-Bitter principles are heterogenous compounds having bitter

taste, usually of vegetable origin and few of them from animal

origin.

-They belong to different chemical groups, most of them

possess terpenoid structures which represent derivatives

of monoterpenes, sesquiterpenes, diterpenes and triterpenes.

-They composed of carbon, hydrogen and oxygen, but free

from nitrogen.

-They belong neither to the alkaloids nor to the glycosides.

-They increase the gastric function to a variable degree due to

direct action on the stomach or the duodenum.

-Bitter principles are found in certain families as Compositae,

Rutaceae, Umbelliferae and Simaroubaceae.

Bitter Principles

Types

12-Rosemary

Leaf

1-Phenolic 4-Others 3-Chromone and

Coumarins

12-Rosemary

Leaf

12-Rosemary

Leaf

12-Rosemary

Leaf

12-Rosemary

Leaf

12-Rosemary

Leaf

12-Rosemary

Leaf 2-Lactones

I- Phenolic Bitter prinicples

Humulone and Lupulone

OO

HO OH

HO

humulone

They are crystalline acidic bitter principles present in the

strobiles of Humulus lupulus, F. Cannabinaceae.

OO

O OH

Lupulone

Chemical tests or characters

-Humulone gives a reddish-violet colour with ferric chloride.

-Lupulone on oxidation with pot. Perminganate yields

valerianic acid.

Uses

Both have a sedative action.

II- Lactone Bitter prinicples

Santonin

CH3

CH3 OH

CH3

COOH

O

CH3

CH3 O

CH3

CO

O

- H2O

santonic acid santonin

-It is crystalline lactone of santonic acid, its molecule having

15 carbon atoms, so it is related to the sesquiterpenes.

- Santonin is the cheif anthelmintic constituent of the dried

unexpanded flower heads of Artemisia cina, F. Astraceae.

Chemical tests

When Santonin warmed with alc. Solution of caustic soda, it

gives a violet-red colour gradually changes to reddish yellow.

Uses

It is very efficient in its action on round worms as Ascaris, with

Less effect on thread worms and non on Taenia.

III- Chromone and coumarin Bitter prinicples

1- Visnagin

OO

O

CH3

OCH3

It occurs in the fruits of Ammi visnaga and used for treatment

of angina pectoris.

- Visnagin when treated with sodium hydroxide, it produces a

rose red colour.

-It can be considered as furnaochromone aglycone.

OO

OCH3

OCH3 O

CH3

2- Khellin (visammin)

-Khellin is structurally related to the furanocoumarins but is a derivative

of 5,6-benzo- 4-pyrone (γ-chromone), rather than 5,6-benzo-2-pyrone

(α-chromone). with two methoxy groups in p-postion on benzene ring

3- Xanthotoxin (ammoidin)

OO

O

OCH3

- Khellin is present in Ammi visnaga fruit and has antispasmodic

properties and was used to ease cramps in the stomach intestines,

Nowadays, it is little used because of its unpleasent side effects as

nausea and vomiting.

It occures in the pericarp of the fruits of Ammi majus And Fragara xanthoxyloids -It is considered as linear furanocoumarins.

Chemical tests

-Few crystals of xanthotoxin are trituated with little H2SO4 in

a porcelin dish, an ornage yellow colour is produced change

to light green.

Uses

-It is used in the treatment of leukoderma, where it increases

melanin pigments in the skin on exposure to UV. It has no

effect on leukoderma due to infections or trauma or

Autoimmune disease.

IV- Other Bitter principles

1- Cantharidin

O

COOH

COOH

O O

O

O

-H2O

cantharidic acid cantharidin

It is of animal origin and obtained from the soft parts of

Cantharides or spanish flies.

-It is monoterpene of a dibasic acid cantharidic acid, where

the insects contain both Cantharidic acid and cantharidin.

Chemical test

It gives brown to black colour by heating with dil.

Formaldehyde H2SO4.

Uses

It is used as a rubifacient, counter irritant specially in

veterinary medicine.

Internally, it has irritant action on the mucous membrane and

tend to produce nephritis.

2- Picrotoxin (Cocculin)

It is obtained from the dried fruits of Anamirta cocculus,

F. Menispermaceae.

-Picrotoxin consists of equimolecular proportions of

picrotoxinin and picrotin. Each is considered as an

oxygenated sesquiterpenoid derivative.

Separation

-Picrotoxin is a mitxure of 2 components which can be

Resolved by boiling with 20 parts of benzene.

-This treatment dissolves picrotoxinin, leaving picrotin which

Is almost insoluble in benzene.

