Study of Alkaloids

• Alkaloids are classified based on their amino acid precursors. Common precursors include:
  • Ornithine
  • Arginine
  • Lysine
  • Phenylalanine
  • Tyrosine
  • Tryptophan
  • Histidine

Ornithine-Derived Alkaloids

• Derived from L-ornithine, a non-protein amino acid from L-arginine.
• The nitrogen (N) atom incorporates into alkaloids forming a C4N structure.
• Types of ornithine-derived alkaloids:
  1. Pyrrolidine Alkaloids
  2. Tropane Alkaloids
  3. Pyrrolizidine Alkaloids

Pyrrolidine Alkaloids

• Example: Hygrine

  • Source: Leaves of Erythroxylum coca (Coca plant)
  • Chemical Formula: $(C8H{15}NO)$; Colorless liquid; b.p. $76.5^{}C$.
  • Uses: Sedative, hypnotic, laxative, diuretic.

• Cuscohygrine

  • Found in Erythroxylum coca and Erythroxylon truxillense.
  • Characteristics: oil which is soluble in water; melts at $40-41^{}C$.
  • Uses: Adjunct in peptic ulcer treatment, digestive disorders.

Tropane Alkaloids

• Formed by combining pyrrolidine and piperidine.
• Major Source: Solanaceae family; exceptions include cocaine from Erythroxylaceae.
• Important alkaloids:
  1. Atropine
  2. Cocaine
  3. Hyoscyamine
  4. Hyoscine (Scopolamine)

Atropine

• Source: Roots and leaves of Atropa belladonna and Datura stramonium.
• Properties: Long prisms; m.p. $118^{}C$; soluble in cold and boiling water.
• Uses: Pre-anesthetic, anticholinergic, mydriatic, antidote for opiate poisoning.

Hyoscyamine

• Source: Similar plant sources as atropine.
• Properties: Tetragonal needles; m.p. $108.5^{}C$.
• Uses: Anticholinergic and antispasmodic.

Cocaine

• Synonyms: Benzoylmethylecgonine
• Source: Leaves of Erythroxylum coca.
• Properties: Monoclinic tablets; m.p. $98^{}C$; volatile above $90^{}C$.
• Uses: Local anesthetic, narcotic, and highly habit-forming drug.

Pyrrolizidine Alkaloids

• Formed from two molecules of ornithine via putrescine.
• Found in families like Leguminosae and Asteraceae.
• Example: Senecionine (obtained from Senecio vulgaris), with uses in controlling pulmonary hemorrhage.

Tyrosine-Derived Alkaloids

• Precursor compounds: Phenylalanine, Tyrosine, Dihydroxy-phenylalanine.
• Examples include:
  • Ephedrine
  • Morphine
  • Colchicine

Ephedrine

• Source: Ephedra vulgaris
• Uses: Bronchodilator and treatment for asthma.

Morphine

• Source: Unripe capsules of Papaver somniferum.
• Uses: Potent narcotic analgesic; habit-forming.

Colchicine

• Source: Dried ripe seeds of Colchicum autumnale.
• Uses: Treats pain and inflammation in gout; causes chromosomal mutation.

Summary of Key Uses

• Alkaloids serve various medicinal purposes from anesthetics (cocaine) to sedatives (hyoscine) and spasmolytics (hyoscyamine).
• Many alkaloids are derived from plant sources; understanding their origin and properties is crucial for pharmaceutical applications.