Secondary metabolite (pharacognosy notes)

Secondary metabolite (pharacognosy notes)

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  Secondary Metabolites (Pharmacognosy) RAJAT SRIVASTAVA AssistantProfessor ARK College of Pharmacy Kaushambi, UP
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  Occurrence: It widelydistributed in higher plants particularly dicotyledons families like Apocynaceae, Rubiaceae, Rutaceae, Papaveraceae, Solanaceae, Papilionaceae. Distribution:  Leaves: Belladona, Datura  Roots and Rhizome: Rauwolfia, Ipecac, Ashwagandha  Bark: Cinchona  Seeds: Nux-vomica, coca  Whole plant: Vinca  Fungus: Ergot  Latex: Opium Function:  It may act as plant stimulants and regulators.  It may act as reservoir for protein synthesis.  It acts as reserve substance to supply nitrogen.  It acts as poisonous substance which affords plant safety from herbivores and insects.  It is an end products of detoxification mechanism, otherwise can cause damage to plants. Alkaloids  The term alkaloid was coined by Messiner a Geraman pharmacist in 1819. The term alkaloid is derived from word alkali like  Alkaloids are physiologially active compound of natural origin, in which one or more nitrogen atom is present in heterocyclic ring. Alkaloids True Alkaloid Proto/Amino Pseudo Alkaloids Ex. Steroidal, Terpenoidal Alkaloids Contain heterocyclic nitrogen Simple amines Not derived from amino acids but from acyl CoA units Ex. Caffeine
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  Physical Properties:  Alkaloidsalts are soluble in polar solvents & insoluble in organic solvents, while all alkaloid bases are soluble in organic solvents & insoluble in polar solvents.  Bitter in taste  Colorless, crystalline solid compound but some are liquid in nature Ex. Nicotine, Coniine,  Few alkaloids are colored. Ex. Berberine is yellow in color. Chemical Properties:  Due to basic nature alkaloid generally exist in plant as salt of organic acid, oxallic acid, citric acid, tartaric acid, tannic acid  Some alkaloid like narceine and nicotine are free in nature.  Few alkaloids are also occurring as glycoside of sugar like glucose, rhamnose, galactose.  Most of alkaloids contain one or more nitrogen atom in tertiary state in a ring system. Chemical test for alkaloids: 1. Dragendroff’s test: Dragendroff’s reagents (Potassium bismuth iodide solution) + Alkaloid drugs ↓ Reddish brown precipitate 2. Hager’s test: Hager reagent (Solution of picric acid) + Allaloid drugs ↓ Yellow precipitate 3. Mayer’s test: Mayer’s reagents (Potassium mercuric iodide solution) + Alkaloid drugs ↓ Cream precipitate 4. Wagner’s test: Wagner’s reagents (Iodine potassium iodide solution) + Alkaloid drugs ↓ Reddish brown precipitate Extraction & Isolation: Isolation of alkaloid are depend on alkaline nature & ability of formation of salts. Following are general steps involved in alkaloid extraction- 1. Sample preparation: Prepare coarse powder of crude drugs 2. Liberation of free alkaloid bases: Free bases are moist with alkali like KOH, NaOH, etc.
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  3. Extraction ofalkaloidal bases: Extract alkali, treated dried powder, ether with water miscible solvents or water immiscible solvents. 4. Purification of crude alkaloidal extract: To the above extract add acid to precipitate required alkaloid in form of salts. 5. Fractionation of crude alkaloid: Purify alkaloidal salts by fractional distillation, crystallisation, derivitization and or salt formation. Chromatographic analysis by TLC: Stationary phase- Silica gel-G Mobile phase- Toluene: ethylacetate: diethylamine (70:20:10) Detection- Spray with dragendroff’s reagents→ Reddish brown precipitate
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  General Method
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  Classification: Alkaloid classifiedin following categories- 1. Biosynthetic classification: The drugs are classified according to their biosynthesis. Ex.- a. Indole alkaloid derived from tryptophan b. Piperidine alkaloid derived from lysine c. Imidazole alkaloid derived from histidine d. Isoquinoline alkaloid derived from tyrosine, etc. 2. Pharmacological classification: The drug classified according to their pharmacological action. Ex.- Pharmacological Action Drug Analgesic Morphine Antimalerial Quinine Bronchodialator Ephedra Anticancer Vinca 3. Taxonomical classification: This classification is done according to their texa. Ex.- a. Solanaceae alkaloid (Tropane alkaloid)- Datura, belladona, Hyoscymus, etc b. Rubiaceae alkaloid- Cinchona c. Papilioaceae alkaloid- Pyrrolidine alkaloid 4. Chemical classification: The main criteria for this classification are type of fundamental ring structure present in alkaloid. They are broadly categorized as- a. Heterocyclic alkaloid (True alkaloid): Divided into group according to nature of their heterocyclic ring. b. Non-heterocyclic alkaloid: Proto alkaloid & biological amines.
