Jawaharlal Nehru Technological University Hyderabad B. Pharmacy II Year PHARMACOGNOSY AND PHYTOCHEMISTRY - I Previous Question Paper (November/December-2020 - R17)

Pharmacognosy is the study of physical, chemical, biochemical, and biological properties of drugs, drug substances, or potential drugs or drug substances of natural origin. The term is derived from the Greek words pharmakon (drug) and gnosis (knowledge).

The history of Pharmacognosy dates back to ancient civilizations. Early records include the Ebers Papyrus (1550 BC) in Egypt, which documented hundreds of medicinal plants. In India, the Ayurveda system, notably the Charaka Samhita and Sushruta Samhita, provided an extensive classification of herbal medicines. The Greeks, including Hippocrates (the Father of Medicine) and Dioscorides, whose work De Materia Medica remained the standard reference for centuries, significantly advanced the field. During the Middle Ages, the Arabian physicians refined drug preparation, and the Renaissance period saw the shift from crude drugs to the isolation of active principles, starting with Sertürner's isolation of morphine in 1806.

The scope of Pharmacognosy is vast and continues to evolve with modern science:

1. Drug Discovery: Identification of new lead compounds from plants, animals, and marine sources for the treatment of diseases like cancer, diabetes, and infectious conditions.
2. Standardization and Quality Control: Development of analytical methods (chromatography, spectroscopy) to ensure the purity, safety, and efficacy of herbal formulations.
3. Phytochemistry: Extraction, isolation, and structural elucidation of secondary metabolites such as alkaloids, glycosides, flavonoids, and terpenoids.
4. Cultivation and Conservation: Application of agricultural techniques, tissue culture, and biotechnology to improve the yield of active constituents and conserve endangered medicinal species.
5. Pharmacological Evaluation: Validation of traditional claims through modern bioassays to establish the mechanism of action of natural products.
6. Industrial Application: Providing raw materials for the pharmaceutical, cosmetic, and nutraceutical industries, bridging the gap between traditional medicine and modern pharmacology.

Evaluation of crude drugs is the process of confirming their identity, purity, and quality. Organoleptic and chemical evaluations are fundamental methods used to ensure the therapeutic efficacy of herbal substances.

Organoleptic Evaluation

This method involves the use of sensory organs to evaluate the physical characteristics of a drug. It provides a quick, preliminary assessment of quality:

• Visual Examination: Assessment of size, shape, color, surface characteristics, fracture, and appearance. For example, the presence of specific colors in bark or the characteristic shape of roots helps in identification.
• Odor: The characteristic smell of the drug, which may be aromatic, pungent, or odorless, often indicating the presence of volatile oils.
• Taste: The sensation produced on the tongue, such as bitter (alkaloids), sweet (glycyrrhizin), or astringent (tannins), which serves as a diagnostic feature.
• Touch/Texture: Assessment of the surface texture (smooth, rough, hairy) and consistency (hard, brittle, fibrous) to determine the nature of the drug material.

Chemical Evaluation

Chemical evaluation involves qualitative and quantitative analysis to determine the chemical constituents present in the drug, which are responsible for its pharmacological activity:

• Qualitative Chemical Tests: These tests are performed to identify the class of phytoconstituents present, such as alkaloids (Dragendorff’s test), glycosides (Borntrager’s test), or tannins (Ferric chloride test).
• Quantitative Chemical Analysis: This involves determining the concentration of active constituents. Methods include:
  • Assay: Determining the exact percentage of active principles using titration or gravimetric methods.
  • Extractive Values: Measuring the amount of active constituents extracted by specific solvents (e.g., alcohol-soluble or water-soluble extractive values).
  • Chromatographic Methods: Techniques like TLC, HPTLC, and HPLC are used to separate and quantify specific chemical markers or active compounds.
  • Chemical Constants: Determination of values like acid value, saponification value, iodine value, and ester value, particularly for fixed oils and fats, to assess purity and detect adulteration.

While organoleptic evaluation provides a rapid macroscopic check, chemical evaluation is essential for standardization and ensuring the drug meets pharmacopoeial requirements for potency and safety.