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Questions and Answers
What is the primary purpose of thin layer chromatography (TLC)?
What is the primary purpose of thin layer chromatography (TLC)?
Which component is typically used as the stationary phase in TLC?
Which component is typically used as the stationary phase in TLC?
What happens during the spotting stage of TLC?
What happens during the spotting stage of TLC?
What is the first step in the phytochemical study process?
What is the first step in the phytochemical study process?
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How does the development of the TLC plate occur?
How does the development of the TLC plate occur?
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Which method is NOT typically used for establishing the identity of a plant in herb authentication?
Which method is NOT typically used for establishing the identity of a plant in herb authentication?
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Which of the following sample sizes is considered optimal for TLC?
Which of the following sample sizes is considered optimal for TLC?
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What type of extraction involves isolating soluble material from an insoluble residue?
What type of extraction involves isolating soluble material from an insoluble residue?
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What is the primary criterion for selecting a solvent for extraction?
What is the primary criterion for selecting a solvent for extraction?
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What is one of the methods used for the identification of isolated compounds?
What is one of the methods used for the identification of isolated compounds?
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Which approach is NOT listed as a method for selecting plant material for drug discovery?
Which approach is NOT listed as a method for selecting plant material for drug discovery?
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What does mass transfer in extraction involve?
What does mass transfer in extraction involve?
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Which of the following solvents is commonly used for extraction?
Which of the following solvents is commonly used for extraction?
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What is a consequence of using an inappropriate extraction method?
What is a consequence of using an inappropriate extraction method?
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What is the first step in the process of solid-liquid extraction?
What is the first step in the process of solid-liquid extraction?
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Why is it important to choose a solvent with a similar polarity to the analyte?
Why is it important to choose a solvent with a similar polarity to the analyte?
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What is the primary purpose of macerating crude drugs in the infusion process?
What is the primary purpose of macerating crude drugs in the infusion process?
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What effect does particle size have on extraction efficiency?
What effect does particle size have on extraction efficiency?
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In the percolation process, how long is the solid mixture usually allowed to stand before being packed?
In the percolation process, how long is the solid mixture usually allowed to stand before being packed?
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What role does temperature play in the extraction process?
What role does temperature play in the extraction process?
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What type of extraction is best suited for heat-stable water-soluble constituents?
What type of extraction is best suited for heat-stable water-soluble constituents?
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What is the primary function of a rotary evaporator?
What is the primary function of a rotary evaporator?
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What is the effect of sample humidity on the extraction process?
What is the effect of sample humidity on the extraction process?
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Which of the following methods is specifically used to extract aromatic compounds from plants?
Which of the following methods is specifically used to extract aromatic compounds from plants?
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What is a key characteristic of liquid-liquid extraction?
What is a key characteristic of liquid-liquid extraction?
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What is the function of solvent agitation during extraction?
What is the function of solvent agitation during extraction?
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Why is it important to avoid excessive heat during digestion?
Why is it important to avoid excessive heat during digestion?
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What does the term 'menstruum' refer to in extraction methods?
What does the term 'menstruum' refer to in extraction methods?
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What is one of the advantages of using novel extraction techniques for nutraceuticals?
What is one of the advantages of using novel extraction techniques for nutraceuticals?
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What is the primary purpose of standardizing herbal extracts?
What is the primary purpose of standardizing herbal extracts?
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What are standardized extracts characterized by?
What are standardized extracts characterized by?
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Which of the following techniques is most effective for separating plant extracts into pure components?
Which of the following techniques is most effective for separating plant extracts into pure components?
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What role do marker substances play in standardization?
What role do marker substances play in standardization?
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Which spectroscopic method is especially useful in identifying hydroxyl groups?
Which spectroscopic method is especially useful in identifying hydroxyl groups?
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What is one main advantage of ultrasound-assisted extraction (UAE)?
What is one main advantage of ultrasound-assisted extraction (UAE)?
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Which extraction method combines microwave energy with traditional solvent extraction?
Which extraction method combines microwave energy with traditional solvent extraction?
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What information can NMR Spectroscopy provide about a compound?
What information can NMR Spectroscopy provide about a compound?
