Page 84 - Pharmd general phytochemistry I-Final2024_LEUCTERS

IX- Cardiac Glycosides (steroidal Glycosides)

Cardiac glycosides act as cardiotonic agents.
• They are characterized by their highly specific action on cardiac
muscle, increasing tone, excitability and contractility of this
muscle; thus allowing the weakened heart to function more
efficiently.

Characteristic features for cardiotonic activity
I. Aglycones ( genins )
The structures of the aglycones are steroidal in nature and
characterized by:

1- An unsaturated 5- or 6- membered lactone ring attached to
steroid nucleus at C-17 with β-configuration.

2- β-hydroxy group at C-3 to which is attached the sugar residue.
3- β-hydroxy group at C-14.
4- The junction of the rings A/B, B/C and C/D are

( Cis - Trans – Cis), respectively
5- Methyl groups at C-10 and C-13
N.B.
The methyl group at C-10 may be replaced by a CHO or CH2OH
group (e.g. Strophanthus glycosides

82