Identification and quantification of glucosinolates in Korean leaf mustard germplasm (Brassica juncea var. integrifolia) by liquid chromatography–electrospray ionization/tandem mass spectrometry

Abstract

In the present investigation, glucosinolate content was identified and quantified in 210 accessions of Korean leaf mustard (Brassica juncea var. integrifolia) by a liquid chromatography (LC) with electrospray ionization (ESI) coupled with a positive-mode ion trap tandem mass spectrometry (LC–ESI–MS/MS). Eleven individual GSLs including two new compounds were identified in the accessions using desulfo-glucosinolates (DS-GSLs) LC–MS library, and they were elucidated by interpreting the fragmentation data ([M + H-glucose]+) obtained. The newly identified GSLs contained aliphatic and hydroxyl functional group in their back bone were named as 1-ethyl-2-hydroxyethyl DS-GSLs (glucosisautricin) or 2-hydroxy-2-methylpropyl DS-GSLs (glucoconringiin) and 3,4,5-trimethoxybenzyl DS-GSLs, respectively. Among all tested accessions, the total DS-GSLs content was found to be varied between 5.3 and 23.2 mg/g dry weight (DW) with an average of 13.0 mg/g DW in the germplasm. Each individual DS-GSLs component was found in decreasing order of sinigrin (41.7 %) >glucoiberverin (21.7 %) >gluconasturtiin (12.6 %) >glucobarbarin (10.0 %) >glucoiberin (5.1 %) >glucocheirolin (3.6 %) >glucobrassicanapin (2.6 %) >gluconapin (2.1 %), and >glucobrassicin (0.6 %). Interestingly, sinigrin and gluconasturtiin were present in higher content, and progoitrin was not detected significantly in the germplasm of Korean leaf mustard. In particular, accession K046197 (purple) was found to show highest total DS-GSL content (23.2 mg/g DW).