- Which one of the following secondary metabolites is characterized by the presence of a central carbon atom that is bound by a sulphur to a glycone group, and N by a nitrogen to a sulfonatedoxime group?
(1) Alkaloids (2) Terpenes
(3) Phenolics (4) Glucosinolates
Correct answer: (4) Glucosinolates
Glucosinolates possess a distinctive core structure featuring a central carbon atom bound via sulfur to a β-thioglucose (glycone) group and via nitrogen to a sulfonated oxime (sulfate-linked aldoxime moiety), characteristic of this Brassicales-specific secondary metabolite class.
Option Analysis
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(1) Alkaloids — Nitrogen-containing heterocyclic bases (e.g., morphine, quinine); lack the specific S-glycone and N-sulfonated oxime structure.
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(2) Terpenes — Isoprenoid hydrocarbons or derivatives; purely carbon/hydrogen/oxygen-based, no sulfur or sulfonated nitrogen.
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(3) Phenolics — Aromatic compounds with hydroxyl groups from phenylpropanoid pathway; no central C-S-glycone-N-sulfonated oxime motif.
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(4) Glucosinolates — Correct; defined by R-CH₂-CH(N-OSO₃⁻)-S-Glc core where central C links S-glycone and N-sulfated aldoxime.
Glucosinolates contain a signature central carbon atom connected through sulfur to a thioglucose moiety and through nitrogen to a sulfonated oxime group, enabling myrosinase-activated release of defensive isothiocyanates upon herbivory.
