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Classification of GlycosidesClassification of Glycosides
A.A. On the basis of sugar moiety such as glucoside , rhamnoside, etc.
A.B. On the basis of therapeutic activity such as - Cardiac glycosides, e.g. Digitalis, Strophenthuss, etc.- Laxative glycosides, e.g. Aloe, Senna, Cascara sagrada, etc.
CH2OH
O C6H11O5
O
OH
O
H
OH
OH
HO
H
CH2OH
HH
OH
Salicin (saligenin + glucose)
Arbutin (hydroquinone + glucose)
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C. On the basis of linkage of sugar molecule with the aglycon a) O- Glycosides: here the sugar is combined with the
alcoholic or phenolic hydroxyl group of the aglycone.
RO
R = Glucose in daucosterol
ORO
OH O
OCH3
OHR = Rhamnose - glucose
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b) N- Glycosides: In these glycosides the amino group (-NH2 / -NH-) is condensed with the sugar, e.g. nucleosides, coenzyme, etc.
N
N
N
N
NH2
H
H H
OCH2OH
H
OH OH
N
NN
N
NH2
H
O OH
H HCH2
P
O
O-O
O
PH O-HO
O
PH
CH2
O-HO
CH3C CH3
CHO CH
H
HN
OH
CH
OH
HN
SH
H
O
Adenosine (Adenine + ribose)
Coenzyme A
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d) C- Glycosides: Condensation of a sugar directly to a carbon atom of the aglycone gives c-glycosides, e.g. aloin, chrysaloin, etc.
OH O OH
H C6H11O5
CH2R
O
CH3
C6H11O5
HO CH3
O
OR = OH, Barbaloin H, Chrysaloin
Aloesin
c) S- Glycosides: These glycosides contain a sugar moiety attached to the sulfur of the aglycone, e.g. isothiocyanate glycosides.
C3H5 C
N
S C6H11O5
O SO3K
Sinigrin
HO CH2 C
S
N O
C6H11O5
SO2-O-K
Sinalbin
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D) On the basis of the chemical nature of aglycone, the glycosides can be classified into following groups:
HO
H
CH3
CH3
OH
OO
+ digitoxoseDigitoxigenin (cardenolide, C23 steroid)
1. Cardioactive • Digitalis • Strophenthus
RO
H
CH3
CH3
OH
O O
• Squill
R = H, Scillarenin A (bufadienolide, C24 steroid) R = rham – glu, Scillaren A
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2. Anthraquinone
H C6H11O5
OH O OH
CH2R
• Cascara sagrada• Aloe• Senna• Rhubarb
R = OH, Barbaloin H , Chrysaloin
• Glycyrrhiza• Dioscorea
3. Saponin
HO
CH3
CH3O
O
+ rhamnose, + glucose
Spiroketal steroid nucleus (neutral)
diosgenin
HO
Β – amyrin (aglycone, pentacyclic triterpenoid, acidic)
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4. Cyanophore C O C6H11O5
H
CN
C OH
H
CNC6H12O6 +
CH OH
H
+ HCN
Mandelonitrile glucoside
Mandelonitrile Benzadehyde
• Wild cherry• Bitter almond
5. Isothiocyanates C3H5 C S
N
C6H11O5
O SO3K
Sinigrin
H2Omyrosin
S C N CH2 CH
CH2 + KHSO4 + C6H12O6
glucoseAllyl isothiocyanate
• Black mustard• White mustard
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6. Flavanol / flavanoid
OHO
OH O
O
OH
OH
C12H21O9
Rutin
• Citrus fruit
7. Alcohol
+ H2O
CH2OH
OH
+ glucose
Salicin Saligenin
CH2OH
O C6H11O5
• Salix • Populus
99
8. Aldehyde CHO
OCH3
ORR = H, vanillin
R = glu, glucovanillin
• Vanilla
9. Lactone
OHO O
Coumarin
• Cantharide• Tonka beans
1010
11. Tannin HO
OH
OH
COO C6H11O5
Glucogallin (glucoside of gallic acid)
• Nutgall• Hamamelis leaf
10. Phenol OC6H11O5
OH
+ H2O
OH
OH
+ glu
Arbutin Hydroquinine
• Uva ursi
1111
R C O
H
+ ROH R' C OR
H
OH
H+
Hemiacetal
R' C OR
H
OH
+ ROH R' C OR
H
OR
H+
Hemiacetal (an alcohol) acetal
An acetal is a molecule with two single bonded oxygen attached to the same carbon atom.
Hemiacetals and hemiketals are compounds derived from aldehyde and ketones respectively. These compounds are formed by formal addition of an alcohol to the carbonyl group.
1212
H HCOOH
NH2H
H HCOOH
NHOHH
H H
CH
NOH
L-Phenylalamime N-Hydroxy-L-phenylalanine Phenylacetaldoxime
H H
C N
H OH
C N
H O
C N
O
H
HHO
OHH
OH
OH
H
H
Mandelonitrile a-Hydroxymandelonitrile
glucosyl transferase
+ UDP glucose
Prunasin
The biosynthetic pathway for the cyanogenic glycoside, prunasin.
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