Isolation and identification of phytoconstituents is an essential B. Pharm topic that equips students with practical and theoretical skills in extracting, separating and characterizing bioactive phytochemicals. Core concepts include solvent selection, maceration, Soxhlet and ultrasonic extraction, liquid–liquid partitioning and bioassay‑guided fractionation. Separation and purification employ TLC, column chromatography, HPLC and GC, while identification relies on spectroscopic techniques—UV‑Vis, IR, NMR and mass spectrometry—and classic phytochemical tests for alkaloids, flavonoids, glycosides, terpenoids and phenolics. Emphasis on method development, Rf and retention time interpretation, hyphenated techniques (GC‑MS, LC‑MS) and validation readies students for research, quality control and herbal drug standardization. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which extraction technique uses continuous reflux of solvent to repeatedly wash plant material?
- Maceration
- Soxhlet extraction
- Percolation
- Cold percolation
Correct Answer: Soxhlet extraction
Q2. Which solvent is most suitable for extracting non‑polar terpenoids from plant material?
- Methanol
- Water
- Hexane
- Ethanol
Correct Answer: Hexane
Q3. What does the partition coefficient (K) represent in liquid–liquid extraction?
- The time required for extraction
- The ratio of solute concentration in organic phase to aqueous phase
- The pH at which extraction is optimal
- The volume ratio of solvents used
Correct Answer: The ratio of solute concentration in organic phase to aqueous phase
Q4. Dragendorff reagent is commonly used to detect which class of phytoconstituents?
- Flavonoids
- Alkaloids
- Saponins
- Carbohydrates
Correct Answer: Alkaloids
Q5. The Liebermann‑Burchard test is primarily used to indicate the presence of which compounds?
- Alkaloids
- Sugars
- Steroids and triterpenoids
- Proteins
Correct Answer: Steroids and triterpenoids
Q6. Molisch’s test is a general qualitative test for which group?
- Proteins
- Carbohydrates
- Alkaloids
- Phenolics
Correct Answer: Carbohydrates
Q7. The Shinoda test is classically used to detect which phytochemical group?
- Flavonoids
- Saponins
- Terpenoids
- Glycosides
Correct Answer: Flavonoids
Q8. A positive ferric chloride test commonly indicates the presence of:
- Alkaloids
- Phenolic compounds
- Carotenoids
- Fatty acids
Correct Answer: Phenolic compounds
Q9. In TLC, the Rf value is defined as:
- Distance traveled by solvent front divided by distance traveled by solute
- Distance traveled by solute divided by distance traveled by solvent front
- Time taken for solute to elute
- Concentration of solute on the plate
Correct Answer: Distance traveled by solute divided by distance traveled by solvent front
Q10. Which stationary phase is most commonly used in reversed‑phase HPLC?
- Silica gel (unmodified)
- Alumina
- C18 (octadecyl silica)
- Cellulose
Correct Answer: C18 (octadecyl silica)
Q11. Retention time in HPLC or GC mainly depends on:
- The detector sensitivity only
- The interaction of analyte with the stationary phase and mobile phase composition
- The color of the analyte
- The sample injection volume only
Correct Answer: The interaction of analyte with the stationary phase and mobile phase composition
Q12. Which detector provides direct information about molecular weight and fragmentation pattern?
- PDA (photodiode array) detector
- Refractive index detector
- Mass spectrometer (MS)
- UV detector
Correct Answer: Mass spectrometer (MS)
Q13. Which hyphenated technique couples liquid chromatography with mass spectrometry for compound identification?
- GC‑MS
- LC‑MS
- IR‑MS
- TLC‑UV
Correct Answer: LC‑MS
Q14. Proton NMR primarily provides information about:
- Elemental composition only
- Functional group vibrations
- Chemical environment and number of hydrogen nuclei
- Melting point
Correct Answer: Chemical environment and number of hydrogen nuclei
Q15. An IR absorption band near 1700 cm−1 is characteristic of which functional group?
