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Questions and Answers
In the saponin detection test, what observation specifically indicates the presence of saponins after shaking and settling?
In the saponin detection test, what observation specifically indicates the presence of saponins after shaking and settling?
What is the primary purpose of using anhydrous sodium sulfate in the Liebermann-Burchard test?
What is the primary purpose of using anhydrous sodium sulfate in the Liebermann-Burchard test?
During the Liebermann-Burchard test, a plant extract is treated with acetic anhydride and concentrated sulfuric acid. What does a blue-green color indicate?
During the Liebermann-Burchard test, a plant extract is treated with acetic anhydride and concentrated sulfuric acid. What does a blue-green color indicate?
Which chemical structural feature of cardiac glycosides is specifically detected by the Kedde test?
Which chemical structural feature of cardiac glycosides is specifically detected by the Kedde test?
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In the context of cardiac glycosides, what is the significance of the sugars being in the β-conformation?
In the context of cardiac glycosides, what is the significance of the sugars being in the β-conformation?
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What role does methanol (MeOH) play in the preparation of the Kedde reagent?
What role does methanol (MeOH) play in the preparation of the Kedde reagent?
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What is the purpose of using Whatman No. 1 paper in the Kedde test procedure for cardiac glycosides?
What is the purpose of using Whatman No. 1 paper in the Kedde test procedure for cardiac glycosides?
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The Keller-Killiani test, the Liebermann-Burchard test, and the Kedde test are all positive. Which compound is most likely present?
The Keller-Killiani test, the Liebermann-Burchard test, and the Kedde test are all positive. Which compound is most likely present?
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Which characteristic is LEAST important when selecting a method for phytochemical screening?
Which characteristic is LEAST important when selecting a method for phytochemical screening?
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Why is it important to extract plant samples on the same day they are collected for phytochemical analysis?
Why is it important to extract plant samples on the same day they are collected for phytochemical analysis?
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What concentration of ethanol or methanol is generally considered suitable for extracting a wide range of phytochemicals from plant samples?
What concentration of ethanol or methanol is generally considered suitable for extracting a wide range of phytochemicals from plant samples?
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After extracting a plant sample with 80% methanol and filtering, what is the next recommended step to prepare the extract for phytochemical screening?
After extracting a plant sample with 80% methanol and filtering, what is the next recommended step to prepare the extract for phytochemical screening?
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In the alkaloid screening process, what is the purpose of adding 2M HCl and heating the plant extract?
In the alkaloid screening process, what is the purpose of adding 2M HCl and heating the plant extract?
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During alkaloid screening, what observation indicates a positive result for the presence of alkaloids?
During alkaloid screening, what observation indicates a positive result for the presence of alkaloids?
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In a field screening for alkaloids, why is chloroform (CHCl3) used in conjunction with ammonia (NH3)?
In a field screening for alkaloids, why is chloroform (CHCl3) used in conjunction with ammonia (NH3)?
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What property of saponins allows for their easy detection?
What property of saponins allows for their easy detection?
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Which of the following best describes the primary mechanism by which maceration achieves extraction?
Which of the following best describes the primary mechanism by which maceration achieves extraction?
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In the context of plant extract preparation, what is the main purpose of frequent stirring during maceration?
In the context of plant extract preparation, what is the main purpose of frequent stirring during maceration?
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What is a key operational difference between maceration and percolation techniques in plant extraction?
What is a key operational difference between maceration and percolation techniques in plant extraction?
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Why is controlling the rate of solvent flow important during percolation?
Why is controlling the rate of solvent flow important during percolation?
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What is a significant limitation of the percolation method when compared to other extraction techniques?
What is a significant limitation of the percolation method when compared to other extraction techniques?
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Which of the following is a suitable container for performing maceration?
Which of the following is a suitable container for performing maceration?
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Which extraction method is most suited for plant materials that readily dissolve or release active ingredients in solvents, particularly volatile compounds?
Which extraction method is most suited for plant materials that readily dissolve or release active ingredients in solvents, particularly volatile compounds?
