Flavonoids as nutraceuticals – Rutin, Naringin, Quercetin, Anthocyanidins, Catechins, Flavones MCQs With Answer

Introduction

Flavonoids are a diverse class of plant-derived nutraceuticals valued for antioxidant, anti-inflammatory, and cardioprotective effects. Key compounds—Rutin, Naringin, Quercetin, Anthocyanidins, Catechins, and Flavones—differ by ring substitution, glycosylation, and saturation, affecting bioavailability, metabolism and therapeutic potential. For B.Pharm students, understanding chemical structures, sources (citrus, tea, berries, buckwheat), mechanisms (free radical scavenging, metal chelation, enzyme modulation), pharmacokinetics (phase II conjugation, microbial hydrolysis) and formulation challenges is essential for drug‑nutrient interaction assessment and nutraceutical development. This topic links pharmacology, pharmacognosy and pharmaceutics for evidence-based use of flavonoid nutraceuticals. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which structural feature most characterizes flavonols like quercetin compared to flavones?

• A double bond between C2 and C3 and a hydroxyl group at C3
• A saturated C2–C3 bond and no hydroxyl at C3
• An additional carbonyl at C4
• A methoxy group at C7

Correct Answer: A double bond between C2 and C3 and a hydroxyl group at C3

Q2. Rutin is best described as which of the following?

• An aglycone of naringin
• Quercetin-3-O-rutinoside (a quercetin glycoside)
• Epigallocatechin gallate
• An anthocyanidin pigment

Correct Answer: Quercetin-3-O-rutinoside (a quercetin glycoside)

Q3. Which flavonoid class includes catechins commonly found in green tea?

• Flavones
• Anthocyanidins
• Flavan-3-ols (catechins)
• Flavonols

Correct Answer: Flavan-3-ols (catechins)

Q4. Naringin is primarily associated with which pharmacological or interaction property?

• Potent induction of CYP3A4 leading to drug underexposure
• Inhibition of CYP3A4/P-gp contributing to grapefruit-drug interactions
• Selective inhibition of acetylcholinesterase
• Strong opioid receptor agonism

Correct Answer: Inhibition of CYP3A4/P-gp contributing to grapefruit-drug interactions

Q5. Which statement about anthocyanidins is correct?

• They are more stable than flavones at high pH
• They are aglycones of anthocyanins and are pH-sensitive pigments
• They are flavanones with saturated C2–C3 bonds
• They are primarily responsible for bitter taste in citrus

Correct Answer: They are aglycones of anthocyanins and are pH-sensitive pigments

Q6. Which metabolic pathway is most important for phase II metabolism of quercetin in humans?

• CYP2D6-mediated hydroxylation
• Glucuronidation and sulfation by UGTs and SULTs
• Direct excretion unchanged via bile
• Oxidative deamination by monoamine oxidase

Correct Answer: Glucuronidation and sulfation by UGTs and SULTs

Q7. Which property typically reduces oral bioavailability of many flavonoids?

• High lipid solubility and strong passive diffusion
• Extensive phase II metabolism and poor intestinal absorption
• Resistance to intestinal microbial hydrolysis
• High stability in acidic gastric pH

Correct Answer: Extensive phase II metabolism and poor intestinal absorption

Q8. Which flavone is a common dietary example and studied for anti-inflammatory effects?

• Apigenin
• Epicatechin
• Cyanidin
• Rutin

Correct Answer: Apigenin

Q9. Which analytical assay is commonly used to estimate antioxidant capacity of flavonoids in vitro?

• ELISA for cytokine quantification
• ORAC or DPPH radical scavenging assays
• Western blot for enzyme expression
• Gas chromatography for volatile profiling

Correct Answer: ORAC or DPPH radical scavenging assays

Q10. Which structural difference distinguishes flavanones from flavones?

• Flavanones have an unsaturated C2–C3 double bond while flavones are saturated
• Flavanones have a saturated C2–C3 bond; flavones have a C2–C3 double bond
• Flavanones always contain a gallate ester
• Flavanones are anthocyanidin derivatives

Correct Answer: Flavanones have a saturated C2–C3 bond; flavones have a C2–C3 double bond

Q11. Which catechin is most abundant and biologically active in green tea?

• Quercetin
• Epigallocatechin gallate (EGCG)
• Naringin
• Rutin

Correct Answer: Epigallocatechin gallate (EGCG)

Q12. Which formulation strategy can improve flavonoid oral bioavailability?

• Complexation with cyclodextrins or lipid-based nanoparticles
• Co-administration with proton pump inhibitors only
• Formulation as unmodified powder with no excipients
• Storage at high temperature to increase solubility

Correct Answer: Complexation with cyclodextrins or lipid-based nanoparticles

Q13. Which mechanism contributes to the antioxidant action of flavonoids?

• Pro-oxidant ionization of cellular thiols
• Electron/hydrogen donation to neutralize free radicals and metal chelation
• Inhibition of phase II conjugation enzymes
• Direct DNA alkylation

Correct Answer: Electron/hydrogen donation to neutralize free radicals and metal chelation

Q14. Which flavonoid is noted for venotonic and capillary-protective effects used in some nutraceuticals?

• Rutin
• Anthocyanidin aglycones
• EGCG
• Naringin

Correct Answer: Rutin

Q15. Which statement about glycosylation of flavonoids is correct?

