Tannins are important polyphenolic phytochemicals widely studied in pharmacognosy and pharmaceutical sciences. This introduction focuses on tannins with emphasis on Pterocarpus species (e.g., Pterocarpus marsupium and Pterocarpus santalinus), their classification into hydrolyzable and condensed tannins, chemical characteristics, common tests (ferric chloride, gelatin, vanillin-HCl), extraction and standardization methods, pharmacological actions (astringent, antioxidant, antimicrobial), traditional uses, and formulation considerations. Understanding tannin chemistry, protein-precipitating behavior and interactions with drugs is essential for B.Pharm students involved in natural product research and quality control. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What are tannins in the context of plant secondary metabolites?
- Low-molecular-weight alkaloids with basic nitrogen
- High-molecular-weight polyphenolic plant metabolites that precipitate proteins
- Saturated fatty acids involved in membrane structure
- Simple carbohydrates used for plant energy storage
Correct Answer: High-molecular-weight polyphenolic plant metabolites that precipitate proteins
Q2. What are the two major chemical classes of tannins?
- Alkaloids and glycosides
- Saponins and terpenes
- Hydrolyzable and condensed tannins
- Flavonoids and coumarins
Correct Answer: Hydrolyzable and condensed tannins
Q3. Hydrolyzable tannins are primarily esters of which compounds?
- Fatty acids and glycerol
- Gallic or ellagic acid with a carbohydrate core
- Flavan-3-ols with glucose
- Sterols with acetate groups
Correct Answer: Gallic or ellagic acid with a carbohydrate core
Q4. Condensed tannins are best described as:
- Polymers of flavan-3-ol units (proanthocyanidins)
- Simple monomeric phenols like catechol
- Glycosylated triterpenes
- Peptide-bound phenolic acids
Correct Answer: Polymers of flavan-3-ol units (proanthocyanidins)
Q5. Which color change is typically observed when tannin-containing extract reacts with ferric chloride?
- Pale yellow to orange
- Blue-black or greenish coloration
- Bright red precipitate
- No visible change
Correct Answer: Blue-black or greenish coloration
Q6. The classical gelatin test for tannins indicates results by:
- Formation of a gelatin-tannin precipitate
- Evolution of a violet gas
- Complete dissolution of gelatin
- Colorless solution remaining unchanged
Correct Answer: Formation of a gelatin-tannin precipitate
Q7. Which plant family does the genus Pterocarpus belong to?
- Rutaceae
- Fabaceae (Leguminosae)
- Myrtaceae
- Moraceae
Correct Answer: Fabaceae (Leguminosae)
Q8. Pterocarpus marsupium is commonly known by which traditional name?
- White sandalwood
- Indian kino (Vijaysar)
- Neem
- Arjuna
Correct Answer: Indian kino (Vijaysar)
Q9. Which primary pharmacological property is associated with tannins?
- Hypnotic action on the central nervous system
- Astringent action via protein precipitation
- Calcium channel blockade
- Beta-adrenergic agonism
Correct Answer: Astringent action via protein precipitation
Q10. The astringent effect of tannins is mainly due to:
- Enhancement of lipid synthesis in membranes
- Precipitation and cross-linking of surface proteins
- Stimulation of mucous secretion
- Blocking sodium channels in nerve endings
Correct Answer: Precipitation and cross-linking of surface proteins
Q11. A known nutritional interaction of dietary tannins is that they can:
- Increase absorption of non-heme iron
- Decrease absorption of non-heme iron
- Enhance vitamin C stability in the gut
- Promote protein digestion efficiency
Correct Answer: Decrease absorption of non-heme iron
Q12. Which reagent is classically used for spectrophotometric estimation of tannins?
- Kjeldahl reagent
- Folin–Denis reagent (Folin–Ciocalteu type assays)
- Biuret reagent
- Benedict’s reagent
Correct Answer: Folin–Denis reagent (Folin–Ciocalteu type assays)
Q13. Which solvents are most suitable for extracting tannins from plant material for analytical purposes?
- Non-polar solvents like hexane
- Polar solvents such as aqueous acetone or methanol
- Pure diethyl ether
- Liquid paraffin
Correct Answer: Polar solvents such as aqueous acetone or methanol
Q14. Tannins are widely used in industry for which application?
- Plastics polymerization
- Leather tanning by cross-linking collagen
- Synthesis of antibiotics
- As fuel additives
Correct Answer: Leather tanning by cross-linking collagen
Q15. Which statement best describes the volatility of tannins?
