terpenes and terpenoids

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Terpenes and Terpenoids : 

Terpenes and Terpenoids PRESENTED BY: Vinit parmar M.Pharm-I Roll No. 090605014 Dept. of Pharmacognosy M.C.O.P.S, Manipal.

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What we are going to study  1. Definition 2. Classification 3. Examples 4. Occurrence

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5. General properties 6. Isolation and separation techniques 7. Biosynthesis of terpenoids 8. Estimation of terpenoids 9. Uses

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1. Definition - Terpenes are the hydrocarbon compounds having molecular formula (C5H8)n. Where as their oxygenated, hydrogenated, dehydrogenated derivatives are called as Terpenoids.

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- Also called as isoprenoids. - Primary constituents of the essential oils of many types of plants and flowers. EXCEPTION: Oils derived from glycosides (e.g. bitter almond oil & mustard oil). - Essential oils are used widely as natural flavour, additives for food, as fragrances in perfumery, in aroma therapy, and AS SPICES.

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History of Use of Spices & Herbs- - No one knows for certain when people began using spices and herbs. 5200 yrs BP Embalming practiced in Egypt 4500 yrs BP Use of garlic and onions 3400 yrs BP Trade routes already established across Asia - The first clear documentation of the use of plant Flavoring agents in food dates to 4500 years ago.

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Christopher Columbus • An Italian sailing under the Spanish Flag searching for a quick oceanic route to India and the Spice Islands! • But he was not the first to “discover” the New World…

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• Magellan – – Arguably the greatest explorer of his day – Started, but didn’t survive the first voyage to circumnavigate the globe – Again, in search of a fast route to the sources of SPICES in the Far East – Was killed by natives of Philippines…..

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* Otto Wallach 1847-1931 -Interest in essential plant oils. -His main research was on terpenes (such as limonene, pinene, etc.) -He formulated the "isoprene rule" for the build-up of terpene structures. -His work had industrial as well as academic significance. He received the 1910 Nobel Prize in Chemistry.

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ISOPRENE RULE – - Wallach stated that the skeleton structure of all naturally occurring terpenoids are built up of isoprene units. (C5H8)

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- A single terpene unit is formed from two molecules of isoprene. Each class of terpenoids except hemiterpenes is further classified into subclasses on the basis of number of rings present: Acyclic : That contains an open chain structure. Monocyclic : That contains one ring in their structure. Bicyclic : That contains two rings in their structure. Tricyclic : That contains three rings in their structure.

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Examples of individual terpenoids with their occurrence:- MONOTERPENOIDS: - Derived from geranyl pyrophosphate & commonly are main ingredient of volatile oils. - Composed of two isoprene unit (each having two double bonds). - Prominent families containing monoterpenoids are Umbelliferae, Lauraceae, Labiateae, Myrtaceae, Burseraceae & Pinaceae.

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Representative Monoterpenes a-Phellandrene(eucalyptus) Menthol(peppermint) Citral(lemon grass)

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Representative Monoterpenes a-Phellandrene(eucalyptus) Menthol(peppermint) Citral(lemon grass)

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Representative Monoterpenes a-Phellandrene(eucalyptus) Menthol(peppermint) Citral(lemon grass)

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2. Sesquiterpenoids – - Derived from three isoprene units having molecular formula C15 H24. - Biosynthesized from farnesyl pyrophosphate. - They have wide occurrence in the nature & found in plants & fungi. - sesquiterpene lactones are considered as more significant due to their marked biological activity.

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Representative Sesquiterpenes a-Selinene(celery) H

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Representative Sesquiterpenes a-Selinene(celery) H

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Representative Sesquiterpenes a-Selinene(celery)

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3. DITERPENOIDS – - C20 carbon compounds. - Derived from four isoprene units and in contrast to mono & sesquiterpenoids they are non-volatile in nature. Biosynthetically prepared from geranyl-geranyl pyrophosphate. - The plant families rich in diterpenoids are Pinaceae, Leguminosae, Burseraceae, Labiateae etc. They are also found in marine animals (colentrates) like soft corals, sea fans.

