Medicinal Herbs Overview

Medicinal Herbs

• A drug derived from the tender parts of plants, including leaves, flowers, and fruits.
• Types of medicinal herbs include:
  • Parts of aerial shoots (e.g., Cannabis).
  • Whole aerial parts (e.g., Lobelia).
  • Complete plants, including roots.
  • Undifferentiated plant bodies, such as Thallophyta (e.g., Ergot and fucus).

Herbs of Medicinal Importance

• Groups based on active constituents:
  • Herbs containing alkaloids (e.g., Vinca, Cannabis).
  • Herbs containing volatile oils (e.g., Mentha, Thyme).
  • Herbs containing resin (e.g., Ergot, Ephedra).

Key Examples of Medicinal Herbs

• Mentha

  • Family: Labiatae (Lamiaceae).
  • Aroma: Characteristic and aromatic.
  • Taste: Aromatic with a cold sensation.
  • Active constituents:
    • Volatile oil (Menthol, Menthone, Menthyl Acetate).
    • Tannins, flavonoids.

• Thyme

  • Family: Labiatae (Lamiaceae).
  • Aroma: Aromatic and pungent.
  • Active constituents:
    • Volatile oil (Thymol, Carvacrol).
    • Tannins, flavonoids, gums, resins.

Microscopical Characteristics

• Mentha Powder

  • Diacytic stomata.
  • Glandular hairs (Labiaceous and Capitate) and non-glandular hair (multicellular).

• Thyme Powder

  • Non-glandular bent hair.

Medicinal Uses

• Mentha

  • Gastrointestinal tract benefits: Carminative, digestive, anti-spasmodic, antimicrobial, anti-emetic, and promotes liver/gall bladder function.
  • Respiratory benefits: Decongestant.
  • External uses: Local anaesthetic, anti-pruritic, anti-parasitic.

• Thyme

  • Gastrointestinal tract benefits: Carminative, digestive, anti-spasmodic, antimicrobial, and anthelmintic.
  • Respiratory benefits: Used for whooping cough, as an expectorant, secretolytic, and disinfectant for inhalations.

Chemical Tests

• Mentha

  • Positive micro-chemical tests with Sudan III.
  • Special test results: Menthol crystals react with H2SO4 and produce color changes.

• Thyme

  • Special test results: Thymol crystals react with glacial acetic acid and other chemicals to yield notable colors.

Contraindications & Drug Interactions

• Mentha

  • Contraindications: Not advisable for GERD, infants, gallstones; can be poisonous in pure form; avoid on irritated skin.

• Thyme

  • Contraindications: High doses of thymol can lead to liver toxicity; concentrated forms are contraindicated in pregnancy.
  • Drug interactions: Can interfere with anticoagulants, increasing bleeding risk.