resins and resin combinations
TRANSCRIPT
DEFINITION Resins are solid or semi-solid, amorphous products
derived from natural living sources and are mostly from the plant origin (exception is shellac that is obtained from the secretions of insect)
Resins are secondary metabolites produced by higher plants and are nothing but oxidative products of terpenes
Obtained as exudates from plants and considered as end product of metabolism
Solid or semi-solid amorphous products of complex chemical nature
PROPERTIES Complex mixtures of several compounds
however isoprene (C5H8) units are the fundamental building blocks of all true resins
Non-crystallizable translucent masses Soften and melt on heating Burns with smoky flames on ignition Having a specific gravity that ranges from
0.9-1.25 Contain a large number of carbon atoms
PROPERTIES The thin film of resin on drying becomes hard
and transparent which is unaffected by moisture and air
Are usually found in homogenous combination with other plant metabolites and hence, collectively known as resin combinations
Practically insoluble in water, but frequently soluble in ethanol, volatile oils, fixed oils, chloral hydrate and non-polar organic solvents (benzene, n-hexane and petroleum ether.
PROPERTIES Regarded as the end products of
destructive metabolism Majority of them undergo slow
atmospheric oxidation whereby their color gets dark with impaired solubility
Acidic resins when treated with alkaline solutions they yield soaps (or resin-soaps)
DISTRIBUTION Resins are generally distributed in plants and
rarely in the insects (e.g. Shellac) They are present in the ducts or cavities
known as schizolysigenous ducts 2 types:
Normal or physiological resin: resins that are preformed in the plants and making injury to the plants can increase their yield (resin of Pinus)
Abnormal or pathological resin: resins that are found in the plants inly when injury or incision is made (benzoin, Tolu balsam)
OCCURENCE Usually occur in different secretory zones
or structures. Examples: Resin cells
Ginger Schizogenous ducts or Shizolysigenous
ducts or cavities Pine wood
Glandular hairs Cannabis
CLASSIFICATION On the basis of their formation
A. Physiological resins – these are formed as a normal product of metabolism without making injury to the plants
B. Pathological Resins – formed as a result of wound, injury or abnormal circumstances (benzoin, colophony, balsams, aloe resin etc.)
CLASSIFICATION On the basis of chemical nature
A. Resin acids – resinolic acidsB. Resin alcohols – resinolsC. Resin phenols – resinotannolsD. Ester resinsE. Resenes
CLASSIFICATION On the basis of occurrence with other secondary
metabolitesA. Oleoresins – naturally occurring mixtures of a
volatile oil and a resinB. Gum resins – resin associated with gumC. Oleo-gum resins – a naturally occurring mix of
volatile oil, gums/mucilagenous compound with a resin
D. Glycoresins – resins in combination with sugar compounds via Glycosidal linkages
E. Balsams – resins in combination with benzoic or cinnamic acid either free or combined
ISOLATION OF RESINS By extracting the drug with alcohol and
precipitating resins present in concentrated extract by addition of large proportion of water (e.g. Jalap, Ipomea, Podophyllum)
By distillation for separation of oils (e.g. Copaiba, Colophony)
By heating the plant parts (e.g. Guacum) As plant exudates my making incision (e.g.
Myrrh, Asafoetida, Balsams)
ISOLATION OF RESINS By collecting fossil resins (e.g. Copal,
Kaury) By processing the incrustations* (e.g.
Shellac) *In some exceptionally rare instances,
the resin occurs as a result of sucking the juice of the plants by scale insects and converting the sucked juice into the resinous substance that ultimately covers the insect itself and twigs of the plant (e.g. Laccifer lacca)
EXTRACTION or ISOLATION methods
Method – APowdered drug
1. Extract the resin with alcohol2. Filter3. Concentrate
Concentrate extract an excess of water, shake
Resins get precipitate
EXTRACTION or ISOLATION methods
Method – BPowdered drug containing oleo-resin, percolate the powdered drug with non-polar solvent (e.g. acetone, chloroform)
Non-polar solvent
Steam distillation Oleo-resinVolatile oils (e.g. Rosin)
IDENTIFICATION TEST 3 types: Physical test
Such as solubility, taste, odor and examination of powder under the microscope
Chemical test – for the identification of resins Acid value Saponification value Iodine value
Specific chemical test – for specific constituents such as Cinnamic acid, Benzoic acid in Benzoin, Tolu balsam and Peru Balsam
CHEMICAL TESTSIDENTIFICATI
ON TESTREAGENTS
USEDPOSITIVE RESULT
COMPOUNDS POSITIVE FOR
THE TEST
HCl TEST HCl Formation of pink color
Presence of resins
FeCl3 TEST Fecl3 Greenish blue color
Presence of resins
Combined Umbelliferone Test(Specific test for Asafoetida)
HCl + conc. NH4OHNitric acidSulfuric acidWashed with water
Blue fluorescenceGreen colorRed colorViolet
Umbelliferone
Copper Acetate test
Petroleum ether Emerald green Abietic acid
CHEMICAL TESTSIDENTIFICATI
ON TESTREAGENTS
USEDPOSITIVE RESULT
COMPOUNDS POSITIVE FOR
THE TEST
Test for Aspidium(Oleoresin)
Diluted alcohol sol’n + FeCl3
GREEN color Filmarone, flavaspidinol, flavaspidic acid
Test for Myrrh(Oleo-gum-resin)
Ether + HNO3Br2 vapor
PURPLISH VIOLETVIOLET
Commiphoric acid
Test for Benzoin(Balsam)
Sumatra benzoin:KMnO4
Petroleum ether solution + H2SO4
faint odor of Benzaldehyde REDDISH BROWN color
Cinnamic acid
CHEMICAL TESTSIDENTIFICATI
ON TESTREAGENTS
USEDPOSITIVE RESULT
COMPOUNDS POSITIVE FOR
THE TESTSiam benzoin:Alc Ext + Alcoholic FeCl3Petroleum ether solution + H2SO4
GREEN color
PURPLE-RED color
Coniferyl benzoate-tannins
Test for Balsam of Tolu
FeCl3
KMnO4
GREEN color
Odor of Benzaldehyde
Cinnamic and benzoic acids (resinotannol)Cinnamic acid
PHARMACEUTICAL APPLICATION Resins are local irritant and hence act as
local cathartics (e.g. Jalap and Ipomea) As anti cancer (Podophyllum) In bronchial asthma (e.g. Cannabis) Used externally as mild antiseptic in the
form of tinctures (Benzoin), ointment and plasters (Turpentine and Colophony)
Used in the preparation of emulsion and sustained released formulations
References: Pharmacognosy Part I: Rumit M. Shah,
Rupesh T. Nayak and Heena K. Kathad. 1st ed. New Delhi, Global Vision Publishing House.
Trease and Evans' Pharmacognosy, 16th Edition. William Charles Evans, BPharm, BSc, PhD, DSc, FIBiol, FLS, FRPharmS. University of Nottingham, Nottingham, UK
http://www.epharmacognosy.com/2012/05/resins-and-resin-combinations.html