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How does the principle of infusion relate to maceration and decoction?
How does the principle of infusion relate to maceration and decoction?
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During the extraction of plant materials, why is reducing the sample size through grinding considered a crucial initial step?
During the extraction of plant materials, why is reducing the sample size through grinding considered a crucial initial step?
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In bioassay-guided isolation, what role does bioactivity screening play in identifying active principles from plant extracts?
In bioassay-guided isolation, what role does bioactivity screening play in identifying active principles from plant extracts?
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Which of the following statements accurately describes the relationship between extraction techniques and the nature of the plant sample?
Which of the following statements accurately describes the relationship between extraction techniques and the nature of the plant sample?
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Why is structural elucidation, using spectroscopic methods, a critical step in obtaining active principles from plants?
Why is structural elucidation, using spectroscopic methods, a critical step in obtaining active principles from plants?
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In the context of plant extraction and compound isolation, how do fractionation and solvent partitioning contribute to the overall process?
In the context of plant extraction and compound isolation, how do fractionation and solvent partitioning contribute to the overall process?
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What is the main difference between 'Spectroscopical data on-line' and 'Spectroscopical data off-line' in the context of active principle isolation from plants?
What is the main difference between 'Spectroscopical data on-line' and 'Spectroscopical data off-line' in the context of active principle isolation from plants?
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Considering the steps involved in obtaining active principles from plants, which of the following sequences represents the MOST logical and efficient order?
Considering the steps involved in obtaining active principles from plants, which of the following sequences represents the MOST logical and efficient order?
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If a researcher aims to isolate a non-polar bioactive compound from a plant, which initial extraction solvent would be MOST suitable?
If a researcher aims to isolate a non-polar bioactive compound from a plant, which initial extraction solvent would be MOST suitable?
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In the context of plant extract preparation, what is the primary difference between infusion and decoction?
In the context of plant extract preparation, what is the primary difference between infusion and decoction?
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Which extraction method is most suitable for isolating essential oils (EOs) and other volatile compounds that are insoluble in water?
Which extraction method is most suitable for isolating essential oils (EOs) and other volatile compounds that are insoluble in water?
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According to Raoult’s law as applied to steam and hydrodistillation, what effect does the presence of volatile compounds have on the boiling point of water in the mixture?
According to Raoult’s law as applied to steam and hydrodistillation, what effect does the presence of volatile compounds have on the boiling point of water in the mixture?
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A researcher needs to extract a specific water-soluble, thermostable compound from a plant sample. Which method would be most appropriate?
A researcher needs to extract a specific water-soluble, thermostable compound from a plant sample. Which method would be most appropriate?
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In hydrodistillation, what is the initial step in the process before heating begins?
In hydrodistillation, what is the initial step in the process before heating begins?
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What is a key advantage of using steam distillation over other extraction methods when dealing with thermo-sensitive bioactive compounds?
What is a key advantage of using steam distillation over other extraction methods when dealing with thermo-sensitive bioactive compounds?
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Why is the maceration time shorter for infusion, compared to other extraction methods?
Why is the maceration time shorter for infusion, compared to other extraction methods?
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Which of the following health applications is specifically mentioned to be associated with infusions in the provided text?
Which of the following health applications is specifically mentioned to be associated with infusions in the provided text?
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In column chromatography, what is the primary reason for using sand at the bottom of the column?
In column chromatography, what is the primary reason for using sand at the bottom of the column?
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Why is it important to prevent the silica gel from drying out during column chromatography?
Why is it important to prevent the silica gel from drying out during column chromatography?
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In preparative thin layer chromatography (PTLC), how are samples typically applied to the plate?
In preparative thin layer chromatography (PTLC), how are samples typically applied to the plate?
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After developing a preparative TLC plate and identifying the band of interest, what is the next step in recovering the compound?
After developing a preparative TLC plate and identifying the band of interest, what is the next step in recovering the compound?
