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forensic toxicology - plant toxins - glycosides

Cyanide, & cardiac glycosides
Quiz by camisadorising
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Last updated: September 12, 2023
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First submittedSeptember 12, 2023
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what are glycosides?
what is a aglycone?
what are the types of glycosides we're interested in for this unit?
any molecule in which a sugar is bound to another functional group via a glycosidic bond
the non-sugar part of a glycoside
cardiac (steroidal) glycosides
cyanogenic glycosides
saponin glycosides
what is cyanide?
what is the mechanism of action of cyanide?
how can this lead to a toxic effect?
what are the physiological consequences of cyanide toxicity?
what is the LD50 of cyanide?
a glycoside with the aglycone cyanide (HCN) - a cyanogenic glycoside
in solution HCN produces cyanide ions (CN-)
because the cells are unable to use oxygen for metabolism, they essentially die through hypoxia
initial symptoms: weakness, confusion, dizziness, headache, and cherry-red skin
1.5mg/kg
CN- attaches to the iron in cytochrome c oxidase (a+a3)
this binding prevents the transfer of electrons from cytochrome c to oxygen
this is followed by loss of consciousness
this shuts down the mitochondrial electron transport chain
final symptoms: seizures and cardiac arrest
which means the cell is no longer capable of aerobic respiration
what is the mechanism of action of cardiac glycosides?
what have cardiac glycoside drugs been used to treat?
how has the mechanism of action of cardiac glycosides allowed them to be developed into a therapeutic medication?
what is an example of a cardiac glycoside drug?
they target Na+/K+ pumps in cell membranes
arrhythmias and congestive heart failure
in low doses, it helps the heart muscle to contract
digoxin
they bind to the pump and stabilise it in a transitional state (meaning it can no longer move Na+ out of the cell, so concentration in the cell decreases
increased Na+ levels also inhibits the NCX pump, which brings Na+ in and moves Ca2+ out
this means Ca2+ level in the cell also increase, which is taken up by the sarcoplasmic reticulum
when Ca2+ is release, myocyte contraction is faster and more powerful
what are saponin glycosides?
what is their toxic action?
amphipathic molecules consisting of a hydrophilic glycoside coupled to a hydrophobic aglycone (they are detergents)
they are haemolytic and cause lysis of red blood cells if injected
toxic action is primarily through membrane disruption
can also block acetylcholinesterase
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