Pharmacognosy PDF

# Pharmacognosy ## Definition - The word "Pharmacognosy" denotes from the Greek word: - "Pharmakon" - medicine - "Gnosis" - knowledge - Pharmacognosy is the study of drugs derived from natural sources. - Plant - Animal - Microbial - Pharmacognosy is the study of the physical, c...

# Pharmacognosy ## Definition - The word "Pharmacognosy" denotes from the Greek word: - "Pharmakon" - medicine - "Gnosis" - knowledge - Pharmacognosy is the study of drugs derived from natural sources. - Plant - Animal - Microbial - Pharmacognosy is the study of the physical, chemical, biochemical and biological properties of drugs, their sources of natural origin as well as the search for new drugs from plant and animal. ## Importance and scope of Pharmacognosy - Pharmacognosy deals with the study of crude drugs. - Pharmacognosy - a service to biomedical industry. Pharmacognosy is an art and a science that helps to understand every step into the market. - Pharmacognosy is closely related to: - Botany - Ethnobotany - Tissue culture - Marine biology - Chemistry (Phytochemistry) - Pharmacology ## Crude drugs - The term "crude drug" generally applies to the productions from plants, animals and marine organisms that are used in medicine - They are not refined after removal from the plant, animal or any other living being. - The most important natural sources are "Drugs, and Higher, and lower, and natural and marine organic substances, and fungal products, microbial, fact, excreta that can be both organic and inorganic in nature - Examples: - **Plant:** - **Leaves:** Senna, Mint - **Flowers:** Saffron, Calendula - **Fruits:** Cinnamon, Cardamom, Clove, Aniseed, etc. - **Bark:** Quinine, Cinnamon - **Roots:** Ginger, Liquorice, etc. - **Animals:** - **Animal sources:** Musk, Cantharides, etc. ## Classification of Crude Drugs - Chemcogonosy is scientific study of crude drugs, it is very essential for standardizing a crude drug product. - Any method of classification should be: - **Simple**: (But very limited) - **Scientific**: (For identifying the source drug care - **Suitable**: (For practical purposes) ### Different types of Classifications: 1. **Alphabetical and chemical list**: - List classifications are made among the alphabetical order of their Latin and English synonyms namely. - **Example:** Asafoetida, Cardamom, Celera etc. - **Example:** Azadirachta indica, Belladonna, etc. - This method of classification is adopted by several bodies and institutions, like: 1. Indian Pharmacopoeia 2. British Pharmacopoeia 3. The United States Pharmacopeia (USP) 4. National Formulary (NF) 5. British Herbal Pharmacopoeia 6. European Pharmacopoeia **Merits**: - It is readily and quite quick for easy accessibility of references - There is no importance given to the chemical constituents present, even though they are important to the therapeutic activity of the crude drugs. **Demerits**: - It is good for listing only, it gives no idea, and what type of chemical constitutes are present and there is no idea to classify plant. - It is not very scientific, it is useless to understand molecular levels. 2. **Taxonomical classification**: - This system is purely botanical classification and is based on phytogenetical relations in plants. - Crude drugs are arranged in groups according to their division, class, family genus and species. - **Example:** - **Division:** Angiospermae - **Class:** Dicotyledoneae - **Order:** Rosales - **Family:** Rosaceae - **Genus:** *Rosa* - *Rosa canina* - **Genus:** *Rubus* - *R. fruticosus* - **Merits:** - Taxonomical classification is helpful for studying rudimentary drugs. - System provides easy identification. - This system bring out the close link that exists between the chemical constituents and biological activities of drugs. 3. **Morphological classification**: - The drugs are arranged in various groups according to the part used and their physical characteristics. - This system does not take into consideration the chemical nature of the drug. - **Example:** - **Organoleptic properties:** 1. **Leaves:** - **Simple:** - **Ex:** *Digitalis purpurea* - ***Ex:** *Aloe barbadensis mill* - **Compound:** - *Ex:* *Senna* 2. **Fruits:** - **Ex:** *Piper nigrum* - ***Ex:** *Foeniculum vulgare* 3. **Barks:** - **Ex:** *Cinchona* 4. **Roots:** - **Ex:** *Glycyrrhiza glabra* - **Whole Drug:** - **Ex:** *Herba* (Whole flowering tops) - **Ex:** *Sambuci flos* (Flowers) - **Ex:** *Radix* (Roots) - **Ex:** *Cortex* (Bark) - **Ex:** *Flos* (Flower) - **Ex:** *Fructus* (Fruit) - **Ex:** *Folium* (Leaf) - **Ex:** *Semen* (Seed) **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 more relevant and is most followed method. - So the drugs having similar action are kept together. - **Example:** Drugs like digitalis, squill and strophanthus having cardiotonic action are grouped together. - **Table: Classification of drugs based pharmacological action.