Uses

-It is used intravenously as antidote in case of barbiturate

poisoning and other narcotics.

-It is CNS and respiratory stimulant. Very small quantities of

the powdered fruits are sufficient to stupefy fish.

O

O

O

picrotin

OOC OH

H3C

O

O

O

OOC OH

H3C

OH

picrotoxinin

C15H16O6 C15H18O7

Polyphenols

• are a group of chemical substances found in plants, characterized by the presence of more than one phenol unit or building block per molecule. Polyphenols are generally divided into hydrolyzable tannins (gallic acid esters of glucose and other sugars) and phenylpropanoids, such as lignins, flavonoids, and condensed tannins.

Classification of

Tannins

1-True

Tannins

2-Pseudo

Tannins

B-Condensed

(Catechol)

A-Hydrolysable

(Pyrogallol)

• Are naturally occurring substances of high enough molecular weight (1000-5000)

• Containing a sufficient large number of phenolic and hydroxy groups

• Forming effective cross-links between proteins and other macromolecules

Industrially

The term tannin are applied to

denote substances present in plant

extracts which are able to combine

the protein of animal hides,

prevent their putrefaction and

convert them into leather, this

process is called tanning process

* Gallic acid, catechins and

chlorogenic acid, may under

certain conditions give

participates with gelatin, be partly

retained by hide powder.

* Such substances of relatively low

molecular weight are called

pseudo tannins

Physical characters

* Non-crystalline amorphous

complex compounds, soluble in water

forming an astringent colloidal

solution

* They are also soluble in dilute

alkalis, alcohol, glycerol and acetone

* They are generally sparingly

soluble in petroleum ether, benzene

and ether

Galls

Hammamelis

Distribution

Function and physiological significance of tannins 1-Source of energy for maturation of the fruits 2-Protective to the plant, inhibit the growth of many fungi, through inhibition of certain enzymes 3-Having respiratory activity, performed by hydrogen transfer in plant cells

Classification of Tannins

Condensed (Catechol)

Hydrolysable

(Pyrogallol)

Hydrolysable 1- Polyhydric alcohol e.g. glucose, esterifies by several molecules of phenolic acids as Gallic 2- Hydrolysed with acid or enzymes Give pyrogallol 3- No colour with bromine water 4- Bluish black colour with FeCl3

Condensed 1- Condensation of two or more molecules of flavanols or flavandiols 2- Difficult be hydrolysed by enzymes Give catechol 3- Buff precipitate with bromine water 4- Green colour with FeCl3

OH

OH

OH

HO

O

Hydrolysable Tannins

HO

HO

OH

OHO

OH

HO

HO

HO O

Gallic acid

Hexahydroxydiphenic acid

HO

HO

OH

OHO

O

O

HO

HO OHO

HO

O

OH

OHO

OO

Dehydrohexahydroxydiphenic acid Ellagic acid

HO

HO

OH

OHO

HO

HO

OH

OHOOH

HO

HO

HO O

Acid

or tannase

Gallic acid

Hexahydroxydiphenic acid

-CO2

Dry distillation

OH

OH

HO

Pyrogallol

HO

HO

O

OH

OHO

OO

Ellagic acid

Types of hydrolysable tannins

Gallitannins Ellagitannins

Gallic acid Ellagic acid

Gallitannins

HOO

HOOH

OG

OH

Galloyl β-1-O-Galloyl-D-glucose

G =

Penta-O-Galloyl-D-glucose

Condensed Tannins

O

OH

OH

OH

OH

HO

R

R = H Catechin

R = OH Leucocyanidin

Catechol tannins polymerize in strong acid solution to

form insoluble amorphous red or brown coloured

phlobaphenes

Pseudotannins Compounds of low molecular

weight than the true tannins and

do not respond to Goldbeater’s

skin test

Present in Rhubarb, Catechu,

Coffee, and Ipecacuanha

Chemical test Goldbeater’s skin test

A piece of Ox-intestine is soaked

in dilute HCl for 2 minutes,

washed thoroughly, then soaked

in the test solution, washed, then

transferred to FeSO4 solution

where it acquires a brown to

black colour

Gelatin test Solution of tannins precipitate 1 % solution of gelatin

Phenazone test

Aqueous extract of the drug, add sodium

acid phosphate, warm and filter. To the

filtrate add 2 % solution of phenazone

All tannins are precipitate is bulky and

often coloured

Reaction with ferric chloride

* Hydrolysable

tannins turn a bluish-black

*Condensed

tannins turn a green colour

Uses of tannins

Astringent

Antiseptic

Antioxidant