Tocopherols, tocotrienols and other vitamins as phytopharmaceuticals MCQs With Answer
This quiz compilation is designed for M.Pharm students studying Advanced Pharmacognosy I, focusing on tocopherols, tocotrienols and other vitamin-based phytopharmaceuticals. It covers chemical structures, biosynthetic pathways in plants, analytical techniques for standardization, formulation and stability issues, pharmacokinetics, biological mechanisms including antioxidant activity, and therapeutic implications. Questions emphasize distinctions between tocopherol isoforms and tocotrienols, extraction and quality control challenges, and interactions with drugs and nutrients. Use these MCQs to test deeper conceptual understanding and to prepare for exams and research discussions in phytopharmaceutical development and vitamin therapeutics.
Q1. Which structural feature primarily distinguishes tocotrienols from tocopherols?
- Saturated phytyl side chain
- Unsaturated isoprenoid side chain with three double bonds
- Presence of an additional phenolic hydroxyl group
- Methylation of the chromanol ring at C-5
Correct Answer: Unsaturated isoprenoid side chain with three double bonds
Q2. Among vitamin E homologues, which isoform has been reported to possess the highest alpha-tocopherol transfer protein affinity and therefore highest systemic retention in humans?
- Gamma-tocopherol
- Delta-tocotrienol
- Alpha-tocopherol
- Beta-tocopherol
Correct Answer: Alpha-tocopherol
Q3. Which analytical technique is most commonly used for quantification and separation of individual tocopherol and tocotrienol homologues in plant extracts?
- UV-Visible spectrophotometry without separation
- Gas chromatography with flame ionization detector after derivatization
- Reverse-phase high-performance liquid chromatography with fluorescence detection
- Thin-layer chromatography only
Correct Answer: Reverse-phase high-performance liquid chromatography with fluorescence detection
Q4. The primary antioxidant mechanism of tocopherols in lipid membranes is best described as:
- Electron donation to water-soluble radicals only
- Scavenging lipid peroxyl radicals by hydrogen atom transfer from the chromanol OH
- Chelation of transition metals in the membrane
- Direct enzymatic breakdown of peroxides
Correct Answer: Scavenging lipid peroxyl radicals by hydrogen atom transfer from the chromanol OH
Q5. During saponification-based extraction of vitamin E from plant oils, the main purpose of the alkaline hydrolysis step is to:
- Convert tocopherols into water-soluble salts
- Hydrolyze triglycerides to free fatty acids and release bound tocopherols
- Methylate the chromanol ring to stabilize tocopherols
- Oxidize tocopherols to tocopheryl quinone for easier detection
Correct Answer: Hydrolyze triglycerides to free fatty acids and release bound tocopherols
Q6. Which statement correctly contrasts biological activities of tocotrienols versus tocopherols?
- Tocotrienols lack antioxidant activity but are potent vitamins for coagulation
- Tocotrienols often show superior neuroprotective and cholesterol-lowering effects compared to tocopherols
- Tocopherols are water soluble while tocotrienols are strictly lipid soluble
- Tocopherols and tocotrienols are identical in membrane distribution and biological effects
Correct Answer: Tocotrienols often show superior neuroprotective and cholesterol-lowering effects compared to tocopherols
Q7. Which form of vitamin E is most effective at inhibiting HMG-CoA reductase activity and thereby affecting cholesterol synthesis?
- Alpha-tocopherol
- Gamma-tocopherol
- Alpha-tocotrienol
- Delta-tocopherol
Correct Answer: Alpha-tocotrienol
Q8. Which analytical parameter is critical to report when assessing the oxidative stability of vitamin E preparations intended as antioxidants in formulations?
- Melting point of pure tocopherol
- Peroxide value and tocopheryl quinone formation over time
- Solubility in water at room temperature
- Color only
Correct Answer: Peroxide value and tocopheryl quinone formation over time
Q9. The RRR- stereochemical designation in alpha-tocopherol refers to which concept important for biological activity?
- Presence of three double bonds in the side chain
- Degree of methylation on the chromanol ring
- Oxidation state of the phenolic OH
Correct Answer: Absolute configuration at the three stereocenters of the chromanol tail affecting affinity to alpha-TTP
Q10. Which vitamin among fat-soluble vitamins has a major role in gamma-carboxylation of glutamate residues in clotting factors?
