Tests for glycosides MCQs With Answer: Glycosides are plant-derived compounds made of an aglycone (genin) and a sugar moiety; accurate identification is essential for pharmacognosy, drug standardization and B. Pharm practicals. This concise introduction summarizes qualitative and confirmatory tests—Molisch, Keller‑Kiliani, Legal’s, Baljet, Bornträger’s, Libermann–Burchard, Salkowski, Shinoda, Bial and Fehling—explaining reagents, chemical basis, expected colour changes and key limitations. Emphasis is on hydrolysis, extraction and interpretation to distinguish cardiac, anthraquinone, steroidal and saponin glycosides, linking lab diagnosis to quality control and formulation decisions for pharmacists. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the principle of the Molisch test used in glycoside analysis?
- Formation of violet ring with alpha-naphthol and conc. H2SO4 indicating presence of carbohydrate (glycone)
- Formation of red precipitate with Fehling’s solution indicating reducing aglycone
- Color change to green with acetic anhydride indicating steroidal aglycone
- Development of orange-red with sodium picrate indicating lactone
Correct Answer: Formation of violet ring with alpha-naphthol and conc. H2SO4 indicating presence of carbohydrate (glycone)
Q2. The Keller‑Kiliani test is diagnostic for which feature of cardiac glycosides?
- Brown ring at interface and bluish‑green upper layer with glacial acetic acid, FeCl3 and conc. H2SO4 indicating deoxy sugar containing cardenolides
- Pink color with sodium nitroprusside indicating anthraquinone glycosides
- Persistent froth indicating saponin content
- Blue fluorescence under UV indicating coumarins
Correct Answer: Brown ring at interface and bluish‑green upper layer with glacial acetic acid, FeCl3 and conc. H2SO4 indicating deoxy sugar containing cardenolides
Q3. Legal’s test is commonly used to detect which type of glycoside and gives what colour?
- Cardiac glycosides; red colour with sodium nitroprusside in pyridine under alkaline conditions
- Anthraquinone glycosides; pink colour after benzene extraction and ammonia
- Saponin glycosides; persistent foam on shaking
- Flavonoid glycosides; yellow colour with NaOH
Correct Answer: Cardiac glycosides; red colour with sodium nitroprusside in pyridine under alkaline conditions
Q4. The Baljet test detects which structural feature of some cardiac glycosides?
- Unsaturated lactone ring; orange‑red colour with sodium picrate
- Phenolic OH groups; green colour with ferric chloride
- Pentosic sugars; green colour with orcinol and HCl
- Saponin foaming capacity; stable froth on dilution
Correct Answer: Unsaturated lactone ring; orange‑red colour with sodium picrate
Q5. Which sequence of steps describes the Bornträger’s test for anthraquinone glycosides?
- Hydrolyze, extract aglycone into benzene, add ammonia to benzene layer to give pink/red colour
- Add alpha‑naphthol and H2SO4 to give violet ring at interface
- Mix with FeCl3 to give blue‑green colour for phenolics
- Shake with water to produce persistent foam indicating saponins
Correct Answer: Hydrolyze, extract aglycone into benzene, add ammonia to benzene layer to give pink/red colour
Q6. The Libermann–Burchard test is most useful for detecting which class and shows what colour change?
- Steroidal glycosides/sterols; green/blue colour with acetic anhydride and conc. H2SO4
- Anthraquinone glycosides; pink colour after benzene extraction and ammonia
- Saponin glycosides; lasting froth on shaking
- Flavonoid glycosides; red on addition of magnesium and HCl
Correct Answer: Steroidal glycosides/sterols; green/blue colour with acetic anhydride and conc. H2SO4
Q7. What result is expected in Salkowski’s test for sterols or triterpenes?
- Red‑brown ring or colouration on addition of concentrated H2SO4
- Violet ring at interface with alpha‑naphthol and conc. H2SO4
- Orange‑red with sodium picrate
- Pink colour with sodium nitroprusside in pyridine
Correct Answer: Red‑brown ring or colouration on addition of concentrated H2SO4
Q8. After acid hydrolysis of a glycoside, which test confirms the presence of reducing sugar?
- Fehling’s test producing a brick‑red Cu2O precipitate
- Libermann–Burchard showing green colour
- Bornträger’s test giving pink colour
- Baljet test giving orange‑red
Correct Answer: Fehling’s test producing a brick‑red Cu2O precipitate
Q9. Which qualitative test indicates presence of saponin glycosides in an aqueous extract?
- Froth test: persistent stable froth on shaking
- Keller‑Kiliani test: brown ring and bluish‑green layer
- Molisch test: violet ring with alpha‑naphthol
- Bial’s test: green colour for pentoses
Correct Answer: Froth test: persistent stable froth on shaking
Q10. What is the main purpose of hydrolysis in glycoside testing?
