Novel Sulfonylurea Derivatives as Potential Antimicrobial Agents: Chemical Synthesis, Biological Evaluation, and Computational Study.

Methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide health threat and has already tormented humanity during its long history, creating an urgent need for the development of new classes of antibacterial agents. In this study, twenty-one novel sulfonylurea derivatives containing phenyl-5-vinyl and pyrimidinyl-4-aryl moieties were designed and synthesized, among which, nine compounds exhibited inhibitory potencies against Gram-positive bacterial strains: MRSA (Chaoyang clinical isolates), S. aureus ATCC6538, vancomycin-resistant Enterococci-309 (VRE-309), and Bacillus subtilis ATCC 6633. Especially, 9i and 9q demonstrated inhibitory activities against the four bacterial strains with minimum inhibitory concentrations (MICs) of 0.78-1.56 µg/mL, and quite a few of other MRSA clinical strains with MICs of 0.78 µg/mL, superior to those of the positive controls vancomycin (MIC of 1 µg/mL) and methicillin (MIC of >200 µg/mL). This is the very first time that sulfonylurea derivatives have been identified as promising inhibitors against different MRSA clinical isolates. In addition, all the MIC values of the synthesized compounds against Candida albicans were greater than 100 µg/mL. Since the reported anti-Candida activities of sulfonylureas were due to acetohydroxyacid synthase (AHAS) inhibition, the molecular target against MRSA for the target sulfonylureas was thought to be a different mode of action. Density functional theory (DFT) calculations were finally performed to understand the structure-activity relationships, based on which, significant differences were observed between their HOMO maps for compounds with strong antibacterial activities and weak anti-MRSA effects. The present results hence provide valuable guidance for the discovery of novel agents to treat bacterial infections, especially against MRSA.

Chemical preparation, degradation analysis, computational docking and biological activities of novel sulfonylureas with 2,5-disubstituted groups.

Based on the previous finding that a substitution at 5-position of the benzene ring is favorable to enhance the degradation rates of sulfonylurea herbicides, a total of 16 novel 2,5-disubsituted sulfonylurea compounds were chemically synthesized and fully characterized by means of 1H NMR, 13C NMR, HRMS and X-ray diffraction. By using HPLC analysis, the degradation behavior of M03, a compound belonging to this family, was studied and confirmed that chlorsulfuron itself is not a degraded product of the 2,5-disubstituted sulfonylureas. Inhibition constants against plant acetohydroxyacid synthase (AHAS) were determined for selected compounds, among which SU3 showed seven times stronger activity against the mutant W574L enzyme than chlorsulfuron. Molecular docking suggested that the substituted group at 5-position of benzene ring is likely to interact with the surrounding residues Met200 and Asp376 of AtAHAS. From the greenhouse herbicidal assay and crop safety test, SU5 and SU6 are considered as herbicide candidates to control dicotyledon weeds in corn, while SU3 is likely to be a promising candidate to control dicotyledon weed species and barnyard grass in wheat. The present research has therefore provided some new insights to understand the structure-activity relationships of herbicidal sulfonylureas with di-substitutions at benzene ring.

Alkaline Soil Degradation and Crop Safety of 5-Substituted Chlorsulfuron Derivatives.

Sulfonylurea herbicides can lead to serious weed resistance due to their long degradation times and large-scale applications. This is especially true for chlorsulfuron, a widely used acetolactate synthase inhibitor used around the world. Its persistence in soil often affects the growth of crop seedlings in the following crop rotation, and leads to serious environmental pollution all over the world. Our research goal is to obtain chlorsulfuron-derived herbicides with high herbicidal activities, fast degradation times, as well as good crop safety. On account of the slow natural degradation of chlorsulfuron in alkaline soil, based on the previously reported results in acidic soil, the degradation behaviours of 5-substituted chlorsulfuron analogues (L101-L107) were investigated in a soil with pH 8.39. The experimental data indicated that 5-substituted chlorsulfuron compounds could accelerate degradation rates in alkaline soil, and thus, highlighted the potential for rational controllable degradation in soil. The degradation rates of these chlorsulfuron derivatives were accelerated by 1.84-77.22-fold, compared to chlorsulfuron, and exhibited excellent crop safety in wheat and corn (through pre-emergence treatment). In combination with bioassay activities, acidic and alkaline soil degradation, and crop safety, it was concluded that compounds L104 and L107, with ethyl or methyl groups, are potential green sulfonylurea herbicides for pre-emergence treatment on wheat and corn. This paper provides a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast, controllable degradation rates, and high crop safety.

Synthesis, Herbicidal Activity, Crop Safety and Soil Degradation of Pyrimidine- and Triazine-Substituted Chlorsulfuron Derivatives.

