ALKALOIDS Flashcards
very diverse group, only characteristic is presence of amine group or nitrogen containing group
alkaloids
Four major groups of N-containing organic compounds in biological systems
✓ amino acids (peptides and proteins)
✓ nucleoside bases (DNA and RNA)
✓ porphyrins
✓ alkaloids
cyclic organic compounds containing nitrogen in a negative state of oxidation with limited distribution among living organisms commonly found in medicinal plants.
alkaloids
- first natural products to be purified, characterized and commercialized
- can be purified from crude extracts by acid-base extraction and recrystallization
alkaloids
(5) classification of alkaloids
- Biosynthetic pathway
- Types of amines
- Basicity
- Chemical skeleton
- Botanical source
Classification according to Biosynthetic pathway
______________- derived from amino acids and have N in a heterocyclic ring (e.g., atropine)
____________- derived from amino acids and do not have N in a heterocyclic ring (e.g., ephedrine)
_______________- not derived from amino acids but have N in a heterocyclic ring (e.g., caffeine)
______________- non alkaloids; give false positive reaction with alkaloidal reagents
true (typical) alkaloids
Protoalkaloids
Pseudo alkaloids
False alkaloids
Classification according to Type of Amines
- alkyl amines (2°, 3°, 4°)
- heterocyclic amines
Classification according to Basicity
weak bases
strong bases
amphoteric
✓ phenolic alkaloids
✓ alkaloids with carboxylic groups
neutral alkaloids
Classification according to Chemical skeleton
phenylalkylamines
pyridine/piperidine
phenanthrene
quinoline
tropane
indole
terpenoid
imidazole
steroidal
Just a note!
the powerful and immediate effects of alkaloids are thought to be due to the presence of the cationizable N-atom which gives it lipid- and water soluble characteristics, and enables it to cross membrane barriers more readily
General Properties of Alkaloids
- most are crystalline solids
- bitter and exert physiological action
- either insoluble or sparingly soluble in water
- optically active, levorotatory
- gives strong alkaline reaction
- can be precipitated
alkaloids are derived from the following:
1) aliphatic amino acids: lysine, glutamic acid, and ornithine
2) aromatic amino acids: phenylalanine, tyrosine, & tryptophan
3) others: secologanin: terpene-derived C10 unit
ornithine is derived from
glutamic acid
ornithine can be derived to what types
pyrrolidine, tropane, pyrrolizidine
lysine is modified following an analogous pathway to ornithine.
The alkaloids produced are the 6-membered
piperidine, homotropane and quinolizidine structures.
have the characteristic fused 6,6-bicyclic group and are derived from lysine.
Quinolizidine alkaloids
Biosynthesis of this group involves simply loss of the carboxylic acid carbon. Some important members of this group are the
hallucinogenic compound mescaline and the drug epinephrine.
alkaloids from phenylalanine/ tyrosine:
Simple phenylethylamines.
______________are important components of a number of culturally, historically and
commercially important plants, in particular coffee, cola (kolanut), tea and cacao (chocolate).
The active constituents are methyl xanthines, the best known of which are: caffeine, which
occurs in coffee (Coffea arabica); theophylline, which is found in tea (Camellia sinensis); and theobromine, which is found in cacao (Theobroma cacao).
Xanthine alkaloids
_________ from hemlock (Conium maculatum) was used by the ancient Greeks for state executions. Its most famous victim was Socrates.
Coniine
_______________-is an opiate produced by
Claviceps purpurea, a parasitic fungus that
grows on some grain crops. The unhygienic practices of medieval Europe caused outbreaks of convulsion which was called “St. Anthony’s Fire”.
Lysergic acid
_______________- is the principal alkaloid in Nicotiana tabacum. It is addictive and has been recently classified as a drug.
Nicotine
______________-was first purified in 1818 by Pelletier and Magendie from the seeds of Strychnos nux-vomica, a plant native to India. It is a deadly poison and was used for many centuries as a rodenticide and vermicide. It is so chemically and biologically stable that it has been found in bodies exhumed after several years (this makes it a bad choice for a poison!)
It was first synthesized in 1954.
Strychnine
_____________ was first purified by Pelletier and Caventou in 1820. It is the major alkaloid from the bark of the Cinchona tree. Christened the “Jesuit bark,” the bark was traditionally used by Peruvian indians for fever due to malaria. It was the principal antimalarial drug up to WW II, after which it was supplanted by chloroquin.
Quinine
_______________ is the chief alkaloid of the South American coca bush. It has anaesthetic properties but is very addictive.
Cocaine