• Glycosides are always more lipophilic than aglycones
• Glycosylation increases water solubility and can affect intestinal absorption
• Glycosides cannot be hydrolyzed by gut microbiota
• Glycosylation eliminates antioxidant activity entirely

Correct Answer: Glycosylation increases water solubility and can affect intestinal absorption

Q16. Which anthocyanidin gives red coloration in many fruits?

• Delphinidin
• Pelargonidin
• Epicatechin
• Kaempferol

Correct Answer: Pelargonidin

Q17. Which cellular transporter can limit flavonoid absorption by efflux back into the intestinal lumen?

• SGLT1
• P-glycoprotein (P-gp/ABCB1)
• Na+/K+ ATPase
• Mitochondrial ATP synthase

Correct Answer: P-glycoprotein (P-gp/ABCB1)

Q18. Which in vivo metabolic reaction commonly methylates some flavonoids (e.g., quercetin) altering activity?

• Sulfation by SULTs only
• Methylation by catechol-O-methyltransferase (COMT)
• γ-Glutamyl transpeptidation
• N-acetylation by NAT enzymes

Correct Answer: Methylation by catechol-O-methyltransferase (COMT)

Q19. Which analytical technique is best for identifying specific flavonoid glycosides in plant extracts?

• HPLC coupled with diode-array detection and mass spectrometry
• Simple pH paper test
• Polarimetry alone
• Infrared imaging of whole fruit

Correct Answer: HPLC coupled with diode-array detection and mass spectrometry

Q20. Which physiological effect is commonly attributed to quercetin in nutraceutical research?

• Proarrhythmic ion channel blockade
• Anti-inflammatory, antioxidant and potential antiviral activities
• Primary mu-opioid receptor agonism
• Direct insulin secretion stimulation from beta cells

Correct Answer: Anti-inflammatory, antioxidant and potential antiviral activities

Q21. Which statement best explains pH sensitivity of anthocyanidins in foods?

• They form stable salts at all pH values
• Their flavylium cation equilibria shift with pH, changing color and stability
• They polymerize irreversibly at neutral pH
• They are unaffected by pH but degraded by light only

Correct Answer: Their flavylium cation equilibria shift with pH, changing color and stability

Q22. Which flavonoid-related factor is most relevant when assessing potential herb–drug interactions?

• Ability to serve as a vitamin precursor
• Inhibition or induction of CYP enzymes and transporters like CYP3A4 and P-gp
• Color of the plant extract
• Presence of essential fatty acids

Correct Answer: Inhibition or induction of CYP enzymes and transporters like CYP3A4 and P-gp

Q23. Which functional group on flavonoids enhances metal chelation and antioxidant potency?

• Methoxy groups at C7 and C5 only
• Ortho-dihydroxyl (catechol) configuration on the B-ring
• Alkyl chain at C3”
• Glycosidic linkage at C4

Correct Answer: Ortho-dihydroxyl (catechol) configuration on the B-ring

Q24. In formulation, which excipient strategy can protect anthocyanidins from degradation?

• Incorporation into microencapsulated systems or low-pH matrices
• Exposure to high-temperature drying without protection
• Mixing with strong alkaline buffers
• Storing in transparent glass at room light

Correct Answer: Incorporation into microencapsulated systems or low-pH matrices

Q25. Which plant source is richest in naringin?

• Green tea leaves
• Grapefruit (Citrus paradisi)
• Blueberries
• Onion

Correct Answer: Grapefruit (Citrus paradisi)

Q26. Which in vitro observation would suggest a flavonoid has direct radical-scavenging activity?

• Increase in ROS production in cell culture
• Reduction of DPPH radical absorbance in a dose-dependent manner
• Activation of CYP450 enzymes
• Precipitation in aqueous solution

Correct Answer: Reduction of DPPH radical absorbance in a dose-dependent manner

Q27. Which enzyme class primarily hydrolyzes flavonoid glycosides in the intestine to release aglycones?

• β-Glucosidases from brush-border or microbial sources
• Proteases
• Lipases
• Nucleases

Correct Answer: β-Glucosidases from brush-border or microbial sources

Q28. Which flavonoid structural family typically lacks a 3-hydroxyl group?

• Flavonols
• Flavones
• Flavan-3-ols (catechins)
• Anthocyanidins

Correct Answer: Flavones

Q29. Which clinical concern is most relevant when recommending high-dose green tea catechin supplements?

• Risk of severe hyperglycemia in all patients
• Potential hepatotoxicity and interaction with medications like warfarin
• Guaranteed improvement in kidney function
• Immediate histamine-mediated anaphylaxis in all users

Correct Answer: Potential hepatotoxicity and interaction with medications like warfarin

Q30. Which experimental observation supports that a flavonoid exerts anti-inflammatory effects via NF-κB modulation?

• Increased nuclear translocation of NF-κB p65 after treatment
• Decreased expression of NF-κB target genes (e.g., TNF-α, IL-6) and reduced p65 nuclear translocation
• Enhanced COX-2 protein levels in treated cells
• Increased LPS-induced cytokine release

Correct Answer: Decreased expression of NF-κB target genes (e.g., TNF-α, IL-6) and reduced p65 nuclear translocation

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com