Flavonoids and polyphenols: resveratrol, rutin, hesperidin, naringin, quercetin, ellagic acid MCQs With Answer

Introduction
This quiz set on flavonoids and polyphenols focuses on resveratrol, rutin, hesperidin, naringin, quercetin and ellagic acid — compounds of high relevance in Advanced Pharmacognosy I. Questions target chemistry, biosynthesis, analytical identification, stability, pharmacokinetics, metabolism, pharmacology and formulation challenges of these natural products. Designed for M.Pharm students, the items emphasize mechanistic understanding (structure–activity relationships, phase I/II metabolism, enzyme interactions), applied laboratory techniques (HPLC, UV detection, hydrolysis), and clinically relevant issues such as bioavailability and drug–herb interactions. Use this set to assess and deepen practical and theoretical competence needed for research and quality control of polyphenolic drugs and botanical preparations.

Q1. Resveratrol belongs to which chemical class of polyphenols?

• Flavone
• Stilbene (resveratrol)
• Isoflavone
• Tannin

Correct Answer: Stilbene (resveratrol)

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

• Quercetin aglycone
• Quercetin-3-O-rutinoside (quercetin + rutinose)
• Hesperetin glycoside
• Ellagic acid dimer

Correct Answer: Quercetin-3-O-rutinoside (quercetin + rutinose)

Q3. Hesperidin is predominantly isolated from which plant source used in pharmacognosy?

• Grapevine (Vitis vinifera) bark
• Citrus species (especially sweet orange) peel
• Pomegranate rind
• Green tea leaves

Correct Answer: Citrus species (especially sweet orange) peel

Q4. Naringin is primarily responsible for the characteristic bitterness of which fruit?

• Lemon (Citrus limon)
• Grapefruit (Citrus paradisi)
• Orange (Citrus sinensis)
• Apple (Malus domestica)

Correct Answer: Grapefruit (Citrus paradisi)

Q5. Which structural feature of quercetin most contributes to its potent radical-scavenging activity?

• The 3,4-dihydroxy (catechol) substitution on the B‑ring
• The C2–C3 saturated bond in the C‑ring
• A methoxy group at C-3′
• The presence of a glycosidic sugar at C-7

Correct Answer: The 3,4-dihydroxy (catechol) substitution on the B‑ring

Q6. Ellagic acid in plants is most commonly derived from which precursor class?

• Condensed tannins (proanthocyanidins)
• Hydrolyzable tannins—specifically hydrolysis of ellagitannins
• Flavanones
• Anthocyanidins

Correct Answer: Hydrolyzable tannins—specifically hydrolysis of ellagitannins

Q7. For HPLC-UV analysis, which approximate wavelength is typically used to detect trans-resveratrol selectively?

• 254 nm
• 306 nm
• 450 nm
• 210 nm

Correct Answer: 306 nm

Q8. Following oral administration, resveratrol is rapidly converted mainly by which phase II processes?

• Oxidative deamination
• Glucuronidation and sulfation forming conjugated metabolites
• Reduction to dihydroresveratrol only
• Direct renal excretion unchanged

Correct Answer: Glucuronidation and sulfation forming conjugated metabolites

Q9. Glycosylation of flavonoids (e.g., rutin vs quercetin) generally affects oral absorption how?

• Glycosides are more lipophilic and absorbed faster than aglycones
• Glycosylation increases passive diffusion across intestinal epithelium
• Glycosides are hydrolyzed by intestinal β‑glucosidases and colonic microflora to aglycones before absorption
• Glycosides are completely resistant to enzymatic hydrolysis in the GI tract

Correct Answer: Glycosides are hydrolyzed by intestinal β‑glucosidases and colonic microflora to aglycones before absorption

Q10. A positive Shinoda test (magnesium + HCl) indicates presence of which class of compounds in a plant extract?

• Alkaloids
• Flavones and flavonols (flavonoids)
• Terpenoids
• Saponins

Correct Answer: Flavones and flavonols (flavonoids)

Q11. Which statement best describes a common stability issue for trans-resveratrol in formulations?

• Resveratrol is highly stable to light and does not isomerize
• Trans-resveratrol undergoes UV-induced isomerization to the cis isomer
• Resveratrol polymerizes readily in acidic media to proanthocyanidins
• Trans-resveratrol is converted enzymatically to rutin in vivo

Correct Answer: Trans-resveratrol undergoes UV-induced isomerization to the cis isomer

Q12. Rutin exerts venotonic and capillary-protective effects mainly through which mechanisms?

• Blockade of beta‑adrenergic receptors in vascular smooth muscle
• Inhibition of hyaluronidase and antioxidant-mediated stabilization of collagen and capillary walls
• Direct nitric oxide donation causing vasodilation
• Increasing platelet aggregation to seal capillary leaks

Correct Answer: Inhibition of hyaluronidase and antioxidant-mediated stabilization of collagen and capillary walls

Q13. Chemically, hesperidin is the glycoside of which aglycone?

• Naringenin
• Hesperetin
• Quercetin
• Resveratrol

Correct Answer: Hesperetin

Q14. A common methylated metabolite of quercetin identified in plasma is which compound?

• Kaempferol
• Isorhamnetin (3′-O-methyl quercetin)
• Hesperetin
• Dihydroquercetin

Correct Answer: Isorhamnetin (3′-O-methyl quercetin)

Q15. Which statement correctly describes ellagic acid solubility relevant to formulation work?

• Ellagic acid is highly water-soluble and suitable for aqueous injections
• Ellagic acid is poorly soluble in water but soluble in polar organic solvents like DMSO and ethanol
• Ellagic acid is lipophilic and easily soluble in nonpolar solvents like hexane
• Ellagic acid forms stable micelles in pure water without surfactants

Correct Answer: Ellagic acid is poorly soluble in water but soluble in polar organic solvents like DMSO and ethanol

Q16. To hydrolyze rutin to yield quercetin aglycone in the lab, which condition is typically employed?

• Neutral aqueous extraction at room temperature
• Acid hydrolysis (e.g., reflux with dilute HCl) to cleave the glycosidic bond
• Base-catalyzed hydrolysis with dilute NaOH at 25°C
• Enzymatic oxidation with laccase without hydrolysis

Correct Answer: Acid hydrolysis (e.g., reflux with dilute HCl) to cleave the glycosidic bond

Q17. For routine HPLC separation of quercetin, rutin and related polyphenols, which column type is most commonly used?

• Ion-exchange cellulose column
• Size-exclusion (gel) column
• Reverse-phase C18 column
• Normal-phase silica column

Correct Answer: Reverse-phase C18 column

Q18. Naringin and related grapefruit flavonoids can cause clinically relevant drug interactions primarily by affecting which pathway?

• Enhancing renal organic anion transporters to increase clearance
• Inhibiting intestinal CYP3A4, increasing bioavailability of CYP3A4 substrates
• Upregulating hepatic glucuronosyltransferases to speed clearance
• Stimulating P‑glycoprotein to decrease drug absorption

Correct Answer: Inhibiting intestinal CYP3A4, increasing bioavailability of CYP3A4 substrates

Q19. In radical-scavenging assays such as DPPH, which of the listed polyphenols typically displays the strongest activity per mole due to its substitution pattern?

• Resveratrol
• Quercetin
• Hesperidin
• Ellagic acid

Correct Answer: Quercetin

Q20. When standardizing a citrus peel extract for quality control, which compound is commonly used as a marker for hesperidin-type flavonoids?

• Rutin
• Hesperidin
• Naringin
• Ellagic acid

Correct Answer: Hesperidin

Download