Introduction to Pharmacognosy

Introduction to pharmacognosy

• Pharmacognosy is the study of medicinal plants and their uses
• The course focuses on the biological origins of drugs, including plant and animal sources.
• Key learning outcomes:
  • Students will learn about the structure and function of plant cells and tissues.
  • Students will identify plant species by their uses and relate plant features to environmental conditions.
  • Students will learn how to identify the uses of plant families.
  • Students will be able to relate taxonomic data to the potential presence of natural products.
• This lecture focuses on the biological and geographical origins of crude drugs.

Biological Origin (Binomial System)

• Linnaeus developed the binomial system for naming plants and animals.
• The binomial system uses two names: genus and species.
• Genus:
  • The first part of the plant name.
  • Always begins with a capital letter.
  • Represents the plant's group name.
  • All plants with the same genus share similar characteristics and are closely related.
• Species:
  • The second part of the plant name.
  • Always begins with a lowercase letter.
  • An adjective that describes the genus.
  • Provides descriptive information about the plant.
  • Both names should be underlined or written in italics.
• Examples:
  • Mentha aquatica (water mint)
  • Mentha arvensis (field mint)
• Taxonomy is the branch of biology that deals with naming and classifying organisms.

Linnaeus vs. Today

• Linnaeus grouped plants based on reproductive characteristics.
• Today, plants are grouped based on phylogeny.
• Phylogeny is the evolutionary history of organisms, indicating how they are related.
• Genetics is used to determine the evolutionary relationships between plants.

Species Names

• The species name often indicates:
• Pharmacological activity:
  • Strychnos nux vomica (nut causing vomiting)
  • Papaver somniferum (hypnotic)
  • Brayera anthelmentica (expelling worms)
• Characteristic color:
  • Piper nigrum (black pepper)
  • Digitalis purpurea (purple)
  • Digitalis lanata (yellow)
  • Nymphaea alba (white)
  • Quercus rubra (red)
• Geographical source:
  • Cannabis indica (grown in India)
• General meaning:
• Atropa (poisonous)
• Morphological characters:
  • Glycyrrhiza glabra (liquorice, smooth)
  • Hyoscyamus muticus (short)
  • Begonia maculata (spotted)
• Plant characters:
  • Myristica fragrans (nutmeg, nice aroma)
  • Caryophyllus aromaticus (clove, aromatic)
• Exception: The species name may start with a capital letter if it is named after the person who discovered the plant or transported its seeds.

Hierarchy of Classification

• The hierarchical classification system starts broadly and gets more specific.
• 7 hierarchies:
  • Kingdom (broad)
  • Phylum (Division)
  • Class
  • Order
  • Family
  • Genus
  • Species (specific)
• Mnemonic: "King Philip Came Over For Great Spain".

Geographical Origin:

• Refers to the habitat of the drug.
• This is the area where the plant or animal source is cultivated, collected or lives.
• Phytogeography: The study of the geographic distribution of plant species.
• Types of plants:
  • Exotic: Non-native plant introduced to a new area.
    • Naturalized: Exotic plant reproducing naturally in the new environment.
    • Invasive: Exotic plant altering the natural ecosystem.
  • Indigenous (Native): Native to a specific locale.
• Habitat information:
  • Soil, altitude, and climate affect the active constituents of plants.
  • Cannabis sativa grown in India has a different chemical profile than Cannabis sativa grown in Italy.

Duration of Plant Cycle:

• The life cycle of plants varies significantly.
• Annual: Plant completes life cycle in one growing season (e.g., watermelon).
• Biennial: Plant needs two growing seasons to complete life cycle (e.g., parsley, carrots).
• Perennial: Plants live for more than two years (e.g., bananas, apples).
  • Herbaceous: Plants with non-woody shoot systems (e.g., lavender)
  • Woody: Plants have stiff woody structures above ground (e.g., trees, shrubs, vines)
• Monocarpic: Plants flower and produce seeds once, then die.

Secondary Metabolites:

• Secondary metabolites are compounds produced by plants that are not essential for basic metabolism.
• These compounds play various roles in plant defense, pollination, and antibiosis.
• Examples:
  • Volatile oils: Odors of plants (e.g., essential oils).
  • Alkaloids: Nitrogen-containing compounds with diverse physiological activities.
  • Glycosides: Sugar-containing compounds.
  • Polyphenols: Compounds with multiple hydroxyl groups on aromatic rings.
• Secondary metabolites are important for medicinal applications due to their various pharmacological activities.