- To cleave the glycosidic bond releasing aglycone and sugar for separate identification
- To precipitate the glycoside as an insoluble salt for weighing
- To convert aglycone into a fluorescent derivative without releasing sugar
- To remove non‑polar impurities by solvent extraction
Correct Answer: To cleave the glycosidic bond releasing aglycone and sugar for separate identification
Q11. Kedde’s test is primarily used to detect which feature of cardiac aglycones?
- Unsaturated lactone (alpha,beta‑unsaturated) in cardenolides; purple colour with 3,5‑dinitrobenzoic acid reagent
- Phenolic OH groups giving blue colour with FeCl3
- Pentosic sugar moiety giving green with orcinol
- Saponin foaming giving persistent froth
Correct Answer: Unsaturated lactone (alpha,beta‑unsaturated) in cardenolides; purple colour with 3,5‑dinitrobenzoic acid reagent
Q12. Bial’s (orcinol) test detects which sugar type after hydrolysis of glycosides?
- Pentosans/pentoses; green colour with orcinol and HCl
- Hexoses; violet ring with alpha‑naphthol
- Deoxy sugars only; brown ring with FeCl3
- Sucrose specifically; red precipitate with Benedict’s
Correct Answer: Pentosans/pentoses; green colour with orcinol and HCl
Q13. The Shinoda test is used to detect which class and what observation indicates a positive result?
- Flavonoids; pink/red or magenta colour on addition of magnesium and concentrated HCl
- Saponins; persistent froth on shaking
- Anthraquinones; pink after benzene extraction and ammonia
- Sterols; green/blue with Libermann–Burchard
Correct Answer: Flavonoids; pink/red or magenta colour on addition of magnesium and concentrated HCl
Q14. A positive ferric chloride test in a glycoside extract indicates which functional group?
- Phenolic hydroxyl groups producing blue/green or black colour
- Unsaturated lactone producing orange colour with picrate
- Pentosic sugars producing green with orcinol
- Saponin glycosides producing foam
Correct Answer: Phenolic hydroxyl groups producing blue/green or black colour
Q15. Which sugar type is specifically suggested by a positive Keller‑Kiliani reaction?
- Deoxy sugars (e.g., digitoxose) commonly found in cardiac glycosides
- Pentosic sugars such as xylose
- Hexoses like glucose and fructose
- Disaccharides such as sucrose
Correct Answer: Deoxy sugars (e.g., digitoxose) commonly found in cardiac glycosides
Q16. Which solvent is typically used to extract the aglycone in Bornträger’s test prior to ammonia addition?
- Benzene (or a similar non‑polar solvent) for extracting liberated anthraquinone aglycones
- Water to dissolve anthraquinones directly
- Acetic acid to form coloured complexes
- Methanol to precipitate glycosides
Correct Answer: Benzene (or a similar non‑polar solvent) for extracting liberated anthraquinone aglycones
Q17. Which reagent combination produces the characteristic violet ring in the Molisch test?
- Alpha‑naphthol reagent followed by careful addition of concentrated sulfuric acid
- Fehling’s solution followed by boiling
- Acetic anhydride and sulfuric acid (Libermann–Burchard)
- Sodium nitroprusside in pyridine
Correct Answer: Alpha‑naphthol reagent followed by careful addition of concentrated sulfuric acid
Q18. Which observation best describes a positive result for flavonoids using the alkaline reagent test?
- Intense yellow colour on addition of dilute NaOH which becomes colourless on acidification
- Persistent froth on dilution with water
- Orange‑red colour with sodium picrate
- Pink colour after benzene extraction and ammonia
Correct Answer: Intense yellow colour on addition of dilute NaOH which becomes colourless on acidification
Q19. Which of the following is a common limitation of simple colour tests for glycosides?
- Low specificity and subjective interpretation leading to possible false positives
- They always destroy the aglycone making further testing impossible
- They require high‑performance instrumentation for interpretation
- They can quantify glycoside content accurately without calibration
Correct Answer: Low specificity and subjective interpretation leading to possible false positives
Q20. Benedict’s test after hydrolysis of a glycoside is used to detect what?
- Reducing sugars (e.g., glucose, fructose) by formation of a coloured precipitate
- Unsaturated lactone rings of cardiac aglycones
- Steroidal nucleus by green/blue coloration
- Anthraquinone aglycones by pink colour in ammonia
Correct Answer: Reducing sugars (e.g., glucose, fructose) by formation of a coloured precipitate
Q21. Which test can be used to indicate coumarin glycosides in a plant extract?