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  Tannins  Tannins arenaturally occurring non-nitrogenous compound. They belong to water soluble polyphenols with high molecular weight ranging from 500 to 30000, up to 20,000.  The term tannin is coined by Sexuin in 1796. They have number of hydroxyls & carboxyl to form strong complexes with various macromolecules.  Tannins are widely distributed in many higher plant species such as aceraceae, combretaceae families. They occur normally in the roots, woods, bark, leaves and fruits of many plants. Physical properties: 1. Tannins are dark brown or reddish brown. 2. They are amorphous, non-crystalline in nature. 3. They are available in the form of powder, flakes or spongy mass. 4. They are water, alkali & alcohol soluble but sparingly soluble in chloroform & other organic solvents. 5. They form colloidal solution with water. 6. They form protective coating in place of wound injury. 7. They have astringent taste. Chemical properties: 1. Tannins are precipitated with proteins, gelatin, alkaloid, etc. 2. They have antioxidant properties due to presence of polyhydroxy phenolic compounds. 3. They have astringent properties due to formation of precipitation with proteins. 4. They yield purple, violet & black precipitate with iron compounds. 5. They react with potassium ferricynide in presence of ammonia to form deep red color solution. 6. They are precipitated by metallic salt like potassium dichromate & lead acetate. 7. They are used in the clarification of wine and bear. Classification: 1. Hydrolysable tannins: These tannins are basically esters of sugar mainly glucose with one or more trihydroxybenzene carboxylic acid. These tannins are hydrolyzed by acids or enzymes. Their structure composed with several polyphenolic acid molecules such as garllic acid and ellagic acid.  Ellagic acid is found in clove, rhubarb  Garllic acid is found in eucalyptus leaves, myrobalan & pomegranate bark.  Hydrolysable tannins are also known as pyrogallol tannins as the components of phenolic acid on dry distillation, converts pyrogallols & phenolic compounds. Ex. Myrobalan, Bahera, Amla, Arjuna, etc.
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  2. Condensed tannins:These tannins are resistant to hydrolysis (do not contain sugar moiety) & they are derived from flavonols, catechins & flavan- 3, 4-diols. On treatment with acids or enzymes they are decomposed into phlobaphenes. On dry distillation they produce catechol hence they are called as catechol tannins. These tannins are found in cinchona bark, male fern, wild cherry bark, black catechu, pale catechu, ashoka, petrocarpus, etc. They produce brownish green color with ferric chlorides. 3. Complex tannins: They are the group of tannins that biosynthesized from both hydrolysable tannin & condensed tannin. Ex. Tea, oak. 4. Pseudo tannins: They are sub group of tannins because they do not response gold beater’s test. They have low molecular weight compound. They are simple phenolic compound. They are found mainly in catechu & nux-vomica. Ex. Chlorogenic acid in coffee & nux-vomica, Ipecacuanhic acid in ipecac and catechins in cocoa. Chemical test: 1. Gelatin test: Solution of tannin + Solution of gelatin + Sodium chloride ↓ White buff colored precipitate formed 2. Gold beater’s skin test: A small piece of gold beater skin (membrane prepared from intestine of an ox) is soaked in 20% HCL, rinsed with distilled water & placed in a solution of tannin for 5 minute. Skin piece is washed with distilled water & kept in a solution of ferrous sulphate ↓ Black or brown color is produced on skin due to presence of tannin 3. Phenazone test: A mixture of aqueous extract of a drug & sodium acid phosphate is heated then cool & filtered. A solution of phenazone is added to the filtrate. ↓ Bulky colored precipitate is formed. 4. Match stick test: A matchstick is dipped in aqueous plant extract, dried near burner & moistened with conc. HCL. On warming near flame ↓ Matchstick wood turns pink or red due to formation of phloroglucinol 5. Chlorogenic acid test: An extract of chlorogenic acid containing drug is treated with aq. Ammonia ↓ A green color is formed on exposure to air.
