cyanogenic glycosides and cardiac glycosides Flashcards Preview

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Flashcards in cyanogenic glycosides and cardiac glycosides Deck (8)
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1

cyanoglycoside

A glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond

The sugar group is then called glycone and the non- sugar part is aglycone

2

cyanogylcoside biology

CGs are produced from amino acids

In plant tissues, CGs are stored in vacuola in inactive forms

• Upon plant injury, specific enzymes remove the sugar parts

• Aglycones are activated; HCN is often produced spontaneously

3

HCN poisoning

In animals, HCN can easily enter the tissues via mucous membranes (from respiratory system and gastrointestinal tract), or from skin surface

HCN inhibits cytochrome C oxidase enzyme (the last enzyme in the respiratory electron transport chain located in the mitochondrial membrane) inhibition of cellular respiration ---> no more ATP (energy) is produced --> death

4

HCN symptoms

- blood, mucous membranes (and skin) of cherry colour; clotting of blood is slow
- nausea, vomiting, breath with smell of bitter almond - heavy breathing
- muscle contraction, spasms
- stumbled walk, coma, death

5

Cardiac glycoside

In cardiac glycosides the aglycone is a steroid

• Both in animals and plants, steroid skeleton is biosynthesised from squalene (one of the most important triterpene)

• Aglycones in cardiac glycosides can be classified into three groups: cardenolides, bufadienolides, and steroidal sapogenins

6

Cardiac mechanism

• Na+/K+ pumps in cell membranes are inhibited increased Na+ levels within cardiac muscle (CM) cells

• Na+/Ca2+ exchangers (NCX, responsible for pumping Ca2+ out of the CM cell and Na+ in) got inhibited also due to the raised levels of intracellular Na+ --> raised Ca2+ levels in CM cells

• Increased cytoplasmic Ca2+ levels cause increased Ca2+ uptake into the sarcoplasmic reticulum (SR)

• Raised Ca2+ stores in the SR allow for a greater Ca2+ release on stimulation, so the (CM) cells can achieve faster and more powerful contractions (positive inotropic effect) decreased heart rate (negative chronotropic effect)

• Slow catabolism of cardiac glycosides

7

Cardiac symptoms

– nausea, vomiting, disorders of color vision, hallucinations

– decreased heart rate, cardiac arrhythmias, tremor, seizures, coma, death

• Low K+ level in blood higher affinity of the toxin to bind to the ATP-pump (due to phosohorylation)

8

Specific heart symptoms

• acute heart failure
• ST depression
• myocardial damages the electrical conduction system of heart is affected
• increased heart rate, weak pulse, irregular heartbeat
• death