UNIT-I Introduction to Pharmacognosy: 10 Hours
1. Definition of Pharmacognosy
1.1 ETYMOLOGY: Origin of the Term
The term Pharmacognosy is derived from two classical Greek words, signifying the "Knowledge of Drugs."
| Greek Word | Meaning |
|---|---|
| Pharmakon | “Drug” or “Remedy” |
| Gnosis | “Knowledge” |
1.2 The Comprehensive Scope of the Discipline (Core Activities)
This discipline encompasses the following core activities concerning natural medicinal substances:
| Aspect | Core Activity | Objective/Description |
|---|---|---|
| Identification | Taxonomic Identification & Authentication | Verification of the correct biological origin and identity of the source material. |
| Sourcing | Sourcing and Sustainable Cultivation | Management of the scientific growth, harvesting, and procurement of medicinal raw materials. |
| Processing | Post-Harvest Processing & Quality Control | Assessment of quality attributes, purity standards, and detection of potential adulteration. |
| Phytochemistry | Phytochemical Isolation & Analysis | Elucidation of the structure and analysis of chemical constituents responsible for observed biological activity. |
| Evaluation | Pharmacological & Therapeutic Evaluation | Determination of the medicinal, pharmacological, and clinical applications of the derived drugs. |
Key Objectives: Source Material, Morphological Study, Authentication, Quality Control, Phytochemistry, and Therapeutics.
Pharmacognosy underpins the continued global use of herbal medicines and is crucial for new drug discovery:
Sources of Drugs
| Area | Significance/Role |
|---|---|
| Pharmaceutical Cornerstone | Serves as the fundamental science for Herbal Drug Technology and the development of phytopharmaceuticals. |
| Natural Product Research | Essential for chemotaxonomy, natural product screening, and bioprospecting. |
| Regulatory Compliance | Indispensable for the standardization, stability testing, and ensuring the quality of botanical drug products. |
2. History of Pharmacognosy
The history reflects the transition from empirical traditional use to structured scientific investigation, leading to the isolation of pure active constituents.
2.1 Ancient Period (Before 1000 BC – 500 AD)
Foundational knowledge transmission through primary medical texts.
| Text / Record | Year | Source/Origin |
|---|---|---|
| Chinese Herbal Texts | 2800 BC | China |
| Ebers Papyrus | 1600 BC | Egypt (Documented over 700 drugs) |
| Charaka Samhita | 1000–600 BC | India (Ayurveda Foundation) |
2.2 Greek and Roman Period (500 BC – 500 AD)
Marked the beginning of scientific observation and organized documentation.
| Scientist | Contribution Highlight |
|---|---|
| Hippocrates (460–370 BC) | Father of Medicine (Rational approach) |
| Dioscorides (1st Century AD) | Authored De Materia Medica (Standard reference for ~1500 years; described ~600 plants) |
2.3 Origin of the Term “Pharmacognosy”
| Year | Scientist | Contribution |
|---|---|---|
| 1815 | C. A. Seydler | First used the term “Pharmacognosy” in his doctoral thesis (Analecta Pharmacognostica). |
2.4 19th Century – Birth of Scientific Pharmacognosy
A transformative period characterized by the isolation of pure active constituents.
| Year | Scientist(s) | Discovery |
|---|---|---|
| 1805 | Friedrich Sertürner | Isolation of Morphine from Opium |
| 1817 | Pelletier & Caventou | Isolation of Quinine from Cinchona |
| 1820 | Pelletier & Caventou | Isolation of Caffeine |
Flow Chart: Milestones in the Evolution of Pharmacognosy
3. Scope of Pharmacognosy
The scope of Pharmacognosy is vast, linking traditional practices to modern industrial and scientific requirements, including new drug discovery and standardization.
