19Intact glucosinolate (GSL) profile (five aliphatic; three aromatic, and one indolic glucosinolate) in 20 the leaves of 50 germplasm collections and commercial cultivars of Brassica rapa, Brassica juncea, and 21 Brassica oleracea collected from six different countries and grown under uniform cultural conditions were 22 compared by UPLC-MS/MS. Total GSLs content ranged from 36.80 to 2383.12 μmol/kg DW. Aliphatic 23 GSLs predominated among the entire samples representing from 23.0 to 98.9% of the total GSLs content, 24 where gluconapin and glucobrassicanapin contributed the greatest proportion. Other GSLs such as, 25 progoitrin (PRO), glucotropaeolin (TRO), and glucobarbarin (BAR) were found in relatively low 26 concentrations. Principal Component Analysis (PCA) yielded three principal components with eigenvalue ≥ 27 1, representing 70.33% of the total variation across the entire data set. Accessions IT260822 & IT32750, and 28 commercial cultivar, "Hangamssam2", were well distinguished from other samples in the PCA plot due to 29 their significantly high amount of BAR, glucobrassicin (GBC), and glucoerucin (ERU), respectively. The 30 inter-and intra-leaf variations of GSLs were examined in three kimichi cabbage varieties. The GSLs content 31 varied significantly among leaves in different positions (outer, middle, and inner) and sections within the 32 leaves (top, middle, bottom, green/red, and white). Higher GSL contents were observed in the proximal half 33 & white section of the leaves and inner positions (younger leaves) in most of the samples. GBC, 34 gluconasturtiin (NAS), and glucoberteroin (BER) should be studied profusely in Brassica plants as some of 35 their degradation products of GBC and NAS are useful in cancer chemopreventive functions, whereas BER 36takes part in the process of suppressing aging of the skin. GSLs are regarded as allelochemicals; hence, the 37 data related to the patterns of GSLs within the leaf and between leaves at different position could be useful to 38 understand the defense mechanism of Brassica plants. The observed variability could be useful for breeders 39 to develop Brassica crops with high GSL content or specific profiles of GSLs as required.
42Glucosinolates (GSLs) also called β-thioglucoside-N-hydroxysulfates are class of sulfur-containing 43 important plant secondary metabolites naturally occurring in almost all Brassica species [1]. GSLs could be 44 classified as aliphatic, aromatic, and indolic glucosinolates based on their side chain structure (R group) 45 which are derived from the amino acid precursors methionine (but also alanine, leucine, isoleucine, or valine 46 in some cases), phenylalanine, and tryptophan, respectively [2]. Most glucosinolates share a basic chemical 47 structure consisting of a β-D-glucopyranose residue linked via a sulfur atom to a (Z)-N-hydroximinosulfate 48 ester and a variable R group [3]. Upon hydrolysis by myrosinases, glucosinolates produce several bioactive 49 products including, isothiocyanates, thiocyanates, and nitriles. Glucosin...