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  6. Vanillin hydrochloricacid test: Sample solution + vanillin HCL (Vanillin 1gm, alcohol 10ml, Conc. HCL 10ml) ↓ Pink or red color is fromed due to formation of phloroglucinol. Isolation:  Fresh or lyophilized drug containing tannins are extracted with water acetone mixture and filtered.  Filtrate is distillated to remove acetone and aqueous extract remaining is then extracted with dichloromethane to remove lipid and fats.  Aqueous extract is further extracted with ethyl acetate to separate demeric proanthocyanidine and gallotannins.  The remaining aqueous phase contains polymeric proanthcyanidine and high molecular weight gallotannins.  Further, desired compounds are separated by appropriate chromatographic technique. Functions:  Used as antidotes, antiseptics, astringent.  Used in Ink manufacturing industries  Used as preservative  Used for vegetable tanning  Used treatment for burn, ulcers, inflammation  Used for treatment of hemorrhoids
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  Flavonoids  Flavonoids arepolyphenolic compound and vastly available in maximum plant tissue. They are generally in yellow colored pigments. They are larger group of glycoside. They are 2- phenylbenzopyrones derivatives & a produce a large number of physiological activities.  Flavonoids are the largest group of naturally occurring phenols & occur in free state in plant as glycoside.  They are largely found in polygonaceae, Rutaceae, Fabaceae & Rosaceae family. Physical properties:  They are crystalline substance with certain melting point.  Catechins, flavanes, Isoflavanes, flavanones, Flavanonols are colorless crystal, while flavones, flavonoles are yellow colored crystals.  Flavonoid glycosides are generally soluble in water & alcohol but insoluble in organic solvents.  Under U.V. light flavonoids shoes fluorescence of diff color. Chemical properties:  Chemically flavonoids are based upon a 15 carbon skeleton (C15) consisting of 2 benzene rings (A&B) linked via a heterocyclic pyrane ring.  They occur as aglycones, glycoside & methylated derivative.  Falavonoids are often hydroxylated at position 3, 5, 7, 2, 3’, 4’, 5’.  Glycosidic linkage is normally located in flavonoid at position 3 or 7. Classification: Flavonoids Based on groups Flavone Flavonol Flavanol Flavanone Based on placeof β ring location True flavonoid Iso flavonoid Neo flavonoid
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  Isolation & extractionof flavonoids: Powered plant material Water extract Precipitate with tannins Supernatant liquid contain flavonoid Precipitate of sugar free flavonoids Acetate free flavonoids Digestion with hot water Treated with lead acetate Acidify with HCL & boiled Extracted with alcohol Functional crystallization
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  Chemical test: 1. Shinodatest: Alcoholic solution of flavones or flavanol treated with metallic magnesium (or zinc) and HCL ↓ Orange, red or violet color gives. 2. Lead sub acetate test: Small quantity of residue + lead sub acetate solution ↓ Yellow colored precipitate formed ↓ Addition of increasing amount of NaOH to residue ↓ Shows yellow coloration ↓ Decolonization after addition of acid. 3. Wilson’s test: Flavonoids forms complex with boric acid, which is not destroyed by addition of citric acid alcoholic solution (or oxalic acid). 4. Antimony pentachloride test: Alcoholic solution of sample + antimony pentachloride ↓ Solution produces violet or red color Function:  They act as powerful antioxidant like quercetin, xanthohumaol & isoxanthohumol.  They control the plant growth.  They inhibit and activate plant enzyme.  They having a role in biochemistry of reproduction.  They have fungicidal properties.  They protect plant from parasites attack.  They are the pigments of flowers that attract insects from pollination.  They are having sufficient therapeutics efficacy such as antiviral, antiallergic, antiplatelets, antitumor, anti-inflammatory, etc.
