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PHYTOCONSTITUENTS Presented by BAHADUR SINGH HOD Department of Pharm. Sciences Govt. Polytechnic college for Girls Patiala.

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1 PHYTOCONSTITUENTS Presented by BAHADUR SINGH HOD Department of Pharm. Sciences Govt. Polytechnic college for Girls Patiala

2 PHYTOCONSTITUENTS: Crude drugs are subjected to a suitable method of extraction for the isolation of Phyto pharmaceuticals/ Phyto constituents known as Active Constituents of the Drugs. These are Biosynthesis: Conversion of Simple chemical substances into complex substances with the help of Enzymes. Main group of Phytoconstituents of therapeutic importance are: Alkaloids, Glycosides, Terpenoids, Steroids, carbohydrates, Flavonoids fixed oils etc.

3 Alkaloids Definition: the term “alkaloid” (alkali- like) is commonly used to designate basic heterocyclic nitrogenous compounds of plant origin that are physiologically active.

4 Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and more rarely other elements such as chlorine, bromine, andphosphoruschemical compoundsbasicnitrogenacidiccarbonhydrogennitrogenoxygensulfurchlorinebrominephosphorus

5 The name "alkaloids" (German: Alkaloide) was introduced in 1819 by the German chemist Carl F.W. Meissner, and is derived from late Latin root Latin: alkali (which, in turn, comes from the Arabic al-qalwī – "ashes of plants") and the suffix Greek: -οειδής – "like" However, the term came into wide use only after the publication of a review article by O. Jacobsen in the chemical dictionary of Albert Ladenburg in the 1880s.GermanLatinGreekAlbert Ladenburg

6 History Friedrich Sertürner, the German chemist who first isolated morphine from opium. Studies of alkaloids began in the 19th century. In 1804, the German chemist Friedrich Sertürner isolated from opium a "soporific principle" (Latin: principium somniferum), which he called "morphium" in honor of Morpheus, the Greek god of dreams; in German and some other Central-European languages, this is still the name of the drug. The term "morphine", used in English and French, was given by the French physicist Joseph Louis Friedrich SertürnermorphineopiumFriedrich SertürnerLatinMorpheusGreekJoseph Louis

7 A significant contribution to the chemistry of alkaloids in the early years of its development was made by the French researchers Pierre Joseph Pelletier and Joseph Bienaimé Caventou, who discovered quinine (1820) and strychnine (1818). Several other alkaloids were discovered around that time, including xanthine(1817), atropine (1819), caffeine (1820 ), coniine (1827), nicotine (1828), colchicine (1833), spart eine (1851), and cocaine (1860 The first complete synthesis of an alkaloid was achieved in 1886 by the German chemist Albert LadenburgPierre Joseph PelletierJoseph Bienaimé Caventouquininestrychninexanthineatropinecaffeineconiinenicotinecolchicinespart einecocaineAlbert Ladenburg

8 Alkaloid Description Contains nitrogen - usually derived from an amino acid. Bitter tasting, generally white solids (exception - nicotine is a brown liquid). They give a precipitate with heavy metal iodides. – Caffeine, a purine derivative, does not precipitate like most alkaloids. Alkaloids are basic - they form water soluble salts. Most alkaloids are well-defined crystalline substances which unite with acids to form salts. In plants, they may exist – in the free state, – as salts or – as N-oxides. Occur in a limited number of plants. Nucleic acid exists in all plants, whereas, morphine exists in only one plant species.

9 Deviation from Definition: Basicity: Some alkaloids are not basic e.g. Colchicine, Piperine, Quaternary alkaloids. Nitrogen: The nitrogen in some alkaloids is not in a heterocyclic ring e.g. Ephedrine, Colchicine, Mescaline. Plant Origin: Some alkaloids are derived from Bacteria, Fungi, Insects, Frogs, Animals.

10 Classification: True (Typical) alkaloids that are derived from amino acids and have nitrogen in a heterocyclic ring. e.g Atropine Proto alkaloids that are derived from amino acids and do not have nitrogen in a heterocyclic ring. e.g Ephedrine Pseudo alkaloids that are not derived from amino acids but have nitrogen in a heterocyclic ring. e.g Caffeine False alkaloids are non alkaloids give false positive reaction with alkaloidal reagents.