** |Pharmacological Action |Items | |:------------------------------------|:-----------------------------------| | **Anti-allergic** | Ephedrine, Vasaka, Tussilaginis | | **Anti-amoebic** | Emetine, Paramylon | | **Anti-anginal** | Cardamom, Cinnamon, Mace | | **Anti-asthmatic** | Adhatoda, Ephedra | | **Antibacterial** | Neem, Basil, Aloe | | **Anti-cancer** | Taxol, Vincristine, Podophyllum | | **Anti-inflammatory** | Guggul, Shallaki, Turmeric | | **Anti-malarial** | Cinchona, Artemisia | | **Anti-oxidant** | Guggul, Amla | | **Anti-pyretic** | Rauwolfia, Cinnamon | | **Anti-septic** | Neem, Basil | | **Anti-spasmodic** | Belladonna, Ajwain | | **Cardiotonic** | Digitalis, Squill, Strophanthus | | **Diuretic** | Buchu, Juniper, Parsley | | **Expectorant** | Vasaka, Tussilaginis | | **Tranquilizer** | Rauwolfia, Valerian | **Merits**: - This system of classification can be used for supplying specific kinds of drugs if they are not available at a particular place or point of time. ** Demerits:** - Drugs having one group of action on the body get classified separately into more than one group, that becomes ambiguous and confusing. - Classification is more difficult because of reasons like - similar drugs affecting different parts of the body - many similar groups of drugs affecting human because of non-enzymatic nature of oxidation. 5. **Phytochemical, Morphological, and Chemotaxonomic classification**: - In the system of Phytochemical classification drugs are classified into different groups according to the chemical components of their most important constituents. - Some use the presence in nature and the distribution of these constituents in plants. - The arranging and identification of drugs is dependant upon the groups of drugs with dissimilar chemotaxonomic characteristics. 1. **Carbohydrate** - **Example:** *Aloe barbadensis mill* 2. **Glycoside** - **Example:** *Digitalis purpurea* 3. **Fatty oils** - **Example:** *Linum usitatissimum* , *Ricinus communis* 4. **Alkaloids** - **Example:** *Solanum tuberosum* 5. **Tannins** - **Example:** *Terminalia chebula* 6. **Resins** - **Example:** *Commiphora mukul* 7. **Volatile Oils** - **Example:** *Eucalyptus globulus* **Merits:** - It is a popular approach for phytochemical studies. - This system is very useful to place the drug containing two different types of chemical constituents together. **Example:** *Cinchona* contains both *alkaloids* and *quinones* 6. **Chemotaxonomical classification:** - This system of classification relies on the chemical similarity of a taxon i.e., it is based on the evidence of relationship between constituents in various plants. - There are certain types of chemical constituents that characterize certain classes of plants. This gives birth to entirely new concepts of chemcogonosy that utilizes chemical facts/characters for understanding the taxonomic status, relations ships and the evolution of the plants. - For example, tropane alkaloids generally occur among the members of Solanaceae thereby, serving as a chemotaxonomic marker. ## Cultivation-Collection-Drying-Storage-Preparation ### of crude drugs ### 1. Cultivation - WILD Source - Cultivation **Disadvantages of wild grown may largely produce toxins.