Definition of Alkaloids
Alkaloids are nitrogen-containing natural compounds, primarily derived from amino acids, known for diverse pharmacological activities and often bitter taste.
Structural Features
Contain basic nitrogen atoms with complex ring and heterocyclic structures.
Classification
Based on biosynthetic origin or structure:
Pyridine/Piperidine: e.g., Nicotine
Indole: e.g., Vincristine
Quinoline/Quinolizidine: e.g., Quinine
Tropane: e.g., Cocaine, Atropine
Isoquinoline: e.g., Morphine, Reserpine
Purine: e.g., Caffeine
Biosynthesis
Derived from amino acids like ornithine, lysine, tyrosine, and tryptophan through complex enzymatic pathways.
Occurrence in Nature
Primarily in plants (e.g., Solanaceae, Papaveraceae, Rubiaceae), also in some fungi and animals.
Biological Activities and Uses
Pharmaceuticals: Medications such as analgesics (morphine), stimulants (caffeine), and anti-malarials (quinine).
Toxicity: Serve as defense compounds.
Psychoactive Effects: Affect the central nervous system (e.g., cocaine, LSD).
Examples
Caffeine: Stimulant in coffee, tea, cacao.
Atropine: Tropane alkaloid for nerve agent/pesticide poisoning.
Quinine: Anti-malarial from cinchona bark.
Reserpine: Isoquinoline alkaloid used to treat high blood pressure and psychotic disorders.