Poisoning Related to Cyanogenic and Cardiac Glycosides Flashcards
What is a Glycoside?
A glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond
What is the sugar called?
glycone
What is the non-sugar part called?
aglycone
How are CGs produced?
From Amino Acids
Biological function of CGs
1) CGs are stored in the vacuole in inactive forms
2) Upon plant injury, specific enzymes remove the sugar parts
3) Aglycones are activated; HCN is often produced spontaneously
How does HCN enter tissues?
Via mucous membranes (from respiratory system and gastrointestinal tract), or from skin surface
What does HCN inhibit?
Cytochrome C Oxidase Enzyme
- Located in the mitochondrial membrane
What happens as a result of the inhibition of Cytochrome C Oxidase Enzyme?
1) Inhibition of cellular respiration
2) No more ATP produced
3) Death
How does Cytochrome C Oxidase Enzyme actually work?
1) Translocates H+ ions across the mitochondrial membrane
2) To establish a transmembrane difference of H+ ion electrochemical potential
HCN Mechanism of Action
1) In the active site: O2 is prepared to produce H2O
2) CN- ion binds to Fe2+ ion and makes active site inactive
HCN Symptoms
1) 15-20 minutes after they are eaten
2) Blood, mucous membranes (and skin) of cherry colour
3) Nausea, vomiting, breath with smell of bitter almond
4) Heavy breathing
5) Muscle contraction, spasms, stumbled walk
6) Coma, death
HCN in Hunans
1) pH is too low in stomach, and too high in the small intestine to provide a suitable environment for HCN release
2) Humans are less sensitive to HCN compared to e.g. Ruminants
Chemical proof of the presence of CGs
Guignard’s reaction
- A white filter paper is soaked in picric acid (yellow) solution
- 2-3 leaves grinded by a glass rod are put into a test tube;
a few drops of water and 0.5 ml of 3N HCl solution are added
- The colour of filter paper turns red
Plants with CG’s
1) DRA
2) RSG
3) Black Elder
Plants with Cardiac Glycosides and the 3 different types
Cardenolides: 1) Purple Foxglove 2) Spring Pheasant's Eye 3) Lily of the Valley Bufadienolides: 1) Purple Hellebore Steroidal Sapogenins: 1) White Swallow Wort
What is a Cardiac Glycoside?
A steroid
Cardiac Glycosides in large amounts:
- rhythm of the heart get lost, ventricular tachycardia is ensued
Mechanism of Action of Cardiac Glycosides
1) Na+/K+ pumps in cell membranes are inhibited
- Increased Na+ levels within cardiac muscle
2) Na+/Ca2+ exchangers inhibited too
- Due to the raised levels of intracellular Na+
3) Raised Ca2+ levels in CM cells
- Increased cytoplasmic Ca2+ levels cause increased Ca2+ uptake into the sarcoplasmic reticulum
4) 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
Cardiac Glycosides Symptoms
1) Hallucinations
2) Loss of colour vision
3) Vomiting
4) Decreased Heart Rate
5) Tachycardia