11 Common amino acid precursors: – Phenylalanine – Tyrosine – Tryptophan – Histidine – Anthranilic acid – Lysine – Ornithine Important general reactions involved: – Decarboxylation The process of removing a carboxyl group from a chemical compound – Transamination The process of transposing an amino group within a chemical compound

12 Distribution and occurrence: Rare in lower plants. Dicots are more rich in alkaloids than Monocots. Families rich in Alkaloids: Apocynaceae, Rubiaceae, Solanaceae and Papaveracea. Families free from Alkaloids: Rosaceae, Labiatae

13 Distribution in Plant: All Parts e.g. Datura. Barks e.g. Cinchona Seeds e.g. Nux vomica Roots e.g. Aconite Fruits e.g. Black pepper Leaves e.g. Tobacco Latex e.g. Opium

14 Forms of Alkaloids: Free bases Salts with Organic acids e.g. Oxalic, acetic acids Salts with inorganic acids e.g. HCl, H 2 SO 4. Salts with special acids: e.g. Meconic acid in Opium Quinic acid in Cinchona Glycosidal form e.g. Solanine in Solanum.

15 Function in Plants They may act as protective against insects and herbivores due to their bitterness and toxicity. They are, in certain cases, the final products of detoxification (waste products). Source of nitrogen in case of nitrogen deficiency. They, sometimes, act as growth regulators in certain metabolic systems. They may be utilized as a source of energy in case of deficiency in carbon dioxide assimilation.

16 Nomenclature: Trivial names should end by "ine". These names may refer to: The genus of the plant, such as Atropine from Atropa belladona. The plant species, such as Cocaine from Erythroxylon coca. The common name of the drug, such as Ergotamine from ergot. The name of the discoverer, such as Pelletierine that was discovered by Pelletier. The physiological action, such as Emetine that acts as emetic, Morphine acts as narcotic. A prominent physical character, such as Hygrine that is hygroscopic.

17 Prefixes and suffixes: Prefixes: "Nor-" designates N-demethylation or N- demethoxylation, e.g. norpseudoephedrine and nornicotine. "Apo-" designates dehydration e.g. apomorphine. "Iso-, pseudo-, neo-, and epi-" indicate different types of isomers. Suffixes: "-dine" designates isomerism as quinidine and cinchonidine. "-ine" indicates, in case of ergot alkaloids, a lower pharmacological activity e.g. ergotaminine is less potent than ergotamine.

18 Physical Properties: I- Condition: Most alkaloids are crystalline solids. Few alkaloids are amorphous solids e.g. emetine. Some are liquids that are either: Volatile e.g. nicotine and coniine, or Non-volatile e.g. pilocarpine and hyoscine. II- Color: The majority of alkaloids are colorless but some are colored e.g.: Colchicine and berberine are yellow. Canadine is orange. The salts of sanguinarine are copper-red.

19 Physical Properties: III- Solubility: Both alkaloidal bases and their salts are soluble in alcohol. Generally, the bases are soluble in organic solvents and insoluble in water Exceptions: Bases soluble in water: caffeine, ephedrine, codeine, colchicine, pilocarpine and quaternary ammonium bases. Bases insoluble or sparingly soluble in certain organic solvents: morphine in ether, theobromine and theophylline in benzene. Salts are usually soluble in water and, insoluble or sparingly soluble in organic solvents. Exceptions: Salts insoluble in water: quinine monosulphate. Salts soluble in organic solvents: lobeline and apoatropine hydrochlorides are soluble in chloroform.

20 IV- Isomerization: Optically active isomers may show different physiological activities. l-ephedrine is 3.5 times more active than d- ephedrine. l-ergotamine is 3-4 times more active than d- ergotamine. d- Tubocurarine is more active than the corresponding l- form. Quinine (l-form) is antimalarial and its d- isomer quinidine is antiarrythmic. The racemic (optically inactive) dl-atropine is physiologically active.

21 Chemical Properties: I- Nitrogen: Primary amines R-NH 2 e.g. Norephedrine Secondary amines R 2 -NH e.g. Ephedrine Tertiary amines R 3 -N e.g. Atropine Quaternary ammonium salts R 4 -N e.g d-Tubocurarine II- Basicity: R 2 -NH > R-NH 2 > R 3 -N Saturated hexacyclic amines is more basic than aromatic amines.

