MCQ on Extraction and Isolation of Bioactive Compounds

🟢 EASY (1–20)

1. What are bioactive compounds?
   a) Inactive molecules
   b) Molecules that cause diseases
   c) Natural compounds with biological activity ✅
   d) Artificial preservatives
   Explanation: Bioactive compounds are natural substances that have effects on living organisms.
2. Which of the following is a common method for extraction?
   a) Filtration
   b) Distillation
   c) Solvent extraction ✅
   d) Crystallization
   Explanation: Solvent extraction is widely used to isolate bioactive compounds.
3. What is the first step in the extraction of plant materials?
   a) Chromatography
   b) Washing
   c) Drying ✅
   d) Isolation
   Explanation: Drying removes moisture and prevents degradation.
4. Which solvent is commonly used for polar compounds?
   a) Hexane
   b) Water ✅
   c) Chloroform
   d) Ether
   Explanation: Polar solvents like water are used for extracting polar compounds.
5. Which method is best for extracting thermolabile compounds?
   a) Boiling
   b) Soxhlet extraction
   c) Cold maceration ✅
   d) Dry heat
   Explanation: Cold maceration prevents heat degradation.
6. Which technique separates compounds based on their boiling point?
   a) Distillation ✅
   b) Filtration
   c) Crystallization
   d) Centrifugation
   Explanation: Distillation separates based on volatility.
7. Soxhlet extraction is mainly used for:
   a) Volatile oils
   b) Heat-sensitive compounds
   c) Continuous solvent extraction ✅
   d) Water-soluble compounds
   Explanation: Soxhlet provides continuous hot solvent extraction.
8. Which method uses water or steam to extract oils?
   a) Maceration
   b) Percolation
   c) Steam distillation ✅
   d) Soxhlet extraction
   Explanation: Common for essential oils.
9. Alkaloids are usually extracted with:
   a) Acidic solvents ✅
   b) Basic solvents
   c) Water
   d) Alcohol only
   Explanation: They are basic and form salts with acids.
10. Which term describes isolating one component from a mixture?
    a) Emulsification
    b) Extraction ✅
    c) Dispersion
    d) Infusion
    Explanation: Extraction involves separating specific components.
11. Which method is suitable for large-scale extraction?
    a) Maceration
    b) Soxhlet
    c) Supercritical fluid extraction
    d) Percolation ✅
    Explanation: Continuous and suitable for industrial use.
12. What is the purpose of using solvents in extraction?
    a) To preserve material
    b) To dissolve bioactive compounds ✅
    c) To boil the extract
    d) To dry the extract
    Explanation: Solvents dissolve and separate desired compounds.
13. Which factor does not influence extraction efficiency?
    a) Solvent type
    b) Particle size
    c) Magnetic field ✅
    d) Temperature
    Explanation: Magnetic field has no direct role.
14. Which technique is commonly used for purification?
    a) Chromatography ✅
    b) Drying
    c) Grinding
    d) Filtration
    Explanation: Chromatography separates based on chemical properties.
15. Flavonoids are commonly extracted using:
    a) Water
    b) Ethanol ✅
    c) Acetone
    d) Benzene
    Explanation: Ethanol is efficient and safe.
16. What is the advantage of ethanol as a solvent?
    a) Toxic
    b) Non-polar
    c) Safe and polar ✅
    d) Expensive
    Explanation: Ethanol is food-grade and extracts a wide range.
17. Which instrument is used in supercritical extraction?
    a) Oven
    b) CO₂ extractor ✅
    c) Heater
    d) Grinder
    Explanation: Supercritical CO₂ is a green solvent.
18. Which of the following is a non-polar solvent?
    a) Water
    b) Methanol
    c) Hexane ✅
    d) Ethanol
    Explanation: Hexane extracts non-polar compounds like lipids.
19. Maceration involves soaking in:
    a) Acid
    b) Hot water
    c) Cold solvent ✅
    d) Alcohol vapor
    Explanation: It involves soaking at room temperature.
20. Crystallization is used to:
    a) Dissolve compounds
    b) Identify compounds
    c) Purify solid compounds ✅
    d) Emulsify compounds
    Explanation: Used to isolate pure compounds from solution.

🟡 MODERATE (21–40)