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Which of the following components will move faster through a chromatography column?
Which of the following components will move faster through a chromatography column?
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What is a characteristic of supercritical fluid extraction?
What is a characteristic of supercritical fluid extraction?
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What is a characteristic absorption peak in IR spectroscopy for an oxo group?
What is a characteristic absorption peak in IR spectroscopy for an oxo group?
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What role do enzymes play in enzyme-assisted extraction?
What role do enzymes play in enzyme-assisted extraction?
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What effect do microwaves have in microwave-assisted extraction?
What effect do microwaves have in microwave-assisted extraction?
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Which extraction method is NOT mentioned as a traditional method?
Which extraction method is NOT mentioned as a traditional method?
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What is the main consideration for a standardized herbal extract?
What is the main consideration for a standardized herbal extract?
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What is one downside of traditional extraction methods?
What is one downside of traditional extraction methods?
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Study Notes
Pharmacognosy and Phytochemistry
- This presentation covers extraction and identification of medicinal plants.
- The presenter is Dr. Farah Al-Mamoori.
Phytochemical Study Points
- Selection of promising plant materials
- Proper collection of selected plants
- Authentication of plant material
- Drying of plant materials
- Grinding of dried plants
- Garbling of dried plants
- Packing, storage and preservation
- Extraction and fractionation of constituents
- Methods of separation and purification
- Methods of identification of isolated compounds (e.g. UV, IR, MS, 1H-NMR and 13C-NMR).
Plant Selection
- Plant selection for drug discovery uses various approaches:
- Random selection
- Ethnopharmacology
- Chemotaxonomy
- Geographical
- Computer-based selection
- Literature information selection
Plant Authentication
- Herb authentication ensures correct plant species and parts are used.
- Authentication can be confirmed by:
- Establishing identity by taxonomic experts.
- Comparing collected plant with a voucher specimen (herbarium sheet).
- This presentation has previously discussed points 4-7:
- Drying of plant materials
- Grinding of dried plants
- Garbling of dried plants
- Packing, storage and preservation
Extraction
- Extraction separates medicinal components of plants from inactive elements using selective solvents.
- Solvents used for extraction include water, ethanol, methanol, chloroform, petroleum ether, acetone, etc.
- Selecting a suitable solvent ensures extraction of active chemical constituents.
- Extraction methods include liquid-liquid and solid-liquid techniques.
- Mass transfer is critical, involving the movement of soluble material from the solid plant to a liquid.
Solvent Extraction Approach
- The extraction method's selection should mirror traditional procedures—e.g, if a culture uses a specific procedure like a water extract, adapt that method to the laboratory.
- Incorrect extraction (e.g., strongly heating biomass with a solvent) can degrade compounds and reduce biological activity.
Solid-Liquid Extraction Mechanism
- The solvent mixes with the plant material.
- The solvent diffuses onto the solid surface.
- The solvent penetrates into the plant particles.
- The solvent gradually dissolves the soluble ingredients.
- Internal diffusion is the movement from within the cell to the surface, while external diffusion involves the transfer from the surface to the bulk of the solvent.
Factors Affecting Extraction Rate
- Solvent: A solvent similar to the product's polarity is ideal. The ideal solvent is non-toxic, non-reactive, environmentally friendly, and affordable.
- Particle size: Grinding the plant material increases the contact area between solvent and material, enhancing extraction efficiency.
- Sample humidity: Water in the plant material can compete with the solvent for the extract, thus sample dryness before extraction is key.
- Temperature: Increased temp enhances the solubility and diffusion of plant components. However, avoid over-heating in order to avoid degradation.
- Solvent agitation: Agitation increases turbulent diffusion and material transfer rates
Extraction Solvents(Table)
- A table is provided with different solvents, their polarity, boiling point, and density at 25°C.
Extraction Solvents(Miscibility-Compatibility Chart)
- A chart displays solvent miscibility in a grid format.
Choice of Solvent
- Nonpolar solvents (e.g., petroleum ether, hexane) dissolve nonpolar compounds (e.g., fats, waxes).
- Polar solvents (e.g., methanol, ethanol, and water) dissolve polar compounds (e.g., alkaloids, salts, sugars).
