RESINS AND RESIN COMBINATIONS

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