Topic 11 - The major groups of azotoids Flashcards by chiara konye

Azotoids

Compounds derived from nitrogen metabolism

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Types of azotoids

Universal azotoids
Simple specific azotoids
Cyanogenic compounds
Glucosinolates
Alkaloids

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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

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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

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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

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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

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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

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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

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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

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Plant families with characteristic alkaloids

o	Papaveraceae
o	Ranunculaceae
o	Fabaceae
o	Apocyanaceae
o	Asclepiadaceae
o	Solanaceae
o	Liliaceae 
o	Amaryllidaceae

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Alkaloids derived from amino acids

True alkaloids

Protoalkaloids

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Alkaloids not derived from amino acids

Pseudoalkaloids:

Nucleotide alkaloids
Terpenoid alkaloids

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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

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True alkaloids dervied from ornithine, lysine and nicotinic acid

Tropane alkaloids

Pyrrolizidine alkaloids (PA)

Quinolizidine alkaloids

Piperidine alkaloids

Pyridine alkaloids

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Tropane alkaloids

Natural occurrence: Solanaceae, Erythroxylaceae, Convolulceae

Major alkaloids are S and R hyoscyamine, scopolamine and cocaine

Ecgonine alkaloids (tropane derivates)

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Muscarinic cholinergic receptors

competitive antagonist of acetylcholine

Inhibition → anticholinergic effects

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Cocaine

Block ion channels in neurons → local analgesic, and strong (psycho)stimulant effect

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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

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Quinolizidine alkaloids

Natural occurrence: Fabaceae family (esp. lupines, cytisus, laburnum genera)

No accumulation in organs

Binding to nicotinic receptors as ACh agonists

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effects of quinolizidine alkaloids

Inhibits phenylalanine tRNA binding to ribosomes and interfere with aspects of translation

Tetratogenic, antibacterial, anti fungal activity

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Major quinolizidine alkaloids

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Sparteine
Cytisene
Lupinine
Lupanine
Anagyrin

Lysine derived Piperidine alkaloids

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Lobelia alkaloids

Piperine alkaloids

Lobelia alkaloids

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Respiratory and ganglionic stimulants → open nicotinic ACh receptors → nicotine-like, but weaker effect

Piperine alkaloids

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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

Topic 11 - The major groups of azotoids Flashcards

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