21. Which factor increases extraction rate?
    a) Decreased temperature
    b) Larger particle size
    c) Increased surface area ✅
    d) Reduced solvent contact
    Explanation: More surface area helps solvent penetration.
22. What is percolation?
    a) Filtration through a membrane
    b) Boiling and condensing
    c) Slow downward movement of solvent ✅
    d) Evaporation of liquid
    Explanation: Solvent percolates through the material.
23. Lyophilization helps in:
    a) Heating
    b) Freezing
    c) Freeze-drying of extracts ✅
    d) Boiling under pressure
    Explanation: Preserves temperature-sensitive compounds.
24. Which of the following is semi-polar solvent?
    a) Chloroform
    b) Methanol ✅
    c) Water
    d) Hexane
    Explanation: Methanol dissolves both polar and non-polar substances.
25. The solvent system in Thin Layer Chromatography (TLC) is called:
    a) Mobile phase ✅
    b) Stationary phase
    c) Extractant
    d) Reagent
    Explanation: Solvent moves the compounds.
26. Which method uses gas as mobile phase?
    a) TLC
    b) GC ✅
    c) HPLC
    d) Paper chromatography
    Explanation: Gas Chromatography uses gas for separation.
27. Column chromatography separates based on:
    a) Density
    b) Boiling point
    c) Polarity and adsorption ✅
    d) pH
    Explanation: Interactions with stationary and mobile phases.
28. Which part of plant yields essential oil in most cases?
    a) Roots
    b) Seeds
    c) Leaves ✅
    d) Stems
    Explanation: Oils are commonly found in aromatic leaves.
29. Tannins are better extracted using:
    a) Hexane
    b) Ether
    c) Water and ethanol ✅
    d) Chloroform
    Explanation: They are polyphenolic and soluble in polar solvents.
30. Bioactivity is tested by:
    a) Filtration
    b) Bioassay ✅
    c) Distillation
    d) Centrifugation
    Explanation: Bioassays assess biological effects.
31. Which is a drawback of Soxhlet extraction?
    a) Too fast
    b) Not effective
    c) High temperature degrades some compounds ✅
    d) No solvent needed
    Explanation: Heat can damage sensitive compounds.
32. Which modern technique uses pressure and CO₂?
    a) Steam distillation
    b) Maceration
    c) Supercritical fluid extraction ✅
    d) Reflux
    Explanation: CO₂ under pressure acts like both liquid and gas.
33. The solid substance left after extraction is called:
    a) Filtrate
    b) Residue ✅
    c) Solvent
    d) Precipitate
    Explanation: Residue is the plant material left behind.
34. A rotary evaporator is used to:
    a) Cool the solvent
    b) Dissolve extract
    c) Remove solvent under reduced pressure ✅
    d) Add solvent
    Explanation: Helps avoid overheating during solvent removal.
35. Which of the following is a method of isolation?
    a) Maceration
    b) Chromatography ✅
    c) Grinding
    d) Drying
    Explanation: Chromatography isolates pure components.
36. What is an eluotropic series?
    a) Series of acids
    b) List of solvents by boiling point
    c) List of solvents by polarity ✅
    d) List of alkaloids
    Explanation: Helps choose solvents for chromatography.
37. Which part is not required in Soxhlet apparatus?
    a) Thimble
    b) Condenser
    c) Flask
    d) Reflux column ✅
    Explanation: It uses a condenser, not a separate reflux column.
38. Which technique separates volatile oils from water?
    a) TLC
    b) Paper chromatography
    c) Steam distillation ✅
    d) Decantation
    Explanation: Used to extract essential oils.
39. In HPLC, the stationary phase is typically:
    a) Liquid
    b) Solid ✅
    c) Gas
    d) Plasma
    Explanation: Solid support with liquid mobile phase.
40. Microwave-assisted extraction is faster due to:
    a) Boiling
    b) Increased surface tension
    c) Rapid heating ✅
    d) High cooling
    Explanation: Microwaves heat rapidly and uniformly.

🔴 HARD (41–50)

41. What is the principle of supercritical fluid extraction?
    a) Heating
    b) Gas-liquid equilibrium
    c) Solubility at critical temperature and pressure ✅
    d) Adsorption
    Explanation: Above critical points, CO₂ has enhanced solvating power.
42. Which bioactive compound class needs acidic medium for extraction?
    a) Alkaloids ✅
    b) Flavonoids
    c) Glycosides
    d) Steroids
43. Polar solvents extract compounds via:
    a) Dispersion
    b) Hydrogen bonding and dipole interactions ✅
    c) Electrolysis
    d) Repulsion
44. What does the ‘Rf’ value indicate in TLC?
    a) Retardation factor ✅
    b) Relative formula
    c) Reaction factor
    d) Radiation frequency
    Explanation: Rf = distance traveled by compound/distance by solvent.
45. Which detection method is used in HPLC?
    a) Flame ionization
    b) UV-Vis absorbance ✅
    c) Magnetic resonance
    d) Conductivity
    Explanation: UV detectors are commonly used.
46. Bioassay-guided fractionation is used for:
    a) Crystallizing compounds
    b) Identifying active compounds ✅
    c) Solvent recovery
    d) Melting point measurement
47. Which plant part is best for glycoside extraction?
    a) Bark
    b) Root
    c) Leaves
    d) All of the above ✅
    Explanation: Glycosides can be present in many parts.
48. Drying under vacuum helps in:
    a) Heating quickly
    b) Avoiding solvent use
    c) Preserving thermolabile compounds ✅
    d) Increasing temperature
49. An example of a non-conventional extraction method is:
    a) Cold maceration
    b) Percolation
    c) Microwave-assisted extraction ✅
    d) Boiling
50. The ideal solvent for extraction should have:
    a) High viscosity
    b) Reactivity with compound
    c) Selective solubility and volatility ✅
    d) Insolubility in water
    Explanation: Good solvents selectively dissolve the desired compound and are easy to remove.