Volatile oils – Mentha MCQs With Answer

Volatile oils – Mentha MCQs With Answer

Volatile oils from Mentha species (peppermint, spearmint, pennyroyal) are rich in monoterpenes like menthol, menthone and carvone and are central to pharmacognosy, quality control, and formulation in B.Pharm studies. Understanding steam distillation, GC fingerprinting, physicochemical tests (refractive index, optical rotation, specific gravity), chemotypes, biosynthesis (GPP precursor), pharmacology (antispasmodic, carminative, antimicrobial) and safety concerns (pulegone hepatotoxicity, oxidation) is essential for drug development and analysis. This set of focused, application-oriented MCQs emphasizes analytical methods, stability, adulteration detection and clinical relevance of Mentha volatile oils. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the major cooling monoterpene found in peppermint oil?

• Menthol
• Menthone
• Pulegone
• Carvone

Correct Answer: Menthol

Q2. Which extraction method is most appropriate for isolating Mentha volatile oils on a commercial scale?

• Soxhlet extraction with ethanol
• Supercritical CO2 extraction only
• Steam distillation
• Maceration in water

Correct Answer: Steam distillation

Q3. Which constituent is the principal component of spearmint oil?

• Menthol
• Carvone
• Menthone
• Linalool

Correct Answer: Carvone

Q4. Mentha volatile oils are predominantly composed of which class of terpenes?

• Monoterpenes (C10)
• Sesquiterpenes (C15)
• Diterpenes (C20)
• Triterpenes (C30)

Correct Answer: Monoterpenes (C10)

Q5. Which statement correctly describes the solubility of Mentha volatile oils?

• Highly soluble in water and insoluble in alcohol
• Insoluble in water, soluble in organic solvents and alcohol
• Soluble in water and fixed oils
• Only soluble in aqueous alkaline solutions

Correct Answer: Insoluble in water, soluble in organic solvents and alcohol

Q6. Which analytical technique provides the most detailed quantitative profile of Mentha oil components?

• Thin-layer chromatography (TLC)
• Gas chromatography (GC) or GC-MS
• Ultraviolet spectroscopy (UV)
• Paper chromatography

Correct Answer: Gas chromatography (GC) or GC-MS

Q7. Which Mentha constituent is associated with hepatotoxicity and requires careful safety consideration?

• Menthol
• Pulegone
• Carvone
• Limonene

Correct Answer: Pulegone

Q8. The immediate biosynthetic precursor for monoterpenes in Mentha is:

• Isopentenyl pyrophosphate (IPP)
• Geranyl pyrophosphate (GPP)
• Squalene
• Mevalonic acid

Correct Answer: Geranyl pyrophosphate (GPP)

Q9. Which simple physicochemical tests are commonly used in preliminary quality control of volatile oils?

• Melting point and boiling range
• Refractive index, specific gravity and optical rotation
• pH and titratable acidity
• Saponification value and iodine value only

Correct Answer: Refractive index, specific gravity and optical rotation

Q10. Which Mentha species is characteristically rich in pulegone and should be used cautiously?

• Mentha piperita (peppermint)
• Mentha spicata (spearmint)
• Mentha pulegium (pennyroyal)
• Mentha arvensis (cornmint)

Correct Answer: Mentha pulegium (pennyroyal)

Q11. For long-term storage of Mentha volatile oil to prevent oxidation, the best practice is:

• Store in clear plastic bottles at room temperature
• Store in amber glass, airtight containers at low temperature
• Keep in metal cans exposed to light
• Dilute with water and refrigerate

Correct Answer: Store in amber glass, airtight containers at low temperature

Q12. Which test can detect dilution of Mentha oil with cheaper fixed oils?

• Determination of refractive index only
• Saponification and detection of non-volatile residue
• Paper chromatography with water as solvent
• Measurement of viscosity only

Correct Answer: Saponification and detection of non-volatile residue

Q13. Which pharmacological action is commonly attributed to peppermint oil in gastrointestinal disorders?

• Prokinetic stimulant
• Antispasmodic and carminative
• Opioid receptor agonist
• Cholinesterase inhibitor

Correct Answer: Antispasmodic and carminative

Q14. Which mentha constituent is a monoterpenone (a ketone) commonly found in peppermint oil?

