The Cardiac The Cardiac Glycosides Glycosides Cardio-active Glycosides Cardio-active Glycosides A Group of steroidal glycosides act A Group of steroidal glycosides act as cardiotonic agent. They increase as cardiotonic agent. They increase tone, excitability and tone, excitability and contractility of cardiac muscles. contractility of cardiac muscles.
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The Cardiac The Cardiac GlycosidesGlycosides
Cardio-active GlycosidesCardio-active Glycosides
A Group of steroidal glycosides act A Group of steroidal glycosides act as cardiotonic agent. They increase as cardiotonic agent. They increase tone, excitability and contractility of tone, excitability and contractility of
cardiac muscles.cardiac muscles.
Structural featuresStructural features::
--SteroidalSteroidal nucleus must nucleus must be presentbe present..
--33-OH group involved in -OH group involved in glycosidic linkageglycosidic linkage..
--1414-OH group at C-14-OH group at C-14.. - -A/B ring junction A/B ring junction cis cis
- - B/C ring junction B/C ring junction transtrans--
--C/D ring junction C/D ring junction ciscis--Additional OH groups at C-5, C-11 and C-16 Additional OH groups at C-5, C-11 and C-16
may be presentmay be present..
--The presence of The presence of lactonelactone ringring::
R
OH
sug-O
R2
R1
3 5
12
16
17
R3
H
H
H
BA
CD
14
According to the type of lactone According to the type of lactone ring Cardiac Glycosides are ring Cardiac Glycosides are classified intoclassified into::
–CardinolidesCardinolides::They are C-23 containing 5-membered They are C-23 containing 5-membered unsaturated lactone ringunsaturated lactone ring
e.g. e.g. DigitalisDigitalis & & StrophanthusStrophanthus
–BufadienolidesBufadienolides::They are C-24 containing 6-membered They are C-24 containing 6-membered unsaturated lactone ringunsaturated lactone ring
e.g. e.g. SquillSquill
OO
17
17
O
O
The Sugar PartThe Sugar Part::The glycosides usually contain 3 to 4 sugars The glycosides usually contain 3 to 4 sugars
attached at C-3 OHattached at C-3 OH..
Beside Glucose and Rhamnose they usually Beside Glucose and Rhamnose they usually contain deoxysugarscontain deoxysugars..
CHO
CH
CH
CH
CH
CH2OH
OH
OH
HO
OH
Glucose
CHO
CH
CH
CH
CH
CH3
OH
OH
HO
Rhamnose
HO
CHO
CH2
CH
CH
CH
CH3
OH
OH
Digitoxose
OH
CHO
CH2
CH
CH
CH
CH3
OH
OH
Cymarose
OCH3
The CardinolidesThe Cardinolides1- 1- DigitalisDigitalis Glycosides Glycosides
Digitalis is Known as “foxgloveDigitalis is Known as “foxglove””The most important species includesThe most important species includes::
Split sugars from the aglycone firstSplit sugars from the aglycone first..
–22 ) )Enzymatic hydrolysisEnzymatic hydrolysis::Split sugars stepwise starting from the Split sugars stepwise starting from the
terminal sugarterminal sugar..
–33 ) )Elevated temperatureElevated temperature::Cause dehydration by removal of C-14 OH Cause dehydration by removal of C-14 OH
group to give inactive anhydro-formgroup to give inactive anhydro-form
OO
OH
Sug-O
OO
Sug-O
High temperature
Anhydro-form
Dehydration of Gitoxin with another OH at C-Dehydration of Gitoxin with another OH at C-16 give a fluorescent compound used as test 16 give a fluorescent compound used as test
for Gitoxinfor Gitoxin
OO
OH
HO
OO
HO
Anhydro-form
H2SO4
OH
Medicinal ImportanceMedicinal Importance::
--They are Cardiotonics used to treat They are Cardiotonics used to treat Congestive heart failureCongestive heart failure..
--They increase force of contraction of They increase force of contraction of cardiac muscles without increasing oxygen cardiac muscles without increasing oxygen consumptionconsumption..
decreases heart ratedecreases heart rate..--Have diuretic effect due to increase amount Have diuretic effect due to increase amount
of blood passing through the kidneyof blood passing through the kidney..
Chemical IdentificationChemical Identification::
General test for steroidsGeneral test for steroids::–Liebermann’s testLiebermann’s test::
Glycoside in acetic anhydride + Few drops of Glycoside in acetic anhydride + Few drops of conc. Hconc. H22SOSO4 4 Reddish violet GreenReddish violet Green
Test for DeoxysugarsTest for Deoxysugars::–Keller-Kiliani’s TestKeller-Kiliani’s Test::
Glycoside in gl. acetic containing traces of FeClGlycoside in gl. acetic containing traces of FeCl33 + conc. H+ conc. H22SOSO4 4 on the wall of the tubeon the wall of the tube