Slide bài giảng Tìm hiểu về glycosides

Classification of glycosides according to glycone part• Glucose _ glucoside group like in Sennoside... Classification of glycosides on the basis of the linkage between glycone and agly

• Definition:

Organic natural compounds present in a lot

of plants and some animals, these

compounds upon hydrolysis give one or

more sugars (glycone) β_form and non form and non

sugar (aglycone) or called genin.

Separation between glycosides parts:

Glycosides glycone +aglycone +HCL

physico-chemical properties of

glycosides(general)

• Colorless, solid, amorphous, nonvolatile (flavonoid- yellow, anthraquinone-red or orange.

• Give positive reaction with Molisch's and Fehling's solution test (after hydrolysis).

• They are water soluble compounds,

insoluble in organic solvents

• Most of them have bitter taste

(except: populin, glycyrrhizin, stevioside)

• Odorless except saponin (glycyrrhizin)

• when a glycosides has a lot of sugars its

solubility in water decrease

• Glycosides hydrolyzed by using mineral acids and temperature or by using enzymes such as:a- Emolsin Bitter almond seeds

b- Myrosin or Myrosinase black mustard

seeds

c- Rhamnase glycosides containing rhamnose

as sugar part

Biosynthesis of glycosides

(O-glycosides)

• UTP(Uridine Triphoshate) +sugar-1-phoshate

UDP-sugar + ppi(Pyrophosphate inorganic).

• UDP-sugar +acceptor (aglycone)

Glycosyl transferase

Enzyme

The function or the role of glycosides in the plant organism

• Converting toxic materials to non or less toxic.

• Transfer water insoluble substances by using monosaccharide.

• Source of energy (sugar reservoir).

• Storing harmful products such as phenol.

• Regulation for certain functions(growth).

• Some have beautiful colours(pollenation process).

…

• Some glycosides have antibacterial

activity, so they protect the plants from bacteria and diseases.

Bitter almond Amygdalin

bacteria

HCN hydrolysis

kill

Eomlsin enzyme

Classification of glycosides

Classifications of glycosides according to their therapeutic effects

• CHF and cardiac muscles stimulators

such as:

a-Digitalis glycosides: digoxin, digitoxin, gitoxin

(Fox glove leaves)

b- Ouabain: Strophanthus gratus seeds

c- K-strophanthin -Strophanthus kombe seeds

d- Scillaren A,B which isolated from red and white Squill bulbs

e- Convolloside:Convallaria majalis – Lily of the

Valley

…

• Laxative group of glycosides:

a- Sennoside A,B,C,D (Senna leaves and fruits).

b- Cascaroside A,B (Cascara bark).

c- Frangulin and glucofrangulin(Frangula bark).

d- Aloin and barbaloin (Aloe vera and Aloe barbadensis juice).

…

• Local irritant group:

a-Sinigrin(Black mustered seeds_Brassica nigra) b-Sinalbin(White mustered seeds_Brasica alba)

• Analgesics and antipyretics:

Salicin Salisylic acid - Willow or Salix bark.

• Keeping elasticity of blood vessels like:

Rutin_Rutoside (Bitter orange peels, Lemon peels)

• Anti-inflammatory group:

a- Aloin for 1)acne 2)peptic ulcer

b-Glycyrrhizin

hydrolysis

Classification of glycosides according to glycone part

• Glucose _ glucoside group like in

Sennoside.

• Rhamnose _ Rhamnoside like in

frangullin

• Digitoxose _ Digitoxoside like in digoxin.

• Glucose and Rhammnose _

Glucorhamnoside _ glucofrangulin.

• Rhamnose and glucose _

Rhamnoglucoside _ Rutin.

Classification of glycosides on the

basis of the linkage between glycone

and aglycone part

• O-glycosides : in these glycosides the sugar part

is linked with alcoholic or phenolic hydroxyl or

carboxyl group

• S-glycosides : in these glycosides the sugar

attached to a Sulfur atom of aglycone such as in sinigrin

• N-glycosides : in these glycosides the sugar

linked with Nitrogen atom of (-NH2,-NH-)amino group of aglycone like in nucleosides DNA,RNA

• C-glycosides : in these glycosides the sugar

linked (condensed) directly to Carbon atom of aglycone like in aloin

N.B C-glycosides are not hydrolyzed by acids or alkalis or by enzymes mainly

Classification of glycosides according to a glycone part :

1- if a glycone part alcohol -this group called alcoholic group like Salicin 2- if a glycone part aldehyde- this group called aldehydic gr like

glucovanillin.

3- if phenol called phenolic group like arbutin

4-if cyanone called cyanogenic or cyanophoric or cyanoside like

amygdalin.