22 According to basicity Alkaloids are classified into: Weak bases e.g. Caffeine Strong bases e.g. Atropine Amphoteric * Phenolic Alkaloids e.g. Morphine *Alkaloids with Carboxylic groups e.g. Narceine Neutral alkaloids e.g. Colchicine

23 III- Oxygen : Most alkaloids contain Oxygen and are solid in nature e.g. Atropine. Some alkaloids are free from Oxygen and are mostly liquids e.g. Nicotine, Coniine.

24 IV- Stability: Effect of heat: Alkaloids are decomposed by heat, except Strychnine and caffeine (sublimable). Reaction with acids: 1- Salt formation. 2- Dil acids hydrolyze Ester Alkaloids e.g. Atropine

25 3- Conc. acids may cause: Dehydration: Atropine → Apoatropine Morphine → Apomorphine Demethoxylation: e.g. Codeine

26 Effect of Alkalies: 1- Dil alkalis liberate most alkaloids from their salts e.g. NH3. 2- They may cause isomerization (racemization) of alkaloid as the conversion of hyoscyamine to atropine. 3- They also can form salts with alkaloids containing a carboxylic group e.g. narceine. 4- Strong alkalis: such as aqueous NaOH and KOH form salts with phenolic alkaloids. 5- Strong alkalis cause hydrolysis of Ester alkaloids (e.g. atropine, cocaine and physostigmine) and Amide alkaloids ( colchicines). 6- Strong alkalis cause opening of lactone ring

27 Effect of light and Oxygen: Some alkaloids are unstable when exposed to light and Oxygen:

28 Qualitative test for Alkaloids: Precipitation Reagents: They are used to: 1- Indicate the absence or presence of Alkaloids 2- Test for complete of extraction Disadvantages: Some non alkaloids interfere such as Proteins, lactones, coumarins

29  Classification of Alkaloids Biogenetic. Based on the biogenetic pathway that form the alkaloids. Botanical Source. According to the plant source of alkaloids. Type of Amines. Primary, Secondary, Tertiary alkaloids. Basic Chemical Skeleton

30

31 Piperidine/Pyridine alkaloids

32 Pyridine Alkaloids Also referred to as Pyrrolizidine alkaloids Include Lobeline (Lobelia herb) – respiratory stimulant  Used in asthma preparations. Nicotine (Nicotiana tabacum and other Nicotina spp) – toxic  used as an insecticide Lobeline

33 Lobelia inflata- Capmanulaceae Definition: Lobelia herb consists of the dried aerial parts of Lobelia inflata. Common Names: Lobelia, Indian Tobacco) History: Traditionally used by the Native Americans for asthma.

34 Lobelia inflata – Constituents Contains Pyrrolizidine Alkaloids Most important Lobeline Also Lobelidine Lobelanine Isolobelanine

35 contain imidazole (glyoxaline) rings PILOCARPINE PILOCARPUS – jaborandi – Consists of leaflets of: Pilocarpus jaborandi Holmes Pilocarpus microphyllus Stapf Pilocarpus pinatifolius Lamaire Indigenous to Brazil IMIDAZOLE ALKALOIDS

36 Uses: Ophthalmic drugs for treatment of galucoma Applied topically Dosage: mL of a 0.25 to 10% solution of Pilocarpine hyrdochloride OR mL of a 0.5 to 6% solution of Pilocarpine nitrate Applied to the conjunctiva, 1-6x a day  Patients should be advised to wash hands immediately after application.

37 Isopto-carpine® Pilocar®

38 Tropane alkaloids Many of these psychoactive alkaloids

39 Tropane Alkaloids Derived from tropine and consist of mandelic, tropic or benzoic acid esters of tropine. Are very closely related to each other All have pronounced physiological actions. Natural alkaloids include Hyoscyamine Hyoscine Atropine Cocaine The above mentioned alkaloids occur within the Solanaceae family (except cocaine – from Erythroxylaceae family)

40 Atropine Hyoscine

41 Datura stramonium - Solanaceae Definition: Stramonium Leaf consists of the dried leaves or dried leaves and flowering tops of Datura stramonium. The drug should contain at least 0.25% alkaloids calculated as hyoscyamine. Common names: Stramonium leaf, Thornapple, Jimson or Jamestown weed

42 Hyoscyamus niger – Allied Drugs Hyoscyamus albus (petiolate stem-leaves and pale yellow, non-veined petals – bottom left). Hyosycamus muticus (top right) Hyoscyamus pusillus Hyoscyamus aureus Hyoscyamus reticulatus (Indian henbane – bottom right)

43 Atropa belladonna - Solanaceae Definition: Belladonna herb consists of the dried leaves and flowering tops of Atropa belladonna, containing at least 0.3% alkaloids (hyoscyamine). Should not contain >3% stem >5mm in diameter. USP also allows A. acuminata in the Belladonna Leaf monograph.

