Introduction: Isolation of atropine from Belladonna is a core practical topic in pharmacognosy for B.Pharm students. This introduction outlines key concepts: Atropa belladonna as the primary source, tropane alkaloid chemistry, acid-base extraction, solvent choice (chloroform, dichloromethane, ethanol), defatting, basification, drying agents, purification (TLC, column chromatography) and instrumental characterization (HPLC, IR, NMR). Emphasis is placed on practical steps, yield optimization, safety and stability of atropine salts (e.g., atropine sulfate). Understanding these principles prepares students for laboratory isolation, qualitative tests (Dragendorff’s, Mayer’s), and quantitative analysis. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which plant is the classical commercial source of atropine?
- Atropa belladonna (deadly nightshade)
- Digitalis purpurea
- Rauvolfia serpentina
- Hyoscyamus niger
Correct Answer: Atropa belladonna (deadly nightshade)
Q2. Atropine belongs to which class of alkaloids?
- Tropane alkaloids
- Indole alkaloids
- Isoquinoline alkaloids
- Pyrrolizidine alkaloids
Correct Answer: Tropane alkaloids
Q3. Chemically, atropine is best described as a:
- Tertiary amine ester (tropane ester)
- Primary amine
- Quaternary ammonium salt
- Carboxylic acid
Correct Answer: Tertiary amine ester (tropane ester)
Q4. Which extraction strategy is most commonly used to isolate atropine from plant material?
- Acid-base extraction
- Steam distillation
- Soxhlet extraction with water only
- Supercritical CO2 without pretreatment
Correct Answer: Acid-base extraction
Q5. What is a typical solvent used for defatting Belladonna plant material before alkaloid extraction?
- Petroleum ether (or hexane)
- Water
- Acetic acid
- Dilute hydrochloric acid
Correct Answer: Petroleum ether (or hexane)
Q6. During initial extraction of atropine, which medium is used to solubilize the alkaloids as salts?
- Acidified water (dilute HCl)
- Pure ethanol
- Neutral buffered saline
- Nonpolar solvent like hexane
Correct Answer: Acidified water (dilute HCl)
Q7. To convert atropine salts to the free base before organic extraction, which step is required?
- Basification with ammonia or sodium carbonate
- Acidification with sulfuric acid
- Heating to 200°C
- Oxidation with potassium permanganate
Correct Answer: Basification with ammonia or sodium carbonate
Q8. Which organic solvent is commonly used to extract the free base of atropine?
- Dichloromethane (methylene chloride)
- Water
- Glycerol
- Acetic acid
Correct Answer: Dichloromethane (methylene chloride)
Q9. Which classical reagent gives a characteristic precipitate with atropine and other alkaloids?
- Dragendorff’s reagent
- Biuret reagent
- Lead acetate
- Fehling’s solution
Correct Answer: Dragendorff’s reagent
Q10. For TLC detection of atropine, which visualization reagent is commonly used?
- Dragendorff’s spray reagent
- Ninhydrin
- Potassium permanganate spray
- Molisch reagent
Correct Answer: Dragendorff’s spray reagent
Q11. A practical TLC mobile phase for separating tropane alkaloids often contains:
- Chloroform:methanol mixtures
- Water alone
- Pure hexane
- Acetonitrile only
Correct Answer: Chloroform:methanol mixtures
Q12. The pKa of the tropane nitrogen in atropine is approximately:
- 9.8
- 4.2
- 2.5
- 13.5
Correct Answer: 9.8
Q13. Atropine is a mixture of stereoisomers; it is best described as:
- A racemic mixture of hyoscyamine (optically inactive overall)
- A single enantiomer (optically active)
- A diastereomeric pair only
- A polymeric alkaloid
Correct Answer: A racemic mixture of hyoscyamine (optically inactive overall)
Q14. Why is an acidic medium used in the initial aqueous extraction of Belladonna?
- To form water-soluble alkaloid salts
- To hydrolyze atropine into amino acids
- To polymerize non-alkaloidal components
- To precipitate atropine immediately
Correct Answer: To form water-soluble alkaloid salts
Q15. Which salt form of atropine is commonly isolated and used pharmaceutically?