** - **Opus:** Only official pharmacopeia - **Biotechnology:** Can help - **Potential access** to forests, mountains areas. - **Difficult:** Difficult transport hard to area of processing - **Collector ignorance**: Advancement of other plants, collection of undeclared plants or storage of similar species during an incorrect season -> loss of precious plant activity - **Damage to natural environment**: Extinction of a spp. ### Advantages of Cultivated Herbs - **Only desired species are collected:** -> uniform quality. - **Collection, transport & access to processing facilities is improved:** - **Better control of soil quality, pests & plant diseases:** - **Supply: Constant & Regular (Controlled):** - **Herb collectors-trained** ### Factors affecting cultivation of drugs - **Climate:** (Important factor in cultivation of medicinal Plants. - **Altitude:** Is a very important climatic variable at the altitude of 1500-2500. - **Examples:** 1. **Tea** : 2500-3000 2. **Cinchona**: 2500-3000 3. **Coca**: 1800-3000 4. **Opium**: 1800-2000 5. **Cardamom**: 1500-3000 6. **Cinnamon**: 2000-2500 7. **Clove**: 1100-1300 8. **Nutmeg**: 1100-1300 9. **Pepper**: 1000-1800 10. **Coffee**: Up to 1400 11. **Balm**: 1500-2500 - **Temperature:** - Temperature, as well as, Stress also affect quality of medicinal plants. - Extreme temperatures can deteriorate, decrease caffeine content, and decrease the quality and can destroy herbs. - **Examples:** - COFFEE AND TEA: Require only cold temperatures - Nutmeg and cinnamon: require wet weather for cultivation. - Saffron: Need only cold weather. - **Rainfall:** - **Examples:** Sapogenic plants like "Cilla papaya" - Most of the plants require sufficient arrangements for irrigation. - Sufficient rainfall for favorable development. - **Soil and soil fertility:** - Soil is the most important and crucial. - Provides mechanical anchorage, it acts as it supports growth of all - Soil provides materials: Nutrients, air, water and essential plant food elements for plant growth. - **The quality of soil decides favorable growth of plants and presence of micro-organisms.** - **The maximum available for plant nutrients is between the pH range of 6.5 to 7.5.** - **Ground nut, sunflower seeds, cotton and rice grow better in acidic soils only.** - **The tobacco, cinnamon, tea, and pomegranate grow well in alkaline soil.** - **Fertilizers:** - Fertilizers are substances which are necessary for the development, growth, and development of plants. - Each crop plant has its own specific nutrient elements for development. - For the every plant, to perform need of air, sunlight, water and minerals. - **Primary essential macro-elements**: - Nitrogen, Phosphorus, Potassium - **Secondary nutrients**: - Calcium, Sulphur - **Micro-elements:** - Zinc, Iron, Manganese - **Trace elements:** Copper, manganese, boron, molybedenum and zinc. - **Carbon, oxygen, hydrogen and calcium are provided to plants from water and air.** ## Plant growth regulators (Plant hormones) - Plant growth regulators are the organic compounds. - Affect the morphological structure or physiological processes of plants in low concentrations. - **Naturally found** - **Synthetically made** **Both groups regulate different aspects of plant growth.** - **Cell division** - **Cell differentiation** - **Root and shoot growth** - **Senescence (Plant aging)** ### 5. Major classes of plant growth regulators (Plant hormones) 1. **Auxins:** - Promote the growth of coleoptiles, roots, - **Examples:** Indoleacetic acid, (IAA), - **Examples:** indole acetic acid (IAA), - **Examples:** indole butyric acid (IBA), - **Examples:** naphthaleneacetic acid (NAA) 2. **Gibberellins (GA):** - **Examples:** Promotes stem growth through a cell division. - Stems have been grown and the Epiphase stretching for the tampe Gibbons and fruit growth, - Commercial supplies for promoting vegetative growth, - flower initiation and seed production. 3. **Cytokinins:** - **Examples:** - **Promote** cell division and leafy growth, - Promote axillary and lateral bud growth - Promote fruit maturity - **Used in growth promoter in tissue culture techniques** - Slow the process of senescence by preventing the breakdown of chlorophyll. 4. **Ethylene:** - **Examples:** - Present in the form of volatile gas - Present in flowering fruits, flowers, leaves, tubers and seeds. 5. **Abscisic acid (ABA):** - **Examples:** - Present in different organs cut of fruits, stems, flowers and buds. ## Collections of botanical plants - Drugs may be collected from cultivated or wild plants. - It is because that the active principles, chemical constituents are affected by the growing condition, age, season, time, soil quality at which the plant is grow. - Proper time of collection is very important to ensure a crop of good quality. ### Factors affecting the collection. 