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Representative Diterpene Vitamin A

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Representative Diterpene Vitamin A

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Representative Diterpene Vitamin A

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4. TRITERPENOIDS – Among the various terpenoid groups, this is the largest one. Triterpenoids are widely distributed in the plant kingdom & few in animals. They are present either in Free State or ester or glycosides. Biosynthetically triterpenoids are C30 carbon compounds prepared from six isoprene unit having molecular formula C30 H48. They are mostly steroidal in nature.

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They are further classified as; -Tetracyclic triterpenoids -Pentacyclic triterpenoids→ α-Amyrin, β-Amyrin, Lupeol. Triterpenoids can also be classified as;a. True triterpenoids b. Steroid c. Saponin d. Cardiac glycoside - The plant families having appreciable quantity of triterpenoids are Cucurbitaceae, Apocynaceae & Leguminosae.

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Representative Triterpene Squalene(shark liver oil) tail-to-tail linkage of isoprene units

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α-Amyrin β-Amyrin Pentacyclic triterpenoids

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5. TETRATERPENOIDS – - C40 compounds. - Biosynthetically prepared by tail to tail condensation of geranyl- geraniol. They contain long sequence of conjugated double bonds. - Popularly known as carotenoids, formed by union of eight isoprene units. Due to presence of long chain of conjugated double bonds, they are coloured such as yellow, orange and red.

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- Carotenoids occur in many plants and are distributed in almost all parts of plants such as roots (carrot), leaves (spinach), fruits (tomato) and seeds (annatto and palm).

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6. POLYTERPENOIDS- - Polyterpenoids are synthesized in plants from acetate via isopentenyl pyrophosphate (C5 unit) and also from the condensation of number of isoprene units. - Found in the latex of the Rubber Tree -Produces Rubber

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GENERAL PROPERTIES OF TERPENOIDS – 1.PHYSICAL PROPERTIES OF TERPENOIDS- - Most are colorless liquids when fresh, but on long standing they oxidize thereby darkening in color. - Characteristic odour - High refractive indices Most of them are optically active - Density is generally lower than water and they are soluble in common organic solvents like ether, alcohol.

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CHEMICAL PROPERTIES OF TERPENOIDS- - They are unsaturated compounds (open chain, or cyclic) - Most isoprenoids are chiral and occur in two enantiomeric forms. - The higher isoprenoids (di-, tri-) occur exclusively as a single optically pure enantiomer, the natural enantiomer. - Carvone occurs as (+)-epimer in spearmint, (-)-epimer in caraway seeds.

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Isolation of terpenoids – Following methods are used for obtaining volatile oils – 1. Water & steam distillation 2. Direct steam distillation 3. Expression (ecuelle) method 4. Enfleurage method 5. Enzymatic hydrolysis 6. Supercritical fluid extraction 7. Solid phase microextraction 8. Advanced phytonics method of extraction 9. Solvent extraction of essential oils

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BIOSYNTHESIS OF TERPENOIDS Isopentenyl Pyrophosphate:The Biological Isoprene Unit

The Biological Isoprene Unit : 

The Biological Isoprene Unit - The isoprene units in terpenes do not come from isoprene. - They come from isopentenyl pyrophosphate. - Isopentenyl pyrophosphate (5 carbons) comes from acetate (2 carbons) via mevalonate (6 carbons).