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What characteristics of alkaloids are exploited in acid-base extraction techniques?
What characteristics of alkaloids are exploited in acid-base extraction techniques?
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Why is the sample ground before performing alkaloid extraction?
Why is the sample ground before performing alkaloid extraction?
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After eluting a compound from the silica in preparative TLC, what is a common method used to check its purity?
After eluting a compound from the silica in preparative TLC, what is a common method used to check its purity?
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In column chromatography, what is the purpose of using sand at the top of the silica column?
In column chromatography, what is the purpose of using sand at the top of the silica column?
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Flashcards
Phytochemical Screening
Phytochemical Screening
A method to analyze plant extracts for various chemical compounds.
Extract Preparation
Extract Preparation
The process of obtaining chemical compounds from plant materials using solvents.
80% Ethanol
80% Ethanol
Common solvent concentration for effective extraction of compounds from plants.
Alkaloid Screening
Alkaloid Screening
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Mayer Reagent
Mayer Reagent
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Saponin Screening
Saponin Screening
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Precipitate Formation
Precipitate Formation
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Foam Test
Foam Test
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Extraction process
Extraction process
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Bioassay Guided Isolation
Bioassay Guided Isolation
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Fractionation
Fractionation
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Chromatography
Chromatography
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Structural elucidation
Structural elucidation
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Hydrodistillation
Hydrodistillation
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Phytochemicals
Phytochemicals
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Bioactivity screening
Bioactivity screening
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Maceration
Maceration
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Purpose of Maceration
Purpose of Maceration
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Molecular Diffusion
Molecular Diffusion
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Percolation
Percolation
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Controlled Rate in Percolation
Controlled Rate in Percolation
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Extraction Types
Extraction Types
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Infusion
Infusion
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Decoction
Decoction
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Saponin Presence
Saponin Presence
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Liebermann-Burchadd Test
Liebermann-Burchadd Test
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Color Change in L-B Test
Color Change in L-B Test
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Cardiac Glycoside Tests
Cardiac Glycoside Tests
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Kedde Test
Kedde Test
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Keller-Killiani Test
Keller-Killiani Test
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Cardiac Glycoside Structure
Cardiac Glycoside Structure
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Common Sugars in Cardiac Glycosides
Common Sugars in Cardiac Glycosides
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Water Soluble Compounds
Water Soluble Compounds
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Steam Distillation
Steam Distillation
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Thermo-sensitive Compounds
Thermo-sensitive Compounds
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Raoult’s Law
Raoult’s Law
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Volatile Compounds
Volatile Compounds
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Thin Layer Chromatography (TLC)
Thin Layer Chromatography (TLC)
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Packing and Loading
Packing and Loading
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Silica Gel
Silica Gel
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Sand in Chromatography
Sand in Chromatography
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Preparative Thin Layer Chromatography (PTLC)
Preparative Thin Layer Chromatography (PTLC)
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Scraping in PTLC
Scraping in PTLC
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Alkaloids
Alkaloids
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Acid-Base Extraction
Acid-Base Extraction
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Study Notes
Extraction of Natural Products
- Extraction is a common technique in organic chemistry used to isolate a target compound.
- In extraction, a solute is transferred from one phase to another to separate it from unreacted starting materials or impurities.
- Liquid-liquid and liquid-solid extractions are two main types where separation is based on solubility.
- Acid-base extraction is a type of liquid-liquid extraction based on acid-base reactions. A substance is extracted when reacting with an acid or base.
- Liquid-liquid extraction can be performed to extract a polar compound from an organic solvent if the organic solvent contains both a polar and a non-polar compound, due to the polar compound being more soluble in a polar solvent like water.
- Extraction is separating the medicinally active mixture of many naturally active compounds usually contained inside plant materials (tissues) using selective solvents through the standard procedure.
- Extraction is also the treatment of plant material with solvent to dissolve medicinally active constituents, leaving most of the inert matter undissolved.
- The purpose of all extraction is to separate the soluble plant metabolites from the insoluble cellular materials known as residue.
