4-(Succinimido)-1-butane sulfonic acid as a Br?nsted acid catalyst for the synthesis of pyrano[4,3-b]pyran derivatives using thermal and ultrasonic irradiation

4-(Succinimido)-1-butane sulfonic acid was shown to be anefficient and reusable Br?nsted acid catalyst for the synthesis of pyrano[4,3-b]pyran derivatives using thermal and ultrasonic conditions. The c...     

Residue level and dissipation pattern of lepimectin in shallots using high‐performance liquid chromatography coupled with photodiode array detection

Lepimectin, as an emulsifiable concentrate, was sprayed on shallots at the recommended dose rate (10 mL/20 L) to determine its residue levels, dissipation pattern, pre‐harvest residue limits (PHRLs), and health risk. Samples were randomly collected over 10 days, extracted with acetonitrile, purified using an amino solid‐phase extraction (NH₂‐SPE) cartridge and analyzed using a high‐performance liquid chromatography–photodiode array detection method. Field‐incurred samples were confirmed using ultra‐performance liquid chromatography–tandem mass spectrometry. The linearity was excellent, with a determination coefficient (R²) of ≥0.9991. The recoveries at two spiking levels (0.2 and 1.0 mg/kg) ranged from 84.49 to 87.64% with relative standard deviations of ≤7.04%. The developed method was applied to field samples grown in separate greenhouses, one located in Naju and one in Muan, in the Republic of Korea. The dissipation pattern was described by first‐order kinetics with half‐lives of 1.9 (Naju) and 1.7 days (Muan). The PHRL curves indicated that, if the lepimectin residues are <0.18 (Naju) and <0.13 mg/kg (Muan) 5 days before harvest, the residue levels will be lower than the maximum residue limit (0.05 mg/kg) upon harvesting. The risk assessment data indicated that lepimectin is safe for use in the cultivation of shallots, with no risk of detrimental effects to the consumer.     

Is Modeling the PSD in Emulsion Polymerization a Finished Problem? An Overview

Significant progress has been made over the past 20–30 years in terms of the ability to develop and solve mechanistic models of emulsion polymerization processes, and in particular models for prediction of the particle size distribution. However, this does not imply that modeling of these economically important processes is by any means a “solved problem,” or that it is no longer necessary to perform fundamental research in this area. There are a number of areas where strong scientific work would increase the understanding of the process, including events in the aqueous phase, radical entry into growing particles, monomer partitioning, and especially the mechanisms and modeling of particle coagulation.

     

Carcinogenic Activities and Sperm Abnormalities of Methicillin Resistance <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and Inhibition of Their Virulence Potentials by Ayamycin

This investigation aimed to study the in vivo harmful effects of the subcutaneous injection of different methicillin resistance Staphylococcus aureus extracts (MRSA2, MRSA4, MRSA10, MRSA69, MRSA70, MRSA76, and MRSA78). Such strains represented the highest minimum inhibition concentration toward methicillin with various multidrug-resistant patterns. The obtained results revealed that rats injected with the MRSA4 extract died immediately after the last dose indicating the high cytotoxicity of MRSA4 strain (100% mortality). While the mortalities in other groups injected by the other MRSA extracts ranged from 50 to 75%. In comparison with the normal animal group, all MRSA extracts induced a hepatotoxic effect which was indicated from the significant (p < 0.01) increases in the activities of the serum alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) enzymes. Moreover, alkaline phosphatase (ALP) combined with a partial nephrotoxicity that was monitored from the significant elevation of serum urea concentration. While serum creatinine levels did not affect. Similarly, a significant elevation was recorded in serum levels of tumor biomarkers (alpha fetoprotein; AFP, carcinoembryonic antigen; CEA, and lactate dehydrogenase; LDH) reflecting their carcinogenic potential. On the other hand, the percentage of micronuclei (MN) in polychromatic erythrocytes from bone marrow cells was statistically significant in all groups as compared to the control group. The percentage of sperm abnormalities was statistically significant compared to the control. Different types of head abnormalities and coiled tail were recorded. Consequently, the current study focused on fighting MRSA virulence factors by the new compound ayamycin, which proved to be potent anti-virulence factor against all MRSA strains under study by significant decreasing of their streptokinase activities, hemolysin synthesis, biofilm formation, and their cell surface hydrophobicity.     

Site‐ and Regioselectivity of the Reaction of Hydrazonoyl Chlorides with Perimidine Ketene Aminal. Antimicrobial Evaluation of the Products

Reaction of hydrazonoyl chlorides with perimidine ketene aminal derivative in dioxane in the presence of triethylamine afforded either pyrrolo[1,2‐a]perimidines or pyrazolyl perimidines depending on the type of hydrazonoyl chloride used. The reaction was found to be site‐ and regioselective according to the suggested mechanism. The structure of the newly synthesized compounds was established on the basis of spectral data and elemental analyses. In addition, the antimicrobial activity of the newly synthesized compounds was evaluated, and the results showed moderate activity of all compounds against the bacterial species.     

Synthesis of Some New Heteroylhydrazono‐1,3‐thiazolidin‐4‐ones

A series of (Z)‐methyl‐2‐[(Z)‐3‐substituted‐4‐oxo‐2‐(2‐picolinoyl‐/thiophene‐2‐carbonyl)‐hydrazonothiazolidin‐5‐ylidene]acetates were synthesized by condensation N‐substituted‐(2‐picolinoyl‐, thiophene‐2‐carbonyl)hydrazinecarbothioamides with dimethylacetylenedicarboxylate. The structure of thiazolidin‐4‐one derivatives has been confirmed unambiguously by single crystal X‐ray crystallography.