The Biological Isoprene Unit : 

The Biological Isoprene Unit 3 Mevalonic acid Isopentenyl pyrophosphate

Isopentenyl Pyrophosphate : 

Isopentenyl Pyrophosphate Isopentenyl pyrophosphate or

Isopentenyl and Dimethylallyl Pyrophosphate : 

Isopentenyl and Dimethylallyl Pyrophosphate Isopentenyl pyrophosphate is interconvertible with2-methylallyl pyrophosphate. Dimethylallyl pyrophosphate has a leaving group (pyrophosphate) at an allylic carbon; it is reactive toward nucleophilic substitution at this position. Isopentenyl pyrophosphate Dimethylallyl pyrophosphate

Carbon-Carbon Bond Formation in Terpene Biosynthesis : 

Carbon-Carbon Bond Formation in Terpene Biosynthesis

Carbon-Carbon Bond Formation : 

Carbon-Carbon Bond Formation - The key process involves the double bond of isopentenyl pyrophosphate acting as a nucleophile toward the allylic carbon of dimethylallyl pyrophosphate.

Carbon-Carbon Bond Formation : 

Carbon-Carbon Bond Formation

After C—C Bond Formation... : 

After C—C Bond Formation... The carbocation can lose a proton to give a double bond.

After C—C Bond Formation... : 

After C—C Bond Formation... OPP The carbocation can lose a proton to give a double bond.

After C—C Bond Formation... : 

After C—C Bond Formation... OPP - This compound is called geranyl pyrophosphate. It can undergo hydrolysis of its pyrophosphate to give geraniol (rose oil). (MONOTERPENES)

After C—C Bond Formation... : 

After C—C Bond Formation... OPP Geraniol H2O

From 10 Carbons to 15 : 

From 10 Carbons to 15

From 10 Carbons to 15 : 

From 10 Carbons to 15

From 10 Carbons to 15 : 

From 10 Carbons to 15 - This compound is called farnesyl pyrophosphate. - Hydrolysis of the pyrophosphate ester gives the alcohol farnesol. (SESQUITERPENES AND TRITEPRENES)

From 15 Carbons to 20 : 

From 15 Carbons to 20 - Farnesyl pyrophosphate is extended by another isoprene unit by reaction with isopentenyl pyrophosphate to give geranyl-geranyl pyrophosphate. (DI AND TETRATERPENES)

Cyclization : 

Cyclization - Rings form by intramolecular carbon-carbon bond formation. E double bond Z double bond

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OH H2O Limonene α-Terpineol

Bicyclic Terpenes : 

Bicyclic Terpenes + + b-Pinene + a-Pinene

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ESTIMATION OF TERPENOIDS: Most quantitative methods for estimation include: a. TLC – Borneol, eugenol, thymol b. HPTLC – Glycyrrhizin c. GC – Pinene, camphene, myrcene d. Column chromatography – Carotenoids e. Spectrofluorimetry f. Colorimetry g.Clavenger apparatus for estimation of volatile oils

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USES:- 1. Primary constituents of many essential oils widely used as natural flavour, as additives in food, as fragrances in perfumery and in aromatherapy. 2. Also used as insect repellent and insecticides. Eg. pyrethrum, azadirachtin. 3. Citral is used as mosquito repellent and starting material for synthesis of vitamin A.

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4. Taxol and cucurbitacins are anti-tumour compounds. 5. Artemisinin has potent anti malarial activity. 6. Derivatives of panaxdiol and panaxtriols are immunostimulants. Antiseptic - geraniol, citral. Spasmolytic & sedative – jatamansone. Anthelmintic - ascaridole in Chenopodium. Vasodilator - forskolin etc. Clove oil – local anesthetic.

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REFERENCES: 1.Peach K., Tracey M.V. “Modern Methods of Plant Analysis” Vol.-2, Page no. 365-372. 2.Phytochemistry & Pharmacognosy by Jean Brunetton, page no 467-475. 3.Evans W.C., Trease, “Pharmacognosy”, 15th edition, 2007, Sort court Publishers, Page No. 167-165. 4.Kokate C.K., Purohit A.P., “Pharmacognosy” 18th ed., 2002, Nirali Prakashan, Page No. 303-311. 5. Australian Journal of Botany 44(5) 601 – 612, “Occurrence of Terpenoid Aldehydes and Lysigenous Cavities in the 'glandless' Seeds of Australian Gossypium Species.” 6.Harborne J.B., “Phytochemical Methods”, III Ed, Page-114-122.