Chapter 3 Introduction to Pharmacognosy PDF

Introduction to Natural Medicines, Semi synthetic drugs -Pharmacognosy- CLO 3. Acquire basic knowledge about the components of Pharmacy curriculum PPRA0101 Orientation to Pharmacy Fall Semester 2024-25 Learning objectives After...

Introduction to Natural Medicines, Semi synthetic drugs -Pharmacognosy- CLO 3. Acquire basic knowledge about the components of Pharmacy curriculum PPRA0101 Orientation to Pharmacy Fall Semester 2024-25 Learning objectives After completion of this unit, students should be able to: Define Pharmacognosy Describe the origin of Pharmacognosy Explain the contribution of plants to medicine and drug discovery The term ‘PHARMACOGNOSY’ has been derived from the two Greek words; ○ pharmakon ‘a drug’ (Greek) ○ gignosco ‘ to acquire knowledge of’ (Greek) ○ OR cognosco ‘to know about’ (Latin) ○ Pharmacognosy means ‘knowledge of drugs’ or to acquire knowledge of drugs. ○ It is systematic study of physical, chemical, biochemical and biological properties of drugs or substances from natural origin. Introduction to Pharmacognosy Pharmacognosy is an applied science which deals with ○ Natural products and is described as ‘ the study of medicinal or therapeutic agents of natural origin i.e. plants, animals and mineral sources. ○ It also includes the study of their history, distribution, cultivation, collection, preparation, identification, evaluation, preservation and commerce. Origins and history of Pharmacognsoy Pharmacognosy is regarded as the mother of all sciences. Pharmacognosy had its origin in the health related activities of the most primitive human race of the past. The early man sought to alleviate his sufferings of illness and injuries by using plants. Discovery of the medicinal properties of plants and other natural products started in the very early days of man’s existence. Naturally occurring substances - Medicinal action: Surgical dressings prepared from natural fibers Flavorings and suspending agents Disintegrants Filtering and support media Other associated fields: Poisonous and hallucinogenic plants Raw materials for production of oral contraceptives Herbicides and insecticides Pharmacognosy is related to: ○ Botany ○ Ethnobotany ○ Marine biology ○ Microbiology ○ Herbal medicine ○ Chemistry (phytochemistry) ○ Pharmacology ○ Pharmaceutics Types of chemical constituents in plants These range from simple compounds eg. Sugars, amino acids to complex molecules eg. Steroids and vitamins Active constituents: the phytochemicals responsible for the biological activity eg. Tannins, alkaloids, glycosides. Inactive/inert constituents: these are present in the plants but do not produce any therapeutic activity eg. Lignin, cellulose etc. Formation of chemical constituents Simple compounds e.g. sugars, amino acids, fatty acids are produced as a result of the plant’s basic metabolism. These are referred to as PRIMARY PLANT METABOLITES These give rise to more complex products called SECONDARY PLANT METABOLITES through biochemical processes called BIOSYNTHESIS or BIOGENESIS. Most active plant constituents are Secondary plant metabolites. Classification ○ Alphabetical (English or Latin) ○ Taxonomic Based on similarities and difference (kingdom, division, class) ○ Morphological Organized drugs: leaves, flowers, fruit, seeds etc Unorganized drugs: extracts, gums, resins, oils etc ○ Pharmacological/therapeutic* Increasingly used with screening Constituents of one drug may fall into several groups ○ Chemical/biogenetic Contribution of plants to medicine and pharmacy 18th century drugs plant based 19th chemical structure of many of the isolated compound were determined 1805 Morphine 1817 Emetine 1819 Strychnine 1820 Quinine 20th century the discovery of important drugs from the animal kingdom particularly hormones and vitamins and microorganism Why plants are so important in medical field? 1. Source of drug molecules Most drugs can be synthesized Still more economical to use the plant Papaver opium -> morphine, codeine (strong medicinal property- pain) Ergot fungus –> Ergotamine (headache), Ergometrine (direct action on uterine muscle) 2. Source of complex molecules that can be modified to medicinal compounds Examples: Droscera yam: molecule -> steroids Soya: saponins -> steroids 3. Source of toxic molecules To study the way the body responds to their pharmacological use Investigating pharmacological mechanisms Picrotoxin – nerve conduction (poisonous crystalline plant compound)- A bitter poison (picros= bitter),CNS stimulant and convulsant  4. Source of novel structures these might never be thought of Catharanthus periwinkle -> vincristine (alkaloid dimer)  5. Source of plant drugs As a powder or extract The pure compound is often not isolated because: ○ Active ingredient is unknown ○ Active ingredient is unstable ○ Isolation process is too costly  Research Future: intense screening ○ Anticancer - NCI ○ Antimicrobial ○ Antiviral ○ Antimalarial ○ Insecticidal ○ Hypoglycaemic ○ Cardiotonic ○ Antiprotozoal ○ Antifertility - WHO Scope of Pharmacognosy The scope of pharmacognosy is quite broad and covers several areas of research and application, some of which are discussed below: Plant Identification and Classification Extraction and Isolation of Natural Products Characterization of Natural Products Synthesis of Natural Products Evaluation of Biological Activity Drug Discovery and Development Quality Control and Standardization Cultivation and Domestication of the Medicinal Plants Analysis of Phytochemicals Conclusion Natural products very important to medicine Exist in range of structures that one wouldn’t think of synthesizing Can act as templates for new drug development Untapped reservoir of new compounds