Topic 11 - The major groups of azotoids Flashcards
Azotoids
Compounds derived from nitrogen metabolism
Types of azotoids
Universal azotoids Simple specific azotoids Cyanogenic compounds Glucosinolates Alkaloids
Universal azotoids
Universal proteinogenic amino acids and metabolic intermediates (e.g. ornithine)
Universal amino acid derivatives - chlorophyll, auxins
Proteins (polypeptides and glycoproteins →lectins)
Universal purine and pyrimidine nucleotides (ATP, GTP, CTP, UTP, TTP) and derivatives (NAD, FAD, CoA)
Nucleic acids
Lectins
Specific glycoproteins (protein + oligosaccharide chain)
Bounds with the cell membrane
Ricine and abri toxalbumin - a disulfide bond connects two polypeptide chains
Fazin in bean species
Viscumine in misteltoe
Non-proteinogenic amino acids
About 200-400 biogenic amino acids
Never found in the protein structure, but perform several biological functions
Derived from universal amino acids with N, S and C, or stereoisomer molecules
Natural occurrence mainly in Fabaceae family
e.g. Lathyrogenes ro canavanine
Biogenic amines and amides
Simple specific azotoids
Nitrogenous compounds derived from amino acid by decarboxylation
With various biological effects
Tryptamine, phenethylamine – psychoactive and simulant effect, increased heart functions
Histamine – local immune and inflammatory response (e.g. nettle)
Alliin – in the garlic
Cyanogenic compounds
Biosynthesised from aliphatic or aromatic amino acids
In glycosidic form
Widely distributed in the plant kingdom, as a defense mechanism against herbivores and pests
Upon plant injury, specific enzymes remove the sugar parts aglycones are activated and HCN is often produced spontaneously poisoning
E.g. amygdalin, lotaustralin, linamarin, dhurrin, taxiphyllin, prunasin
Glucosinolates
Biosynthesised from amino acids glucose bounds with S-glycosidic bond (thioglycoside) and with another sulphate group
Natrual occurrence only in a few families, mainly Brassicaceae
Hydrolysis results isothiocyanates (mustard oil) goitrogen effect
E.g. sinigrin, sinalbin
Alkaloids
Specific, mainly alkaline plant metabolites with a nitrogen content
Products of the nitrogen metabolism
Approximately 21 000 different alkaloids described from 4000 plant taxons
Stored in vacuoles
Even a small dose can lead strong biological effects
Plants are able to decompose the stored alkaloids and re-use them again
Plant families with characteristic alkaloids
o Papaveraceae o Ranunculaceae o Fabaceae o Apocyanaceae o Asclepiadaceae o Solanaceae o Liliaceae o Amaryllidaceae
Alkaloids derived from amino acids
True alkaloids
Protoalkaloids
Alkaloids not derived from amino acids
Pseudoalkaloids:
- Nucleotide alkaloids
- Terpenoid alkaloids
Major effects of alkaloids
Stimulate the CNS – caffeine
Paralyze the CNS – scopolamine
Stimulate the PNS – efedrin
Paralyze the PNS – hyoscamine
Vasoconstrictor effect – ergot alkaloids
Vasodilator effect – theophylline
Increase blood pressure – vincamine
True alkaloids dervied from ornithine, lysine and nicotinic acid
Tropane alkaloids
Pyrrolizidine alkaloids (PA)
Quinolizidine alkaloids
Piperidine alkaloids
Pyridine alkaloids
Tropane alkaloids
Natural occurrence: Solanaceae, Erythroxylaceae, Convolulceae
Major alkaloids are S and R hyoscyamine, scopolamine and cocaine
Ecgonine alkaloids (tropane derivates)
Muscarinic cholinergic receptors
competitive antagonist of acetylcholine
Inhibition → anticholinergic effects
Cocaine
Block ion channels in neurons → local analgesic, and strong (psycho)stimulant effect
Pyrrolizidine alkaoids
Natural occurrence: Heliotropium spp., Cyneglossum spp., symphytum spp., Senecio spp., Eupaotrium spp.
