Pharmacology of Cardiovascular System Cardiac glycosides Digitalis Classification

1. Pharmacology of Cardiovascular System
•Cardiac glycosides
•Digitalis

2. Cardiac glycosides
•Class of organic compounds that increase the output
force of the heart and decrease its rate of contractions by
acting on the cellular sodium-potassium ATPase pump.
•Medical uses are as treatments for congestive
heart failure and cardiac arrhythmias
•Commonly found as Secondary
metabolites in several plants such as foxglove
plants

3. • Steroid molecule attached to a sugar (glycoside) and an R group.
•General structure
•The steroid nucleus consists of five fused rings to which other
functional groups such as methyl, hydroxyl,
and aldehyde groups can be attached to influence the overall
molecule’s biological activity.

4. Classification
• Bufadienolide.•Cardenolide

5. Cardenolide
Presence of an “enolide,” a five-membered ring with a
single double bond, at the lactone end.
•Cardenolides are more
commonly used medicinally,
primarily due to the
widespread availability of the
plants from which they are
derived.
• Digitalis purpurea and Digitalis lanata

6.  Bufadienolide
•Contain a “dienolide,” a six-membered ring with two
double bonds, at the lactone end.
Derived from the venom
of the cane toad Bufo
marinus

7. •Convallaria majalis
•Antiaris toxicaria
•Strophanthus kombe
•ouabain (g-strophanthin) and other strophanthins
•Digitalis lanata and Digitalis purpurea :digoxin, digitoxin
•Nerium oleander : oleandrin
•Asclepias sp. (milkweed): oleandrin
•Adonis vernalis (Spring pheasant's eye): adonitoxin
•Kalanchoe daigremontiana and
other Kalanchoe species: daigremontianin and others
Plants from which cardenolides can
be derived

8. •Leonurus cardiaca (motherwort): scillarenin
•Drimia maritima (squill): proscillaridine A
•Bufo marinus (cane toad): various bufadienolides
Organisms from which bufadienolides
can be derived

9. •Mechanism of action
• Affect the sodium-potassium ATPase pump in cardiac muscle cells.
•Increases intracellular sodium concentration.
• Cardiac glycosides and potassium compete for binding to the ATPase
pump
• Raised intracellular sodium levels inhibit the function of a second membrane ion
exchanger, NCX, which is responsible for pumping calcium ions out of the cell and
sodium ions in at a ratio of 3Na+
/Ca2+
. Thus, calcium ions are also not extruded and will begin to build up inside the cell as
well
Raised calcium stores in the SR allow for greater calcium release on stimulation, so the
myocyte can achieve faster and more powerful contraction by cross-bridge
cycling. The refractory period of the AV node is increased.

10. Cardenolide • A type of steroid.
Etymology:
The term derives card- "heart“ and the suffix -
enolide, referring to the lactone ring at C17.

11. •Cardenolides are C(23)-steroids with methyl groups at C-
10 and C-13 and a five-membered lactone at C-17.
Structure:
• The class includes cardadienolides and cardatrienolides.
•acetyldigitoxins
•acetyldigoxins
•cymarine
•digitoxin
•digitoxigenin
•digoxigenin
•digoxin
•medigoxin
•neoconvalloside
•ouabain
•strophanthins
•strophanthidin

12. Bufadienolide:
•bufadienolides and their glycosides are toxic;
specifically, they can cause an atrioventricular
block, bradycardia (slow heartbeat), ventricular
tachycardia (a type of rapid heartbeat), and possibly
lethal cardiac arrest.
Etymology:
•The term derives from the toad genus Bufo that contains
bufadienolide glycosides, the suffix -adien- that refers to
the two double bonds in the lactone ring, and the ending -
olide that denotes the lactone structure.

13. Bufadienolide:
Classification:
•bufadienolides and bufanolides are classified as follows:
•Polycyclic compounds
•Steroids
•Cardanolides
•Cardiac glycosides
•Bufanolides (includes bufenolides, bufadienolides,
bufatrienolides)
•Proscillaridin
•Daigremontianin

14. Digitalis
Digitalis purpurea (Common foxglove)
Kingdom:
Plantae
Clade:
Angiosperms
Clade:
Eudicots
Clade:
Asterids
Order:
Lamiales
Family:
Plantaginaceae
Tribe:
Digitalideae
Genus:
Digitalis

16. Structure:

17. Mechanism of action
• Affect the sodium-potassium ATPase pump in cardiac muscle cells.
•Increases intracellular sodium concentration.
• Cardiac glycosides and potassium compete for binding to the ATPase
pump
• Raised intracellular sodium levels inhibit the function of a second membrane ion
exchanger, NCX, which is responsible for pumping calcium ions out of the cell and
sodium ions in at a ratio of 3Na+
/Ca2+
. Thus, calcium ions are also not extruded and will begin to build up inside the cell as
well
Raised calcium stores in the SR allow for greater calcium release on stimulation, so the
myocyte can achieve faster and more powerful contraction by cross-bridge
cycling. The refractory period of the AV node is increased.

18. Digitalis lutea
A patch of Digitalis
purpurea and Digitalis lutea in Seattle,
WA.