AIM for Extraction
- Two most fundamental questions at the outset of an extraction are:
- What am I trying to isolate?
- Why am I trying to isolate it?
- Possible isolating targets include:
- Unknown compounds responsible for biological activity.
- A particular compound produced by a specified organism.
- A group of compounds within an organism with a common feature.
- All metabolites produced by a source, but not produced by a different control source, e.g., different species, or same organism, different conditions.
- A chemical dissection of an organism to characterize its metabolites, useful for chemical, ecological or chemotaxonomic reasons.
Why Isolate Active Compounds?
- To purify a compound for full or partial characterization.
- To provide sufficient material for confirming or denying proposed structures. Comparison with known structures requires less material; even partially pure compound may suffice.
- To generate a maximum quantity of a known compound for further research, e.g., extensive biological testing.
Purity of Compound
- For complete compound characterization, typically 95-100% purity is required for NMR.
- If a compound is highly concentrated in the starting material and a standard exists for comparison, less pure material may suffice.
- For biological testing, to generate pharmacological data, very pure compounds (≥99%) are required.
- For X-ray crystallography, compound purity is often required to be extremely high (≥99.9%).
Drug Discovery Cycle
- Steps involved in a drug discovery cycle include:
- Compound collections
- Primary Assays (high-throughput, in vitro)
- Secondary Assays (counter screen, bioavailability, toxicity, metabolism, etc.)
- Chemical Synthesis (direct or indirect).
- Lead Compounds and SAR; Structural characterisation of Protein-Ligand Complex
- Clinical Candidate
Early Drug Discovery, Preclinical Studies, Clinical Development, FDA review, Post-Market Monitoring
- Identifying and validating drug targets.
- Discovering hits via assay development and screening; high throughput screening.
- Optimization of hits to leads.
- Preclinical studies include in vitro, in vivo, and ex vivo assays; proof of concept; drug delivery, optimization, and bioavailability. Dose-ranging and enabling IND studies. IND application.
- Clinical development includes phases I-III, healthy volunteer studies, patient population studies. Dose escalation and safety and efficacy analysis; pharmacokinetic and bioanalytical method validation.
- FDA review includes NDA/ANDA/BLA application, and drug registration.
- Post-market monitoring includes FDA Adverse Event Reporting system (FAERS) reporting.
Key Phytochemical concepts
- Phytochemistry involves the study of chemical compounds in plants, including isolation, purification, and structural elucidation.
- Isolated compounds may display various activities in medicine, agriculture and aquaculture.
- Phytochemical screening is a simple method used for determining secondary metabolites present in extracts. This includes specific compounds like alkaloids, saponins, steroids, cardiac glycosides, and phenolic compounds (e.g., flavonoids).
- Requirements for phytochemical screening include simple or easy methods, speed, minimum apparatus, high sensitivity (even at low concentration), clear results, and reproducibility.
Extract Preparation
- Plant samples are often extracted on the day of collection to avoid physiological changes.
- Commonly, 80% ethanol or methanol is used for extraction.
- A typical extract preparation process involves pulverizing ~200 g of plant material, adding it to 600 ml of 80% MeOH, and heating slowly for ~1 hour.
- Filtering using Buchner or Whatman No. 1 filter paper is necessary.
- The extracts are concentrated to ~1 g/mL using a rotary evaporator at ~40°C.
Alkaloid Screening
- Plant extracts (equivalent to ~20 g) are evaporated to a concentrated syrup.
- Sample is treated with 10 mL of 2M HCL, heated for 10 minutes, and 0.5 g of clarifying agent is added.
- The mixture's volume is adjusted to ~5 mL and divided into 4 portions.
- Control test tube (A) and three test tubes (B, C, D) are prepared for various tests using Mayer, Wagner, and Dragendorff reagents, respectively.
- Precipitate or cloudy solution formation indicates positive results. Quantitative testing is based on clarity (1+, 2+) or precipitate level (3, 4+) which is determined using specific colour observations with the respective reagents.
