Castor oil is a unique vegetable oil rich in ricinoleic acid, a hydroxylated fatty acid that defines its chemistry and pharmaceutical value. B.Pharm students should master its botanical sources (Ricinus communis), methods of preparation (cold pressing, solvent extraction, refining), and key physicochemical properties (saponification, iodine, acid values, refractive index). Understanding evaluation, preservation, storage and quality control (GC, IR, peroxide value, detection of adulteration) is essential for safe use. Clinically, castor oil has laxative, emollient and anti-inflammatory roles but requires caution in pregnancy; commercially it yields versatile derivatives (sebacic acid, undecylenic acid) for industry. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary fatty acid responsible for castor oil’s characteristic properties?
- Oleic acid
- Linoleic acid
- Ricinoleic acid
- Palmitic acid
Correct Answer: Ricinoleic acid
Q2. The botanical source of commercial castor oil is:
- Cocos nucifera
- Ricinus communis
- Helianthus annuus
- Glycine max
Correct Answer: Ricinus communis
Q3. Which method typically gives the highest quality, least altered castor oil suitable for pharmacopoeial use?
- Hydrogenation
- Cold pressing (expeller-pressing)
- High-temperature steam distillation
- Saponification and re-esterification
Correct Answer: Cold pressing (expeller-pressing)
Q4. Castor oil is classified pharmacologically as a:
- Stimulant laxative
- Bulk-forming laxative
- Osmotic laxative
- Local anesthetic
Correct Answer: Stimulant laxative
Q5. Which physico-chemical test indicates degree of unsaturation in castor oil?
- Saponification value
- Acid value
- Iodine value
- Refractive index
Correct Answer: Iodine value
Q6. A high acid value in castor oil usually indicates:
- Low free fatty acids content
- High peroxide content
- Hydrolytic rancidity / free fatty acids from breakdown
- High unsaponifiable matter
Correct Answer: Hydrolytic rancidity / free fatty acids from breakdown
Q7. The dominant chemical form of fatty acids in castor oil is:
- Free fatty acids
- Monoacylglycerols
- Diacylglycerols
- Triglycerides
Correct Answer: Triglycerides
Q8. Which analytical technique is most appropriate for detailed fatty acid profiling of castor oil?
- UV-Vis spectroscopy
- Gas chromatography (GC) as methyl esters
- Paper chromatography
- Colorimetry
Correct Answer: Gas chromatography (GC) as methyl esters
Q9. Which derivative is commercially produced from castor oil and used in polymer chemistry?
- Sebacic acid
- Palmitic acid
- Lauric acid
- Stearic acid
Correct Answer: Sebacic acid
Q10. Presence of the toxic protein ricin is primarily a concern in:
- Refined castor oil
- Castor seeds/meal
- Hydrogenated castor oil
- Bleached castor oil
Correct Answer: Castor seeds/meal
Q11. Which storage condition best preserves castor oil quality?
- Open containers at room temperature
- Exposure to direct sunlight
- Hermetic, dark containers at cool temperature with minimal air
- Dilution with water and kept refrigerated
Correct Answer: Hermetic, dark containers at cool temperature with minimal air
Q12. An increased peroxide value in castor oil indicates:
- Increased antioxidant activity
- Primary oxidative rancidity
- Hydrolysis by water
- Complete saturation of fatty acids
Correct Answer: Primary oxidative rancidity
Q13. Which preservative or practice helps retard oxidation of castor oil?
- Exposure to air
- Adding tocopherols (vitamin E) or storing under nitrogen
- Heating to high temperature periodically
- Mixing with saline solution
Correct Answer: Adding tocopherols (vitamin E) or storing under nitrogen
Q14. The saponification value of castor oil is relatively high because of:
- Short-chain fatty acids predominance
- High molecular weight triglycerides
- Low glycerol content
- Presence of ricin protein
Correct Answer: Short-chain fatty acids predominance
Q15. Which IR absorption band is characteristic of the hydroxyl group in ricinoleic acid within castor oil?