44 Quinoline alkaloids

45 Quinoline Alkaloids Consist of alkaloids and alkaloid salts obtained from the bark of certain Cinchona species (Quinine, Quinidine, Cinchonine, Cinchonidine). The amount of alkaloids present depend on the species, environment of the tree, age, and method of bark collection. Quinine: Anti-malarial Synthetic alkaloids are now used as substitutes for quinine for malaria.

46 Cinchona Bark - Rubiaceae Definition: Cinchona bark consists of the various species races and hybrids of Cinchona, large trees indigenous to Colombia Equador, Peru & Bolivia INCLUDES C. Succirubra, C. calisaya, C. ledgeriana, C. officinalis

47 Cinchona Bark - Uses Bitter tonics Stomachics Used as gargles (tannins in bark – astringent) Malaria Prophylaxis of cardiac arrhythmias Treatment of atrial fibrillation

48 Isoquinoline alkaloids

49 Opium Alkaloids – Opium Definition: Opium (Raw Opium) is the latex obtained by incision from the unripe capsules of Papaver somniferum, from the Papaveraceae Family. It is dried partially by spontaneous evaporation and partly by artificial heat. Commercially known as Indian opium. BP monograph: opium is intended only as a starting point for the manufacture of galenicals, and should not be dispensed as such.

50 Papaver somniferum - Constituents 30 Alkaloids 6 main ones Morphine Codeine Thebaine Noscapine Narceine papaverine

51 Ipecac Alkaloids - Ipecacuanha Definition: Ipecacuanha (Ipecacuanha Root) is the dried root or rhizome and root of Cephaelis ipecacuanha of the Rubiaceae family. It should contain at least 2% alkaloids

52 Ipecacuanha Constituents Ipecac alkaloids (isoquinoline) alkaloids Mainly Emetine Psychotrine Cephaeline Also Emetamine Psychotrine methylether Ipecoside (glycoside)

53 Indole alkaloids Vindoline Vinblastine (Catharanthus)

54 Indole Alkaloids These are found in Ergot & Nux Vormica Ergot alkloids: based on lysergic acid (LSD – lysergic acid diethylamide) Nux Vormica: 2 important alkaloids: strychinine and brucine. Strychinine: CNS stimulant, lethal in large doses (uses as a poison )

55 1.Rauwolfia -reserpine -rescinamine -deserpidine 2. Catharanthus (vinca) -vinblastine -vincristine 3. Nux vomica -strychnine -brucine INDOLE ALKALOIDS 4. physostigma- physostigmine 5. Ergot -ergotamine -ergonovine

56 Ergot (Ergot of Rye) Defintion: Ergot (Ergot of Rye) is the dried sclerotium of a fungus, Claviceps purpurea, arising in the ovary of the rye, Secale cereale. Controlled field cultivation on rye is the main source of crude drug.

57 Catharanthus roseus or Vinca ( Sadabhar) Vinca alkaloids are used in the treatment of cancer. They are a class of cell-cycle-specific cytotoxic drugs that work by inhibiting the ability of cancer cells to divide: Acting upon tubulin, they prevent it from forming into microtubules, a necessary component for cellular division. Vinca alkaloids are now produced synthetically and used as drugs in cancer therapy and as immunosuppressive drugs. These compounds include vinblastine, vincristine, vindesine, and vinorelbine.microtubulescellular divisionvinblastinevincristinevindesinevinorelbine

58 Traditionally used in labour to assist the delivery Reduce post-partum haemorrhage Ergometrine produces oxyticic effects. Ergot - Uses

59 Nux Vormica - Constituents 2-5% Indole alkaloids Mainly Strychine Brucine Strychine is more physiological active than brucine

60 Rauwolfia serpentine - Apocynaceae Defintion: Rauwolfia consists of the dried rhizome and roots of Rauwolfia serpentiana. (a small shrub found in India, Pakistan, Java and Thailand). Common name: Rauwolfia, Indian Snakeroot

