Flavonoids – Ruta MCQs With Answer

Flavonoids – Ruta MCQs With Answer

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Flavonoids – Ruta MCQs With Answer
Flavonoids are polyphenolic secondary metabolites abundant in Ruta species (e.g., Ruta graveolens) and are essential topics in pharmacognosy for B. Pharm students. Key keywords include flavonoids, rutin, quercetin, glycosides, aglycone, phenylpropanoid pathway, chalcone synthase, antioxidant, vasoprotective activity, HPLC analysis, and bioavailability. Ruta-derived flavonoids such as rutin (quercetin-3-O-rutinoside) exhibit antioxidant, anti-inflammatory and venotonic effects and influence extraction, identification and formulation strategies. Understanding structure–activity relationships, biosynthesis, analytical tests and safety aspects is critical for pharmaceutical applications and quality control. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which major flavonoid glycoside is most characteristically associated with Ruta graveolens?

  • Rutin
  • Hesperidin
  • Naringin
  • Genistein

Correct Answer: Rutin

Q2. Rutin is the glycoside of which flavonoid aglycone?

  • Quercetin
  • Kaempferol
  • Apigenin
  • Luteolin

Correct Answer: Quercetin

Q3. The disaccharide rutinose consists of which two monosaccharides?

  • Rhamnose and glucose
  • Glucose and galactose
  • Arabinose and xylose
  • Fructose and mannose

Correct Answer: Rhamnose and glucose

Q4. Which enzyme catalyzes the first committed step in flavonoid biosynthesis from phenylalanine?

  • Phenylalanine ammonia-lyase (PAL)
  • Chalcone synthase (CHS)
  • Flavonol synthase (FLS)
  • Chalcone isomerase (CHI)

Correct Answer: Phenylalanine ammonia-lyase (PAL)

Q5. Formation of chalcone from p-coumaroyl-CoA and malonyl-CoA is catalyzed by which enzyme?

  • Chalcone synthase (CHS)
  • Chalcone isomerase (CHI)
  • Flavanone 3-hydroxylase (F3H)
  • Anthocyanidin synthase (ANS)

Correct Answer: Chalcone synthase (CHS)

Q6. Conversion of naringenin chalcone to naringenin (a flavanone) is catalyzed by which enzyme?

  • Chalcone isomerase (CHI)
  • Chalcone synthase (CHS)
  • Flavone synthase (FNS)
  • Flavonoid 3′-hydroxylase (F3’H)

Correct Answer: Chalcone isomerase (CHI)

Q7. Which enzyme directly converts dihydroflavonols into flavonols during flavonoid biosynthesis?

  • Flavonol synthase (FLS)
  • Flavanone 3-hydroxylase (F3H)
  • Dihydroflavonol 4-reductase (DFR)
  • Anthocyanidin synthase (ANS)

Correct Answer: Flavonol synthase (FLS)

Q8. How are rutin and similar compounds best classified chemically?

  • Flavonol glycosides
  • Isoflavones
  • Anthocyanidins
  • Flavan-3-ols (catechins)

Correct Answer: Flavonol glycosides

Q9. Flavonoids typically show two characteristic UV absorption bands; Band I and Band II roughly correspond to which wavelength regions?

  • Band I: 300–380 nm; Band II: 240–285 nm
  • Band I: 200–220 nm; Band II: 280–320 nm
  • Band I: 400–450 nm; Band II: 300–350 nm
  • Band I: 150–200 nm; Band II: 210–230 nm

Correct Answer: Band I: 300–380 nm; Band II: 240–285 nm

Q10. Compared to aglycones, flavonoid glycosides (like rutin) are generally:

  • More water-soluble
  • Less polar
  • More volatile
  • Less stable in acidic media

Correct Answer: More water-soluble

Q11. Which pharmacological activities are most prominently attributed to Ruta flavonoids such as rutin?

  • Antioxidant and vasoprotective effects
  • Antibiotic and antiviral effects
  • Psychostimulant and opioid-like effects
  • Metal chelation used as anticancer cytotoxins

Correct Answer: Antioxidant and vasoprotective effects

Q12. Which analytical technique is most commonly used for quantitative determination of rutin in plant extracts?

  • High-performance liquid chromatography (HPLC)
  • Paper chromatography
  • Infrared spectroscopy (IR)
  • Flame photometry

Correct Answer: High-performance liquid chromatography (HPLC)

Q13. The Shinoda test (Mg + HCl) is used in preliminary identification of flavonoids. What color indicates a positive result for many flavonols/flavones?

  • Orange–red
  • Blue–green
  • Violet
  • Colorless

Correct Answer: Orange–red

Q14. In rutin, the glycosidic linkage to quercetin is at which position of the aglycone?

