Page 170 - PG 504-theoretical notes-phyto-1-2024-2025..

Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

The sugar moiety in cardiac glycosides is characterized by:

❑ Being attached to C-3 of the steroidal nucleus.

❑ Having a variable number of sugar units ranging from 1 to 4.

❑ Including different types of sugars such as: hexoses, methyl pentoses or deoxy sugars.
Examples are:

Hexose :

▪ glucose

▪ Methyl pentose (6-deoxy hexose) : rhamnose

▪ 2, 6-deoxy hexose: digitoxose.

▪ 2, 6-deoxy hexose,3-methyl ether: cymarose.

Properties of cardiac glycosides

Stability: Effect of acids: Split the sugar from the aglycone

• dilute acids result in hydrolysis of glycosidic bond and liberation of the aglycones and
the sugar units.

• Enzymatic hydrolysis splits the cardiac glycosides stepwise starting from the terminal
sugar.

Effect of alkalis:

- Mild alkali (Na2CO3) results in deacetylation in acylated sugars to yield the
deacylated glycoside

(e.g: lanatoside A which by alkali yields purpurea A glycoside).

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