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Questions and Answers
Which method is NOT used to isolate terpenoids?
What indicates the presence of terpenoids in an identification test?
Which of the following is NOT a therapeutic effect of terpenoids?
Glycosides are composed of which two components?
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In the enfleurage process, which material is used to absorb essential oils from flowers?
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Which of the following is NOT mentioned as a use of terpenoids in pharmaceuticals?
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What is the role of glucose in glycosides?
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Which method involves the use of a soxhlet apparatus for glycoside extraction?
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Which plant source is associated with glandular hairs?
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What is a typical method for isolating oils from plant sources?
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Which of the following is a physical test in the identification of resins?
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Which of these resins is known for its use in treating bronchial asthma?
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Which of the following compounds can be tested using a specific chemical test for identification of resins?
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What indicates the presence of tannins in a sample during the identification test?
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Which method is used for the isolation of volatile oils from plants not injured by boiling?
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What is the therapeutic effect of tannins as mentioned in the content?
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What indicates the presence of carotenoids in the identification test?
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What type of plants commonly contain volatile oils as detailed in the information?
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Which of the following is not a pharmaceutical application of tannins?
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Which method is primarily used for the isolation of glycosides?
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Which of the following isolation methods involves the use of steam to extract volatile oils?
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Which plants are known to have a high occurrence of alkaloids?
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What function do alkaloids serve in animals?
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What characteristic of volatile oils is emphasized in their description?
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What solvent is used for the extraction of alkaloids after fats and oils are removed?
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Which part of the plant is NOT mentioned as containing volatile oils?
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Which of the following is NOT a pharmaceutical application of glycosides?
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What testing reagent is combined with glacial acetic acid to identify certain compounds?
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Which of the following trees is mentioned as a source of tannins?
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What is a primary use of essential oils extracted from plants?
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Which method allows for the mechanical extraction of citrus oils?
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What is a characteristic of abnormal or pathological resins?
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Which of the following tests is NOT used to identify volatile oils?
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How is eucalyptus oil commonly administered for therapeutic use?
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What does the freezing point test measure in the physical properties of essential oils?
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What type of chromatography is used to check the purity and composition of essential oils?
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Which essential oil is commonly used in mouthwashes and gargles for its antiseptic properties?
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Study Notes
Terpenoids
- Naturally occurring chemicals found in leaves, stems, barks, roots, and flowers of plants
- Present in essential/volatile oils, such as oleoresin, ovinine, and ergotamine
- Can be isolated using stem distillation, solvent extraction, and enfleurage processes
