Introduction: Volatile oils are complex, lipophilic mixtures of aromatic compounds studied in pharmacognosy and pharmaceutical analysis. Fennel volatile oil, obtained from seeds of Foeniculum vulgare, is rich in trans-anethole, fenchone and estragole and shows carminative, antispasmodic and expectorant activities. B.Pharm students must master botanical identification, extraction techniques (steam distillation, hydrodistillation), physicochemical parameters (specific gravity, refractive index, optical rotation), analytical methods (GC, GC-MS, TLC), pharmacopeial standards (IP, BP), assay procedures, common adulterants, stability and formulation considerations. This knowledge supports quality control, therapeutic application and safe use of fennel oil in pharmaceutical products. ‘Now let’s test your knowledge with 30 MCQs on this topic.’
Q1. Which is the major constituent typically responsible for the sweet aroma of fennel volatile oil?
- Trans-anethole
- Fenchone
- Estragole
- Limonene
Correct Answer: Trans-anethole
Q2. Fennel oil is most commonly obtained from which plant part for pharmacognostic use?
- Leaves
- Seeds
- Roots
- Flowers
Correct Answer: Seeds
Q3. Which extraction method is standard for isolating volatile oil from fennel seeds in the laboratory?
- Soxhlet extraction with ethanol
- Steam distillation / hydrodistillation
- Cold maceration
- Supercritical CO2 extraction only
Correct Answer: Steam distillation / hydrodistillation
Q4. Which physicochemical parameter is commonly used to assess purity and identity of fennel oil?
- Melting point
- Refractive index
- pH
- Viscosity at 100°C
Correct Answer: Refractive index
Q5. Which analytical technique provides the most detailed qualitative and quantitative composition of fennel volatile oil?
- Thin-layer chromatography (TLC)
- Gas chromatography-mass spectrometry (GC-MS)
- UV-Visible spectrophotometry
- Infrared paper chromatography
Correct Answer: Gas chromatography-mass spectrometry (GC-MS)
Q6. Presence of which compound suggests a fennel oil variety often termed “bitter fennel”?
- High trans-anethole
- High fenchone
- High linalool
- High geraniol
Correct Answer: High fenchone
Q7. Which test is commonly used in the lab to detect presence of anethole or phenylpropanoids in volatile oils?
- Salkowski test
- Kedde reagent test
- Sodium nitroprusside test
- Liebermann-Burchard test
Correct Answer: Sodium nitroprusside test
Q8. In quality control, specific gravity of fennel oil at 20°C is measured. This parameter helps to:
- Determine the oil’s pH
- Assess adulteration and purity
- Measure microbial contamination
- Estimate viscosity at high temperature
Correct Answer: Assess adulteration and purity
Q9. Which monograph or pharmacopeia commonly contains standards for fennel oil?
- United States Pharmacopeia only
- Indian Pharmacopoeia (IP) and British Pharmacopoeia (BP)
- Japanese Botanical Index only
- USP-NF exclusively for essential oils
Correct Answer: Indian Pharmacopoeia (IP) and British Pharmacopoeia (BP)
Q10. Which constituent of fennel oil is considered potentially hepatotoxic or genotoxic and is monitored in quality control?
- Trans-anethole
- Fenchone
- Estragole (methyl chavicol)
- Cineole
Correct Answer: Estragole (methyl chavicol)
Q11. In TLC profiling of fennel oil, which stationary phase is most commonly used for volatile oil components?
- Cellulose TLC plates
- Silica gel TLC plates
- Ion-exchange paper
- Polyacrylamide gel
Correct Answer: Silica gel TLC plates
Q12. Optical rotation measurement of fennel oil helps to:
- Determine aqueous solubility
- Differentiate enantiomers and assess composition
- Measure density compared to water
- Detect microbial contaminants
Correct Answer: Differentiate enantiomers and assess composition
Q13. The classical pharmacological action of fennel oil used in formulations is primarily:
- Hypoglycemic
- Carminative and antispasmodic
- Anticoagulant
- Local anesthetic only
Correct Answer: Carminative and antispasmodic
Q14. Adulteration of fennel oil is often detected by increased levels of which simple hydrocarbon?
- Isopropyl myristate
- Petroleum hydrocarbons (light ends)
- Sucrose residues
- Ethyl cellulose
Correct Answer: Petroleum hydrocarbons (light ends)
Q15. Which storage condition best preserves the quality of fennel volatile oil?
