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The Cardiac Glycosides Cardio-active Glycosides

The Cardiac Glycosides Cardio-active Glycosides. A Group of steroidal glycosides act as cardiotonic agent. They increase tone, excitability and contractility of cardiac muscles. Structural features :. - Steroidal nucleus must be present. -3 b -OH group involved in glycosidic linkage.

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The Cardiac Glycosides Cardio-active Glycosides

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  1. The Cardiac GlycosidesCardio-active Glycosides A Group of steroidal glycosides act as cardiotonic agent. They increase tone, excitability and contractility of cardiac muscles.

  2. Structural features: -Steroidal nucleus must be present. -3b-OH group involved in glycosidic linkage. -14b-OH group at C-14. - A/B ring junction cis – - B/C ring junction trans- -C/D ring junction cis -Additional OH groups at C-5, C-11 and C-16 may be present. -The presence of lactone ring: 14

  3. According to the type of lactone ring Cardiac Glycosides are classified into: • Cardinolides: They are C-23 containing 5-membered unsaturated lactone ring e.g. Digitalis & Strophanthus • Bufadienolides: They are C-24 containing 6-membered unsaturated lactone ring e.g. Squill

  4. The Sugar Part: • The glycosides usually contain 3 to 4 sugars attached at C-3 OH. • Beside Glucose and Rhamnose they usually contain deoxysugars.

  5. The Cardinolides1- Digitalis Glycosides • Digitalis is Known as “foxglove” • The most important species includes: • 1) Digitalis purpurea • 2) Digitalis lanata

  6. Digitalis contain three major aglycones:

  7. 2- StrophanthusGlycosides Obtained from Strophanthus kombé The used part is the seeds. The common aglycone is K-strophanthidin

  8. 14 10

  9. Bufadienolides1- Squill Glycosides • They have 6-membered lactone ring. • Obtained from Squill bulbs. • Aglycone contains only two hydroxyl groups at C-3 and C-14.

  10. Physical and Chemical properties of cardiac glycosides: • Solubility: • Glycosides are soluble in water and alcohols. • Increase number of sugars increase water solubility. • Aglycones soluble in CHCl3 and EtOAc.

  11. Stability: 1) Acid hydrolysis: Split sugars from the aglycone first. 2) Enzymatic hydrolysis: Split sugars stepwise starting from the terminal sugar. 3) Elevated temperature: Cause dehydration by removal of C-14 OH group to give inactive anhydro-form

  12. Medicinal Importance: • -They are Cardiotonics used to treat Congestive heart failure. • -They increase force of contraction of cardiac muscles without increasing oxygen consumption. • -Increase cardiac output. • The diastolic phase lasts longer, thus decreases heart rate. • -Have diuretic effect due to increase amount of blood passing through the kidney.

  13. Chemical Identification: General test for steroids: Liebermann’s test: Glycoside in acetic anhydride + Few drops of conc. H2SO4 Reddish violet Green Test for Deoxysugars: Keller-Kiliani’s Test: Glycoside in gl. acetic containing traces of FeCl3 + conc. H2SO4 on the wall of the tube Acetic acid layer acquire Bluish-greencolour (Digitalis) Acetic acid layer acquire Red colour (Squill)

  14. Test for 5-membered lactone ring: • Legal’s test: • Cardenolide in pyridine + Na nitroprusside + NaOH deep redcolour. • Kedde’s test: • Cardenolide + 3,5 dinitrobenzoic acid (Kedde’s reagent A) + NaOH (Kedde’s reagent B) violet colour.

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