Steam Distillation
- Distillation of a liquid inner current of steam, used to purify liquids that are not very volatile and are immiscible with water
- Plant is subjected to maceration before being distilled
- Distillates are mixed with a purified solvent and dried
- Solvent is removed by evaporation to obtain pure oil
Solvent Extraction
- Plant is subjected to maceration before being mixed with a mixture of ether and benzene
- The mixture is then filtered, and the solvent is removed by evaporation
- This process yields the desired oil
Enfleurage Process (for Flowers)
- Petals are spread over a molten fat layer
- Essential oils are absorbed by the fat
- The mixture is dissolved using pure ethanol
- The fat is removed by cooling below 20°C
- Ethanol is evaporated at 0°C to obtain the oil
Identification Test
- Dissolve 2 ml of the organic extract in 2 ml of CHCl3
- Evaporate the mixture to dryness
- Add 2 ml of concentrated H2SO4 and heat for 2 minutes
- Development of a greyish colour indicates the presence of terpenoids
Therapeutic Effects of Terpenoids
- Terpenoids have been found useful in the prevention and therapy of several diseases and cancer
- Anti-microbial
- Anti-fungal
- Anti-parasitic
- Anti-viral
- Anti-allergic
Pharmaceutical Application
- Used as the active ingredient in agricultural pesticides
- Paclitaxel, a terpenoid from the Pacific yew tree, is used in cancer treatment
Glycosides
- Glycosides are composed of a sugar (glycon) and a non-sugar (aglycon)
- The sugar component is typically a monosaccharide, such as glucose
- Glucose increases the solubility and bioavailability of the sample
Occurrence of Glycosides
- Mostly occurring in plants and animal tissues
- Examples: digitalis, Apocyanaceae, Aracideae, Legumanceae
Isolation of Glycosides
- Dried plant material is ground into a coarse powder
- The powder is extracted in a Soxhlet apparatus using aqueous ethanol
- Non-glycosidal impurities are removed by precipitation with legal acetate solution
- Excess lead acetate is removed by passing H2S gas through the extract
- The lead precipitates as lead sulfide and is filtered out
- The filtrate contains the glycosides
- The solvent is removed under reduced pressure to obtain the glycosides
- Further purification of the isolated glycosides is done by column chromatography
Identification Test
- Treat 5 ml of plant extract with 2 ml of glacial acetic acid containing 1 drop of ferric chloride solution
- Underlayer this mixture with 1 ml of concentrated H2SO4
- A brown ring at the interface indicates the presence of carotenoids
- A violet ring may appear below the brown ring in the acetic acid layer
- A greenish ring may appear gradually throughout the acetic acid layer
Therapeutic Effects of Glycosides
- In plants: regularity function, protective function, sanitary function
- In animals: cardioactive, local irritant function
- Used in the synthesis of steroidal diuretics, coffee, tea, sex hormones, and oral contraceptives
Pharmaceutical Applications of Glycosides
- Flavouring Agent
- Colouring Agent
- Carrier for drugs and medicine
Alkaloids
- 90% of alkaloids are present in plants such as Rubiaceae, Asteraceae, and Paperceaeae
- Also present in fungi, Pteridophytes, and Gymnosperms
- Typically crystalline in substances
Isolation of Alkaloids
- Dried and powdered plant material is extracted with petroleum ether or hexane to remove fats, oils, terpenes, and waxes
- The extract is subjected to an alcohol extraction using methanol or ethanol
- The extract is evaporated to leave a crude alkaloids mixture
- This mixture is then precipitated between dilute aqueous tartaric acid solution and ethyl acetate
- Other acids, such as citric acid, can also be used
- The ethyl acetate layer contains neutral and weakly basic alkaloids
- The solvent is evaporated to isolate these alkaloids
- The aqueous layer is neutralized with ammonia or sodium carbonate and extracted with ethyl acetate
- The organic layer contains basic alkaloids, while the aqueous layer contains quaternary ammonium ions
Identification Test
- Treat 5 ml of plant extract with 2 ml of glacial acetic acid containing 1 drop of ferric chloride solution
- Underlayer this mixture with 1 ml of concentrated H2SO4
- A brown ring at the interface indicates the presence of carotenoids
- A violet ring may appear below the brown ring in the acetic acid layer
- A greenish ring may appear gradually throughout the acetic acid layer
Occurrence of Tannins
- Found in oak, hemlock trees, and legumes, such as hallo-tannins and condensed tannins
Identification Test
- Boil 0.5 g of the dried powdered sample in 20 ml of water
- Filter the solution
- Add a few drops of ferric chloride
- A brownish-green or blue-black color indicates the presence of tannins
Isolation of Condensed Tannins