- Vitamin A (retinol)
- Vitamin D (calciferol)
- Vitamin K (phylloquinone/menaquinone)
- Vitamin E (tocopherol)
Correct Answer: Vitamin K (phylloquinone/menaquinone)
Q11. In chromatographic quantification of tocopherols, why is fluorescence detection preferred over UV detection?
- Tocopherols do not absorb in UV range
- Fluorescence provides greater sensitivity and selectivity for chromanol ring fluorescence
- UV detectors cannot operate with normal phase columns
- Fluorescence avoids any need for sample cleanup
Correct Answer: Fluorescence provides greater sensitivity and selectivity for chromanol ring fluorescence
Q12. Which dietary factor is known to markedly enhance intestinal absorption of tocopherols?
- Concurrent intake of large amounts of water
- Presence of dietary fat and bile salts to form micelles
- High dietary fiber that binds lipids
- Taking tocopherol with acidic beverages only
Correct Answer: Presence of dietary fat and bile salts to form micelles
Q13. Gamma-tocopherol displays a unique biological property relative to alpha-tocopherol by more effectively:
- Scavenging peroxynitrite-derived reactive nitrogen species
- Binding strongly to alpha-tocopherol transfer protein (alpha-TTP)
- Being retained longer in plasma than alpha-tocopherol
- Enhancing vitamin K-dependent clotting
Correct Answer: Scavenging peroxynitrite-derived reactive nitrogen species
Q14. Which extraction solvent system is typically preferred for recovering tocopherols and tocotrienols from plant matrices prior to HPLC analysis?
- Pure water
- Nonpolar solvents or mixtures such as hexane/isopropanol or hexane/ethanol after saponification
- Strong acids like HCl
- Carbon dioxide only without modifiers
Correct Answer: Nonpolar solvents or mixtures such as hexane/isopropanol or hexane/ethanol after saponification
Q15. Which pharmacokinetic feature distinguishes tocotrienols when administered orally compared to tocopherols?
- Tocotrienols are absorbed exclusively via peptide transporters
- Tocotrienols often exhibit rapid clearance and lower plasma retention than alpha-tocopherol
- Tocotrienols are converted to tocopherols in vivo
- Tocotrienols have unlimited oral bioavailability independent of dose
Correct Answer: Tocotrienols often exhibit rapid clearance and lower plasma retention than alpha-tocopherol
Q16. For a phytopharmaceutical product standardized to total vitamin E activity, which reference is most appropriate to express potency?
- Milligrams of crude oil only
- International Units (IU) or mg alpha-tocopherol equivalents based on biological activity
- Number of tocopherol isomers present regardless of potency
- Percentage of water content
Correct Answer: International Units (IU) or mg alpha-tocopherol equivalents based on biological activity
Q17. Which adverse interaction is a recognized risk when high-dose vitamin E supplements are taken concomitantly with anticoagulant therapy?
- Vitamin E increases vitamin K synthesis and causes thrombosis
- High-dose vitamin E may potentiate anticoagulant effects and increase bleeding risk
- Vitamin E neutralizes anticoagulants rendering them ineffective
- There is no interaction; vitamin E is inert with anticoagulants
Correct Answer: High-dose vitamin E may potentiate anticoagulant effects and increase bleeding risk
Q18. Which of the following is a validated in vitro assay commonly used to demonstrate antioxidant activity of tocopherol/tocotrienol preparations?
- Minimum inhibitory concentration (MIC) for bacteria
- DPPH radical scavenging assay and ORAC (oxygen radical absorbance capacity)
- ELISA for tocopherol receptor binding
- ATP content measurement in hepatocytes only
Correct Answer: DPPH radical scavenging assay and ORAC (oxygen radical absorbance capacity)
Q19. Which plant source is particularly rich in tocotrienols and frequently used for commercial tocotrienol extracts?
- Olive oil
- Palm oil (Elaeis guineensis)
- Soybean oil
- Flaxseed oil
Correct Answer: Palm oil (Elaeis guineensis)
Q20. When developing a topical phytopharmaceutical formulation containing tocopherols/tocotrienols, what is the primary formulation strategy to enhance skin delivery and stability?
- Use of aqueous-only gels without any lipids
- Incorporation into lipid-based carriers (liposomes, nanoemulsions) and addition of antioxidants to prevent oxidation
- Heating tocopherols above their boiling point during manufacture
- Maximizing exposure to air to allow controlled oxidation
Correct Answer: Incorporation into lipid-based carriers (liposomes, nanoemulsions) and addition of antioxidants to prevent oxidation
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