5-if thio called glycosides or isothiocyanate glycoside like sinigrin or sinalbin (-S=C=N-) (SCN)

6-anthracene -> anthraquinone glycoside –sennoside-.

7-steroid - steroidal glycoside (cardiac) Digoxin

8-flavone ,flavonol, flavanone –flavonoid glycoside

9-triterpenoid –saponin glycoside –glycyrrhizin ,melanthin (nigella

seeds) or ginsenoside

Most of glycoside may be named according to the plant from which they isolated for example:

Always glycosides founded in the plant with the enzymes which hydrolyzed them.

We must damage these enzymes first to extract these glycoside by the following steps:

1-drying the plants fresh in special oven at 100 c for 30 minutes.

2-boiling them with organic solvents for 20 minutes

3- boiling them with acetone 5 minutes

N.B.

If present in this plant tannins or resins we add lead acetate to precipitate them.

Classification of glycosides according to a glycone part.

1- phenolic group of

glycosides:-Such as arbutin which isolated from bearberry leaves

Uses: UTI as antiseptic and antibacterial & mild diuretic

Drugs :

-Esoterica :cream :age spots

-hydroquinone solution : wet hands

2- saponin group of glycoside

a Important group of glycosides which widely distributed specially in the higher plants parts

b Most of them are neutral compounds, soluble in water insoluble in the organic solvents.

d Irritant compounds for mucous membranes

e They form with hydrolysis glycone part which usually β-D-glucose or it’s acids (glucuronic acid) + Sapogenin

f Their aqueous solutions from froths (foam) on shakin and form emulsions on shaking and heating with oils and fats

g They destroy RBC (corpuscles) specially for fish and cold blooded animals

m Sapogenin (Triterpenoid) divided to

:

1

- steroidal Sapogenin 2- pent acyclic Sapogenin

Examples:- licorice roots contain saponin glycoside which called Glycyrrhizin Glycyrrhizin hydrolysis glycyrrhetic acid + Z.M glucyr acid

Sweet taste : solution in H 2 O bitter taste insoluble in H 2 O

expectorant anti-inflammatory

Ginseng roots Panax roots Panax quinquefolius ,panax ginseng -contains saponin glycoside – ginsenoside ( panaxoside)

Triterpenoid + steroidal nucleus

Ginseng root uses : 1- stimulant 2- Tonic 3- anti-stress 4-adaptogenic agent

Drugs :

1- geriatric pharmaton

2- gerimax

3- polyvit

Anthraquinone group of

glycosides

1.They are anthracene derivatives (anthracene

= is the main nucleus for anthraquinone

4.With hydrolysis they give aglycone part

which is di,tri or tetra hydroxy anthracene

derivatives.

5.They hydrolyzed only by acids or by

enzymes, but not hydrolyzed by alkalines.

6.They have orange or red color (most of

9 Anthraquinone may be free state

compounds (free from sugar)

or anthraquinone glycoside.

Relationship between anthracene derivatives

According to linkage between glycone part

and aglycone part anthraquinone glycoside may classified to :

1.C-glycoside … very stable to hydrolysis.

2.O-glycoside … 3-o and c- glycoside.

Alcoholic group of

glycosides

Such as: Salicin which obtained from Salix

bark, Willow bark.

Salicin hydrolyzed by:

1.Enzyme emolsin

2.Acid like HCl,HNO 3

3.Alkaline solutions like NaOH

The effect of salicylic acid :

1 Analgesic.

2 Anti-pyretic.

3 Anti-coagulant (anticlotting agent).

4 Anti- inflammatory activity (Rheumatism)

5 Wart and corn remover

6 Prevents colon cancer

Aldehydic group of glycoside

Such as :

Glucovanillin which obtained from :

Vanilla beans (fruits)

** Vanillin : volatile oil which used as flavoring agent

** vanillin : 1.phenolic group volatile oils

2.aldehyde group of volatile oils

Isothiocyanate group of glycoside

( sulfur glycoside or thio glycoside )

1 Group of glycosides which contains sulfur

(S-glycoside)

2 Present in many cruciferous plants, on

hydrolysis.

3 They produce isothiocynate (SCN) aglycone

Such as : 1.sinigrin which founded in Black

These plants contain also enzyme myrosin (myrosinase) which hydrolyze these

glycosides.

Properties of Mustard oil :

1.Irritant for mucous membrane

Sinapine : alkaloids – alkaloidal amine group (protoalkaloid properties of Acrinyl

Uses of white mustard seeds

Condiment, carminative, counter irritant,

emetic

Organic sulfur drugs

Garlic cloves :

Characteristic odor of Garlic

Allicin : yellow liquid responsible for the odor of Garlic.

5.Immune system stimulant

** Coated tablet and capsules

stomach acid inactivates alliinase

enzyme.