At least 560 types described → most important: jacobins and senecionine
Hepatotoxic effect → secondary photosensitisation
Accumulation in organs
Quinolizidine alkaloids
Natural occurrence: Fabaceae family (esp. lupines, cytisus, laburnum genera)
No accumulation in organs
Binding to nicotinic receptors as ACh agonists
effects of quinolizidine alkaloids
Inhibits phenylalanine tRNA binding to ribosomes and interfere with aspects of translation
Tetratogenic, antibacterial, anti fungal activity
Major quinolizidine alkaloids
Sparteine Cytisene Lupinine Lupanine Anagyrin
Lysine derived Piperidine alkaloids
Lobelia alkaloids
Piperine alkaloids
Lobelia alkaloids
Respiratory and ganglionic stimulants → open nicotinic ACh receptors → nicotine-like, but weaker effect
Piperine alkaloids
An amide of piperidine: responsible of pungency of black pepper depressant and anticonvulsant effect
Non-lysine derived piperidine alkaloids
Piperidine alkaloids → pseudoalkaloids
Piperidine alkaloids
Lysine derived
Non-lysine derived
Conium alkaloids
Conium alkaloids
Absorbed through the skin, mucous membranes and it can cross the placenta
In the peripheral nervous system coniine block the nicotine receptors on the post-synaptic membrane of neuromuscular junctions → blocking movements
Pyridine alkaloids
Synthesised from nicotinic acid → the heterocyclic ringed, nitrogen containing nucleus is unsaturated
Widely distributed in nature, provide aroma of food stuffs
Use and effects of pyridine alkaloids
Natural insecticides → Synthesis increase after insect attack
Respiratory stimulant, but larger dose causes respiratory depression
Nicotine acts as an agonist at nicotinic acetylcholine receptors
Major pyridine alkaloids
Nicotine, anabasine, arecholine
True alkaloids derived from phenylalanine and tyrosine
Isoquinoline alkaoids
Benzylisoquinoline alkaloids
Phenylethylisoquinoline alkaloids
Isoquinoline alkaoids
Two six membered aromatic rings with nitrogen
Various effects:
- Antispasmodic
- Antibilious but also cytotoxic → anti-tumor drugs
Major isoquinoline alkaloids
Cheliodnine
Chelerythrine
Sanguinarine
Benzylisoquinoline alkaloids
Synthesised from two units of tyrosine
Important as medicine, but large dose can be highly toxic
Act on the opioid receptors: suppression of transmission of pain signals
Carcinogenic effects
Types of Benzylisoquinoline alkaloids
Papaverin: basic Benzylisoquinoline backbone
Morphinian derivates: opiates
Codeine and noscapine: antitussive effect (cough suppressive)
Morphine and thebaine: painkillers, sedative
Phenylethylisoquinoline alkaloids
Small group with only a few molecules
Treatment of gout
colchicine
binds with tubulin dimers → inhibition of microtubule formation → inhibition of cell division
True alkaloids derived from tryptophan
Quinoline alkaloids
Indole alkaloids
Quinoline alkaloids
Nitrogene in different position than isoquinoline alkaloids
With a monoterpenoid chain (C10)
The most important antimalarial drugs
Quinine (Cinchona officinalis)
Indole alkaloids
Simple indole derivates or isoprenoid alkaloids with a C9 or C10 monoterpenoid fragment
Molecules are similar to serotonin, dopamine and epinephrine → bind to receptors as agonists
Effect of indole alkaloids
Vasodilator effect → increased blood and oxygen supply to the brain
Cytotoxic activity → anticancer drug
Psilocybin → psychedelic compound
Vasoconstrictor, styptic and psychedelic effects
Protoalkaloids
N atom derived from an amino acid but it’s not of the heterocyclic
Types of protoalkaloids
Ephedrine: a bronchodilator with psychostimulant effect, act as adrenaline
Mescaline: strong hallucinogene effect
Cathinone: amphetamine-like effect, psychostimulant
Capsaicin: active component of chili peppers
Pseudoalkaloids
The classification based on the precursor molecule
The backbone not derived from the nitrogen pathway the nitrogen incorporated in a different way
Terpenoid alkaloids
Monoterpenoid alkaloids
Diterpenoid alkaloids
(Triterpene) Steroid alkaloids
Diterpenoid alkaloids
Various molecules due to the basic terpenoid structure
Nitrogen bounds with amination (an amine group introduction to the molecule)
Affects ion channels → CNS and cardiac effects
(Triterpene) Steroid alkaloids
Steroidal backbones are triterpene derivates, nitrogen bounds with amination
Many of them occur as glycosides
Open Na+ channels permanently – paralyzing effect
Alkaloids derived from nucleotids
Purine alkaloids
Pyrimidine alkaloids
Pyridine alkaloids
Purine alkaloids
Synthesised from purine nucleotids
Their role in plants is currently undetermined (chemical defense or allelopathic effect)
Stimulate the CNS
Pyrimidine alkaloids
Synthesized from purine nucleotides
Many of them occur as glycosides
During degradation, oxidizing agents (H2O2) produced
