Tannins – Catechu MCQs With Answer

Tannins – Catechu MCQs With Answer

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Tannins – Catechu MCQs With Answer

Tannins are polyphenolic plant metabolites with significant relevance in pharmacognosy, formulation science and therapeutics. Catechu, derived from Acacia catechu and Uncaria gambir, is a catechin-rich extract notable for astringent, antioxidant, antimicrobial and anti-diarrheal activities. B. Pharm students should master tannin classification (hydrolyzable vs condensed), structural features (gallic, ellagic and proanthocyanidin units), extraction and standardization techniques (Folin–Ciocalteu, UV, HPLC), chemical tests (ferric chloride, gelatin, vanillin-HCl), pharmacological mechanisms (protein precipitation, iron chelation) and formulation challenges. This focused review links phytochemistry, analysis and clinical implications. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the best concise definition of tannins?

  • Glycosidic alkaloids with bitter taste
  • Polyphenolic compounds capable of precipitating proteins
  • Volatile terpenes responsible for aroma
  • Saponin-type surfactants found in plant roots

Correct Answer: Polyphenolic compounds capable of precipitating proteins

Q2. On what basis are tannins broadly classified into hydrolyzable and condensed types?

  • Their solubility in chloroform
  • Their ability to be oxidized by air
  • Their hydrolytic behaviour into sugars and phenolic acids versus flavan-3-ol polymers
  • Their capacity to form complexes with metals

Correct Answer: Their hydrolytic behaviour into sugars and phenolic acids versus flavan-3-ol polymers

Q3. Which major flavonoid-type compound is characteristic of catechu (Acacia catechu) extracts?

  • Quercetin
  • Catechin (flavan-3-ol)
  • Rutin
  • Kaempferol

Correct Answer: Catechin (flavan-3-ol)

Q4. What is the primary botanical source of commercial catechu used in pharmacognosy?

  • Terminalia chebula
  • Acacia catechu heartwood extract
  • Camellia sinensis leaves
  • Quercus cortex

Correct Answer: Acacia catechu heartwood extract

Q5. Which pharmacological property of catechu is most directly due to tannin chemistry?

  • Sedative activity
  • Astringent activity through protein precipitation
  • Hypoglycemic action via insulin release
  • Bronchodilator effect

Correct Answer: Astringent activity through protein precipitation

Q6. Which classical qualitative test gives a blue-black or greenish coloration with tannin-containing extracts?

  • Molisch test
  • Ferric chloride test
  • Ninhydrin test
  • Biuret test

Correct Answer: Ferric chloride test

Q7. The gelatin test for tannins is based on which observable outcome?

  • Evolution of gas
  • Precipitation of a protein–tannin complex
  • Formation of a violet color
  • Disappearance of turbidity

Correct Answer: Precipitation of a protein–tannin complex

Q8. Condensed tannins are chemically best described as:

  • Esters of gallic acid with glucose
  • Polymers of flavan-3-ol units (proanthocyanidins)
  • Sulfonated phenolics
  • Simple phenolic acids only

Correct Answer: Polymers of flavan-3-ol units (proanthocyanidins)

Q9. Which assay is commonly used to estimate total phenolic content in catechu and tannin preparations?

  • Folin–Ciocalteu colorimetric assay
  • Kjeldahl nitrogen estimation
  • Bradford protein assay
  • DPD chlorine test

Correct Answer: Folin–Ciocalteu colorimetric assay

Q10. A traditional therapeutic use of catechu relevant for B. Pharm students is:

  • Antihypertensive agent
  • Anti-diarrheal and mucosal astringent
  • Systemic anticoagulant
  • Topical anesthetic

Correct Answer: Anti-diarrheal and mucosal astringent

Q11. How do tannins from catechu affect non-heme iron absorption?

  • They enhance absorption by forming soluble complexes
  • They have no effect on iron absorption
  • They reduce absorption by chelation and precipitation with iron
  • They convert Fe2+ to Fe3+ increasing uptake

Correct Answer: They reduce absorption by chelation and precipitation with iron

Q12. Which extraction method is classically used to obtain catechu from Acacia catechu heartwood?

  • Cold hexane maceration
  • Aqueous hot extraction (decoction/aqueous extraction)
  • Supercritical CO2 extraction only
  • Sublimation under vacuum

Correct Answer: Aqueous hot extraction (decoction/aqueous extraction)

Q13. Tannins are prone to which chemical change that affects storage and color of extracts?

  • Rapid esterification to give volatile esters
  • Oxidation to quinones and polymeric dark products
  • Spontaneous glycosylation
  • Conversion to alkaloids

Correct Answer: Oxidation to quinones and polymeric dark products

Q14. Which analytical technique offers high specificity for quantifying catechin and related tannin constituents in catechu?

  • Thin layer chromatography without standards
  • High-performance liquid chromatography (HPLC)
  • Simple refractometry
  • Gravimetric ash value

Correct Answer: High-performance liquid chromatography (HPLC)

Q15. Upon acid-catalyzed depolymerization, condensed tannins (proanthocyanidins) yield which class of compounds?

