cyanogenic glycosides and cardiac glycosides

Question 1

cyanoglycoside

Answer 1

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

Question 2

cyanogylcoside biology

Answer 2

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

Question 3

HCN poisoning

Answer 3

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

Question 4

HCN symptoms

Answer 4

• 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

Question 5

Cardiac glycoside

Answer 5

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

Question 6

Cardiac mechanism

Answer 6

• 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

Question 7

Cardiac symptoms

Answer 7

– 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)

Question 8

Specific heart symptoms

Answer 8

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