- Hydroxyl (O–H)
- Carbonyl (C=O)
- Alkane C–H
- Nitrile (C≡N)
Correct Answer: Carbonyl (C=O)
Q16. UV‑Vis spectroscopy is most useful for detecting compounds with:
- Strong ionic bonds
- Conjugated chromophores and π‑systems
- Only aliphatic chains
- No chromophore
Correct Answer: Conjugated chromophores and π‑systems
Q17. For analysis by GC, an ideal analyte should be:
- Non‑volatile and thermolabile
- Volatile and thermally stable
- Highly polar and ionic
- Polymeric
Correct Answer: Volatile and thermally stable
Q18. Why is derivatization performed before GC analysis of many phytochemicals?
- To increase sample pH only
- To decrease detector response
- To increase volatility, thermal stability and detectability
- To convert them into polymers
Correct Answer: To increase volatility, thermal stability and detectability
Q19. What is the aim of bioassay‑guided fractionation in natural product research?
- To randomly separate compounds
- To isolate compounds based on polarity only
- To isolate biologically active compounds by iterative fractionation and testing
- To determine molecular weight
Correct Answer: To isolate biologically active compounds by iterative fractionation and testing
Q20. Which simple qualitative test indicates the presence of saponins in an extract?
- Fehling’s test
- Foam (persistent frothing) test
- Dragendorff’s test
- Molisch’s test
Correct Answer: Foam (persistent frothing) test
Q21. Which hydrolytic condition is typically used to cleave glycosidic bonds in plant glycosides?
- Base hydrolysis with dilute NaOH at low temperature
- Neutral hydrolysis with water only
- Acid hydrolysis with dilute mineral acid
- Enzymatic hydrolysis is never used
Correct Answer: Acid hydrolysis with dilute mineral acid
Q22. Which statistical parameter is commonly used to express precision of an analytical method?
- Mean absolute error
- Limit of detection (LOD)
- Relative standard deviation (%RSD)
- p‑value
Correct Answer: Relative standard deviation (%RSD)
Q23. What does LOD stand for in analytical method validation?
- Level of dilution
- Limit of detection
- Linearity of data
- Loss on drying
Correct Answer: Limit of detection
Q24. In reversed‑phase HPLC which statement is correct about stationary and mobile phases?
- Stationary phase is polar and mobile phase is non‑polar
- Stationary phase is non‑polar (e.g., C18) and mobile phase is relatively polar
- Both stationary and mobile phases are non‑polar
- Mobile phase must always be water only
Correct Answer: Stationary phase is non‑polar (e.g., C18) and mobile phase is relatively polar
Q25. Which stationary phase is most commonly used in normal‑phase TLC?
- C18 bonded silica
- Silica gel (polar)
- Cation exchange resin
- Reversed‑phase polymer
Correct Answer: Silica gel (polar)
Q26. Which chromatographic parameter in TLC is largely independent of the amount of sample spotted?
- Spot intensity
- Retention factor (Rf)
- Color of spot
- Spot diameter
Correct Answer: Retention factor (Rf)
Q27. Mass spectrometric fragmentation patterns are most useful for:
- Determining solubility only
- Providing molecular weight and structural subunit information
- Measuring melting point
- Assessing optical rotation
Correct Answer: Providing molecular weight and structural subunit information
Q28. Before extracting polar phytochemicals, plant material is often defatted using which solvent?
- Water
- Methanol
- Petroleum ether
- Acetonitrile
Correct Answer: Petroleum ether
Q29. Which qualitative test is used to detect reducing sugars in a plant extract?
- Benedict’s test
- Liebermann‑Burchard test
- Dragendorff’s test
- Foam test
Correct Answer: Benedict’s test
Q30. Which international organization provides guidelines and monographs for quality evaluation and standardization of herbal medicines?
- FDA only for all countries
- World Health Organization (WHO)
- UNESCO
- International Monetary Fund (IMF)
Correct Answer: World Health Organization (WHO)
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com