- Tannin preparations are a mixture of condensed and hydrolysable tannins, which are not suitable as a standard for the determination of condensed tannins in plant extracts
- The biological activity of these isolated tannins is expected to be similar to that of the tannins present in the leaves
Pharmaceutical Applications of Tannins
- Plants containing tannins possess astringent, hemostatic, and antiseptic properties
- Used to treat diarrhea
- Used to stop minor hemorrhages
Therapeutic Effects of Tannins
- Bind to protein enzymes
- Block digestion
- Antioxidants
Volatile Oils
- The odorous, volatile principle of plant and animal sources is known as volatile oil
- Lighter than air, highly active, have a high refractive index, and possess distinct odours
- Found in glandular hairs (Labiatae), modified parenchyma cells (Piperaceae), special tubes or oil tubes in the pericarp of fruits (Umbelliferae), lysogenous and schizogenous cavities (Rutaceae), and in all tissues of conifers
- Examples: petals of rose, bark of cinnamon, fruits of coriander, leaves of peppermint
Isolation of Volatile Oils
1. Distillation by Water
- Used for plants that are not damaged by boiling
- Turpentine oil is obtained using this method
- Crude turpentine is mixed with water and subjected to heat below 4°C
- A mixture of oil and water is collected as a distillate
- The distillate separates into two layers, with the oil being withdrawn through the upper outlet of the condenser and water through the lower outlet
2. Water and Steam Distillation
- Used for substances that are injured by direct heat
- Examples: clove, cinnamon
- Dried, ground drug is covered with a layer of water
- Steam, generated in a separate chamber, is passed through the mixture
- The vapor containing volatile oil is condensed and collected
3. Destructive Distillation Without Air (Vacuum)
- Used for members of Pinaceae
- Tough materials, such as barks, seeds, and roots, are comminated to facilitate extraction
- Pieces of wood are heated with water in a vacuum
- The decomposition of wood generates volatile oils, which are collected through the condenser
4. Ecuelle Method
- Used for extracting citrus oils
- Oil cells in the rind are ruptured mechanically using pointed projections
- The raw material is twisted over these projections in a clockwise direction, either manually or mechanically
Therapeutic Application of Volatile Oils
- Counterirritant
- Eucalyptus oil administered as an inhalant
- Improves local circulation
- Carminative, shows antispasmodic properties
- Thymol is used in mouthwashes and gargles
- Local anesthetic
- Reduces lung secretion in cough and asthma
- Antiseptic, antibacterial, antifungal
- Anti-helminthic
- Used in aromatherapy (eg: lavender, rosemary)
Identification of Volatile Oils
- Physical tests: determine relative density, refractive index, optical rotation, freezing points, etc.
- Chemical tests: include acid value and peroxide value
- Chromatographic methods: Use thin layer chromatography and gas-liquid chromatography (GLC) to check purity and composition, and detect impurities present
Occurrence of Resins
- Resins are generally distributed in plants and rarely in insects
- Found in ducts or cavities known as schizolysogenous ducts
- Two types of resins: Normal/physiological resin and Abnormal/pathological resin
1. Normal or Physiological Resins
- Formed in plants naturally
- Injury to plants can increase resin yield
- Example: Resin of pinus
2. Abnormal or Pathological Resins
- Found in plants only after injury or incision
- Examples: Benzoin, toles balsam
Isolation of Resins
- Extraction with alcohol and precipitation with water: Examples: jalap, ipomea, podophyllum
- Distillation (for separation of oils): Example: colophony
- Heating the plant parts: Example: Guaum
- Making incisions: Examples: Asfoetida, Balsams
- Processing incrustation: Example: shellac
Identification Test for Resins
1. Physical Test
- Properties such as solubility, taste, odor, and examination of powder under the microscope can be helpful
2. Chemical Test
- Acid value
- Iodine value
- Saponification value
-
Specific chemical tests:
- Cinnamic acid
- Benzoic acid and benzoin
- Tolu balsam
- Peru balsam
Therapeutic Effects of Resins
- Local irritant and cathartic: Examples: jalap and ipomea
- Anti-cancer: Example: podophyllum
- Used in bronchial asthma: Example: cannabin
- Used in tinctures: Example: benzoin
- Used in ointments and plasters: Examples: terpentine and colophony
- Used in the production of emulsions
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Description
Explore the fascinating world of terpenoids, natural chemicals integral to plants. This quiz covers essential oil extraction methods, including steam distillation, solvent extraction, and the enfleurage process. Test your knowledge and understanding of these botanical compounds and their uses.