1. **Time of the year:** - The best hour to collect any article, which is to be preserved, are number of hrs. after sunrise. - **Example:** **Fruits:** Fruits are best collected in the summer or the - **Example:** **Leaves:** Leaves in the winter. - **Seed:** best collected in the Fall. - **Continuous rains**: Is very much harmful and should be avoided at harvest time. - Drugs are best collected by hand to avoid any contamination. - The best season to collect leaves: summer. - Seeds, fruits, and roots should be collected when the plant is in a dry condition. - Drugs containing alkaloids are best collected during the month of Feb. to May. 2. **Time of the day:** - Some drugs, like **Digitalis**, contain different amounts of active constituents in different times of the day. Being higher in the afternoon. - **The value and amount of active constituents of many drugs depends on the stage of maturity and age.** - **Example:** **Fruits**: The **seeds** of fruits are mature and are fully **Example:** **Seeds**: The **flowers** of **Senna** are collected when the plant is in the flowering stage. 3. **Stage of maturity and age**: - **Example:** **Fruits:** The **leaves** of fruits are collected when it starts to open, The **summer leaves** are rich in **anthraquinones** - **Example:** **flowers**: The **roots** are collected at the end of the vegetative period, ie before the formation of flowers. ### Rules for collection - **The following general rules are based on assuming that the material is best collected when the organ is in question to remove in its optimal time of development.** 1. **Roots:** Roots are collected at the end of the vegetation period, i. e before they flower. 2. **Fruits:** Fruits are collected after they matured and washed free of adhering soil and sand. - **Bark:** Is collected in the spring. - **Leaves and herbs:** are collected at the flowering stage. - **Flowers:** Are usually gathered when fully developed - **Fronds and seeds:** are collected when they are ripe. ### Methods of collection - **The most common plants** must be completely collected by hand, - **Example:** These plants must be completely collected by hand. This is especially true in medicinal plant collection. - **Example:** These plants must be completely collected by hand. This is especially true in medicinal plant collection. - **With collection on a large scale**, it may be possible to use modern agricultural innovations. ## Drying of crude drugs - The most common method for preserving plant material drying. - Living plant material for a high water content leaves may contain up to 85% water, roots, and rhizomes up to 75%, and wood may contain 50% water." - The lower percentages, often no more than 5-15%; is found in seeds. **Reasons for drying** 1. **To help in their preservation**, by preventing reactions that may occur in presence of water 2. **To fix their constituents** 3. **To prevent the growth of** micro-organisms such as bacteria and fungi. 4. **To facilitate their grinding** 5. **To reduce their size and weight** 6. **To reduce their drying and spoilage by micro-organisms** and make it possible the enzymatic destruction.. ### Methods of drying 1. **Natural drying (Sun drying)** - This is accomplished by exposure to air, usually air, usually material at room temp. of 40 - 60 degrees Celcius 2. **Artificial drying** - This is a rapid method done at well-controlled temperature and to accomplished by - Use of electric heated ovens - Use of heated stones. - Use of hovers. 3. **Lyophilization (Freeze drying)** - Process material is frozen at - 18 degrees *C* water vapor from the frozen material passes directly to a cold surface - **Prevents**: - **Oxidation.** - **Degradation** - **Enzymatic degradation.** 4. **Chemical drying using desiccants:** - **Used for drying** - **Example:** **Example:** herbs, medicines, and powders only. *Lyophilization.* - **Example:** Examples: Dried fruits in this case end up dried and when exposed to air they absorbed the air and formed a complex activity drug. ## Storage of crude drugs - It is essential to store them in a dry condition in safely and closed container. - Storage represents the last stage of preparing crude drugs, drugs usually deteriorate along the time and storage. - Improper method of storing, *rising of crude drug* during storage can cause a pronounced deterioration **There are two principal reasons for deterioration:** **Physical factors:** - Moist - Heat - Light **Biological factors:** - Fungi - Bacteria - Insects & rodents. ## Pharmacognostic Evaluation Of Medicinal