Cyanogenic glycosides

Group glycosides which widely distributed

between the members

2 Prunasin : present in Wild Cherry bark (( Prunus sertina))

Flavonoids

Large group of glycosides which widely distributed

in the plants kingdom and in all plants parts

(leaves, roots, rhizomes, fruits peels)

Various colors in flowers( yellow, orange, red,

purple.)

They are benzo-gama-pyrone derivatives.

Their chemical structure based on (C 6 C 3 C 6 ).

The general uses of Flavonoids and Flavonoid

glycosides.

1 Increase elasticity of blood vessels specially

Rutin and hesperidin which known as vitamin (p)

2 Anti inflammatory activity like Taxifolin

3 Anti spasmodic activity like Thyme and

sage flavonoids.

4 Cytostatic activity.

Classification of Flavonoids according to

the main nucleus

Main nucleus flavonoids Flavonoids

glycosides Flavonol

**

C.G (Cardiac glycosides) : group of glycosides which has powerful action on

cardiac muscles (cardiac muscle stimulant)

2 Bufadienolide: (contain two double bonds, lactone ring)

Has six member ( unsaturated ) lactone ring attached at C-17 alpha – position

What is important for activity of C.G

:-1 )

The presence of hydroxyl group in C14 position makes the glycoside very active and gives rapid action in the body, but if we change it to (H+) group the drug will be inactive or less active

.

2 )

The presence of Alpha & Beta unsaturated lactone ring increases the

activity of C.G, but if we make it saturated the C.G will lose its

activity

.

3 )

The ring junctions Cis, Trans, Cis make the nucleus very stable so more active

.

4 ) The sugar part increases absorption and distribution of C.G in the body

S.P : Glucose, Rhamnose, Cymarose, Digitoxose

Examples of Cardenolides

1 ) Digitalis glycosides

2 ) Strophanthus gratus C.G :

Oubain

3 ) Strophanthus Kombe glycoside :

K- strophanthin

Bufadienolide example

Squill bulb glycoside

Scillaren

**

Chemical tests

:-1 ) Keller Kiliani test : C.G + CH 3 COOH + H 2 SO 4 + FeCl 3 brown

2 ) Legal test : C.G + pyridine sodium nitroprusside Red to pink colour

* Uses : 1-CHF 2- arrhythmias

* General properties of C.G : 1- Amorphous powder 2-bitter taste

3

-

sol In H 2 O 4-Insol In Org solvents

5

Tannins

• Complex natural organic compounds,

polyphenolic, polyhydroxy benzoic acid

derivatives or Flavanol derivatives.

• Widely distributed in the nature (leaves, barks,

immature fruits but, they disappear during

ripening process).

• They protect the plants from herbivorous

animals, insects, bacteria and others specially during growth, like in new leaves which contain high percentage of tannins.

• Some of them have low molecular weight but,

most of them have very large molecular weight

Physico_chemical properties

1 They form colloidal solutions with water.

2 Non crystalline substances.

3 Their aqueous solution is acidic.

4 They have sharp puckering taste.

5 They have astringent property.

6 They precipitated by: alkaloids, gelatin, salts of heavy metals, proteins (enzymes).

Tannins are classified into

:

1.True tannins (hydrolysable)+ hydrolysable).

(non-2 Pseudo tannins.

Classification of tannins

:

1)True tannins:

(a)Hydrolysable group:

1- Hydrolyzed by acids or enzymes (Tannase).

2- They are esters of a sugar (β-D-glucose) with one or more trihydroxybenzene carboxylic

acid.

3-The tannins which derived from Gallic acid

called Gallo-tannin or glucogallin like in

Rhubarb rhizomes, Clove buds, Bearbers

leaves.

4- tannis which derived from ellagic acid called ellagotannin or glucoellagin like in Pomegranate roots bark and Eucalyptus leaves (which also

contain Tannic acid which is Gallotannin).

5- They form (H.T) with FeClз dark blue color.

(b) Non hydrolysable group of tannin, condensed tannins or called proanthocyanidin tannins:

1- has resistance to hydrolysis by acids or

enzymes.

2- they are Flavanol derivatives:

1) Flavan-3-ol like catechin

2) Flavan-4-ol like leucocyanidin

- they are founded

:

In barks like: Cinnamon (Phlobatannins),

Cinchona (Cinchotannin), Wild cherry

2 ) Pseudo tannins

:

1

- they have low molecular weight

.

2

- they occur

The general uses of tannins

Chemical tests

:

1) With FeClз :

(a) H.T→ dark blue

(b) Non H.T → dark green

2) ppt with alkaloids, gelatin, proteins, and salts

of heavy metals like lead acetate, copper

acetate.

4) Vanillin_HCl reagent → red to pink color.