Introduction to Pharmacognosy
The foundational unit of Pharmacognosy. It covers the rich history of plant-based medicine, the systematic classification of natural drugs, and the critical processes of quality control. Understanding how to detect adulterants and evaluate raw botanical materials using quantitative microscopy is crucial for maintaining the safety and efficacy of herbal medicines.
Syllabus & Topics
- 1Definition of Pharmacognosy: Coined by C.A. Seydler (1815) from ‘pharmakon’ (drug) and ‘gignosco’ (to acquire knowledge). The objective study of crude drugs of natural origin.
- 2History and Development: Papyrus Ebers (1500 BC), Hippocrates (Father of Medicine), Dioscorides (De Materia Medica), Galen (Galenicals), and the modern extraction of active constituents like Morphine by Serturner (1806).
- 3Scope of Pharmacognosy: Link between botany and pharmacology. Crucial for discovering new drugs, cultivating medicinal plants, identifying adulterants, and developing standardized herbal formulations.
- 4Sources of Drugs: Plants (Senna, Digitalis), Animals (Beeswax, Shark liver oil), Marine (Sponges, Corals yielding antivirals), Minerals (Kaolin, Bentonite), and Plant Tissue Culture.
- 5Organized vs Unorganized Drugs: Organized drugs have distinct cellular structures (leaves, roots, bark – e.g., Senna leaf). Unorganized drugs lack cellular structure and are derived by extraction/incision (dried juices, latex, resins, gums – e.g., Opium, Acacia).
- 6Classification of Crude Drugs – Alphabetical & Morphological: Alphabetical (Dictionaries/Pharmacopoeias). Morphological groups drugs by plant part (Leaves, Roots, Seeds).
- 7Classification of Crude Drugs – Taxonomical & Chemical: Taxonomical categorizes by botanical family (e.g., Solanaceae, Umbelliferae). Chemical classification is based on active constituents (Alkaloids, Glycosides, Volatile oils).
- 8Classification of Crude Drugs – Pharmacological & Chemotaxonomical: Pharmacological groups drugs by therapeutic action (Laxatives, Cardiotonics). Chemotaxonomy links chemical constituents to botanical classification.
- 9Quality Control – Adulteration: The debasement of an article. Types: Substitution with inferior drugs, artificially manufactured substitutes, exhausted drugs, harmful adulterants, and vegetative matter.
- 10Organoleptic & Microscopic Evaluation: Organoleptic uses sensory organs (color, odor, taste, texture). Microscopic evaluation identifies cellular structures (trichomes, stomata, calcium oxalate crystals) under a microscope.
- 11Physical Evaluation: Determination of moisture content, specific gravity, optical rotation, refractive index, melting point, viscosity, and solubility.
- 12Chemical Evaluation: Using specific chemical tests to detect active principles (e.g., Keller-Kiliani test for cardiac glycosides, Dragendorff’s test for alkaloids). Includes instrumental methods (TLC, HPLC).
- 13Biological Evaluation: Assessing drug potency by its effect on living organisms (animals or microbes) when chemical evaluation is not possible (e.g., bioassay of Digitalis).
- 14Quantitative Microscopy – Leaf Constants: Stomatal number (stomata per sq mm), Stomatal index (percentage of stomata to total epidermal cells), Vein-islet number, and Veinlet termination number.
- 15Quantitative Microscopy – Lycopodium Spore Method: Used to calculate the percentage purity of powdered drugs containing distinct particles (like starch grains) by mixing with a known weight of uniform Lycopodium spores (94,000 spores/mg).
Learning Objectives
Frequently Asked Questions (FAQs)
Q1. What is the Difference Between Organized and Unorganized Crude Drugs?
Organized crude drugs possess a definite cellular structure and represent direct plant parts such as leaves, stems, roots, or flowers. Examples include Senna leaf and Cinchona bark. Unorganized crude drugs lack cellular structure and are obtained as plant exudates or extracts such as gums, resins, latex, or dried juices. Examples include Acacia gum and Opium.
Q2. What is the Lycopodium Spore Method?
The Lycopodium spore method is a quantitative microscopy technique used to determine the percentage of impurities in powdered crude drugs. It utilizes the constant number of spores in Lycopodium powder, where 1 mg contains exactly 94,000 spores. By counting Lycopodium spores alongside characteristic drug particles under a microscope, the proportion of genuine drug to adulterant can be accurately calculated.
Q3. What are Leaf Constants in Pharmacognosy?
Leaf constants are specific microscopic parameters of a leaf that remain relatively constant regardless of environmental conditions. These include stomatal index, stomatal number, vein-islet number, and vein termination number. They serve as reliable identification tools for leaf drugs and help detect adulteration.
Q4. What is Chemotaxonomical Classification?
Chemotaxonomy is the classification of plants based on their characteristic chemical constituents, particularly secondary metabolites. It is based on the assumption that plants belonging to the same botanical family share similar chemical compounds. For example, tropane alkaloids are characteristic of the Solanaceae family.
Q5. How is Biological Evaluation Different from Chemical Evaluation?
Chemical evaluation determines the quantity of a specific chemical constituent using reagents and analytical instruments. Biological evaluation (bioassay) measures the pharmacological effect or toxicity of a drug on living tissues, animals, or microorganisms. It is particularly useful when the active constituent is unstable, cannot be isolated, or when therapeutic activity results from a combination of synergistic compounds.