Concise Notes on Alkaloids

Page 1

Introduction to Alkaloids

• Focus on pharmacognosy and plant chemistry.
• Offered by Our Lady of Fatima University College of Pharmacy, various campuses.

Page 2

Learning Outcomes
Students will be able to:

1. Trace biosynthetic pathways for alkaloids.
2. Classify and characterize alkaloids, listing their uses.
3. Identify sources of alkaloids, including Philippine medicinal plants.

Page 3

Readings

1. Trease and Evans Pharmacognosy, 16th ed.
2. Shah & Seth, Textbook of Pharmacognosy and Phytochemistry.

Page 4

Outline

1. Biosynthesis of Alkaloids
2. Classes of Alkaloids
   • Pyridine and piperidine
   • Tropane
   • Solanaceous
   • Quinoline
   • Isoquinoline
   • Indole

Page 5

Definition of Alkaloids

• Basic heterocyclic nitrogenous compounds from plants, physiologically active.

Page 6

Distribution and Occurrence

• Rare in lower plants; dicots richer in alkaloids compared to monocots.

Page 7-10

Families Rich in Alkaloids

• Apocynaceae (Dogbane Family)
• Rubiaceae (Coffee Family)
• Solanaceae (Nightshade Family)
• Papaveraceae (Poppy family)
• Rosaceae (Rose Family)
• Labiatae (Mint Family)

Page 13

Chemical Properties of Alkaloids

1. Nitrogen:
   • Primary amines, e.g. $R-NH_2$
   • Secondary amines, e.g. $R_2-NH$
   • Tertiary amines, e.g. $R_3-N$
2. Basicity: R2-NH > R-NH2 > R_3-N

Page 16

Solubility of Alkaloids

• Soluble in alcohol and organic solvents; usually insoluble in water.
• Salts are generally soluble in water.

Page 20

Major Alkaloid Classes and Precursors

• Examples:
  • Pyrrolidine: Ornithine (Nicotine)
  • Tropane: Ornithine (Atropine, Cocaine)
  • Indole: Tryptophan (Psilocybin, Reserpine)

Page 22-26

Classification of Alkaloids
Based on ring structure or nucleus:

• Pyridine
• Tropane
• Quinoline
• Isoquinoline
• Indole
• Purine
• Steroidal
• Alkaloidal amines (e.g. Mescaline)

Page 32

Areca Alkaloids

• Arecoline: Most abundant; liquid in nature.
• Used as an anthelmintic in veterinary practice with doses specific to animal type.

Page 35

Lobelia (Indian Tobacco)

• Contains Lobeline, an emetic agent.
• 2 mg of lobeline sulfate used in aiding tobacco cessation.

Page 39

Tropane Alkaloids

• Formed from pyrrolidine and acetate; include Hyoscyamine and Atropine.

Page 46-49

Atropine

• Used as an anticholinergic agent for various conditions.
• Toxicity can occur from overdose.

Page 50

Belladonna

• Contains up to 1% alkaloids; predominant ones include Hyoscyamine and Atropine.

Page 70-89

Coca and Cocaine

• Coca leaves contain ecgonine derivatives including cocaine.
• Used for its stimulant and anesthetic properties; abuse potential.

Page 91-99

Cinchona Alkaloids

• Includes Quinine and Quinidine from cinchona bark.
• Quinine primarily used for antimalarial effects.

Page 108-113

Quinine Uses

• Antimalarial action via interference with Plasmodium's DNA.
• Dosage varies based on condition being treated.