  • Tannic acid only
  • Anthocyanidins (colored flavonoid aglycones)
  • Alkaloids
  • Polysaccharides

Correct Answer: Anthocyanidins (colored flavonoid aglycones)

Q16. Another name commonly used for condensed tannins is:

  • Hydrolyzable tannins
  • Proanthocyanidins
  • Glycosidic tannins
  • Tannic acids

Correct Answer: Proanthocyanidins

Q17. Hydrolysis of hydrolyzable tannins typically yields which phenolic acid(s)?

  • Gallic and/or ellagic acid
  • Cinnamic acid only
  • Ascorbic acid
  • Salicylic acid only

Correct Answer: Gallic and/or ellagic acid

Q18. Why are tannins valuable in the leather industry?

  • They dissolve collagen making hides softer
  • They cross-link and stabilize collagen fibers (tanning)
  • They bleach hides to a white color
  • They act as enzymatic dehairing agents

Correct Answer: They cross-link and stabilize collagen fibers (tanning)

Q19. Which statement best describes a major safety or nutritional concern with high tannin intake?

  • Tannins are potent vitamins and cause hypervitaminosis
  • Tannins have antinutritional effects, reducing protein digestibility and mineral bioavailability
  • Tannins universally increase carbohydrate absorption
  • Tannins are inert and have no effect on nutrition

Correct Answer: Tannins have antinutritional effects, reducing protein digestibility and mineral bioavailability

Q20. Which color test is commonly used to detect catechin-type condensed tannins producing a red color?

  • Vanillin–HCl test
  • Benedict’s test
  • Libermann–Burchard test
  • Salkowski test

Correct Answer: Vanillin–HCl test

Q21. The molecular basis of astringency produced by tannins is due to:

  • Stimulation of opioid receptors
  • Enzyme inhibition of cytochrome P450 only
  • Precipitation and aggregation of salivary and mucosal proteins
  • Blocking sodium channels in taste buds

Correct Answer: Precipitation and aggregation of salivary and mucosal proteins

Q22. For routine spectrophotometric estimation of tannin-rich extracts, which wavelength is often monitored for total phenolics?

  • 280 nm (UV) for phenolic chromophores
  • 600 nm for chlorophyll absorption
  • 720 nm for carbohydrate assays
  • 525 nm for betalain pigments

Correct Answer: 280 nm (UV) for phenolic chromophores

Q23. Which formulation incompatibility is most likely when using tannin-rich extracts in multi-component herbal products?

  • Complexation and precipitation with proteins and alkaloids
  • Conversion to volatile oils that evaporate
  • Catalytic degradation of enteric coatings
  • Complete neutralization of pH to 7.0

Correct Answer: Complexation and precipitation with proteins and alkaloids

Q24. Which chromatographic technique is preferred for profiling and quantifying individual catechins in catechu?

  • High-performance liquid chromatography (HPLC) with photodiode array or MS detection
  • Paper chromatography without a detector
  • Simple column chromatography with silica gel and water only
  • Gas chromatography without derivatization

Correct Answer: High-performance liquid chromatography (HPLC) with photodiode array or MS detection

Q25. Which tannin type is readily hydrolyzed by weak acids or enzymes to yield sugars and phenolic acids?

  • Condensed tannins
  • Hydrolyzable tannins
  • Saponins
  • Terpenoids

Correct Answer: Hydrolyzable tannins

Q26. Which common commercial name refers to the extract obtained from Acacia catechu?

  • Opium
  • Cutch (Katha)
  • Ginger oil
  • Myrrh

Correct Answer: Cutch (Katha)

Q27. The antioxidant activity of catechu tannins is mainly attributed to:

  • Alkyl chain length
  • Polyphenolic structure and free-radical scavenging ability
  • High sulfur content
  • Presence of heavy metals

Correct Answer: Polyphenolic structure and free-radical scavenging ability

Q28. Which spray reagent is commonly used on TLC plates to detect phenolic spots, including tannins?

  • Dragendorff’s reagent
  • Ferric chloride spray
  • α-Naphthol reagent for sugars
  • Thymol blue

Correct Answer: Ferric chloride spray

Q29. Which processing parameter typically increases extraction yield of tannins from plant material?

  • Lowering temperature to 0 °C
  • Using hot polar solvents (e.g., hot water or aqueous ethanol)
  • Using nonpolar solvents like hexane exclusively
  • Short sonication for 5 seconds only

Correct Answer: Using hot polar solvents (e.g., hot water or aqueous ethanol)

Q30. In quality control, total tannin content of catechu is often expressed relative to which standard compound?

  • Sucrose equivalents
  • Tannic acid equivalents or gallic acid equivalents (as standard)
  • Cholesterol equivalents
  • Urea equivalents

Correct Answer: Tannic acid equivalents or gallic acid equivalents (as standard)

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