61 Rauwolfia - Constituents 30 Alkaloids Main alkaloid Reserpine Also Rauwolfine Serpentine Serpentinin e

62 Rauwolfia - Uses Essential Hypertension Malignant Hypertension Neuropsychiatric Disorders Cardiac arrhythmias Circulatory Disease

63 Quinolizidine alkaloids

64 Characterized by the cyclopentanophenanthrene nucleus either formed from cholesterol or have a common precursor with cholesterol VERATRUM VIRIDE AKA American hellebore or green hellebore Veratum: “vere” = truly, “ater” = black Viride = green Consists of the dried rhizome and roots of Veratum viride Alton STEROIDAL ALKALOIDS

65 Steroidal e.g. Solanum and Veratrum alkaloids cyclopentanophenanthrene ring

66 VERATRUM VIRIDE Grows in wet meadows in the mountainous section of New England and the Eastern United States, North Carolina, Tennessee, and northern Georgia Veratum: “vere” = truly, “ater” = black Obtained by: – digging the rhizomes – Cleaning – Cutting longitudinally – drying

67 Protoalkaloids Alkaloid-like amines. Have no nitrogen as part of the heterocyclic ring. Examples: ephedrine and adrenaline Both cause dilation of the bronchi (asthma), increase heart rate and peripheral vasoconstriction.

68 Ephedra - Constituents Alkaloids (protoalkaloids) Mainly Ephedrine Pseudoephidrine Also contains ephedradines – hypotensive properties

69 Ephedra - Uses Asthma, colds, flu and Hayfever medications (action is more prolonged than adrenaline. Additional advantage: need not be given by injection, but can be administered orally). Allopathic: Sinumed (dries a runny nose) Weight loss (increases metabolism, decreases appetite – CNS stimulant – acts on adrenergic receptors) Above ground parts are normally used, although the roots are better to use (less alkaloids)

70 Colchicine Constituent in colchium seeds and corm. Amorphous, yellow- white alkaloid (darkens on exposure to light). Gives a strong yellow coloration with strong mineral acids. Dissolves readily in water, alcohol and chloroform, but only slightly in ether or petroleum spirit. Weak base

71 Purine Alkaloids Also known as non-alkaloids (xanthines) * synthetic origin does not contain an intact AA * Amphoteric Character * Peculiar solubility in warm water and in chlorinated solvents. Examples are caffeine (seeds of coffee plants, kola plants, tea leaves and guarana seeds), theobromine (Theobroma cocao) and theophylline (tea leaves & cola nuts). Beverages such as tea and coffee owe their stimulant action to the purine alkaloids.

72 Theobromine Theophylline 3,7-dimethylxanthine

73 Classification of Alkaloidal precipitating agents: 1- Reagents that form double salts: a- Mayer’s Reagent: Potassium Mercuric Iodide. b- Dragendorff’s Reagents: Potassium Iodobismethate. c- Gold Chloride. 2- Reagents Containing Halogens: a- Wagner’s Reagent: Iodine/ Potassium Iodide. 3-Organic Acids: a- Hager’s Reagent: Picric Acid b- Tannic Acid. 4- Oxygenated High Molecular Weight Acids: a- Phosphomolybdic acid b- Phosphotungestic acid c- Silicotungestic Acid

74 Tests for Alkaloids

75 Extraction, Purification and Isolation of Alkaloids from Powdered plants Extraction and purification Method I: The powder is treated with alkalis to liberates the free bases that can then be extracted with water immiscible organic solvents. Method II: The powdered material is extracted with water or aqueous alcohol containing dilute acid. Alkaloids are extracted as their salts together with accompanying soluble impurities. Method III: The powder is extracted with water soluble organic solvents such as MeOH or EtOH which are good solvents for both salts and free bases.

76 Extraction in an Alkaline Medium Step 1: Powdered, defatted herb is mixed with an alkaline aqueous solution. This displaced alkaloids from their salt combinations. Free bases are then extracted with organic solvents. Normally aqueous ammonia is used, but a carbonate solution is used when alkaloids contain fragile elements such as a ester or lactone. In some cases, e.g. Cinchona bark, a mixture of calcium hydroxide & sodium hydroxide should be used as the alkaloids are bound to tannins. Organic solvent: chloroform, dichloromethane or ethyl acetate – depends on the toxicity, safety, cost & ease of recovery and recycling of the solvent).

77 The Soxhlet Apparatus Industry: uses solid-liquid extractors based on the principle of counter- current extraction, such Soxhlet apparatus.