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  Glycosides  Glycoside maybe defined as the organic compound from plant & animal source which on hydrolysis (enzymatic/acidic) gives a sugar & non sugar moiety.  Sugar moiety is known as glycone part & non sugar moiety is known as aglycone part. Aglycone part is responsible for pharmacological action. Physical properties:  Glycosides are solid and amorphous powder.  They are colorless but some are colored.  They are water soluble but insoluble in organic solvents.  They are mostly bitter in taste.  They are odorless.  Non volatile in nature.  Many sugar containing glycoside are insoluble in water but soluble in alcohol.  They are hydrolyzed by acid/enzyme to form glycone & aglycone part.  Glycone part is water soluble where as aglycone part is alcohol soluble.  After hydrolysis they react with molish’s reagents Fehling’s test. Chemical properties:  Glycoside hydrolysis with acid it give sugar & non-sugar part. Classification: 1. Based on nature of linkage of glycon and aglycon part:  O-glycoside: Sugar is combined with alcoholic or phenolic function of aglycon. Ex. Digitoxin  N-glycoside: In these glycoside nitrogen of amino group (-NH2/-NH) is condensed with a sugar. Ex. Nucleotide  S-glycoside: This glycoside contains a sugar moiety attached to sulphur of the aglycon. Ex. Isothiocynate glycoside  C-glycoside: Condensation of a sugar directly to a carbon atom gives rise to C- glycoside. This glycoside not hydrolyzed with acids, alkali and enzymes. Ex. Aloine, cascaroside. 2. Based on nature of sugar moiety:  Glucoside: sugar portion is glucose.  Rhamnoside: Sugar portion is rhamnose.  Pentoside: sugar portion is pentose.  Fructoside: sugar portion is fructose.  Arabinoside: sugar portion is arabinose.
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  3. Based onnature of non sugar moiety:  Anthraquinone glycoside: Anthraquinone moiety is aglycone. Ex. Senna  Cardiac glycoside: Aglycon portion is steroid molecule. Ex. Digitalis  Saponin glycoside:  Cynogentic glycoside: Ex. White cherry bark  Isothiocynate glycoside: Ex. Black mustard  Flavonoid glycoside: Ex. Lemon, sweet orange  Coumarin glycoside: Ex. Celery fruit  Aldehyde glycoside: Ex. Vanilla pods  Phenol glycoside: Ex. Arbutin  Bitter glycoside: Ex. Chirata, gentian 4. Based on therapeutic nature:  Cardiac glycoside: Ex. Digitalis  Laxative glycoside: Ex. Senna  Anti-ulcer glycoside: Ex. Liquorice  Bitter glycoside: Ex. Quassia wood Extraction and Isolation:  The drug containing glycoside is finely powdered & subjected to successive extraction in a soxhlet apparatus with alcohol or suitable solvent.  After extraction, extract is collected and treated with lead acetate to precipitate tannins.  Filtered the solution and H2S gas is passed to the filtrate.  Precipitate of lead sulphide form, which is removed by filtration.  The filtrate is subjected to fractional crystallization, distillation or chromatography gives pure glycoside.  Further the molecular structure is determined by spectrophotometer, IR, NMR & mass spectroscopy. Chemical test: I. Test for general glycoside: Test A Few mg of powdered drug + sulphuric acid + 5% NaOH ↓ Added for neutralization ↓ Added Fehling’s A & B to the above mixture ↓ Red color produced
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  Test B Few mgof powdered drug is dissolved in sufficient amount of water to make solution ↓ Tested with Fehling’s A & B solution ↓ Red color produced, indicating presence of reducing sugar in drug. → Both red color in separate test tube are compared. If color of test A is more intense than test B. Then presence of glycoside is conformed. II. Test for anthraquinone glycoside:  Brontrager’s test: Powdered drug dissolved in dil. H2SO4 ↓ Mixture is boiled ↓ Filtered solution ↓ Filtrate is extracted with organic solvent like chloroform ↓ Chloroform layer is separated & ammonia is added ↓ Ammonia layer gives pink color →This test is performed for O-glycoside. Test is positive for senna.  Modified Brontrager’s test: Powder drug + dil. HCL + FeCl3 ↓ Filter the solution ↓ Filtrate is extracted with organic solvent like chloroform ↓ Chloroform layer is separated & ammonia is added ↓ Ammonia layer gives pink color →This test is performed for C-glycoside. Test is positive for aloe.