3.1 Conceptual Mnemonic for Scope (P.H.A.R.M.A.C.O.G.N.O.S.Y.)
| Letter | Area of Scope | Primary Function |
|---|---|---|
| P | Plant Identification & Authentication | Verification of the correct biological source and taxonomic identity. |
| H | Herbal Drug Industry | Development, formulation, and quality assurance of phytopharmaceuticals. |
| A | Adulteration Detection | Application of analytical methods for purity assurance and adulterant detection. |
| R | Research & Education | Bioprospecting and scientific screening for novel biological activities. |
| M | Marine & Animal Drugs | Scientific investigation of non-botanical natural sources (e.g., marine organisms). |
| A | Agriculture | Establishment of Good Agricultural Practices (GAP) for optimal sourcing. |
| C | Chemical Analysis (Phytochemistry) | Isolation, structure elucidation (Spectroscopic analysis), and quantification of active principles. |
| O | Official Standards | Establishment of monographs and quality control standards in Pharmacopoeias. |
| G | Gene Conservation & Tissue Culture | Genetic resource conservation and application of plant tissue culture technologies. |
| N | Natural Product Drug Discovery | Identification of novel structural scaffolds and lead compounds for synthetic modification. |
| S | Standardization of Herbal Medicines | Implementation of rigorous protocols to ensure batch-to-batch consistency and therapeutic reliability. |
| Y | Yield Improvement (Biotechnology) | Biotechnological approaches to enhance the yield and concentration of target metabolites. |
3.2 Overall Flow of Pharmacognosy Scope
4. Development of Pharmacognosy
The development of Pharmacognosy illustrates a systematic shift from simple observation to high-tech molecular analysis, categorizing its evolution into four distinct stages.
Stages of Pharmacognosy Development
| Stage | Time Period Focus | Main Focus | Key Output |
|---|---|---|---|
| 1. Descriptive Stage | Ancient to Pre-19th Century | Identification and description of crude drugs by external (organoleptic) features. | Herbal manuscripts and traditional documentation. |
| 2. Analytical Stage | 19th Century | Chemical analysis, isolation, and purification of active constituents. | Pure alkaloid and glycoside compounds (e.g., Morphine, Quinine). |
| 3. Pharmacological Stage | Early to Mid-20th Century | Biological evaluation and scientific validation of therapeutic claims. | Toxicity profiles and systematic dose-response data. |
| 4. Modern Stage | Late 20th Century – Present | Biotechnology, advanced standardization, and drug discovery using molecular techniques. | Phytopharmaceuticals and genetically engineered metabolites (DNA Fingerprinting). |
Flow Chart: Stages of Pharmacognosy Development
SOURCES OF DRUGS
| S. No. | Source Type | Drug Examples | Key Constituents/Products |
|---|---|---|---|
| 1. | PLANT (Oldest Source) | Digitalis purpurea, Nux Vomica, Clove, Acacia | Alkaloids (Opium, Cinchona), Glycosides (Digitalis, Senna), Volatile oils, Resins, Carbohydrates. |
| 2. | ANIMAL | Pancreas, Sheep thyroid, Cod liver, Cochineal | Hormones (Insulin, Thyroxin), Enzymes (Pancreatin, Pepsin), Vitamins (A & D), Carbohydrates (Honey). |
| 3. | MARINE (5,00,000+ species) | Marine Sponges, Cone Snails | Antimicrobial agents (Cephalosporins), Antiviral Agents (Vidarabine (Ara-A)), Anticancer agents (Sinularin, Crassin Acetate), Anticoagulants (Carrageenan). |
| 4. | PLANT TISSUE CULTURE | In-vitro produced Phytopharmaceuticals | Secondary Metabolites, Phytopharmaceuticals, products of Biochemical Conversions, Clonal Propagations. |
PLANT TISSUE CULTURE PROCESS
Application Example: Extraction process leading to Flaxseed Oil Cake Extract (FOCE).
ORGANIZED AND UNORGANIZED DRUGS
| Feature | Organized Drugs (Cellular Structure) | Unorganized Drugs (Non-Cellular) |
|---|---|---|
| Source | Direct parts of plants/animals. | Products of plants/animals/minerals, obtained by extraction, incision, or distillation. |
| Structure | Have proper cellular structures (e.g., leaves, roots, barks, seeds). | Do not have well-defined cellular structure (e.g., gum, resin, mucilage). |
| Identification | Identified by morphological characters and microscopic section studies (Transverse section). | Identified by organoleptic properties and physical parameters (density, viscosity, chemical tests). |
| Nature | Solid in nature. | Solid, semi-solid, or liquid in nature. |
| Examples | Digitalis Leaves, Cinchona Bark, Nux-Vomica Seed, Clove. | Dried Latex (Opium), Dried Juices, Gums (Acacia), Resins, Waxes, Volatile Oils. |
EXAMPLES OF UNORGANIZED DRUGS
Dried Latex
Milky sap that coagulates on exposure to air. Produced in laticiferous cells or vessels (e.g., Opium).
