Chemical evaluation of crude drugs is an essential subject for B.Pharm students, covering phytochemical screening, qualitative tests, and quantitative assays to ensure quality, purity and safety. This topic includes identification of marker compounds, extraction techniques, solvent selection, ash values, loss on drying, chromatographic methods (TLC, HPTLC, HPLC), and spectroscopic tools (UV-Vis, FTIR) used for standardization. Understanding reagent-based tests (Dragendorff, Mayer, Bornträger, Keller‑Kiliani, Liebermann‑Burchard), chromatographic interpretation (Rf, resolution), and pharmacopoeial specifications equips students to assess adulteration and potency of herbal drugs. Focus on both principles and practical interpretation strengthens analytical reasoning for quality control. ‘Now let’s test your knowledge with 30 MCQs on this topic.’
Q1. What is the primary purpose of chemical evaluation of crude drugs?
- To identify and quantify active constituents for quality control
- To determine pharmacological mechanism of action
- To measure therapeutic efficacy in clinical trials
- To assess patient compliance to herbal medicines
Correct Answer: To identify and quantify active constituents for quality control
Q2. Phytochemical screening of a crude drug primarily detects which of the following?
- Major classes of secondary metabolites such as alkaloids, flavonoids, tannins and glycosides
- Only volatile oil content
- Clinical side effects of the crude drug
- Manufacturing impurities like solvents
Correct Answer: Major classes of secondary metabolites such as alkaloids, flavonoids, tannins and glycosides
Q3. Which reagent typically gives an orange-brown precipitate with alkaloids?
- Dragendorff’s reagent
- Mayer’s reagent
- Ferric chloride
- Molisch reagent
Correct Answer: Dragendorff’s reagent
Q4. Mayer’s reagent used in alkaloid detection is a solution of which compound?
- Potassium mercuric iodide
- Bismuth subnitrate
- Ferric chloride
- Sodium nitroprusside
Correct Answer: Potassium mercuric iodide
Q5. The Shinoda test is commonly used to detect which class of phytochemicals?
- Flavonoids (producing red/pink color with magnesium and HCl)
- Alkaloids (producing cream precipitate)
- Saponins (producing persistent foam)
- Carbohydrates (producing purple ring)
Correct Answer: Flavonoids (producing red/pink color with magnesium and HCl)
Q6. Bornträger’s test is specific for detecting which compounds in crude drugs?
- Anthraquinone glycosides
- Alkaloids
- Saponins
- Terpenoids
Correct Answer: Anthraquinone glycosides
Q7. The Keller‑Kiliani test is diagnostic for which group of compounds?
- Cardiac glycosides (deoxy sugars producing brown ring and blue‑green color)
- Flavonoids
- Anthraquinones
- Alkaloids
Correct Answer: Cardiac glycosides (deoxy sugars producing brown ring and blue‑green color)
Q8. Which reagent is commonly used to detect steroids and triterpenoids producing a green/blue color?
- Liebermann‑Burchard reagent
- Molisch reagent
- Dragendorff’s reagent
- Seliwanoff reagent
Correct Answer: Liebermann‑Burchard reagent
Q9. A blue‑black color with ferric chloride indicates the presence of which constituents?
- Phenolic compounds and tannins
- Alkaloids
- Carbohydrates
- Saponins
Correct Answer: Phenolic compounds and tannins
Q10. Molisch’s test is a general test for which class of substances?
- Carbohydrates (giving violet ring with α‑naphthol)
- Alkaloids
- Terpenoids
- Proteins
Correct Answer: Carbohydrates (giving violet ring with α‑naphthol)
Q11. Seliwanoff’s test differentiates which types of sugars?
- Ketoses react rapidly to give a cherry‑red color, distinguishing them from aldoses
- Aldoses react rapidly to give a cherry‑red color
- Monosaccharides from polysaccharides
- Reducing from non‑reducing sugars
Correct Answer: Ketoses react rapidly to give a cherry‑red color, distinguishing them from aldoses
Q12. Barfoed’s test is used to distinguish which of the following?
- Monosaccharides from disaccharides based on rate of copper reduction
- Ketoses from aldoses
- Reducing sugars from non‑reducing sugars
- Starch from cellulose
Correct Answer: Monosaccharides from disaccharides based on rate of copper reduction
Q13. Persistent frothing on shaking an aqueous extract indicates the presence of which class?
- Saponins (persistent foam formation)
- Flavonoids
- Alkaloids
- Glycosides
Correct Answer: Saponins (persistent foam formation)
Q14. Which ash parameter indicates siliceous (sand) contamination in crude drugs?
- Acid‑insoluble ash
- Total ash
- Water‑soluble ash
- Loss on drying
Correct Answer: Acid‑insoluble ash
Q15. Loss on drying (LOD) of a crude drug is a measure of what?