- Fluorescence under UV light after alkaline treatment indicating coumarin derivatives
- Pink colour with sodium nitroprusside indicating cardiac glycosides
- Violet ring with alpha‑naphthol indicating pentose sugars
- Green/blue colour with Libermann–Burchard indicating sterols
Correct Answer: Fluorescence under UV light after alkaline treatment indicating coumarin derivatives
Q22. Which test outcome suggests a glycoside contains an anthrone or anthraquinone nucleus after hydrolysis?
- Pink/red colour in ammonia following benzene extraction (Bornträger’s positive)
- Green/blue colour with sodium hydroxide (flavonoids)
- Intense yellow with NaOH (alkaline reagent for flavonoids)
- Brick‑red precipitate with Fehling’s (reducing sugars)
Correct Answer: Pink/red colour in ammonia following benzene extraction (Bornträger’s positive)
Q23. Which test specifically detects pentose sugars liberated from glycosides?
- Bial’s (orcinol) test producing a green colour with orcinol and concentrated HCl
- Molisch test producing violet ring with alpha‑naphthol
- Fehling’s test producing brick‑red Cu2O
- Libermann–Burchard giving green/blue for sterols
Correct Answer: Bial’s (orcinol) test producing a green colour with orcinol and concentrated HCl
Q24. Which test result would most likely indicate a phenolic glycoside?
- Blue/green or black colour on addition of ferric chloride
- Persistent froth on shaking
- Pink colour after benzene extraction and ammonia
- Orange‑red with sodium picrate
Correct Answer: Blue/green or black colour on addition of ferric chloride
Q25. The Kedde test and Baljet test both relate to cardiac glycosides. How do they differ in principle?
- Kedde detects alpha,beta‑unsaturated lactone by purple colour; Baljet detects lactone by orange‑red with sodium picrate (differences in reagent chemistry and sensitivity)
- Kedde detects pentoses; Baljet detects hexoses
- Kedde is for saponins; Baljet is for flavonoids
- Kedde uses boric acid; Baljet uses alpha‑naphthol
Correct Answer: Kedde detects alpha,beta‑unsaturated lactone by purple colour; Baljet detects lactone by orange‑red with sodium picrate (differences in reagent chemistry and sensitivity)
Q26. Which test is most appropriate to confirm the presence of flavonoid glycosides after hydrolysis?
- Shinoda test giving pink/red or magenta colour with magnesium and HCl
- Bornträger’s test giving pink after benzene extraction and ammonia
- Baljet test giving orange‑red with sodium picrate
- Froth test producing persistent foam
Correct Answer: Shinoda test giving pink/red or magenta colour with magnesium and HCl
Q27. Which chromatographic or instrumental follow‑up is commonly used after a positive colour test to confirm a glycoside identity?
- TLC or HPLC coupled with reference standards to confirm identity of aglycone and sugar
- Only repeating colour tests since they are definitive
- Measuring foam height as a quantitative metric
- Using Benedict’s test to determine molecular weight
Correct Answer: TLC or HPLC coupled with reference standards to confirm identity of aglycone and sugar
Q28. Which statement correctly describes the role of extraction before chemical tests for glycosides?
- Selective extraction (polar or non‑polar solvents) isolates glycoside or aglycone fractions improving specificity of subsequent tests
- Extraction is unnecessary because colour tests work on crude powdered drug only
- Extraction always destroys glycosides and must be avoided
- Only supercritical CO2 extraction is suitable for glycosides
Correct Answer: Selective extraction (polar or non‑polar solvents) isolates glycoside or aglycone fractions improving specificity of subsequent tests
Q29. A plant extract gives violet ring in Molisch, positive Fehling’s after hydrolysis and Libermann–Burchard green colour. Which combination of constituents is most likely present?
- Carbohydrate (glycone), reducing sugar on hydrolysis, and steroidal nucleus (steroidal glycoside)
- Only anthraquinone glycosides without sugars
- Only saponins without any sugars
- Only flavonoids and no carbohydrate content
Correct Answer: Carbohydrate (glycone), reducing sugar on hydrolysis, and steroidal nucleus (steroidal glycoside)
Q30. Why are multiple complementary tests recommended when analysing glycosides in pharmacopeial work?
- Because single colour tests lack absolute specificity; combining hydrolysis, selective extraction, and multiple reagents reduces false positives and supports confirmation
- Because one test is sufficient but multiple tests are done only for tradition
- Because colour tests can quantify precisely, eliminating need for chromatography
- Because combining tests always yields negative results which simplifies reporting
Correct Answer: Because single colour tests lack absolute specificity; combining hydrolysis, selective extraction, and multiple reagents reduces false positives and supports confirmation
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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