Gums and Mucilage
Similar constitution, yielding sugars and uronic acids upon hydrolysis. Gums are generally pathological products, while mucilage is formed by normal metabolism (e.g., Acacia gum).
Oleoresins
Naturally occurring mixtures of oil and resin, insoluble in water (e.g., Copaiba, Ginger). Often associated with gums, forming Oleo-gum-resins (e.g., Gum Myrrh, Asafoetida).
CLASSIFICATION OF DRUGS
1. ALPHABETICAL CLASSIFICATION
Drugs are arranged alphabetically based on their Latin or English names (e.g., Acacia, Agar, Amla, Ashoka...). This method is widely used in official compendia:
- Indian Pharmacopoeia (IP 1955 - Latin; IP 1966 - English)
- British Pharmacopoeia (BP), United States Pharmacopoeia (USP), European Pharmacopoeia.
Advantages:
- Simplicity and ease of retrieval for specific drugs.
- Useful for organizing books and reference materials.
Disadvantages:
- Lacks information regarding scientific nature, original source, or chemical class.
2. MORPHOLOGICAL CLASSIFICATION
Arrangement based on the morphological or external characters of the plant part used (e.g., leaf, bark, root, seed, exudates).
Morphological Categories:
- Organized Drugs (e.g., Leaves, Roots, Barks)
- Un-organized Drugs (e.g., Gums, Resins, Oils)
Advantages:
- Easy to classify and identify drugs based on their physical form.
- Helpful in detecting adulterants through macroscopic examination.
Disadvantages:
- Does not reflect chemical constituents or therapeutic use.
- Organized and unorganized drugs are often mixed within categories.
3. TAXONOMICAL CLASSIFICATION
Based on botanical relationships (Kingdom, Phylum, Class, Order, Family, Genus, Species).
Example: Atropa Belladonna is classified under Family Solanaceae, Order Tubiflorae.
Advantages:
- Provides comprehensive information about the scientific nature and biological origin of drugs.
Disadvantages:
- Inability to classify drugs of non-living origin (minerals) or unorganized drugs effectively.
4. CHEMICAL CLASSIFICATION
Arrangement based on the chemical nature of the active constituents (e.g., Alkaloids, Glycosides, Volatile Oils).
| Chemical Constituents | Drug Examples |
|---|---|
| Alkaloids | Vinca, Datura, Lobelia |
| Glycosides | Digitalis, Senna |
| Tannins | Catechu, Ashoka |
| Volatile Oils | Clove, Eucalyptus |
Advantages:
- Facilitates the study of chemical constituents and their correlation with medicinal use.
- Provides insights into structure-activity relationships.
Disadvantages:
- Difficulty in classifying drugs with multiple major constituents (e.g., those containing both volatile oil and resin).
- Drugs of diverse botanical origins may be grouped under the same chemical title, obscuring their natural relationships.
5. PHARMACOLOGICAL CLASSIFICATION
Arrangement based on the therapeutic effect or pharmacological action of the crude drugs.
| Pharmacological Action | Drug Examples |
|---|---|
| Anti-amoebic | Kurchi Bark, Ipecac |
| Anti-asthmatic | Ephedra, Vasaka |
| Carminative (Acting on GIT) | Fennel, Cardamom |
| Expectorant (Acting on Respiratory System) | Vasaka, Liquorice |
Advantages:
- Drugs whose chemical constituents are unknown can still be classified based on their observed effects.
- Useful for suggesting potential substitutes with similar therapeutic actions.
Disadvantages:
- Does not provide information about morphology, source, or taxonomical status.
- A single drug may exhibit multiple pharmacological actions, making classification challenging.
6. CHEMOTAXONOMIC AND SEROTAXONOMICAL CLASSIFICATION
Chemotaxonomic Classification:
Applies chemical data to systematics, classifying drugs based on chemical similarity within specific taxonomic groups. For example, Tropane alkaloids are characteristic of the Solanaceae family, aiding in the classification of drugs like Belladonna and Datura.
Serotaxonomical Classification:
Based on serology—the study of antigenic materials and antibodies—used to establish relationships between organisms. This method analyzes proteins and other macromolecules to infer taxonomic connections.
QUALITY CONTROL OF DRUGS OF NATURAL ORIGIN
ADULTERATION OF DRUGS
Adulteration is the admixing or substitution of authentic drugs with inferior, defective, or useless substances, leading to a loss of quality, efficacy, or purity. This can manifest as deterioration, accidental admixture, intentional sophistication, substitution, or spoilage.