78 Extraction of Alkaloids: Step II Organic solvent containing alkaloids (bases) is separated from residue & concentrated by distillation under pressure if needed. Solvent is stirred with an acidic aqueous solution: alkaloids go into the solution as salts. Impurities remain in the organic phase. Repeated until the organic phase no longer contains alkaloids. Many acids can be used (HCL, Sulfuric, citric, tartaric), but always in very dilute concentrations (1-5%)

79 Alkaloid Extraction: Step III Aqueous solution of alkaloid salts is washed with an apolar solvent (hexane) Alkalinized with a base using an organic solvent not miscible with water. Alkaloids precipitate and dissolve in the organic phase. Extraction of aqueous phase continues till all alkaloids have moved into the organic phase (tested when Mayer’s reaction on the aqueous phase becomes negative). This purification step may be carried out in a separation funnel or in centrifugal extractors. Separation Funnel

80 Final Step Organic solvent containing alkaloid bases is decanted, freed from water traces (drying over anhydrous salt e.g. sodium sulphate) and evaporated under reduced pressure. A dry residue remains: total basic alkaloids. Kava Powder

81 Alkaloid Extraction in Acidic Medium 2 Methods possible Pulverized drug is extracted directly with acidified water Or Pulverized drug is extracted with acidified alcoholic or a hydroalcoholic solution. This is then followed by distillation under vacuum (eliminates that alcohol, leaving behind and acidic aqueous solution of alkaloid salts) Vacuum Distillation

82 In both cases: Results = aqueous solution of alkaloid salts needing purification. Purification achieved by Alkalinizing solution & extracting bases with an immiscible organic solvent. Selectively absorb the alkaloids contained in the solution on an ion exchange resin, then eluting them with a strong acid. Precipitating the alkaloids as iodo mercurates. The resulting alkaloids are recovered by filtration, dissolved in a mixture of water, alcohol and acetone and decomposed by passing through an ion-exchange resin.

83 Ion-Exchange Resin

84 Isolation of Alkaloids All methods of alkaloid extraction yield impure compounds, so alkaloids therefore have to be separated. TLC and HPLC are most commonly used. Under the best conditions, alkaloids can be obtained by direct crystallization: simply by neutralizing the acidic extraction medium. Crystals of Hydrastine

85 Alkaloid Extraction Extraction method normally depends on the raw material, the purpose of extraction & the scale on which is to be performed. For research purposes: chromatography allows for quick and reliable results. TLC plate

86 In medicine Medical use of alkaloid-containing plants has a long history, and, thus, when the first alkaloids were isolated in the 19th century, they immediately found application in clinical practice. Many alkaloids are still used in medicine, usually in the form of salts, including the following: Alkaloid Action Ajmaline antiarrhythmic Atropine, scopolamine, hyoscyamineanticholinergic Vinblastine, vincristineantitumor Vincaminevasodilating, antihypertensive Codeinecough medicine Cocaineanesthetic Colchicineremedy for gout Morphineanalgesic Reserpineantihypertensive TubocurarineMuscle relaxant Physostigmineinhibitor of acetylcholinesterase Quinidineantiarrhythmic Quinineantipyretics, antimalarial Emetineantiprotozoal agent Ergot alkaloidssympathomimetic, vasodilator, Ajmalineantiarrhythmic Atropinescopolaminehyoscyamineanticholinergic Vinblastinevincristineantitumor Vincaminevasodilatingantihypertensive Codeinecough medicine Cocaineanesthetic Colchicinegout Morphineanalgesic Reserpineantihypertensive Tubocurarine Physostigmineacetylcholinesterase Quinidine Quinine Emetineantiprotozoal agent Ergot alkaloidssympathomimetic

87 Terpenoids There are many different classes of naturally occurring compounds. Terpenoids also form a group of naturally occurring compounds majority of which occur in plants, a few of them have also been obtained from other sources. Terpenoids are volatile substances which give plants and flowers their fragrance. They occur widely in the leaves and fruits of higher plants, conifers, citrus and eucalyptus.