- Moisture and volatile matter content determined by weight loss on heating
- Total inorganic ash content
- Extractable active constituents in methanol
- Microbial contamination level
Correct Answer: Moisture and volatile matter content determined by weight loss on heating
Q16. What does an extractive value indicate in chemical evaluation of crude drugs?
- The amount of constituents soluble in a particular solvent, reflecting potency or extraction efficiency
- The inorganic residue after combustion
- The moisture content only
- The bitterness index of the drug
Correct Answer: The amount of constituents soluble in a particular solvent, reflecting potency or extraction efficiency
Q17. In thin layer chromatography (TLC), Rf value is defined as:
- Ratio of distance moved by the compound to distance moved by the solvent front
- Absolute distance moved by the compound from origin
- Time taken for the solvent to reach the top of the plate
- Width of the spot on the plate
Correct Answer: Ratio of distance moved by the compound to distance moved by the solvent front
Q18. Compared to conventional TLC, HPTLC offers which main advantage?
- Higher resolution and improved quantitation with densitometry
- Larger spot size for easier visualization
- Less sensitivity to solvent choice
- Elimination of need for mobile phase
Correct Answer: Higher resolution and improved quantitation with densitometry
Q19. UV‑Visible spectrophotometry is most useful in crude drug analysis for:
- Quantitation of chromophoric marker compounds after suitable extraction
- Direct identification of terpenoids without derivatization
- Separating complex mixtures without chromatography
- Measuring ash values
Correct Answer: Quantitation of chromophoric marker compounds after suitable extraction
Q20. Which analytical technique is most appropriate for precise quantification of specific marker compounds in crude drugs?
- High‑performance liquid chromatography (HPLC)
- TLC without densitometry
- Foam test
- Molisch’s test
Correct Answer: High‑performance liquid chromatography (HPLC)
Q21. What is the preferred method for isolating volatile oils from plant material for analysis?
- Steam distillation
- Soxhlet extraction with methanol
- Cold maceration with hexane
- Gravimetric ash determination
Correct Answer: Steam distillation
Q22. Which solvent is generally most suitable for extracting polar glycosides from crude drugs?
- Methanol (polar solvent)
- n‑Hexane (nonpolar solvent)
- Petroleum ether
- Carbon tetrachloride
Correct Answer: Methanol (polar solvent)
Q23. Which color change with ferric chloride is characteristic of tannins?
- Blue‑black or green‑black color
- Cherry red color
- Orange precipitate
- Violet ring
Correct Answer: Blue‑black or green‑black color
Q24. Which reagent gives a cream‑colored precipitate specifically with many alkaloids?
- Mayer’s reagent
- Dragendorff’s reagent
- Liebermann‑Burchard reagent
- Molisch reagent
Correct Answer: Mayer’s reagent
Q25. How are coumarins typically detected in crude drug extracts?
- Showing blue fluorescence under UV light after treatment with dilute ammonia
- Forming a brown ring with nitric acid
- Producing persistent foam on shaking
- Giving a violet ring with α‑naphthol
Correct Answer: Showing blue fluorescence under UV light after treatment with dilute ammonia
Q26. Berberine, an alkaloid marker in some crude drugs, is notable for what analytical property?
- Yellow fluorescence under UV light
- Green precipitation with Dragendorff
- Blue color with Molisch reagent
- Persistent foam formation
Correct Answer: Yellow fluorescence under UV light
Q27. Which reagent is commonly used as a spot test for lead contamination in crude drugs?
- Sodium rhodizonate test (forms red complex with lead)
- Dragendorff’s reagent
- Mayer’s reagent
- Molisch reagent
Correct Answer: Sodium rhodizonate test (forms red complex with lead)
Q28. Why is acid hydrolysis performed during chemical evaluation of glycoside‑containing crude drugs?
- To cleave glycosidic bond and release aglycone for identification
- To remove inorganic ash content
- To precipitate proteins
- To measure moisture content
Correct Answer: To cleave glycosidic bond and release aglycone for identification
Q29. On silica gel TLC, a compound that has a very low Rf value compared to the solvent front is typically:
- More polar than the mobile phase and strongly retained by the polar stationary phase
- Nonpolar and travels with the solvent front
- Volatile and evaporated during development
- Decomposed by the mobile phase
Correct Answer: More polar than the mobile phase and strongly retained by the polar stationary phase
Q30. Which official source provides monographs and standards widely used for chemical evaluation of crude drugs in India?
- Indian Pharmacopoeia (IP)
- United States Pharmacopeia (USP) only
- European Pharmacopoeia (EP) only
- Food and Drug Administration (FDA) monographs only
Correct Answer: Indian Pharmacopoeia (IP)
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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