Synthetic antioxidants – BHT and BHA MCQs With Answer

Synthetic antioxidants – BHT and BHA are widely used phenolic stabilizers in pharmaceutical formulations to prevent lipid peroxidation and oxidative degradation of drugs and excipients. Butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) act as chain‑breaking free radical scavengers, are oil‑soluble, and are important in improving oxidative stability, shelf life, and formulation compatibility. B. Pharm students should understand their chemistry, mechanism, solubility, analytical assays, regulatory status (E320/E321), safety issues and interactions with metals or co‑antioxidants. This knowledge helps in excipient selection, stability testing and risk assessment in drug product development. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which chemical class do BHT and BHA belong to?

• Polymeric stabilizers
• Phenolic antioxidants
• Chelating agents
• Sulfite preservatives

Correct Answer: Phenolic antioxidants

Q2. What are the full chemical names of BHT and BHA?

• Butylated hydroxyanisole and butylated hydroxytoluene
• Butylated hydroxytoluene and butylated hydroxyanisole
• Butylhydroquinone and butylated hydroxyanisole
• Butylated hydroxybenzoate and butylated hydroxytoluene

Correct Answer: Butylated hydroxytoluene and butylated hydroxyanisole

Q3. What is the primary antioxidant mechanism of BHT and BHA in pharmaceutical systems?

• Metal ion chelation
• Chain‑breaking free radical scavenging
• Singlet oxygen quenching by energy transfer
• pH buffering to prevent oxidation

Correct Answer: Chain‑breaking free radical scavenging

Q4. Which structural feature is critical for the antioxidant activity of BHT and BHA?

• Phenolic hydroxyl group
• Ether linkage between rings
• Carboxylic acid functionality
• Primary amine group

Correct Answer: Phenolic hydroxyl group

Q5. BHT is correctly described by which structural name?

• 2,6‑di‑tert‑butyl‑4‑methylphenol
• 2,4‑di‑tert‑butyl‑phenol
• 4‑tert‑butyl‑2‑hydroxyanisole
• 3,5‑di‑tert‑butyl‑4‑hydroxybenzoic acid

Correct Answer: 2,6‑di‑tert‑butyl‑4‑methylphenol

Q6. BHA is typically supplied as which of the following?

• Pure single isomer compound only
• A mixture of two tert‑butyl isomers of hydroxyanisole
• A polymeric antioxidant blend
• An inorganic antioxidant complex

Correct Answer: A mixture of two tert‑butyl isomers of hydroxyanisole

Q7. Which statement best describes the solubility of BHT and BHA?

• Highly water‑soluble and used in aqueous injections
• Moderately soluble in water and ethanol
• Lipophilic, oil‑soluble with poor aqueous solubility
• Only soluble in supercritical CO2

Correct Answer: Lipophilic, oil‑soluble with poor aqueous solubility

Q8. What are the EU/food additive E‑numbers for BHA and BHT?

• BHA E321 and BHT E320
• BHA E320 and BHT E321
• BHA E110 and BHT E210
• BHA E200 and BHT E201

Correct Answer: BHA E320 and BHT E321

Q9. Which antioxidant is generally considered more lipophilic and often more effective in oil systems?

• BHA
• BHT
• Ascorbic acid
• Sodium bisulfite

Correct Answer: BHT

Q10. In formulation design, what is a major advantage of using BHT or BHA?

• They act as primary preservatives against microbes
• They prevent oxidative degradation of unsaturated lipids and drugs
• They increase aqueous solubility of hydrophobic drugs
• They catalyze esterification reactions for drug activation

Correct Answer: They prevent oxidative degradation of unsaturated lipids and drugs

Q11. Which additive is commonly combined with BHT/BHA to provide synergistic antioxidant protection in lipid systems?

• Sodium chloride
• Tocopherol (vitamin E)
• Hydrogen peroxide
• Citric acid only

Correct Answer: Tocopherol (vitamin E)

Q12. At excessive concentrations and under certain conditions, phenolic antioxidants such as BHT/BHA may:

• Convert into strong chelators that stabilize metals
• Exhibit pro‑oxidant behavior and accelerate oxidation
• Become highly water‑soluble and inactive
• Polymerize to form inert plastics

Correct Answer: Exhibit pro‑oxidant behavior and accelerate oxidation

Q13. Which analytical technique provides the most specific confirmation of BHT in a complex lipid matrix?

• Thin layer chromatography (TLC) only
• Gas chromatography‑mass spectrometry (GC‑MS)
• Simple UV spectrophotometry without extraction
• Gravimetric analysis

Correct Answer: Gas chromatography‑mass spectrometry (GC‑MS)

Q14. Which functional group in BHA increases its polarity compared with BHT?

• Nitro group
• Methoxy group
• Carboxyl group
• Primary amine

Correct Answer: Methoxy group

Q15. Long‑term high‑dose studies in rodents raised safety concerns primarily for which organ with BHT/BHA exposure?

• Heart
• Kidney
• Liver
• Bone marrow

Correct Answer: Liver

Q16. Which regulatory statement is true regarding BHT and BHA in pharmaceuticals/foods?

