Poisoning Related to Cyanogenic and Cardiac Glycosides

Question 1

What is a Glycoside?

Answer 1

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

Question 2

What is the sugar called?

Answer 2

glycone

Question 3

What is the non-sugar part called?

Answer 3

aglycone

Question 4

How are CGs produced?

Answer 4

From Amino Acids

Question 5

Biological function of CGs

Answer 5

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

Question 6

How does HCN enter tissues?

Answer 6

Via mucous membranes (from respiratory system and gastrointestinal tract), or from skin surface

Question 7

What does HCN inhibit?

Answer 7

Cytochrome C Oxidase Enzyme

- Located in the mitochondrial membrane

Question 8

What happens as a result of the inhibition of Cytochrome C Oxidase Enzyme?

Answer 8

1) Inhibition of cellular respiration
2) No more ATP produced
3) Death

Question 9

How does Cytochrome C Oxidase Enzyme actually work?

Answer 9

1) Translocates H+ ions across the mitochondrial membrane

2) To establish a transmembrane difference of H+ ion electrochemical potential

Question 10

HCN Mechanism of Action

Answer 10

1) In the active site: O2 is prepared to produce H2O

2) CN- ion binds to Fe2+ ion and makes active site inactive

Question 11

HCN Symptoms

Answer 11

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

Question 12

HCN in Hunans

Answer 12

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

Question 13

Chemical proof of the presence of CGs

Answer 13

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

Question 14

Plants with CG’s

Answer 14

1) DRA
2) RSG
3) Black Elder

Question 15

Plants with Cardiac Glycosides and the 3 different types

Answer 15

Cardenolides:
1) Purple Foxglove
2) Spring Pheasant's Eye
3) Lily of the Valley
Bufadienolides:
1) Purple Hellebore
Steroidal Sapogenins:
1) White Swallow Wort

Question 16

What is a Cardiac Glycoside?

Answer 16

A steroid

Question 17

Cardiac Glycosides in large amounts:

Answer 17

• rhythm of the heart get lost, ventricular tachycardia is ensued

Question 18

Mechanism of Action of Cardiac Glycosides

Answer 18

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

Question 19

Cardiac Glycosides Symptoms

Answer 19

1) Hallucinations
2) Loss of colour vision
3) Vomiting
4) Decreased Heart Rate
5) Tachycardia