- Atropine sulfate
- Atropine nitrate
- Atropine acetate
- Atropine chloride
Correct Answer: Atropine sulfate
Q16. Which stationary phase is most commonly used for TLC separation of atropine?
- Silica gel
- Cellulose only
- Polystyrene beads
- Aluminum foil
Correct Answer: Silica gel
Q17. In IR spectroscopy, which absorption indicates the ester group present in atropine?
- Strong C=O band near 1730 cm⁻¹
- O–H stretch at 3400 cm⁻¹
- N–H stretch at 3300 cm⁻¹
- NO2 band at 1550 cm⁻¹
Correct Answer: Strong C=O band near 1730 cm⁻¹
Q18. Which drying agent is suitable to remove trace water from organic extracts of atropine?
- Anhydrous sodium sulfate
- Sodium chloride solution
- Calcium carbonate slurry
- Concentrated sulfuric acid
Correct Answer: Anhydrous sodium sulfate
Q19. Which technique is commonly used to concentrate organic extracts of atropine under reduced pressure?
- Rotary evaporation
- Open beaker boiling
- Freeze-drying (lyophilization) of non-aqueous solvent
- Simple vacuum dessication without cooling
Correct Answer: Rotary evaporation
Q20. For purification of crude atropine fraction in the lab, which method is frequently employed?
- Column chromatography on silica
- Gel electrophoresis
- Paper chromatography only
- Dialysis
Correct Answer: Column chromatography on silica
Q21. Which analytical technique provides the most reliable quantitative assay for atropine in an extract?
- High-performance liquid chromatography (HPLC)
- Paper chromatography with spot matching
- Simple color comparison by eye
- Thin-layer chromatography without densitometry
Correct Answer: High-performance liquid chromatography (HPLC)
Q22. Which laboratory safety precaution is essential when handling atropine-containing extracts?
- Wear gloves and protective eyewear due to systemic toxicity risk
- No protection is necessary because it is non-toxic
- Only wear a dust mask; gloves are optional
- Store all extracts at room temperature without labeling
Correct Answer: Wear gloves and protective eyewear due to systemic toxicity risk
Q23. Atropine salts demonstrate greater chemical stability under which condition?
- Acidic medium (salts are more stable)
- Strong alkaline medium
- Prolonged exposure to sunlight
- High humidity and base
Correct Answer: Acidic medium (salts are more stable)
Q24. Which technique distinguishes atropine from its optical isomer hyoscyamine?
- Optical rotation (polarimetry)
- Simple Dragendorff test
- Flame test
- pH strip test
Correct Answer: Optical rotation (polarimetry)
Q25. The main pharmacological action of atropine is:
- Antimuscarinic (anticholinergic) activity
- Beta-adrenergic agonism
- ACE inhibition
- Prostaglandin synthesis inhibition
Correct Answer: Antimuscarinic (anticholinergic) activity
Q26. One classical therapeutic use of atropine is as a:
- Mydriatic agent for pupil dilation
- Long-term antihypertensive
- Topical antibiotic
- Hypoglycemic agent
Correct Answer: Mydriatic agent for pupil dilation
Q27. Which practical step commonly increases the extraction yield of atropine from dried leaf powder?
- Reducing particle size by fine grinding to increase surface area
- Using larger intact leaf pieces without grinding
- Extracting at 100°C for many hours without solvent replacement
- Skipping defatting to save time
Correct Answer: Reducing particle size by fine grinding to increase surface area
Q28. Which method gives the most reliable assessment of purity for an isolated atropine sample?
- HPLC with appropriate standards
- Color comparison against an unlabeled sample
- Estimating by odor
- Melting point without reference
Correct Answer: HPLC with appropriate standards
Q29. To ensure conversion of atropine salts to the free base, the aqueous phase should be adjusted to approximately which pH?
- pH 9–10
- pH 2–3
- pH 5–6
- pH 1–2
Correct Answer: pH 9–10
Q30. Which reagent produces an orange-red precipitate with many alkaloids and is used for qualitative confirmation during isolation?
- Dragendorff’s reagent
- Benedict’s reagent
- Biuret reagent
- Silver nitrate solution
Correct Answer: Dragendorff’s reagent
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