• They are universally banned worldwide
• They are permitted with specified limits by agencies such as FDA and EFSA
• They are approved only for parenteral aqueous solutions
• They are classified as antibiotics

Correct Answer: They are permitted with specified limits by agencies such as FDA and EFSA

Q17. What precaution is commonly recommended for formulations containing BHT/BHA to minimize degradation?

• Expose to direct sunlight during storage
• Protect from light and store at controlled temperature
• Store in highly acidic aqueous media
• Mix with strong oxidants to stabilize

Correct Answer: Protect from light and store at controlled temperature

Q18. Which spectroscopic method will show a characteristic broad band for the phenolic OH of BHT/BHA?

• IR spectroscopy
• Fluorescence spectroscopy only
• Atomic absorption spectroscopy
• Raman scattering exclusively

Correct Answer: IR spectroscopy

Q19. Primary metabolic pathways for phenolic antioxidants like BHT and BHA in mammals typically involve:

• Phase I oxidation only with no conjugation
• Conjugation (e.g., glucuronidation) and phase I transformations
• Excretion unchanged in urine only
• Cleavage to amino acids

Correct Answer: Conjugation (e.g., glucuronidation) and phase I transformations

Q20. For quantitative assay of BHT/BHA in an oily pharmaceutical, the recommended sample preparation step is:

• Direct injection of oil into HPLC without cleanup
• Solvent extraction followed by cleanup and chromatographic analysis
• Drying the oil and weighing the residue only
• Homogenization with saline only

Correct Answer: Solvent extraction followed by cleanup and chromatographic analysis

Q21. Beyond pharmaceuticals and foods, BHT and BHA are also used industrially as:

• Polymer stabilizers to prevent oxidative degradation
• Primary structural monomers for plastics
• Fuel additives to increase octane number
• Heavy metal extraction agents

Correct Answer: Polymer stabilizers to prevent oxidative degradation

Q22. Which in‑vitro assay is commonly used in research labs to compare radical scavenging ability of BHT and BHA?

• DPPH radical scavenging assay
• Benedict’s sugar test
• Kjeldahl nitrogen estimation
• Limulus amoebocyte lysate test

Correct Answer: DPPH radical scavenging assay

Q23. Which statement about the thermal stability of BHT is generally true?

• BHT is extremely volatile and unsuitable for heated processes
• BHT has steric hindrance that enhances its thermal stability compared with less‑hindered phenols
• BHT decomposes immediately at room temperature
• BHT polymerizes readily at low temperatures

Correct Answer: BHT has steric hindrance that enhances its thermal stability compared with less‑hindered phenols

Q24. To minimize metal‑catalyzed oxidation when using BHT/BHA, formulators often include:

• EDTA or other metal chelators
• Strong oxidizing agents
• High concentrations of transition metals
• Hydroperoxides

Correct Answer: EDTA or other metal chelators

Q25. Which analytical separation technique is commonly used to resolve BHT and BHA isomers for quantitation?

• High‑performance liquid chromatography (HPLC)
• Paper chromatography only
• NMR without separation
• Simple filtration

Correct Answer: High‑performance liquid chromatography (HPLC)

Q26. Which of the following is a documented regulatory toxicology concern from high‑dose rodent studies of BHA/BHT?

• Reversible irritation at therapeutic doses in humans
• Carcinogenic or tumor‑promoting effects at very high doses in some rodent studies
• Immediate teratogenic effects in all species at low doses
• Complete absence of any adverse findings in long‑term studies

Correct Answer: Carcinogenic or tumor‑promoting effects at very high doses in some rodent studies

Q27. Which pharmaceutical dosage forms most commonly require addition of BHT or BHA?

• Oil‑based formulations, lipid suspensions and creams
• Buffered aqueous injections where antioxidants are unnecessary
• Lyophilized sterile powders guaranteed oxidation‑free
• Immediate release tablets that contain no lipids

Correct Answer: Oil‑based formulations, lipid suspensions and creams

Q28. When analyzing a complex emulsion for BHT/BHA, which analytical challenge is most relevant?

• Complete miscibility of antioxidants in water complicates separation
• Interference from lipids and matrix requires efficient extraction and cleanup
• Antioxidants fluoresce excessively, preventing detection
• They cannot be chromatographically separated from sugars

Correct Answer: Interference from lipids and matrix requires efficient extraction and cleanup

Q29. Which storage practice reduces the risk of antioxidant loss and formation of degradation products in a drug formulation?

• Store in transparent bottles under fluorescent lights
• Store protected from air and light, in cool conditions
• Store at high temperature and high humidity
• Exposing to frequent freeze–thaw cycles

Correct Answer: Store protected from air and light, in cool conditions

Q30. A high log P value for BHT indicates which property important for formulation scientists?

• High aqueous solubility and rapid renal clearance
• Strong hydrophilicity and inability to partition into oils
• High lipophilicity, favoring partitioning into lipid phases
• Low molecular weight volatility

Correct Answer: High lipophilicity, favoring partitioning into lipid phases

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