After Extraction
- Filtration: Separates the solid components from the liquid extract.
- Rotary evaporator: Used to remove solvent under reduced pressure, boiling at lower temperatures.
- Freeze-drying: Removes water while maintaining bioactive ingredients.
- Maceration: Whole/coarsely powdered drug is placed in a container with a liquid solvent and allowed to stand at room temperature with frequent agitation.
- Infusion: Crude drug soaked briefly in cold or hot water to extract readily soluble components (dilute solution).
- Decoction: Crude drug is boiled in a particular amount of water to extract water-soluble, heat-stable components.
- Digestion: Similar to maceration but with slight warming to increase efficiency.
- Percolation: Moistened drug is packed in a filter-aided container with the solvent percolated through the material.
Hot Continuous Extraction (e.g., Soxhlet)
- A diagram of the apparatus and a detailed explanation of each component and stage of the process are provided.
Steam Distillation (Hydrodistillation)
- A common technique for separating aromatic compounds (essential oils) from plants.
- The steam creates a vapor mixture that is later cooled and separated into an oil layer and water layer (hydrosol), which are then collected.
- Diagrams are provided
Liquid-Liquid Extraction
- A process, also called partitioning, to transfer a solute between two immiscible or partially miscible solvents.
- A separating funnel is used to separate the two layers.
Various Novel Techniques
- Various novel extraction techniques are introduced.
- Ultrasound-assisted extraction
- Microwave-assisted extraction
- Supercritical fluid extraction
- Enzyme-assisted extraction
Ultrasound-Assisted Extraction (UAE)
- Ultrasound increases the contact surface area between solvents and samples, improving permeability of cell walls.
- Physical and chemical properties of materials are modified to disrupt plant cell walls.
- This process enhances mass transport of solvents into plant cells.
- A detailed diagram and figure are provided.
Microwave-Assisted Extraction (MAE)
- Combines microwave and classical solvent extraction.
- Electromagnetic waves cause structural changes in cells to facilitate extraction.
- Diagram of apparatus is provided
Supercritical Fluid Extraction
- Is a technique that involves using solvents at their critical temperature and pressure to extract compounds from solid matrices.
- The critical state of the solvent provides intermediary properties between gases and liquids.
- CO2 is a common solvent due to its renewability
Enzyme-Assisted Extraction
- Enzymes are used to disrupt cell walls, increasing extraction yield of bioactive compounds.
- The scanning electron microscopy diagrams show the effect of enzymes on plant cell walls before and after treatment.
Calculation of Percentage Yield
- Percentage yield measures the efficiency of extract isolation based on the ratio of crude to extracted weight.
Standardized Herbal Extracts
- Standardized herbal extracts have a consistent concentration of specific components.
- This consistency is beneficial for the consumer.
- Standardized extracts are used when there is wide variation in composition, quality, and therapeutic effects of crude extracts.
Preliminary Phytochemical Screening
- The table provides qualitative tests for alkaloids, glycosides, tannins, phenolic compounds, resins etc.
Isolation (Column Chromatography)
- Column chromatography is a highly effective method to separate plant extracts.
- A diagram illustrating the process of column chromatography is shown
- Elution, separation and collection are demonstrated in diagrams.
- The principle explaining the separation mechanism, based on affinity to the stationary phase, is described
- Elution involves separation based on components relative affinity to the mobile and stationary phase.
Spectroscopic Methods
- Various spectroscopic methods are helpful for the structure confirmation of natural compounds and the products of their degradation.
- UV spectroscopy (conjugated dienes, α,β-unsaturated ketones)
- IR spectroscopy (hydroxyl groups, oxo groups, isopropyl groups)
- NMR spectroscopy (double bonds, types of functional groups, number of rings, and orientation of groups)
- Mass spectroscopy (molecular weight, molecular formula, functional groups)
Thin Layer Chromatography (TLC)
- TLC is a technique to separate and qualitatively identify compounds in a mixture.
- A method to determine components in a mixture, the identity of components and purity is described in detail.
- Silica gel is a typical stationary phase in TLC.
- Steps in performing TLC are detailed in pictures and text, including spotting, development, visualization of spots.
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