Q.50 Which of the following plant natural products is/are cyanogenic glycoside(s)?
(A) Linustatin
(B) Limonene
(C) Luteolin
(D) Linamarin
Linustatin and linamarin qualify as cyanogenic glycosides, while limonene and luteolin belong to different classes of plant natural products. These compounds occur in plants like linseed and cassava, where cyanogenic glycosides release hydrogen cyanide (HCN) upon hydrolysis as a defense mechanism.
Option Analysis
Linustatin (A)
Linustatin is a cyanogenic diglucoside found in linseed and Hevea brasiliensis seeds, where it stores nitrogen and mobilizes during germination via enzymatic cleavage to release HCN. It features a cyanohydrin aglycone linked to two glucose units, confirming its classification.
Limonene (B)
Limonene is a monoterpene hydrocarbon abundant in citrus peels, functioning as a volatile essential oil component rather than a glycoside. It lacks a cyanide group and does not undergo cyanogenic hydrolysis.
Luteolin (C)
Luteolin is a flavone flavonoid present in vegetables like celery and broccoli, known for antioxidant properties. While some glycosylated forms exist, it does not contain a cyanohydrin moiety essential for cyanogenesis.
Linamarin (D)
Linamarin is a cyanogenic monoglucoside derived from valine in cassava, hydrolyzed by linamarase to produce toxic HCN as a plant defense. Biosynthesis involves CYP71E7 enzyme converting oximes to cyanohydrins.
Cyanogenic glycosides represent key plant natural products that release hydrogen cyanide (HCN) upon tissue damage, serving as anti-herbivore defenses in species like cassava and linseed. This article explores the question: “Which of the following plant natural products is/are cyanogenic glycoside(s)?” with options Linustatin, Limonene, Luteolin, and Linamarin, providing detailed explanations ideal for CSIR NET Life Sciences aspirants.
What Are Cyanogenic Glycosides?
Cyanogenic glycosides consist of a sugar moiety linked to a cyanohydrin aglycone, stored in plant vacuoles until β-glucosidase and hydroxynitrile lyase enzymes activate HCN release during hydrolysis. Plants detoxify endogenous cyanide via β-cyanoalanine synthase. Linamarin and lotaustralin exemplify this in cassava, while linustatin occurs in flax.
Detailed Breakdown of Options
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Linustatin: A diglucoside cyanogenic glycoside in linseed meal, protecting against selenium toxicity and mobilized in seedlings.
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Limonene: No cyanide group; it’s a chiral monoterpene from citrus oils used in flavors and solvents.
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Luteolin: Flavonoid with anti-cancer potential, found in parsley and celery, but lacks cyanogenic properties.
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Linamarin: Valine-derived monoglucoside in cassava, biosynthesized via a metabolon and hydrolyzed to acetone cyanohydrin + HCN.
| Compound | Class | Cyanogenic? | Key Plant Source | Function |
|---|---|---|---|---|
| Linustatin | Cyanogenic diglucoside | Yes | Linseed | N-storage, defense |
| Limonene | Monoterpene | No | Citrus peels | Aroma, solvent |
| Luteolin | Flavone flavonoid | No | Celery, broccoli | Antioxidant |
| Linamarin | Cyanogenic monoglucoside | Yes | Cassava | Chemical defense |
Biological Significance
These glycosides highlight plant secondary metabolism, with cyanogenic types like linamarin posing toxicity risks in food processing, while non-cyanogenic ones like limonene offer commercial value. For competitive exams, recognize cyanogenic glycosides by their HCN-releasing potential.
