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

Sugar moiety

1. The sugar moieties have no cardiac activities, but when attached to the 3-OH group of the
steroid they influence the activity (potency & toxicity), the solubility, the distribution and
the absorption the cardiac glycosides.

2. The free aglycones are less potent than any of their glycosides.

3. The glycosides usually contain from 3-4 sugar units attached to C-3, Cardiac glycosides
usually contain 6-deoxy sugar.

Aglycone moiety: the following are essential feature for cardiac activity

▪ Steroidal nucleus.

▪ The activity of the cardiac glycosides is due to the aglycone part, in particular to
the lactone ring so opening by alkali, results in loss of the activity.

▪ Double bond at C20 and C22 of the lactone ring, Saturation of the lactone ring
destroy the cardiac activity.

▪ OH gr. At positions 3 and 14.

▪ A/B ring junction cis

▪ B/C ring junction trans

▪ C/D ring junction cis

Plants containing cardiac glycosides

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