Volatile Glucosinolate Hydrolysis Products of Barbarea vulgaris From Serbia: Organ‐Specific Patterns, P‐Type Chemistry in a G‐Type Morph, and Storage‐driven Barbarin Isomerization

We profiled volatile glucosinolate (GSL) degradation products in a Serbian population of Barbarea vulgaris by gas chromatography/mass spectrometry. Twelve metabolites were identified across essential oil and organ‐separated autolysates, including isothiocyanates, nitriles, oxazolidinones, thiazolidinones, and indole‐derived products. Aerial autolysates were dominated by ( S )‐5‐phenyl‐1,3‐oxazolidine‐2‐thione (barbarin), whereas roots were enriched in 2‐phenylethyl isothiocyanate, evidencing organ‐specific turnover of homophenylalanine‐derived GSLs. The phenolic isothiocyanate 2‐(4‐hydroxyphenyl)ethyl isothiocyanate (RI 1799) was secured by synthesis and co‐injection. Enantiomer‐selective nuclear magnetic resonance with Eu(hfc) 3 established ( S )‐barbarin as the sole enantiomer in both organs. Strikingly, the chemical profile indicates a P‐type signature despite G‐type morphology, consistent with hidden hybridization or a distinct southern genotype. Finally, we document complete conversion of barbarin to 5‐phenyl‐1,3‐thiazolidin‐2‐one under mild storage (4°C, months; or room temperature, weeks)—to our knowledge, the first such report–supporting an ionic pathway in autolysate matrices and underscoring the risk of storage artifacts in GSL hydrolysate analysis. Collectively, these data refine chemotype assignment in B. vulgaris and emphasize stringent sample‐handling to avoid mis‐annotation of downstream sulfur heterocycles.