Types of Adulteration:
| Type of Adulteration | Description | Example |
|---|---|---|
| Substitution with Substandard Varieties | Use of morphologically similar but chemically weaker or less potent varieties. | Using a less active species of Digitalis instead of Digitalis purpurea. |
| Sophistication | Intentional and fraudulent adulteration, often with cheaper, unrelated materials to increase bulk or mimic appearance. | Adulterating expensive Saffron (Crocus sativus) with less valuable Safflower (Carthamus tinctorius). |
| Substitution with Exhausted Drugs | Mixing drug material from which the active constituents have already been extracted. | Mixing exhausted Clove (after volatile oil extraction) with fresh Clove. |
| Admixture | Addition of vegetative matter from the same plant, other plant parts, or harmful foreign matter due to careless collection. | Presence of stems and other plant debris in a leafy crude drug. |
DRUG EVALUATION METHODS
Drug evaluation confirms identity, determines purity and quality, and detects adulteration through various methods.
| Method | Description & Focus | Examples |
|---|---|---|
| 1. Organoleptic Evaluation | Assessment through gross morphology and sensory profile (colour, odour, taste, touch, texture). | Shape of leaves (Oval, Ovate), Bark (Quill, Flat), Odour (Aromatic, Pungent, Spicy). |
| 2. Microscopic Evaluation | Anatomical and histological evaluation of organized drugs (especially in powdered form) using transverse sections and cell characters. | Identification of Stomata types (Diacytic, Paracytic), Trichome structure (Glandular, Covering), Calcium oxalate crystals. |
| 3. Chemical Evaluation | Qualitative and quantitative determination of active principles using specific chemical reactions and analytical techniques. | Dragendroff's test (for Alkaloids), Keller-Kiliani test (for Cardiac Glycosides), Molisch test (for Carbohydrates). |
| 4. Biological (Bioassay) Evaluation | Determining the potency and efficacy based on the extent of pharmacological activity using living organisms, isolated tissues, or cell lines. | Hot plate method (for Analgesic activity), Carrageenan-induced edema (for Anti-inflammatory activity). |
| 5. Physical Evaluation | Determination of physical constants and physicochemical properties using analytical techniques. | Ash value, Moisture content, Specific gravity, Optical rotation, Extractive values. |
Physical Constants Examples:
Moisture Content: Essential for drug stability and prevention of microbial growth, as excess moisture can lead to degradation. Example: Digitalis has a specified limit of not more than 5%.
Ash Content: Represents the total inorganic residue remaining after ignition. It includes both physiological ash (from plant tissue) and non-physiological ash (e.g., sand, soil, indicating contamination), providing an assessment of purity.
Fluorescence Analysis: Observes the characteristic color emitted by drugs under ultraviolet (UV) light, which can be useful for identification and detection of adulteration. Example: Cinchona bark exhibits a distinctive purple-blue fluorescence.
QUANTITATIVE MICROSCOPY
A precision technique used to calculate the percentage purity of crude drugs, especially in powdered form, by counting specific microscopic elements.
Lycopodium Spore Method:
This method is used for drugs that contain measurable, definite particles (like starch grains, fiber fragments, or specific cell types).
Principle: Lycopodium spores (standardized at 2,86,000 spores per milligram) are added as a reference standard to the powdered drug. The ratio of characteristic structures (N) of the drug to the number of Lycopodium spores (S) allows for the calculation of purity.
Leaf Constants:
These parameters are relatively constant for a particular plant species and are used for the standardization and identification of powdered leaves.
| Leaf Constant | Definition/Significance |
|---|---|
| Stomatal Index | The percentage proportion of the number of stomata to the total number of epidermal cells, crucial for distinguishing species. |
| Palisade Ratio | The average number of palisade cells located beneath each epidermal cell, consistent for a given leaf drug. |
| Vein Islet Number | The number of vein islets (small areas of photosynthetic tissue surrounded by veins) per square millimeter of leaf surface. |
Camera Lucida:
An optical device used to accurately trace or draw microscopic objects by superimposing the magnified image onto tracing paper. It is essential for precise microscopic measurements and detailed documentation of anatomical features.
Mechanism: Utilizes a prism and a mirror (such as Swift Ives or Abbe models) to reflect light from the drawing paper into the observer's eye. This mechanism allows the user to simultaneously view the microscopic image and the pencil on the tracing paper, enabling accurate drawing.
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