88 The term ‘terpene’ was given to the compounds isolated from terpentine, a volatile liquid isolated from pine trees. The simpler mono and sesqui terpenes are chief constituent of the essential oils obtained from sap and tissues of certain plant and trees. The di and tri terpenoids are not steam volatile. They are obtained from plant and tree gums and resins. Tetraterpenoids form a separate group of compounds called ‘Carotenoids’

89 The term ‘terpene’ was originally employed to describe a mixture of isomeric hydrocarbons of the molecular formula C 10 H 16 occurring in the essential oils obtained from sap and tissue of plants, and trees. But there is a tendency to use more general term ‘terpenoids’ which include hydrocarbons and their oxygenated derivatives. However the term terpene is being used these days by some authors to representterpenoids By the modern definition: “Terpenoids are the hydrocarbons of plant origin of the general formula (C 5 H 8 ) n as well as their oxygenated, hydrogenated and dehydrogenated derivatives

90 90 : The Isoprene Rule. Isoprenoids- C 10 (terpenes), C 15 (sesquiterpenes) and C 20 (diterpenes) plant; essential oils Ruzicka isoprene rule: terpenoids are derived from “isoprene units” (C 5 ) isoprene (2-methyl-1,3-butadiene )

91 91 The precursor to C 10 terpenoids (monoterpenes) is geraniol diphosphate (diphosphate), which consists of two C 5 “isoprene units” that are joined “head-to-tail” head - tail head - tail head tail PP = C 15 sesquiterpenoids are derived from farnesyl diphosphate, which consists of three C 5 “isoprene units” that are joined “head-to-tail ” C 20 diterpenoids are derived from geranylgeranyl diphosphate, which consists of four C 5 “isoprene units” that are joined “head-to-tail”

92 92 C 25 sesterpenoids are derived from geranylfarnesyl diphosphate, which consists of five C 5 “isoprene units” that are joined “head-to-tail ” C 30 triterpenoids and steroids are derived from squalene, which consists of two C 15 farnesyl units” that are joined “tail-to-tail” C 40 tetraterpenoids are derived from phytocene, which consists of two C 20 geranylgeranyl units” that are joined “tail-to-tail ”

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95 Classification of Terpenoids Most natural terpenoid hydrocarbon have the general formula (C 5 H 8 )n. They can be classified on the basis of value of n or number of carbon atoms present in the structure. Table-1: Classification of Terpenoids S.No. Number of carbon atoms Value of n Class Monoterpenoids(C 10 H 16 ) Sesquiterpenoinds(C 15 H 24 ) Diterpenoids(C 20 H 32 ) Sesquiterpenoids(C 25 H 40 ) Triterpenoids(C 30 H 48 ) Tetraterpenoids(C 40 H 64 ) 7. >40 >8 Polyterpenoids(C 5 H 8 )n

96 Isolation of mono and sesquiterpenoids Both mono and sesquiterpenoids have common source i.e essential oils. Their isolation is carried out in two steps: i) Isolation of essential oils from plant parts ii) Separation of Terpenoids from essential oils.

97 i) Isolation of essential oils from plant parts: The plants having essential oils generally have the highest concentration at some particular time. Therefore better yield of essential oil plant material have to be collected at this particular time. e.g. From jasmine at sunset. There are four methods of extractions of oils. a) Expression method b) Steam distillation method c) Extraction by means of volatile solvents d) Adsorption in purified fats Steam distillation is most widely used method. In this method macerated plant material is steam distilled to get essential oils into the distillate form these are extracted by using pure organic volatile solvents. If compound decomposes during steam distillation, it may be extracted with petrol at 50 o C. After extraction solvent is removed under reduced pressure

98 ii) Separation of Terpenoids from essential oil: A number of terpenoids are present in essential oil obtained from the extraction. Definite physical and chemical methods can be used for the separation of terpenoids. They are separated by fractional distillation. The terpenoid hydrocarbons distill over first followed by the oxygenated derivatives. More recently different chromatographic techniques have been used both for isolation and separation of terpenoids.

99 General properties of Terpenoids 1. Most of the terpenoids are colourless, fragrant liquids which are lighter than water and volatile with steam. A few of them are solids e.g. camphor. All are soluble in organic solvent and usually insoluble in water. Most of them are optically active. 2. They are open chain or cyclic unsaturated compounds having one or more double bonds. Consequently they undergo addition reaction with hydrogen, halogen, acids, etc. A number of addition products have antiseptic properties. 3. They undergo polymerization and dehydrogenation 4. They are easily oxidized nearly by all the oxidizing agents. On thermal decomposition, most of the terpenoids yields isoprene as one of the product.

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