Variations of Major Glucosinolates in Diverse Chinese Cabbage (Brassica rapa ssp. pekinensis) Germplasm as Analyzed by UPLC-ESI-MS/MS.

In this study, the variability of major glucosinolates in the leaf lamina of 134 Chinese cabbage accessions was investigated using Acquity ultra-performance liquid chromatography (UPLC-ESI-MS/MS). A total of twenty glucosinolates were profiled, of which glucobrassicanapin and gluconapin were identified as the predominant glucosinolates within the germplasm. These two glucosinolates had mean concentration levels above 1000.00 µmol/kg DW. Based on the principal component analysis, accessions IT186728, IT120044, IT221789, IT100417, IT278620, IT221754, and IT344740 were separated from the rest in the score plot. These accessions exhibited a higher content of total glucosinolates. Based on the VIP values, 13 compounds were identified as the most influential and responsible for variation in the germplasm. Sinigrin (r = 0.73), gluconapin (r = 0.78), glucobrassicanapin (r = 0.70), epiprogoitrin (r = 0.73), progoitrin (r = 0.74), and gluconasturtiin (r = 0.67) all exhibited a strong positive correlation with total glucosinolate at p < 0.001. This indicates that each of these compounds had a significant influence on the overall glucosinolate content of the various accessions. This study contributes valuable insights into the metabolic diversity of glucosinolates in Chinese cabbage, providing potential for breeding varieties tailored to consumer preferences and nutritional demands.

Variability of Glucosinolates in Pak Choy (Brassica rapa subsp. chinensis) Germplasm.

Glucosinolates are sulfur-containing phytochemicals generally abundant in cruciferous vegetables such as pak choy. Glucosinolates participate in a range of biological activities essential for promoting a healthy human body. In this study, we aimed to elucidate glucosinolate variability present in pak choy germplasm that are under conservation at the Rural Development Administration Genebank, Jeonju, Republic of Korea. The Acquity Ultra-Performance Liquid Chromatography (UHPLC) analytical system was used in profiling the glucosinolate content in leaf samples of various accessions. We identified a total of 17 glucosinolates in the germplasm. Based on principal compoment analysis performed, three separate groups of the accessions were obtained. Group 1 contained the cultivar cheongsacholong which recorded high content of glucobrassicin (an indole), glucoerucin (aliphatic), gluconasturtiin (aromatic) and glucoberteroin (aliphatic). Group 2 consisted of six accessions, BRA77/72, Lu ling gaogengbai, 9041, Wuyueman, RP-75 and DH-10, predominatly high in aliphatic compounds including glucoiberin, glucocheirolin, and sinigrin. Group 3 comprised the majority of the accessions which were characterized by high content of glucoraphanin, epiprogoitrin, progoitrin, and glucotropaeolin. These results revealed the presence of variability among the pak choy germplasm based on their glucosinolate content, providing an excellent opprtunity for future breeding for improved glucosinolate content in the crop.

Transetherification of 2,4-dimethoxynitrobenzene by aromatic nucleophilic substitution.

In view of the few reports concerning aromatic nucleophilic substitution reactions featuring an alkoxy group as a leaving group, the aromatic nucleophilic substitution of 2,4-dimethoxynitrobenzene was investigated with a bulky t-butoxide nucleophile under microwave irradiation. The transetherification of 2,4-dimethoxynitrobenezene with sodium t-butoxide under specific conditions, namely for 20 min at 110°C in 10% dimethoxyethane in toluene, afforded the desired product in 87% yield with exclusive ortho-selectivity. A variety of reaction conditions were screened to obtain the maximum yield. The aromatic nucleophilic substitution of 2,4-dimethoxynitrobenzene with t-butoxide should be carried out under controlled conditions in order to avoid the formation of byproducts, unlike that of dihalogenated activated benzenes. Among the formed byproducts, a major compound was elucidated as 2,4-dimethoxy-N-(5-methoxy-2-nitrophenyl)aniline by X-ray crystallography.

Identification of novel scaffolds for potential anti-Helicobacter pylori agents based on the crystal structure of H. pylori 3-deoxy-d-manno-octulosonate 8-phosphate synthase (HpKDO8PS).

The crystal structure of 3-deoxy-d-manno-octulosonate-8-phosphate synthase (KDO8PS) from Helicobacter pylori (HpKDO8PS) was determined alone and within various complexes, revealing an extra helix (HE) that is absent in the structures of KDO8PS from other organisms. In contrast to the metal coordination of the KDO8PS enzyme from Aquifex aeolicus, HpKDO8PS is specifically coordinated with Cd(2+) or Zn(2+) ions, and isothermal titration calorimetry (ITC) and differential scanning fluorimetry (DSF) revealed that Cd(2+) thermally stabilizes the protein structure more efficiently than Zn(2+). In the substrate-bound structure, water molecules play a key role in fixing residues in the proper configuration to achieve a compact structure. Using the structures of HpKDO8PS and API [arabinose 5-phosphate (A5P) and phosphoenolpyruvate (PEP) bisubstrate inhibitor], we generated 21 compounds showing potential HpKDO8PS-binding properties via in silico virtual screening. The capacity of three, avicularin, hyperin, and MC181, to bind to HpKDO8PS was confirmed through saturation transfer difference (STD) experiments, and we identified their specific ligand binding modes by combining competition experiments and docking simulation analysis. Hyperin was confirmed to bind to the A5P binding site, primarily via hydrophilic interaction, whereas MC181 bound to both the PEP and A5P binding sites through hydrophilic and hydrophobic interactions. These results were consistent with the epitope mapping by STD. Our results are expected to provide clues for the development of HpKDO8PS inhibitors.