks, and stems) and occur in immature fruits but disappear during ripening. **Types of Tannins:** | Type | Description | |------|-----| | **True tannins** | These possess high molecular weight compounds; their solutions show a positive reaction with the Goldbeaters skin test. **Hydrolysable** | | **Pseudo tannins** | These are low molecular weight compounds; their solutions show a negative reaction with the Goldbeaters skin test. | **Chemical Test for 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 placed in a solution of tannins for 5 minutes. The skin is then washed with water and kept in a solution of FeSO4. A brown or black color indicates the presence of tannins. - **Vanillin test:** When vanillin hydrochloride is added to a drug solution, the formation of a pink or red color indicates the presence of tannins. - **Matchstick test:** A matchstick dipped in a drug solution, dried near a burner, then moistened with concentrated HCl, and warmed near the burner produces a pink or red color, indicating the presence of tannins. #### **Alkaloids:** - Alkali-like compounds that are basic in nature. - Derived from amino acids present in plant sources. - Contain one or more nitrogen atoms, which are often found in a heterocyclic ring. - Their presence is indicated by a marked physiological action on humans and other animals. #### **Deviation from Definition:** - Some alkaloids are not basic (Colchicine, Piperine). - The nitrogen in some alkaloids is not in a heterocyclic ring (Ephedrine). #### **Types of Alkaloids:** | Type | Description | |------|-----| | **True Alkaloids** | Nitrogen is part of a heterocyclic ring. **Derived from Amino acids** **Example:** Quinine, Colchicine | | **Proto Alkaloids** | Do not have heterocyclic rings with nitrogen. **Example:** Colchicine | | **Pseudo Alkaloids** | Nitrogen is part of a heterocyclic ring, but not derived from Amino acids. **Example:** Caffeine | #### **Occurrence and Distribution of Alkaloids:** **PLANTS:** - Rare in lower plants. - About 10% to 25% in higher plants. - Dicots are richer in alkaloids than Monocots. - **Families rich in alkaloids:** Apocynaceae, Loganiaceae, Liliaceae, Rubiaceae, Solanaceae, and Papaveraceae. - **Families free from alkaloids:** Rosaceae, Labiatae - **Ergot alkaloids:** Ergotamine and egrometrine are found in *Ergot fungus.* - **Muscopyridine:** Found in Musk deer. - **Lycopodine:** Found in *Lycopodium spores.* **Animals:** - Found in animals but are less common than in plants. #### **Distribution in Plants:** - **All Parts:** *Catharanthus* - **Barks:** *Cinchona* - **Seeds:** *Nux vomica* - **Roots:** *Aconite* - **Rhizomes:** *Rauwolfia* - **Flowering tops:** *Datura* - **Fruits:** *Black Pepper* - **Leaves:** *Tobacco* - **Latex:** *Opium* #### **Function of Alkaloids in Plants:** - **Protection:** They act as protective agents against insects and herbivores due to their bitterness and toxicity. - **Nitrogen Source:** In cases of nitrogen deficiency, they serve as a source of nitrogen. - **Growth Regulators:** They sometimes act as growth regulators in certain metabolic systems. - **Energy Source:** During carbon dioxide assimilation and in cases of deficiency, they can be utilized as a source of energy. #### **Qualitative Tests for Alkaloids:** - Dragendorff's reagent (potassium bismuth iodide): Results in an orange colored precipitate. - Mayer's reagent (potassium mercuric iodide): Results in a cream colored precipitate. - Wagner's reagent (iodine in potassium iodide): Results in a red-brown colored precipitate. - Hager's reagent (picric acid): Results in a yellow precipitate. The presence of alkaloid is determined by the formation of a precipitate upon reaction with a specific reagent.

Pharmacognosy Past Paper PDF 2025-2024

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