Plants ### Preparation of crude drugs - Extracts can be defined as the solvent used in making extract. - Substances which are soluble in the solvent, it extracts which contain all the solubilites are prepared by extracting of the crude drug with five to ten parts of solvent at varying concentration, without concentration of the final product. ### Choice of solvent - The solvent with the extracted compound or biologically active constituent should be ideally selective for a certain compound to be extracted 1. Not react with the extracted compound or with other compounds in the plant material, 2. Be volatile, 3. Be low in price and so as to the environment, 4. Have low toxicity, 5. Be completely volatile. - According to the plant mycotoxins, *ethyl alcohol* is the solvent of choice for obtaining different extracts such as *tannins*. - The extract is usually mixed with water: - To induce better blending of the plant material. - To increase the solubility in it. - To reduce the amount of heat with water which balances the differential of temperature from retort to the surrounding solvent. - For extraction of *flavonoids* water, ethanol and methanol are alcohol/water ratios (between 7:3 to 9:1). - For extraction of *phenolic* groups the boil toll is mostly preferred, in order to avoid chances of any injury. ### Methods of extraction - **There are many procedures for extracting matters**: 1. Infusion: - It’s the simplest method of extraction. 2. Decoction: - It’s a method employed for extracting matters. 3. Digestion: - It’s continued but slow. 4. Soxhlet extraction: 5. Liquid-liquid extraction: (Oil extract) - Specific extraction. ## Cell Constituent - All cells in a living organism are in constant energy output. The energy is arrived from various metabolic process in the cell. Metabolism requires very active chemical reaction, takes place over a wide range of temperature, and with very high energy, so the cells need to either diffuse or move the required cells into other organs for uptake. These cells require the very active molecules such as cell residue. **Living cells:** **Eg:** medicines, *plants, animals, cytoplasm, etc.* **Non-protoplasm in cell contents:** **Classified in various** **Examples** - Starch - Gums - Oils **Very well to be identified.** ## Viscosity Acid - They are colorless principles found in plants, *mucilage* when exposed to air at ordinary temperatures. - It is present in all parts (contain secretory parts) such as: - Seeds - Roots - Parenchyma cells. - It is made up of polysaccharides. - It is colorless, odorless and tasteless - It is *non-reducing* in nature. - The main component of *hemicelluloses* and *pentoses* - The main component are *not* lemon and orange - They are *not* visible with the naked eye - They are soluble in *water* and are generally in *degree* (2-4) % (d). - It have high refractive indices and *they* are optically active - They are effective solutions and are therefore valuable in *certain* medicines. - Mostly soluble in *aqueous* ethanol, methanol, glycerol, and *method* which are soluble in 15 *C*. ## Tannins - Tannins are complex, *non-nitrogenous* derivatives of *polyhydroxy* phenolic acids. - Tannins are *commonly found* in barks, *catechu,* *arula* bark, *galls,* *myrobalans,* *hibiscus,* *nutgalls*. - **The most common in herbs** - **Example:** *Cinchona* - **They** are known by giving particular *color* with iron salts - **Example:** **Black color** - The *tannins* are *soluble* in water, *alcohol,* and *solutions* of sodium salts. - **They** are generally *not* soluble in *ether*. - The use of tannin in *tanning of hides* - **They** are *used* as *anti-inflammatory* agents - **They** are sometimes *used* in the *treatment* of burns and *wounds*. ## Types of tannins - **True tannins** - High molecular weight compounds - **Example:** Gives a *precipitate* with gelatin - **Pseudo tannins** - Low molecular weight compounds. - No precipitate with gelatin - **Example:** **Example:** Gallic acid, *methyl gallate* ### Chemical test for tannins - **Ferric chloride test** - **Example:** **Example:** A small piece of *gallotannin* in a test tube - **Procedure:** A small piece of *gallotannin* in a test tube. - **Procedure:** A few drops of *ferric chloride solution* is added - *Dark blue black color* - **Example:** **Example:** The *color* is observed to change from *light blue* to *dark