BP405T Unit 1 Notes – Introduction to Pharmacognosy
By Arvind Sharma, B.Pharm, M.Pharm, Assistant Professor, MUIT
PHARMACOGNOSY MASTERCLASS: FROM CRUDE DRUGS TO MODERN PHARMACEUTICALS
UNIT-I Introduction to Pharmacognosy: 10 Hours
1. Definition of Pharmacognosy
CORE DEFINITION:
Pharmacognosy is the specialized branch of pharmaceutical science dedicated to the systematic study of crude drugs—substances obtained directly from natural sources such as plants, animals, marine organisms, and microorganisms.
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:
- Taxonomic Identification and Authentication: Verification of the correct biological origin and identity of the source material.
- Sourcing and Sustainable Cultivation: Management of the scientific growth, harvesting, and procurement of medicinal raw materials.
- Post-Harvest Processing and Quality Control: Assessment of quality attributes, purity standards, and detection of potential adulteration.
- Phytochemical Isolation and Analysis: Elucidation of the structure and analysis of chemical constituents responsible for observed biological activity.
- Pharmacological and 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.
1.3 Significance in Modern Pharmacy
It underpins the continued global use of herbal medicines and is crucial for new drug discovery:
- 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 foundational medical texts.
| Text / Record | Year | Source/Origin |
|---|---|---|
| Chinese Herbal Texts | 2800 BC | China (Factual Correction) |
| 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
The 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 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 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, Nuxvomica, 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 (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 Flower. | 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...). Used widely in official compendia:
- Indian Pharmacopeia (IP 1955 - Latin; IP 1966 - English)
- British Pharmacopeia (BP), United States Pharmacopeia (USP), European Pharmacopeia.
Advantage:
- Simple, easy tracking, useful for books and references.
Disadvantage:
- No information on 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 Classification
- Organized Drugs (Leaves, Roots, Barks)
- Un-organized Drugs (Gums, Resins, Oils)
Advantage:
- Easy to classify and useful in identifying adulterants based on physical form.
Disadvantage:
- Does not reflect chemical constituents or therapeutic use. Organized and un-organized drugs are mixed.
3. TAXONOMICAL CLASSIFICATION
Based on botanical relationships (Kingdom, Phylum, Class, Order, Family, Genus, Species).
Example: Atropa Belladonna is classified under Family Solanaceae, Order Tubiflorae.
Advantage:
- Provides information about the scientific nature of drugs.
Disadvantage:
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 |
Advantage:
- Very easy for the study of chemical constituents and linking them to medicinal use.
Disadvantage:
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) | Vasaka, Liquorice |
Advantage:
- Drugs whose chemical constituents are unknown can still be classified. Useful for suggesting substitutes.
Disadvantage:
- Does not provide information about morphology, source, or taxonomical status.
6. CHEMOTAXONOMIC AND SEROTAXONOMICAL CLASSIFICATION
Chemotaxonomic:
Applies chemistry to systematics, classifying drugs based on chemical similarity within taxonomic groups. (E.g., Tropane alkaloids characterize the Solanaceae family.)
Serotaxonomical:
Based on serology—the study of antigenic materials and antibodies, used to establish relationships between organisms.
Quality control of Drugs of Natural Origin:
ADULTERATION OF DRUGS
Adulteration is the admixing or substitution of original drugs with inferior, defective, or useless substances, leading to loss of quality (deterioration, admixture, sophistication, substitution, inferiority, spoilage).
Types of Adulteration:
- Substitution with Substandard Varieties: Use of morphologically similar but chemically weaker varieties.
- Sophistication: Intentional, fraudulent adulteration (e.g., Crocus sativus adulterated with Carthamus tinctorius).
- Substitution with Exhausted Drugs: Mixing drug material from which active constituents have already been extracted (common in volatile oil drugs like Clove).
- Admixture: Addition of vegetative matter from the same plant or harmful foreign matter.
DRUG EVALUATION METHODS
Drug evaluation confirms identity, determines purity and quality, and detects adulteration.
| Method | Description & Focus | Examples |
|---|---|---|
| 1. Organoleptic | Evaluation through gross morphology and sensory profile (colour, odour, taste, touch). | Shape of leaves (Oval, Ovate), Bark (Quill, Flat), Odour (Aromatic, Pungent). |
| 2. Microscopic | Anatomical/Histological evaluation of organized drugs (powdered form) using T.S. and cell characters. | Stomata types (Diacytic, Paracytic), Trichome structure (Glandular, Covering), Calcium oxalate crystals. |
| 3. Chemical | Qualitative and quantitative determination of active principles using chemical reactions. | Dragendroff's test (Alkaloids), Killer Killiani test (Cardiac Glycosides), Molish test (Carbohydrates). |
| 4. Biological (Bioassay) | Determining potency based on the extent of pharmacological activity using living organisms or tissues. | Hot plate method (Analgesic activity), Carageenan induced edema (Anti-inflammatory). |
| 5. Physical | Determination of physical constants using physicochemical techniques. | Ash value, Moisture content, Specific gravity, Optical rotation, Extractive values. |
Physical Constants Examples:
- Moisture Content: Important for stability (e.g., Digitalis limit: Not more than 5%).
- Ash Content: Measures total inorganic residue.
Physiological Ash (from plant tissue) + Non-physiological Ash (sand, soil) = Total Ash.
- Fluorescence Analysis: Observing colour under UV light (e.g., Cinchona shows Purple Blue fluorescence).
QUANTITATIVE MICROSCOPY
A precision technique used to calculate the percentage purity of crude drugs, especially in powdered form.
Lycopodium Spore Method:
Used for drugs that contain measurable, definite particles (like starch grains or fiber fragments).
Principle: Lycopodium spores (2,86,000 spores/mg) are added as a standard reference to the powdered drug. The ratio of characteristic structures (N) to Lycopodium spores (S) allows calculation of purity.
Leaf Constants:
Used for standardization of powdered leaves as these parameters are relatively constant for a species.
- Stomatal Index: Percentage proportion of the number of stomata to the total number of epidermal cells (relatively constant).
- Palisade Ratio: Number of palisade cells under each epidermal cell.
- Vein Islet Number: Number of vein islets per square mm of leaf surface.
Camera Lucida:
An optical device used to trace or draw microscopic objects with high accuracy by superimposing the image onto tracing paper. Essential for precise microscopic measurements and documentation.
Mechanism: Uses a prism and a mirror (Swift Ives or Abbe model) to reflect light from the drawing paper into the observer's eye, allowing the pencil and the microscopic image to be seen simultaneously.