Phytopharmaceuticals: carotenoids, xanthophylls and lutein MCQs With Answer

Introduction: This quiz collection on Phytopharmaceuticals: carotenoids, xanthophylls and lutein is designed for M.Pharm students studying Advanced Pharmacognosy I. It focuses on chemical structure, biosynthesis, analytical methods, pharmacology, formulation and regulatory aspects relevant to carotenoids and xanthophylls with emphasis on lutein. Questions are crafted to test conceptual understanding and practical knowledge required for research, quality control and development of phytopharmaceutical products. Use these MCQs to assess strengths, identify areas for deeper study, and prepare for examinations that demand an integrated view of natural product chemistry and pharmaceutical applications.

Q1. What is the core chemical classification of carotenoids?

• Tetraterpenoids with a C40 carbon skeleton
• Monoterpenoids with a C10 backbone
• Polyketides derived from acetyl-CoA
• Alkaloids containing nitrogen

Correct Answer: Tetraterpenoids with a C40 carbon skeleton

Q2. How do xanthophylls differ from carotenes chemically?

• Xanthophylls contain oxygen functional groups while carotenes are hydrocarbons
• Carotenes contain oxygen, xanthophylls are purely hydrocarbon
• Xanthophylls are glycosylated carotenoids while carotenes are esterified
• There is no chemical difference; names are interchangeable

Correct Answer: Xanthophylls contain oxygen functional groups while carotenes are hydrocarbons

Q3. Lutein is best described chemically as:

• A dihydroxy xanthophyll (β,ε-carotene-3,3′-diol)
• A mono-epoxide carotene
• A glycosylated tetracyclic alkaloid
• A carotenoid ketone derivative

Correct Answer: A dihydroxy xanthophyll (β,ε-carotene-3,3′-diol)

Q4. Which statement correctly describes the stereochemistry of lutein?

• It has two chiral centers at C3 and C3′ giving stereoisomeric forms
• It is an achiral molecule with no stereocenters
• It contains a single stereocenter at C5 only
• It is a racemic mixture of four unrelated stereocenters

Correct Answer: It has two chiral centers at C3 and C3′ giving stereoisomeric forms

Q5. The primary biosynthetic precursor for carotenoids in plants is:

• Isopentenyl diphosphate (IPP) via the MEP pathway
• Malonyl-CoA via polyketide synthase
• Shikimate leading to phenylpropanoids
• Amino acids via non-ribosomal peptide synthetases

Correct Answer: Isopentenyl diphosphate (IPP) via the MEP pathway

Q6. Which factor most strongly enhances intestinal absorption of lutein?

• Co-ingestion with dietary fat to promote micelle formation
• Taking lutein on an empty stomach without fat
• Concomitant high-dose vitamin C supplementation
• Simultaneous intake of antibiotics

Correct Answer: Co-ingestion with dietary fat to promote micelle formation

Q7. The principal protective function of lutein in the macula is:

• Selective absorption of blue light and antioxidant protection
• Acting as a retinal pigment for color vision
• Stimulating photoreceptor cell proliferation
• Inhibiting tear production in the eye

Correct Answer: Selective absorption of blue light and antioxidant protection

Q8. Which conditions most accelerate degradation of carotenoids during processing?

• Exposure to oxygen, light and elevated temperature
• Storage in the dark under inert gas
• Low humidity refrigerated conditions
• Microencapsulation in a polymer matrix

Correct Answer: Exposure to oxygen, light and elevated temperature

Q9. The most commonly used chromatographic method for quantifying lutein in plant extracts is:

• Reverse-phase HPLC (C18) with photodiode array detection around 450 nm
• Gas chromatography with FID without derivatization
• Size-exclusion chromatography with evaporative light scattering
• Thin-layer chromatography with ninhydrin staining

Correct Answer: Reverse-phase HPLC (C18) with photodiode array detection around 450 nm

Q10. In nature, the predominant geometric configuration of lutein is:

• All-trans configuration
• All-cis configuration exclusively
• A racemic mixture of Z and E retinal-like forms
• Only 9-cis isomer is found naturally

Correct Answer: All-trans configuration

Q11. Which dietary sources are richest in lutein?