- Strong band near 3400 cm⁻¹
- Sharp band at 1700 cm⁻¹
- Band at 2100 cm⁻¹
- Absence of OH band
Correct Answer: Strong band near 3400 cm⁻¹
Q16. Adulteration of castor oil is commonly detected by monitoring changes in:
- Boiling point only
- Fatty acid profile and specific gravity/refractive index
- Color of seed husk
- Seed weight
Correct Answer: Fatty acid profile and specific gravity/refractive index
Q17. Which test is used to estimate the amount of unsaponifiable matter in castor oil?
- Saponification value determination followed by extraction of unsaponifiable fraction
- Peroxide value test
- Iodine value test only
- Visual inspection
Correct Answer: Saponification value determination followed by extraction of unsaponifiable fraction
Q18. Therapeutic use of castor oil as a laxative is primarily due to:
- Glycerol content
- Ricinoleic acid stimulating intestinal motility and secretion
- High viscosity creating bulk
- Presence of protein ricin
Correct Answer: Ricinoleic acid stimulating intestinal motility and secretion
Q19. Which quality control parameter helps detect hydrolytic rancidity in castor oil?
- High iodine value
- Low refractive index
- Elevated acid value
- High melting point
Correct Answer: Elevated acid value
Q20. For topical emollient formulations, castor oil is chosen mainly for its:
- High water solubility
- High polarity and humectant properties due to ricinoleic hydroxyl group
- Strong fragrance
- Complete lack of viscosity
Correct Answer: High polarity and humectant properties due to ricinoleic hydroxyl group
Q21. Which processing step removes color and some impurities from crude castor oil?
- Cold pressing
- Bleaching with adsorbents
- Saponification without neutralization
- Direct bottling without filtration
Correct Answer: Bleaching with adsorbents
Q22. The typical content of ricinoleic acid (as percentage of total fatty acids) in good-quality castor oil is approximately:
- 10–20%
- 30–40%
- 85–90%
- 100%
Correct Answer: 85–90%
Q23. Which commercial derivative of castor oil is widely used as a corrosion inhibitor and lubricating additive?
- Undecylenic acid
- Hydrogenated vegetable oil
- Castor oil methyl ester only
- Fatty acid esters and ricinoleate derivatives (e.g., estolides)
Correct Answer: Fatty acid esters and ricinoleate derivatives (e.g., estolides)
Q24. During refinement, deodorization of castor oil typically uses:
- High vacuum steam distillation to remove volatile odorous components
- Simple air drying
- Centrifugation without heat
- Addition of salt
Correct Answer: High vacuum steam distillation to remove volatile odorous components
Q25. Which statement about castor oil’s drying property is correct?
- Castor oil is a drying oil suitable for paint film formation
- Castor oil is a semi-drying oil
- Castor oil is a non-drying oil
- Castor oil polymerizes instantly on exposure to air
Correct Answer: Castor oil is a non-drying oil
Q26. A pharmacopeial test to confirm identity of castor oil may include:
- TLC or IR showing characteristic ricinoleate features
- Measurement of optical rotation only
- Testing for cyanide only
- Counting seed number
Correct Answer: TLC or IR showing characteristic ricinoleate features
Q27. Which adverse effect necessitates caution or avoidance of castor oil in certain populations?
- Hypertension in children
- Uterine contractions and risk during pregnancy
- Causes diabetes
- Increases bone density
Correct Answer: Uterine contractions and risk during pregnancy
Q28. Which solvent is commonly used for laboratory extraction of castor oil from seed material for analysis?
- Water
- Hexane or petroleum ether
- Ethanol only
- Acetic acid
Correct Answer: Hexane or petroleum ether
Q29. Which parameter is most useful to monitor oxidation stability during shelf-life studies of castor oil?
- Melting point
- Peroxide value and anisidine value
- Seed germination rate
- Protein content
Correct Answer: Peroxide value and anisidine value
Q30. In pharmaceutical formulation, castor oil’s high viscosity is advantageous for:
- Oral tablets as a filler
- Use as a solvent for polar drugs and as a semi-solid base for suppositories and topical vehicles
- Increasing powder flow in capsules
- Rapid evaporation in inhalation products
Correct Answer: Use as a solvent for polar drugs and as a semi-solid base for suppositories and topical vehicles
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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