- Additional field screening involves grinding 2-4 g of sample with sand, then adding 10 mL of CHCl3, followed by 10 mL of CHCl3/NH3, filtration, and then 20 drops of 2M H2SO4 and shaking. The aqueous layer is separated and tested using Mayer reagent.
Saponin Screening
- Triterpenoid saponins, steroid saponins, and sapogenins can be detected easily. The ability to form honey comb foam, hemolyse blood cells, and kill small organisms (like fish) are characteristics of saponins.
- Saponins dissolve readily in 80% MeOH or EtOH.
- Saponin hydrolysis using 2M HCl is a potential technique.
- An equivalent of ~2g plant extract is prepared and 10 mL of water is added to form foam (determined after vigorous shaking followed by resting).
Lieberman-Burchard (L-B) Test
- The test determines whether the sample contains steroid or triterpenoid saponins.
- Aplant extract (equivalent to 10 g) is treated using 10 mL of diluted H₂SO₄, heated for 10 minutes, cooled down and then extracted with 10 mL of CHCl₃.
- The separated CHCl₃ extract is dried using anhydrous sodium sulphate.
- 3 drops of acetic anhydride and 1 drop of conc. sulphuric acid are added to the extract and let to mix slowly.
- The colour changes observed for 1 hour, with blue/greenish-blue colours indicating steroid saponins and red/purple colours indicating triterpenoid saponins.
Cardiac Glycoside
- Various tests are available to determine the composition including steroid skeleton (using the L-B test), unsaturated lactone (using the Kedde test), deoxy sugars/sugars (using the Keller Killiani test).
- A positive test for all three tests indicates cardiac glycoside activity.
- One to four sugars that are attached to the 3β-OH group define the sugar moiety. Common sugars include L-rhamnose, D-glucose, D-digitoxose, D-digitalose, D-digginose, D-sarmentose, L-vallarose, and D-fructose. These preferentially exist in the 𝛽 -conformation.
- The presence of acetyl groups on the sugar can change the lipophilic character and kinetics of the entire glycoside. The aqueous layer obtained with 0.1–0.2 mL of plant extract spotted on Whatman No. 1 paper , is developed in CHCl₃ and dried, followed by spraying Kedde reagent allows the determining of the Unsaturated lactone component.
Flavonoid Screening
- Most flavonoids are based on the flavon nucleus and are easily soluble in MeOH or EtOH.
- Flavonoids are phenolic compounds that exhibit colour changes when treated with a base, which can be observed on a chromatogram or in solution.
- Flavonoids are conjugated aromatic compounds. Flavonoids usually show strong absorption in the UV or Visible spectral region, and many are attached to sugars.
- Flavonoid identification involves extracting plant extracts equivalent to ~10g of plant to dryness , followed by evaporation , then defatting with repeated removal /dissolution by hexane extraction. The residues are then dissolved in 20 mL of 80% MeOH and four test tubes, one for control and the remainder for separate tests. Separate tests using different chemical solutions include the Wilstatter Cyanidin test (using 0.5ml conc HCI and 1cm Mg ribbon) and Bate-Smith and Metcalf test (using 0.5ml conc HCl) and Leucoantocyanidin test ( using steam bath for 15 minutes with 0.5ml conc HCl).
Sample Selection for Phytochemical Studies
- Random sampling can be used.
- Sampling can be based on traditional uses (ethno-pharmacological) as well as the specific genera or family , such as (for examples cardenolides found in families such as Crassulaceae, Hyacinthaceae, Iridaceae, Melianthaceae, Ranunculaceae, and Santalaceae); and alkaloids within Ranunculaceae, Leguminosae, Papaveraceae, Menispermaceae, and Loganiaceae.
- Sampling can be based on specific compounds, e.g., alkaloids.
General Extraction Procedure
- Extraction with organic solvent (Percolation, maceration, Soxhlet apparatus).
- Extraction with water (infusion, decoction, steam/hydrodistillation).