• Green leafy vegetables (e.g., spinach, kale) and egg yolk
• Citrus fruits and root vegetables only
• Muscle meats and dairy products only
• Legumes and white rice primarily

Correct Answer: Green leafy vegetables (e.g., spinach, kale) and egg yolk

Q12. Compared with carotenes, xanthophylls are generally:

• More polar due to oxygen-containing functional groups
• Less polar because they lack double bonds
• Unstable in all solvents and cannot be analyzed by HPLC
• Identical in polarity to carotenes

Correct Answer: More polar due to oxygen-containing functional groups

Q13. Under Indian phytopharmaceutical regulatory guidance, a “phytopharmaceutical” typically means:

• A purified and standardized botanical-derived product with defined chemical entities and demonstrated pharmacological activity
• A crude powdered herbal drug sold without standardization
• A homeopathic dilution of plant material
• A traditional decoction prepared at home

Correct Answer: A purified and standardized botanical-derived product with defined chemical entities and demonstrated pharmacological activity

Q14. Structurally, lutein and zeaxanthin differ primarily by:

• Positioning of double bonds and ring types (ε-ring in lutein vs β-ring in zeaxanthin)
• Presence of a sulfate group in lutein only
• Lutein is a carotene while zeaxanthin is an alkaloid
• Zeaxanthin contains nitrogen but lutein does not

Correct Answer: Positioning of double bonds and ring types (ε-ring in lutein vs β-ring in zeaxanthin)

Q15. Which solvent system is commonly used for efficient extraction of lutein from plant matrices?

• Hexane–acetone (or hexane/acetone mixture) to combine non-polar and slightly polar extraction
• Pure water since lutein is highly water soluble
• Strong base only to hydrolyze the matrix
• Concentrated hydrochloric acid for direct extraction

Correct Answer: Hexane–acetone (or hexane/acetone mixture) to combine non-polar and slightly polar extraction

Q16. The antioxidant mechanism of carotenoids like lutein primarily involves:

• Quenching singlet oxygen and dissipating excess excitation energy
• Acting as pro-oxidants to generate free radicals
• Chelating transition metals as the main action
• Direct enzymatic turnover by catalase

Correct Answer: Quenching singlet oxygen and dissipating excess excitation energy

Q17. Following absorption, lutein shows preferential tissue distribution to:

• The macula of the retina and adipose tissue
• The renal cortex exclusively
• The cerebrospinal fluid at high concentrations
• The bone marrow as the primary depot

Correct Answer: The macula of the retina and adipose tissue

Q18. Which formulation strategy is commonly used commercially to improve lutein stability and shelf-life?

• Esterification and microencapsulation to protect from oxidation
• Formulating as a free aqueous syrup without antioxidants
• Dry heating at high temperature to polymerize lutein
• Mixing with strong oxidants to maintain color

Correct Answer: Esterification and microencapsulation to protect from oxidation

Q19. Why is saponification performed prior to HPLC analysis of lutein from some plant samples?

• To hydrolyze esterified carotenoids and remove lipids, yielding free lutein for analysis
• To convert lutein into a water-soluble sugar conjugate
• To oxidize lutein to a detectable ketone derivative
• To completely destroy carotenoids so only contaminants remain

Correct Answer: To hydrolyze esterified carotenoids and remove lipids, yielding free lutein for analysis

Q20. Which enzymes are primarily responsible for enzymatic cleavage of carotenoids in animals?

• Carotenoid cleavage dioxygenases such as BCO1 and BCO2
• Cyclooxygenases COX-1 and COX-2
• Alcohol dehydrogenase family only
• Acetylcholinesterase in neural tissues

Correct Answer: Carotenoid cleavage dioxygenases such as BCO1 and BCO2

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