- Highly volatile and responsible for aroma
- Non-volatile, high molecular weight compounds
- Volatile only at room temperature
- Evaporate readily during drying
Correct Answer: Non-volatile, high molecular weight compounds
Q16. The term “kino” in Pterocarpus refers to:
- A volatile essential oil from leaves
- A reddish-brown resinous exudate rich in tannins
- A type of seed oil high in triglycerides
- A protein-rich latex used as food
Correct Answer: A reddish-brown resinous exudate rich in tannins
Q17. Traditionally, extracts of Pterocarpus marsupium have been used in folk medicine primarily for:
- Treatment of epilepsy
- Management of diabetes mellitus
- Inducing sedation
- As a laxative
Correct Answer: Management of diabetes mellitus
Q18. Hydrolysis of ellagitannins yields which characteristic phenolic acid?
- Cinnamic acid
- Ellagic acid
- Palmitic acid
- Succinic acid
Correct Answer: Ellagic acid
Q19. The vanillin-HCl reagent is used in tannin analysis to detect:
- Hydrolyzable tannins selectively
- Condensed tannins (proanthocyanidins) producing a red color
- Alkaloids via blue fluorescence
- Saponins by frothing
Correct Answer: Condensed tannins (proanthocyanidins) producing a red color
Q20. Which tannin type is readily cleaved by heating with dilute acid?
- Condensed tannins only
- Hydrolyzable tannins
- Both are completely resistant
- Tannic steroids
Correct Answer: Hydrolyzable tannins
Q21. The antioxidant activity of tannins is primarily due to:
- Ability to chelate metals and donate hydrogen from phenolic OH groups
- High lipid solubility disrupting membranes
- Inhibition of cytochrome P450 solely
- Blocking of sodium channels
Correct Answer: Ability to chelate metals and donate hydrogen from phenolic OH groups
Q22. Tannins exert antimicrobial effects primarily by:
- Denaturing microbial proteins and inactivating enzymes
- Serving as a nutrient source for bacteria
- Functioning as nucleic acid analogues
- Acting as beta-lactamase inhibitors
Correct Answer: Denaturing microbial proteins and inactivating enzymes
Q23. Which analytical technique is commonly used for profiling tannin components in pharmaceutical research?
- Gas chromatography of volatile tannins
- High-performance liquid chromatography (HPLC)
- Protein electrophoresis
- Thin-layer chromatography using non-polar eluents only
Correct Answer: High-performance liquid chromatography (HPLC)
Q24. One antinutritional effect of tannins in animal feed is:
- Increased vitamin A absorption
- Decreased protein digestibility and feed efficiency
- Enhanced enzymatic digestion of starch
- Promotion of rapid weight gain
Correct Answer: Decreased protein digestibility and feed efficiency
Q25. Which compound is commonly used as a marker for hydrolyzable (gallo) tannins?
- Catechin
- Gallic acid
- Cholesterol
- Quinoline
Correct Answer: Gallic acid
Q26. Tannic acid is best described as:
- A synthetic antibiotic unrelated to tannins
- A specific form of gallotannin (a hydrolyzable tannin)
- A terpene derivative found in essential oils
- A protein commonly found in serum
Correct Answer: A specific form of gallotannin (a hydrolyzable tannin)
Q27. Pterocarpus santalinus (red sandalwood) heartwood is often used pharmaceutically as:
- A source of volatile oils for aromatherapy
- A source of red dye and tannin-rich material for formulations
- A source of opiate alkaloids
- A primary source of vitamin C
Correct Answer: A source of red dye and tannin-rich material for formulations
Q28. Typical molecular weight range for many tannins is approximately:
- 10–50 Da
- 500–3000 Da or higher
- 50–100 Da
- Less than 10 Da
Correct Answer: 500–3000 Da or higher
Q29. Tannins can interact with certain pharmaceutical alkaloids leading to:
- Improved alkaloid bioavailability
- Formation of insoluble complexes and reduced absorption
- Chemical conversion of alkaloids into peptides
- Complete enzymatic breakdown of alkaloids
Correct Answer: Formation of insoluble complexes and reduced absorption
Q30. Which of the following is a common approach to quantify tannin content in a herbal formulation?
- Titration with sodium hydroxide only
- Spectrophotometric assay using Folin-type reagents
- Measuring odor intensity of the extract
- Determining melting point of the crude drug
Correct Answer: Spectrophotometric assay using Folin-type reagents
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.
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