Chlrosulfuron, a classical sulfonylurea herbicide that exhibits good safety for wheat but causes a certain degree of damage to subsequent corn in a wheat-corn rotation mode, has been suspended field application in China since 2014. Our previous study found that diethylamino-substituted chlorsulfuron derivatives accelerated the degradation rate in soil. In order to obtain sulfonylurea herbicides with good crop safety for both wheat and corn, while maintaining high herbicidal activities, a series of pyrimidine- and triazine-based diethylamino-substituted chlorsulfuron derivatives (W102-W111) were systematically evaluated. The structures of the synthesized compounds were confirmed with 1H NMR, 13C NMR, and HRMS. The preliminary biological assay results indicate that the 4,6-disubstituted pyrimidine and triazine derivatives could maintain high herbicidal activity. It was found that the synthesized compounds could accelerate degradation rates, both in acidic and alkaline soil. Especially, in alkaline soil, the degradation rate of the target compounds accelerated more than 22-fold compared to chlorsulfuron. Moreover, most chlorsulfuron analogs exhibited good crop safety for both wheat and corn at high dosages. This study provided a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast degradation rates, and high crop safety.

Genomic instability induced by ionizing radiation in human hepatocytes.

The aim of this study was to characterize genomic instability induced by ionizing radiation (IR) in human hepatocytes as reflected by alterations in cloning efficiency, micronucleus (MN) frequency, and apoptosis. The human normal liver 7702 cell line (HL7702) was subjected to initial irradiation of (60)Co-γ ray at doses of 0 (control group), 2, 4, 6, 8, or 10 Gy in each group. Progeny of surviving cells from a second irradiation at dose of 2 Gy were cultured for 15 passages until they were transferred. The cloning efficiency, MN frequency, and apoptotic rate were measured after the initial irradiation, and repeated at passage 15 before and after the second irradiation. The initial irradiation resulted in a dose-dependent decline in cloning efficiency and an increase in MN frequency and apoptotic rate. At passage 15 in progeny of initially irradiated cells, cloning efficiency, MN frequency returned to control levels while apoptotic rate rose. After the second irradiation, cloning efficiency fell while a rise in MN frequency and apoptosis occurred. Our results show that the second irradiation may further enhance cell progeny injury induced by initial irradiation, such that genomic instability that may be difficult to detect after one irradiation is more apparent with subsequent irradiation.

Proteomic alterations in progeny of irradiated human liver cells.

This study was designed to characterize the differential protein expression in the progeny of human liver cells surviving exposure to ionizing radiation. The progeny of irradiated cells were derived from a human liver cell line exposed to 0, 2, 4, or 6 Gy of (60)Co gamma-irradiation. Total protein of the cells was extracted by two-dimensional electrophoresis (2-DE) and analyzed with ImageMaster 2D Platinum software. In total, 42 differentially expressed proteins from the progeny of irradiated cells were screened, of which 17 were identified by matrix assistant laser desorption ion-top flight-mass spectrometry (MALDI-TOF-MS) analysis. There were 4 upregulated and 13 downregulated proteins detected. The upregulated expression of two proteins, mitochondrial heat-shock 60-kD protein (HSP60) and globin transcription factor 1 (GATA-1), was further confirmed by immunoblotting. Database search revealed that these differentially expressed proteins may function in cell cycle regulation, cytoskeleton maintenance, stress response, and tumor metastasis, indicating an effect of radiation-induced genomic instability (RIGI) in the progeny of irradiated cells. Analysis on functional roles of the screened proteins may provide insight into further mechanistic investigations underlying molecular events induced by RIGI.

Flavobacterium saliperosum sp. nov., isolated from freshwater lake sediment.

An aerobic, yellow-pigmented, Gram-negative bacterium, designated strain S13T, was isolated from freshwater sediment of Taihu Lake in central China. The taxonomy of strain S13T was studied by using phenotypic and phylogenetic methods. Cells of strain S13T were rod-shaped, non-motile and with a size range of 0.35-0.55x1.5-2.5 microm. The nearly complete 16S rRNA gene of strain S13T was amplified and sequenced. A blast search and phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain S13T was related to members of the genus Flavobacterium, with the highest sequence similarity of 93.8% to Flavobacterium columnare (ATCC 23463T). Cells contained menaquinone-6 (MK-6) as the major respiratory quinone and the genomic DNA G+C content was 41 mol%. The major fatty acids were iso-C15:0 (28.2%) and iso-C17:1omega9c (19.0%). It is proposed that S13T (=CGMCC 1.3801T=JCM 13331T) represents the type strain of a novel species, Flavobacterium saliperosum sp. nov.

[Effects of seeding and sowing methods on the yields of root tubers of Curcuma longa].

OBJECTIVE: To provide a scientific basis for standardizing the cultivation method for Curcuma longa. METHOD: Plant heights and seeding numbers were sampled periodically, the plot yields were counted a tharvested. RESULT: The effects of seeding method on yields, plant height and number were significant. The effects of different sowing ways on the yields were very little. CONCLUSION: The hole seeding method using mother tuber or blastostyle bearing three to four knots was shown to be the best may, worthy to be widely applied in production.