ALKA

• Alkaloids


  Physiologically active basic plant constituents, in which at least one N-atom forms a part of a cyclic system
• Alkaloids


  • Generally form precipitates with alkaloidal reagents
  • Contaminants (CHON - protein) can cause false positive results due to N
• Alkaloids


  • Bitter in taste
  • Most end in -ine
• Genus


  Atropine - atropa
• Species


  Cocaine - coca
• Common name


  Ergotamine - ergot
• Physiologic activity


  Emetine - emetic
• Discoverer


  Pelletrine - Pelleter
• Alkaloids


  • Colorless
  • Crystalline solids which are basic
  • Have a ring structure
  • Have definite melting points
  • Most are chiral molecules with nonsuperimposable mirror images
  • Free bases are soluble in organic solvents and insoluble in water, salts are soluble in water and partially soluble in organic solvents
  • Some are not basic and others are brightly colored or liquid
• Alkaloids that are liquid

  • Coniine
  • Arecoline
  • Nicotine
  • Spartein
• Spartein


  • Anti-arrhythmic
  • From Lupinus mutabilis (Lupin) and Cysticus coparious (Scotch broom)
• Classification of alkaloids


  • True alkaloids
  • Protoalkaloids
  • Pseudoalkaloids
• True alkaloids


  • Derive from amino acids and share a heterocyclic ring with nitrogen
  • Highly reactive substances with biological activity even in low doses
  • All have a bitter taste and appear as a white solid, except nicotine (brown liquid)
  • Form water-soluble salts
  • Most are well-defined crystalline substances which unite with acids to form salts
  • May occur in plants in the free state, as salts, or as N-oxides
  • Primary precursors are amino acids like L-ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-histidine
• True alkaloids


  • Cocaine
  • Quinine
  • Dopamine
  • Morphine
• Protoalkaloids


  • Compounds where the N atom derived from an amino acid is not part of the heterocyclic ring
  • Derived from L-tyrosine and L-tryptophan
  • Structurally simple alkaloids with a closed ring
• Protoalkaloids


  • Hordenine
  • Mescaline
  • Yohimbine
• Pseudoalkaloids


  • Compounds with basic carbon skeletons not derived from amino acids
  • Derived from precursors or post-cursors (derivatives in the degradation process) of amino acids
  • Can also be derived from non-amino acid precursors
• Pseudoalkaloids


  • Coniine
  • Capsaicin
  • Ephedrine
  • Solanidine
  • Caffeine
  • Theobromine
• Basis of chemical structure


  • Atypical (nonheterocyclic, N in aliphatic chain)
  • Typical (heterocyclic, N in ring system)
• Alkaloidal reagents


  • Mayer's (Mercuric Potassium Iodide) - cream ppt
  • Marmes' (Cadmium in Potassium Iodide) - yellow ppt
  • Dragendorff's (Potassium Bismuth Iodide) - orange ppt
  • Wagner's (Iodine in Potassium Iodide) - red-brown ppt
  • Valser's (Mercuric Iodide) - white ppt
  • Sonnenschein's (Phosphomolybdic acid)
  • Scheibler's (Phosphotungstic acid)
  • Gold salts
  • Picric acid (Hager's) - intense yellow ppt
  • Tannic acid - white ppt
• Alkaloids by parent compound


  • Pyridine-piperidine (Nicotine, Lobeline, Arecoline, Coniine)
  • Tropane (Atropine, Hyoscyamine, Scopolamine)
  • Quinoline (Quinine, Quinidine)
• Nicotine


  • Potent CNS stimulant, highly addictive (direct acting parasympathomimetic - N selective)
  • Varenicline and Bupropion are smoking deterrents
  • Nicoderm is for long-term use
• Lobeline


  CNS stimulant, less addictive than nicotine
• Arecoline


  • CNS stimulant, anthelminthic
  • Areca nut can cause esophageal cancer due to tannin content
• Coniine


  From Cicuta maculata (Water hemlock)
• Atropine


  • Antimuscarinic/cholinergic receptor antagonist
  • Clinical uses: management of symptomatic bradycardia, antidote for cholinergic poisoning
• Hyoscyamine


  Primary constituent of Belladonna, racemic form of atropine
• Scopolamine


  CNS acting antimuscarinic, used for motion sickness (Trans-scop or Transderm)
• Mandragorine


  Emetic, from roots of Mandragora (European mandrake) - very poisonous/potent
• Cocaine


  First ester local anesthetic agent, potent analgesic, used for terminal cancer pain (Brompton's Cocktail)
• Quinine


  • Antimalarial, can cause "cinchonism" (toxicity with temporary loss of hearing and tinnitus)
  • Quinidine can prolong QT interval and cause arrhythmia
• Artemisinin Combination Therapy (artemether-lumefantrine) is the drug of choice for malaria
• Other oral antimalarial options include atovaquone-proguanil, quinine, and mefloquine