-bitter principles are heterogenous compounds having bitter
TRANSCRIPT
-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
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.
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.
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
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
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
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