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  III. Test forcardiac glycoside:  Raymond test: Drug + few ml of 50% ethanols + 0.1 ml of 1% metadinitrobenzene solution ↓ Add 2-3 drops 20% NaOH ↓ Violet color appears  Lagal test: Drug + few ml of pyridine + 2 drops of nitropruside + 2 drops 20% NaOH ↓ Deep red color produced  Killer kilani test: Powder drug extracted with chloroform ↓ Add few ml of ferric sulphate & glacial acetic acid ↓ Add 2 drops of conc. H2SO4 ↓ Blue color develop due to deoxy sugar  Baljet test: Powered drug + sodium picrate reagent ↓ Yellow to orange color produce  Xanthydrol test: Crude drug + 0.1 – 5% of xanthydrol in glacial acetic acid containing 1% HCL ↓ Red color produced due to presence of 2-deoxy sugar  Antimony trichloride test: Solution of glycoside + solution of antimony trichloride + trichloro acetic acid ↓ Heat the mixture ↓ Appearance of blue or violet color due to presence of cardinolide
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  IV. Test forcynogenetic glycoside:  Sodium picrate test: Drug + dil. H2SO4 ↓ Add sodium picrate ↓ Red color is produced  Mercuric acetate test: Solution of drug + mercuric acetate ↓ Drug acetate & mercury separate out ↓ Confirm the presence of cynogenetic glycoside V. Test for saponin glycoside:  Foam test: Drug + water solution in test tube ↓ Shake ↓ Stable foam is formed  Haemolysis test: Drug extract or dry powder + few ml of blood ↓ Mix well & placed on a glass slide ↓ Haemolytic zone appear Function of glycoside: 1. In plant:  They convert toxic material into non toxic form.  They are the source of energy by storage of sugar.  They store harmful plant products such as phenol.  They regulate growth. Some glycosides have antibacterial activity so they protect plant from bacterial & other disease. 2. In animals:  Glycoside have wide group of chemical nature due to they are used as many therapeutics activities such as laxative, cardio protective, analgesic, local irritant, etc.  Sugar part in glycoside help in the solubilisation of non sugar parts for increasing bioavailability of drugs.
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   Phenolic glycosidesare used as urinary antiseptic effect.  Alcohol glycosides are used as analgesic, antipyretics and anti-inflammatory action.  Cardiac glycoside used for heart disease.  Biller substances have antimicrobial as well as antibiotic action.  Thiol glycosides are used as pain killer.  Antharquinone glycosides are used as laxative action.
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  Resins  The termresin is applied to more or less solid, amorphous products of complex chemical nature. These are amorphous mixture of essential oil, oxygenated products of terpenes and carboxylic acid.  Resins are produced in plants during normal growth or secreted as a result of injury to the plants.  Resin is the most specific use of term is a hydrocarbon secretion of many plants, particularly coniferous trees.  Other liquid compound found in plants or exuded by plants such as latex or mucilage are sometimes confused with resin but are not same. Functions:  Herbivores  Insecticides Physical properties:  They are hard, transparent or translucent brittle material.  They are more or less amorphous material but rarely crystallisable.  On being heated at relatively low temperature resins first get softened & ultimately melt down there by forming either an adhesive or sticky massive fluid without undergoing any sort of decomposition or volatilization.  On being heated in air in the presence of oxygen resins usually burn readily with a smoky flame by virtue of the presence of large number carbon atom in the structure.  Resins are heavier than water.  On being heated in closed container in absence of oxygen they undergo decomposition & very often give rise to empyreumatic products (i.e. product chiefly comprising of hydrocarbons).  They are practically insoluble in water but frequently soluble in ethanol, volatile oil, fixed oil, chloroform & ether. Chemical properties:  Resins are enriched with carbons, deprived of nitrogen & contain a few oxygen in their respective molecules.  Majority of them undergo slow atmospheric oxidation whereby their color gets darkened with impaired solubility.  Resins are found to be mixture of numerous compounds rather than a single pure chemical entity. Their chemical properties are based upon functional group present in these substances.