  • 3-OH position
  • 7-OH position
  • 5-OH position
  • 4′-OH position

Correct Answer: 3-OH position

Q15. Ruta species can cause which adverse reaction due to non-flavonoid constituents such as furanocoumarins?

  • Photodermatitis (photosensitivity)
  • Severe hypoglycemia
  • Hearing loss
  • Renal lithiasis

Correct Answer: Photodermatitis (photosensitivity)

Q16. The strong antioxidant activity of quercetin-type flavonoids is largely attributed to which structural feature?

  • Ortho-dihydroxy (catechol) arrangement on the B-ring
  • Presence of a methoxy group at C-7
  • Absence of a 4-keto group
  • Glycosylation at C-3 only

Correct Answer: Ortho-dihydroxy (catechol) arrangement on the B-ring

Q17. Which solvent is typically most efficient for extracting rutin from Ruta leaves for analytical purposes?

  • Methanol (or aqueous methanol)
  • Hexane
  • Chloroform
  • Petroleum ether

Correct Answer: Methanol (or aqueous methanol)

Q18. Besides radical scavenging, flavonoids can chelate metal ions. Which structural motif commonly contributes to metal chelation?

  • 3-hydroxy-4-keto and 3′,4′-dihydroxy groups
  • Aliphatic methyl branches on ring A
  • Saturated C2–C3 bond without oxygen
  • Glycosidic linkage at C-7

Correct Answer: 3-hydroxy-4-keto and 3′,4′-dihydroxy groups

Q19. Which enzyme (or activity) is responsible for converting rutin into quercetin and sugars during metabolism?

  • Rutinase (a glycosidase)
  • Oxidase
  • Methyltransferase
  • Acetyltransferase

Correct Answer: Rutinase (a glycosidase)

Q20. Which of the following compounds is a representative flavonol commonly found in Ruta extracts?

  • Quercetin
  • Genistein
  • Cyanidin
  • Epicatechin

Correct Answer: Quercetin

Q21. In plant cells, where are flavonoids like rutin predominantly stored?

  • Vacuoles
  • Mitochondria
  • Chloroplast stroma
  • Cell wall cellulose fraction only

Correct Answer: Vacuoles

Q22. The biosynthetic enzymes for flavonoid synthesis are largely associated with which cellular structure?

  • Endoplasmic reticulum (ER) surface in the cytosol
  • Mitochondrial inner membrane
  • Plasma membrane lipid rafts
  • Nuclear envelope lumen

Correct Answer: Endoplasmic reticulum (ER) surface in the cytosol

Q23. For reverse-phase HPLC analysis of rutin, which stationary phase is most commonly used?

  • C18 (octadecyl silica)
  • Silanized silica for normal phase
  • Ion-exchange resin
  • Gel-permeation column

Correct Answer: C18 (octadecyl silica)

Q24. What structural feature differentiates flavonols from flavones?

  • Presence of a 3-hydroxyl group in flavonols
  • Absence of the 4-keto group in flavonols
  • A saturated C2–C3 bond in flavonols
  • Glycosylation exclusively at C-7 in flavonols

Correct Answer: Presence of a 3-hydroxyl group in flavonols

Q25. Which treatment is typically used to hydrolyze flavonoid glycosides to yield aglycones in the lab?

  • Acid hydrolysis
  • Oxidative bleaching
  • Alkaline condensation
  • Photolytic cleavage under UV only

Correct Answer: Acid hydrolysis

Q26. Rutin’s oral bioavailability is limited because:

  • It requires deglycosylation by intestinal microbiota before absorption
  • It is highly volatile and evaporates in the GI tract
  • It is rapidly converted to steroid hormones
  • It readily crosses the blood–brain barrier reducing plasma levels

Correct Answer: It requires deglycosylation by intestinal microbiota before absorption

Q27. Which TLC spray reagent is commonly used to visualize flavonoids as fluorescent spots under UV?

  • Natural Product reagent (NP/PEG)
  • Dragendorff’s reagent
  • Potassium permanganate
  • Salkowski reagent

Correct Answer: Natural Product reagent (NP/PEG)

Q28. Which spectroscopic technique provides detailed information on sugar identity and attachment position in flavonoid glycosides?

  • Nuclear magnetic resonance (NMR) spectroscopy
  • Flame atomic absorption spectroscopy
  • UV–Vis spectrophotometry only
  • Polarimetry

Correct Answer: Nuclear magnetic resonance (NMR) spectroscopy

Q29. Which plant part of Ruta is typically richest in rutin for medicinal extraction?

  • Leaves
  • Roots
  • Seeds
  • Bark

Correct Answer: Leaves

Q30. Use of Ruta or high doses of Ruta-derived preparations is contraindicated in which condition due to uterotonic effects?

  • Pregnancy
  • Controlled hypertension
  • Type II diabetes
  • Hyperthyroidism

Correct Answer: Pregnancy

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