Glycosides 1

Question 1

What are glycosides?

Answer 1

Compounds that yield upon hydrolysis, one or more sugars among their products

Question 2

The sugar part of a glycoside is referred to as …..

Answer 2

GLYCONE

Question 3

The non-sugar part of a glycoside is referred to as……

Answer 3

AGLYCONE

Question 4

List the types of beta linkages…..

Answer 4

C-O-C ‘O’- GLYCOSIDES

        C-C                       ‘C’- GLYCOSIDES

       C-S-C                     ‘S’- GLYCOSIDES

       C-N-C                    ‘N’- GLYCOSIDES

Question 5

Hydrolysis of glycosides………..

Normally ethers are fairly __________, but the proximity of the __________ atom in the ring of the sugar assists with the hydrolysis due to the possibility of a ___________-intermediate that can accommodate the charge through the ____________.

Glycosides are hydrolyzed under _____________.

Answer 5

Normally ethers are fairly stable, but the proximity of the oxygen atom in the ring of the sugar assists with the hydrolysis due to the possibility of a stabilized intermediate that can accommodate the charge through the acetal linkage.

Glycosides are hydrolyzed under acidic conditions.

Question 6

List antibiotics that are glycosides ELAS

Answer 6

Erythromycin A,
Streptomycin,
Lincomycin and
Adriamycin

Question 7

List the classifications of glycosides according to the aglycone and their examples…

match these examples

tannins and lignans

wild cherry bark (Prunus serotina)

Senna alexandrina

Digitalis species

Basic general structure has C6-C3-C6

Triterpenoids b. Steroidal
eg liquorice eg soya
(Glycrrhiza spp) (Glycine

Coumarins, eg celery fruit

(may be as alcohols, aldehydes, or phenol glycosides)

Answer 7

1. Cardioactive √
   eg Digitalis species

2 Anthracene √
eg Senna alexandrina

3 Saponins √
a. Triterpenoids b. Steroidal
eg liquorice eg soya
(Glycrrhiza spp) (Glycine max)
4 Cyanogenetic
yield HCN upon hydrolysis
eg wild cherry bark (Prunus serotina)

5 Flavonoids √ and Anthrocyanidins
Basic general structure has C6-C3-C6

6 Lactone
Coumarins, eg celery fruit

7 Phenol
(may be as alcohols, aldehydes, or phenol glycosides)

8 Others
e.g tannins and lignans

Question 8

Facts about cardiac glycosides

Cardiac glycosides occur in a number of _____________
The aglycones of cardiac glycosides are characteristic and have a _________and an ______________ ring, which is a side-chain at ____________.
These have a direct, specific action on the heart muscle. They increase _____________ and ______________-.
The action on the heart muscle is dependent on the_____________
the sugar part improves _________ and aids interaction with the __________.
_____________ leaf BP

Small doses are used to treat _____________________.

Answer 8

Cardiac glycosides occur in a number of plant species
The aglycones of cardiac glycosides are characteristic and have a steroid nucleus and an unsaturated lactone ring, which is a side-chain at C-17.
These have a direct, specific action on the heart muscle. They increase tone and excitability.
The action on the heart muscle is dependent on the aglycone
the sugar part improves solubility in aqueous media and aids interaction with the heart tissue.
Digitalis purpurea leaf BP

Small doses are used to treat congestive heart failure.

Question 9

Facts about fresh leaves of Purpurea Glycosides

Fresh leaves have _____________
on drying ______________ is lost by the action of ___________
Hence, the plant is collected and dried at _______o C to prevent this and further ______________ as much as possible.

Answer 9

Fresh leaves have tetraglycosides
on drying one sugar is lost by the action of enzymes
Hence, the plant is collected and dried at 60o C to prevent this and further hydrolysis as much as possible.

Question 10

State the type of glycoside found in Digitalis purpurea

Answer 10

Digitoxin

Question 11

What is the problem with using digitoxin to treat congestive heart failure?

Answer 11

Digotoxin suffers from having a long half-life of 6 days.

Also, excretion is after metabolism by the liver (slower than by the kidneys). Hence, there is the risk of overdosage

Question 12

The glycosides in Digitalis lanata are called …..

Answer 12

Lanatosides (they are structurally related to purpurea glycosides

Question 13

What plant is the main source of Digoxin?

Answer 13

Digitalis lanata

Question 13

What plant is the main source of Digoxin?

Answer 13

Digitalis lanata

Question 14

Digoxin is useful for……

Answer 14

Arterial fibrillation and flutter,

and also in congestive heart failure

Question 15

Explain why Digoxin is not used where rapid response is required?

Answer 15

It has a half-life of 36 hours and hence maintenance dose should not be required within 24 hours

Question 16

How is Digoxin eliminated from the body?

Answer 16

It is excreted by the kidneys and hence this organ is required to be functioning normal

Question 17

What can cause toxicity to Digoxin?

Answer 17

Hypercalcaemia, hypomagnesaemia and hypokalaemia

Question 18

If toxicity is suspected or established when using Digoxin, what should be used?

Answer 18

Dig Fab®’.