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   Resins maybe the final products in destructive metabolism. Many are believed to be the oxidation products of the terpenes.  The acidic resin is treated with alkaline solution they yield soap. Source of resins: 1. Natural sources: Resins are obtained from plant & animal are known as natural source resins. They are obtained in different parts of plant & by various methods depending on nature of resins. They are found inside plants are exuded by plants such as sap, latex or mucilage forms. Plant source resin: Ex. Asafoetida, myrrh, ginger, etc. Animal source resin: Ex. Shellac 2. Chemical resins: They are synthetic resins and are useful in various preparations like nailpolish. It is made up of organic compound. They are generally liquid monomer of thermosetting plastics. Ex. Acrylic phenolic resin, urea formaldehyde resin, etc. 3. Derived resins: They are transparent & translucent mass derivation of resins that are not produced directly from plant & animals. Ex. Rosin. It is prepared by solidified resin from which the volatile terpene components have been removed by distillation. It have vitreous fracture & finally yellow or brown color, having turpentine odor & taste. It is insoluble in water but soluble in alcohol & other organic solvents. Classification of resins: 1. Acid resins: They are mixture of carboxylic acids, found in tree. They have the basic skeleton of three fused ring. Acid resins are tacky, yellow gums that are water insoluble. They are used to produce soap. 2. Ester resins: They are resins in which esters groups are presents in basic structure of resins. Ex. benzyl benzoate in benzoin, cinnamyl cinnamte in styrax, etc. 3. Alcohol resins: High molecular weight alcoholic group are present in structure of resins. They sometime form complex & are found either in free state or as ester form. Ex. balsam of peru. 4. Resinols: They are the resins that give showing negative specific tannin reaction withy iron salts. They are of different types like benzo resinol (ex. benzoin), eto resinol (ex. styrax). 5. Glycoresins: They are the combination of resin & sugar. Ex. Jalap, Podophyllum 6. Resenes: They are the chemically inert substance & have no chemical properties. They do not undergo hydrolysis or any salt formation.
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  7. Oleo resins:A naturally occurring mixtures of essential oils & resins, extracted from various plants. They obtained by extraction with non aqueous solvent followed by removal of solvent by evaporation & by super critical fluid extraction. Ex. Ginger, capsicum 8. Oleo gum resins: It is solid plant exudation consisting of mixture of volatile oil, gum & resin. It has a nature that is partially soluble in water & alcohol. Ex. Asafoetida, myrrh, turmeric. 9. Balsams: They are also known as turpentine. They are resinous exudates or sap form certain kinds of trees & shrubs. They mainly contain cinnamic & benzoic acids. They are oily & odorless substances. Ex. balsam of Tolu, balsam of Peru Isolation:  It is difficult to isolate due to presence of various combinations.  Extraction with alcoholic solvents and then the subsequent precipitation by adding concentrated alcoholic extract to a large proportion of water.  Hydro distillation or distillation can be used for separation of volatile oil from resins. Chemical test: 1. Heat small amount of benzoin slowly in a dry test tube→ melts & white fumes are produced. 2. Benzoin when heated with potassium permagnate solution→ odor of benzaldehyde (Sumatra benzoin) 3. Benzoin is extracted with alcohol and to the extract adds water→ milky white solution is formed. 4. Powdered drug triturated with water→ yellowish emulsion is produced. 5. The drug is boiled with HCL for 5 minutes→ filtered→ ammonia is added to the filtrate→ a blue fluorescence is observed. 6. Drug is treated with few drops of 50% HNO3→ green color is produced. 7. Drug is treated with few drops of shulphuric acid→ red colors produced which change in violet on washing with water Uses of resins:  Use for paints, varnishes.  Used for perfumery preparation.  Used for pharmaceutical aids.  Used for expectorants, antiseptics, flavouring agents, carminative, stomachic.
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  Volatile oil  Plantsthat contain aromatic liquid (derived from shrubs, flowers trees, roots bushes, herbs & seeds) are known as volatile oil or essential oil.  These oils provide protection to the plants from insects, harsh environment condition & disease.  They are concentrating hydrophobic liquid contain volatile aroma & they are also known as ethereal oil, aetherolea or oil of plants.  Due to presence of essence, they are commonly known as essential oil. Types of volatile oil:  Alcohol volatile oil: ex. Menthol (Mentha), Santol (Sandal wood), Coriandrol (Coriander)  Aldehyde volatile oil: ex. Cinnamaldehyde (Cinnamon), Citral  Ester volatile oil: ex. Lavender, Mustard  Hydrocarbon volatile oil: ex. Turpentine, Caryophyllene  Ketone volatile oil: ex. Carvone (Caraway), Camphor, Menthone  Oxide volatile oil: ex. Ascaridole (Chenopodium oil), Cineol (Eucalyptus oil)  Phenolic ether volatile oil: ex. Chavicol (Anise), Anethol (Dill)  Phenol volatile oil: ex. Eugenol (clove) Terpenes & Terpenoids  The abundant distributed compounds that present in essential oil are terpenes and sesqueterpenes & also oxygenated compounds.  Terpens → hydrocarbon which has basic simple isoprene (C5H8) molecule.  Terpenoids are a compound having same features like terpene structure.  Terpenes are diverse group of organic hydrocarbons produced by a wide variety of plants.  They are important for certain odors, harmones, vitamins, pigments, steroids, resins, essential oils, etc.  They are naturally released from plants when temperature is high. They interact with each other for different smells & effects.