- Sample selection: Fresh or dried samples can be used; dried samples preferred due to preservation.
- Drying methods include open air drying, shallow trays with good air circulation , and oven drying; cold temperature (<30°C) is crucial to maintain thermolabile components.
- Grinding reduces particle size to increase solvent contact and enhance extraction efficiency; a uniform particle size is critical.
- Obtaining the active ingredients in a complex mix requires separation of the plant metabolites in liquid or solid-state by using different solubility differences between components and solvent used, time parameters, and particle size. Three common types include liquid/solid, liquid/liquid, and acid/base extractions,.
- Choosing an appropriate solvent that is the best for the compounds being extracted.
- Choosing a proper extraction procedure is crucial to get a pure compound. This includes careful selection of plant samples, solvents, and extraction time for the particular class of compounds or plant species being tested.
Other Extraction Techniques
- Microwave-assisted extraction (MAE) uses microwaves of light (300 MHz ;λ= 1m to 300 GHz ; λ=1mm) and the elevated temperature for faster heating and thus better extraction yields, and is preferable for thermolabile compounds.
- Supercritical fluid extraction (SFE) uses CO₂ as an extracting solvent at a low temperature, which avoids degradation from heat and maintains the quality of the product, e.g., fragrances and aromas. In cases when polarity limitations are present, CO₂ can be mixed with organic solvents for better extraction in the SFE procedure.
- Soxhlet extraction is the method in which the extractant solvents are heated in a round bottom flask, the sample is placed in a thimble, vapourisation of the solvent causes the solvent to go to the sample thimble, condensed in a condenser, and drips back into the bottom flask. Heating and solvent movement via condensation is repeated until the process is complete.
Chromatography
- Chromatography is a laboratory technique used for separating components of a mixture. It's based on differential partitioning within a mobile and stationary phase.
- Various chromatography techniques may be used, including thin layer chromatography (TLC), column chromatography (CC), and other variations.
Thin Layer Chromatography (TLC)
- TLC use silica gel as the adsorbent, calcium sulphate (gypsum) serves as a binder, and water.
- The process is faster with better separations using various stationary phases for visualization purposes.
- Various spray reagents or visualization are used to visualize the colorless components, including iodine vapors or a fluorescence compound (e.g., manganese-activated zinc silicate).
- Rf value for the component is obtained by determining the distance the compound travelled as compared to the total distance traveled by the solvent (the solvent front). Values can vary based on the solvent used, the TLC plate, and are not physical constants.
- For preparative TLC (PTLC), larger quantities of mixtures (10mg-1 gram) of substances , can be separated by scraping the separated bands off the plate, and using a suitable solvent to extract the material from the adsorbent for further purification.
Column Chromatography (CC)
- CC uses chromatography columns using a stationary phase (e.g., silica gel, alumina).
- A solvent (or mixture of solvents) is used to dissolve the sample and separate by differential adsorption, and is typically run as a slurry or dry-method.
High-Throughput Screening (HTS)
- HTS refers to the identification of one or more positive candidates from a pool of possible candidates based on specific criteria; this is a widely adopted drug-discovery process.
- HTS is a translational research technology used for identifying effectors (compounds, peptides, and biologics) that modulate target-specific assays and the biological activity of a large number of compounds.
- HTS methods emphasize automation with multiple sample analysis; this is advantageous for larger compound collections (>100,000 per day) and thus more cost-effective R&D protocols.
Other Methods
- Alkaloid Extraction - Acid Base - This involves specific steps to extract alkaloids from other impurities based on their basic nature and reaction with various acids.
- Flavonoid extractions.
- Carotenoid Extraction - involves a specific choice of solvents according to polarity of the compound.
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Description
Questions about methods to detect saponins, cardiac glycosides. Topics include the Liebermann-Burchard, Kedde, and Keller-Killiani tests and their applications in identifying plant compounds. Assessing understanding of chemical reactions and interpretation of results in phytochemical screening.