• Menthol
• Menthone
• Carvone
• Linalool

Correct Answer: Menthone

Q15. The antimicrobial effect of menthol and other monoterpenes is primarily due to:

• Inhibition of DNA replication
• Disruption of microbial cell membrane integrity
• Blocking ribosomal protein synthesis
• Chelation of essential metal ions

Correct Answer: Disruption of microbial cell membrane integrity

Q16. Which optical property is useful to monitor compositional changes in Mentha oils during storage?

• Fluorescence intensity
• Optical rotation (specific rotation)
• Magnetic susceptibility
• Dielectric constant

Correct Answer: Optical rotation (specific rotation)

Q17. Which instrumental technique is most useful to identify functional groups in volatile oil constituents?

• Mass spectrometry alone
• Infrared spectroscopy (IR)
• Flame photometry
• Polarimetry

Correct Answer: Infrared spectroscopy (IR)

Q18. Which constituent is characteristic of peppermint oil and contributes to a strong minty odor and local anesthetic effect?

• Menthol
• Carvone
• Pulegone
• Eugenol

Correct Answer: Menthol

Q19. A rapid fingerprinting technique combining separation and mass identification for Mentha oils is:

• HPLC-UV
• GC-MS
• Paper chromatography
• Gel electrophoresis

Correct Answer: GC-MS

Q20. Which of the following is NOT typically a constituent of Mentha volatile oil?

• Menthol
• Menthone
• Carvone
• Eugenol

Correct Answer: Eugenol

Q21. Peppermint oil relaxes intestinal smooth muscle partly by which mechanism?

• Beta-adrenergic receptor activation
• Calcium channel blockade
• Inhibition of acetylcholine release centrally
• Stimulation of serotonin receptors

Correct Answer: Calcium channel blockade

Q22. Oxidative rancidity of Mentha oils during storage primarily produces:

• Saponins
• Peroxides and oxidized terpenoids
• Polysaccharides
• Proteins

Correct Answer: Peroxides and oxidized terpenoids

Q23. Which carrier gas is commonly used in GC analysis of volatile oils in most analytical labs?

• Oxygen
• Carbon dioxide
• Helium
• Nitrous oxide

Correct Answer: Helium

Q24. The natural stereoisomer of menthol predominantly found in peppermint is:

• (+)-Menthol (d-menthol)
• (-)-Menthol (l-menthol)
• Racemic menthol
• Meso-menthol

Correct Answer: (-)-Menthol (l-menthol)

Q25. Which plant part is the primary source of Mentha volatile oil for commercial extraction?

• Roots
• Leaves and flowering tops (aerial parts)
• Seeds
• Bark

Correct Answer: Leaves and flowering tops (aerial parts)

Q26. A simple organoleptic and sensory difference: peppermint oil is richer in _____ compared to spearmint oil.

• Carvone
• Menthol
• Eugenol
• Cineole

Correct Answer: Menthol

Q27. To differentiate natural from synthetic menthol in quality control, the most decisive method is:

• Polarimetry only
• Gas chromatography with chiral column or enantiomeric analysis
• Simple smell test
• Measurement of boiling point

Correct Answer: Gas chromatography with chiral column or enantiomeric analysis

Q28. Which Mentha oil constituent is a monoterpene oxide sometimes present and detectable by GC-MS?

• Cineole (eucalyptol)
• Menthone
• Carvone
• Pulegone

Correct Answer: Cineole (eucalyptol)

Q29. Which quality parameter would increase if Mentha oil is adulterated with oxidized products?

• Optical rotation becomes zero
• Peroxide value increases
• Specific gravity always decreases to 0.5
• Refractive index becomes identical to water

Correct Answer: Peroxide value increases

Q30. For official pharmacopeial identification and assay of Mentha oils, which combination of tests is most commonly recommended?

• GC fingerprint, refractive index, and optical rotation
• Flame test, boiling point, and pH
• Spectrophotometry at 260 nm only
• Gel electrophoresis and X-ray diffraction

Correct Answer: GC fingerprint, refractive index, and optical rotation

G S Sachin

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