- Transparent glass at room light
- Dark glass container, cool and dry place
- Open container in refrigerator door
- High humidity environment
Correct Answer: Dark glass container, cool and dry place
Q16. Which component contributes to the minty-camphoraceous note found in some fennel oil chemotypes?
- α-Pinene
- Fenchone
- Myristicin
- Safrole
Correct Answer: Fenchone
Q17. During GC analysis of fennel oil, retention indices are used primarily for:
- Quantifying water content
- Identifying compounds by comparison with standards
- Measuring optical rotation
- Assessing microbial load
Correct Answer: Identifying compounds by comparison with standards
Q18. Which safety consideration is important when using fennel oil in pediatric formulations?
- High dose topical use is always safe
- Avoid oral use in neonates due to potential toxicity
- No restrictions; safe for all ages
- Can be used without dilution in infants
Correct Answer: Avoid oral use in neonates due to potential toxicity
Q19. A high percentage of trans-anethole and low fenchone characterizes which fennel oil type?
- Bitter fennel oil
- Sweet fennel oil
- Wild fennel root oil
- Flower oil chemotype
Correct Answer: Sweet fennel oil
Q20. Which technique is most suitable to quantify estragole content in fennel oil for regulatory compliance?
- Gravimetric analysis
- HPLC with refractive index detector
- GC-FID or GC-MS with calibration standards
- Paper chromatography
Correct Answer: GC-FID or GC-MS with calibration standards
Q21. Which of the following is a characteristic odour test reagent for anethole (sweet note) in a qualitative lab test?
- Ferric chloride (gives green color)
- Sodium hydroxide (no odour change)
- Sulfuric acid leading to sweet-smelling derivative
- Lead acetate (forms black ppt)
Correct Answer: Ferric chloride (gives green color)
Q22. Which factor does NOT significantly influence yield and composition of fennel volatile oil?
- Genotype/chemotype of plant
- Harvesting time and maturity
- Method of distillation
- Color of packaging label
Correct Answer: Color of packaging label
Q23. Which pharmacological effect of fennel oil is explained by smooth muscle relaxation in the gut?
- Antipyretic
- Carminative effect
- Hypolipidemic
- Immune suppression
Correct Answer: Carminative effect
Q24. Which is a common pharmaceutical application of fennel oil in dosage forms?
- Injectable analgesic solution
- Flavoring and carminative in oral emulsions and syrups
- Antineoplastic topical cream
- Intravenous nutritional supplement
Correct Answer: Flavoring and carminative in oral emulsions and syrups
Q25. Which adulterant would most likely decrease the refractive index of authentic fennel oil?
- Addition of heavy, high refractive index oils
- Addition of light petroleum ether fractions
- Addition of pure trans-anethole
- Addition of high-boiling natural resins
Correct Answer: Addition of light petroleum ether fractions
Q26. Which biosynthetic class do the major fennel oil constituents (anethole, estragole) belong to?
- Monoterpenes
- Sesquiterpenes
- Phenylpropanoids
- Alkaloids
Correct Answer: Phenylpropanoids
Q27. For shelf-life studies of fennel oil-containing preparations, which parameter is least relevant?
- Oxidative stability of oil
- Change in organoleptic properties
- Microbial growth in non-sterile products
- Color of raw seeds in supplier catalog
Correct Answer: Color of raw seeds in supplier catalog
Q28. Which is an appropriate internal standard consideration for GC quantification of fennel oil components?
- Use water as internal standard
- Use a compound not present in the sample, with similar volatility
- Use trans-anethole when quantifying trans-anethole
- Use ethanol as internal standard for non-alcoholic samples
Correct Answer: Use a compound not present in the sample, with similar volatility
Q29. Which adverse effect is most associated with high doses or prolonged use of estragole-containing oils?
- Renal analgesia
- Potential carcinogenicity/hepatotoxicity in animal studies
- Immediate anaphylaxis in all users
- Permanent blindness
Correct Answer: Potential carcinogenicity/hepatotoxicity in animal studies
Q30. In a formulation lab, which excipient choice helps solubilize fennel oil in an oral syrup?
- Hydrophobic polymer only
- Non-ionic surfactant or appropriate emulsifier
- Dry lactose powder alone
- Activated charcoal
Correct Answer: Non-ionic surfactant or appropriate emulsifier
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.
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