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   Terpenoids arealso known as isoprenoids. They are large & diverse class of naturally occurring organic chemicals similar to terpenes.  Terpenoids derived from five carbon nits assembled & modified in various ways.  Terpenoids are classified according to the number of isoprene units as well as classified according to number of cyclic structure present in structure. Classification: Isoprene unit Carbon atom Classification Example 1 5 Hemiterpene Isoprene, Prenol 2 10 Monoterpene Limonene, Pinene 3 15 Sesquiterpene Farresnol 4 20 Diterpene Retinol 5 25 Sesterpene Rare compounds 6 30 Triterpene Squalene 8 40 Tetretrpene β carotin >8 >40 polyterpene Rubber Distribution: widely distributed in certain plant family, ex. Pinaceae, Lauraceae, Rutaceae, Myrtacese, Umbelliferae, Labiatae and Composite. Occurrence:  Mono & Sesquiterpenoids: These are essential oils obtained from sap and tissue of certain plants & trees; are volatile & account for fragrance.
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   Di &Tritrepenoids: They are obtained from plant & tree gum & resins.  Tetra terpenoids: It form a group of compounds known as carotenoids; carotene, xanthophyllus, carotenoidic acid.  Polyterpenoids: Rubber Properties:  Most of terpenoids are colorless or pale yellow liquid. They are lighter than water & boiled between 150 & 180℃.  They are insoluble in water but soluble in organic solvents. Many of essential oil are optically active.  They undergo polymerization & dehydrogenation in ring.  They are very easily oxidized by all the oxidizing agents due to presence of olefin bond.  They readily isomerize in the presence of acids into more stable forms.  On thermal decomposition they yield isoprene as one of the products. Extraction methods for volatile oil: 1. Water distillation: plant material placed into still, water added & vessel fire heated water & oil distilled together & gets condensed. Oil & water layer separated subsequently. 2. Water & steam distillation: water distillation is employed for either dried or fresh substance that may be injured by boiling. In the case of dried material the drug is placed at ground & then covered with layer of water. Steam is passed through macerated mixture. The oily layer of the condensed distillate is separated from aqueous layer & oil can be marked with or without processing. 3. Steam distillation: It is applicable to fresh material. Fresh material is cut & supported on grid & saturated stem is injected directly into metal distillation tank. So those plant materials do not come directly in contact with water. Stem is forced through the fresh herb & carries oil droplets through vapor pipe attached at top of tank to the condensing chamber. 4. Expression (Ecuelle method): some volatile oil cannot be distilled without decomposition is usually obtained from expression method. It involves puncturing of oil glands by sharp projection that are long enough to penetrate epidermis & pierce the oil glands located in outer portion of peel. A pressing action on fruit removes oil from glands & fine spray of water washes the oil from mashed peel. Resulting oil water emulsion is se0perated by centrifugation. 5. Enfleurage method: fat is taken in glass plates is warmed to about 50℃ then its surface is covered with the petals & allowed to kept for severa days. Until the fat is saturated with the essential oil for which old petals may be replaced by fresh ones. Petals are removed and &
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  fat is saturatedwith the essential oil for which the old petals may be replaced by fresh. Petals are then removed & fat is digested with ethyl alcohol & if some fat is also dissolved during digestion it is removed by cooling at 20℃. Extract having ethyl alcohol & essential oil is ditiled under reduced pressure to remove solvents. General chemical test (volatile oil):  To the thin section of the drug, add alcoholic solution of sudan III. Red color obtained by globules indicates the presence of volatile oil.  To the thin section of the drug, add a drop of tincture alkana. Red color indicates the presence of volatile oil.  Most of volatile oils are soluble in (90% ethanol) organic solvents.  Volatile oil does not leave any translucent spot on filter paper when applied, but fixed oil leaves greasy spot on the paper. Applications:  Used in pharmaceutical preparations.  Used in dental preparation (tooth paste, tooth powder, mouthwashes).  Used in food beverages as flavouring agent.  Used in tobacco industries.  Used in paint industry (paint, varnish).  Used in petroleum industry (lubricant, oil, wax). Pharamcognosy Notes (D.Pharma & B. Pharma) Prepared by:- Rajat Srivastava Asst. Professor ARK College of Pharmacy, Kaushambi