blue* - **Gelatin test** - **Example:** **Example:** The *solution* is mixed together in a tube, **Procedure:** **Example:** **Example:** A little *gallotannin* solution is added to a tube. - **Procedure:** A 1% *gelatin solution* - **Procedure:** **Example:** **Example:** A *precipitate* is formed. *Yellow color* - **Lead acetate test** - **Example:** **Example:** Add a drop of *lead acetate solution* - **Example:** **Example:** A *white precipitate* is formed. - **Bromine water test:** - **Example:** **Example:** Add a drop of *gallotannin* solution - **Example:** **Example:** Add *bromine water* - **Example:** **Example:** A *white precipitate* is formed. *Yellow color* - **Vanillin test:** - **Example:** **Example:** Take a drop of *gallotannin* solution - **Procedure:** **Example:** Add a few drops of *vanillin in a test tube* - **Procedure:** Add a few drops of *concentrated HCl* in a test tube. - **Example:** **Example:** A **red color* is observed in the test tube, ## Alkaloids ## Defination - Alkaloids are basic in nature - Derived from amino acid present in plant sources - Contains one or more nitrogen atoms, formally in a *heterocyclic ring* - Marked physiological action on man or other animals. - **Examples:** **Examples** - **Atropine**: *Belladonna* - **Caffeine**: *Coffee* - **Morphine**: *Poppy* - **Quinine**: *Cinchona* - **Strychnine**: *Nux vomica* - **Nicotine**: *Tabacum* ### Deviation from Defination - **Basicity:** - Some alkaloids are not basic. - **Example:** **Example:** *Colchicine* - **Example:** *Piperine* - **Nitrogen:** - The nitrogen in some alkaloids is not in a heterocyclic ring. - **Example:** **Example:** *Ephedrine* - **Example:** Colchicine ### Types of alkaloids 1. **True alkaloids:** - Nitrogen is part of - **Example:** *Heterocyclic ring* - **Example:** *Piperine* 2. **Proto alkaloids:** - Does not have heterocyclic - **Example:** *Ring with nitrogen* 3. **Pseudo alkaloids:** - Nitrogen is part of - **Example:** *Heterocyclic ring* - **Example:** *Not derived from* - **Example:** *Amino acid* - **Example:** *Caffeine* **Example:** *Cinchona* - **Example:** *Quinine* - **Example:** *Cinchonidine* - **Example:** *Cinchonine* **Examples:** * **True alkaloids:** - **Example:** *Quinine* - **Example:** derived from *tryptophan* - **Example:** *Piperine* - **Example:** derived from *phenylalanine* * **Proto alkaloids:** - **Example:** *Caffeine* - **Example:** *derived from xanthine* ## Occurrence and Distribution **PLANTS** - **Rare in lower plants.** - **In higher plants**: About 20 to 25% - **Dicots are much rich in alkaloids than Monocots.** - **Plants are more rich in alkaloids** - **Example:** Apocynaceae, Leguminosae, Liliaceae, - **Example:** Rubiaceae, Solanaceae and Papaveraceae. - **Families**: These alkaloids contain *Aconitine*, *Lobeline*, * **Example:** *Ephedrine* and *Ergotamine* are present in *Ephedra* - **Example:** *Hyoscyamine* from *Hyoscyamus* - **Example:** *Lycopodium* from *Lycopodium* spores. **ANIMALS** - **Rare alkaloids** - **Examples:** *Ephedrine* and *ergotamine* from *Ephedra* fungi. ## Distribution in plants - **All parts**: - **Example:** *Catharanthus* - **Barks**: - **Example:** *Cinchona* - **Seeds**: - **Example:** *Nux vomica* - **Roots**: - **Example:** *Aconite* - **Rhizomes**: - **Example:** *Rauwolfia* - **Flowering tops**: - **Example:** *Datura* - **Fruits**: - **Example:** *Black pepper* - **Leaves**: - **Example:** *Tobacco* - **Latex**: - **Example:** *Opium* ## Function in plants - They may act as protective against insects and herbivores due to their bitterness and toxicity. - **Examples:** *Tobacco* - **Source of nitrogen** in case of nitrogen deficiency. - **They, sometimes, act as growth regulators** in certain metabolic systems. - **Examples:** *Nicotine*: - **They may be utilized as a source of energy in case** of deficiency in carbon dioxide assimilation. - **Example:** *Caffeine*: ### Qualitative test for alkaloids - Indicate the presence or absence of *Alkaloids* - **Dragendorff’s reagent** - **Example:** *Potassium Bismuth iodide* - **Mayer’s reagent** - **Example:** *Potassium mercuric iodide* - **Wagner's reagent** - **Example:** *Iodine in potassium iodide* - **Hager’s reagent** - **Example:** *Picric acid* **Color Changes:** - **Orange coloured ppt.** - **Cream coloured ppt.** - **Red brown coloured ppt.** - **Yellow ppt.**