80 research outputs found
Glycosides of fluorinated p-nitrophenol offer improved sensitivity for detection of β-galactosidase and β-glucuronidase in Escherichia coli and other Enterobacterales
Get PDFWe describe the synthesis and evaluation of six halogenated nitrophenyl glycosides for detection of β-galactosidase and β-glucuronidase enzyme activity among Enterobacterales (“coliforms”) and Escherichia coli, respectively. These were evaluated alongside the established substrates; o-nitrophenyl-β-D-galactopyranoside (ONPG), p-nitrophenyl-β-D-galactopyranoside (PNPG) and p-nitrophenyl-β-D-glucuronide (PNP-GUR). The evaluation was performed using 30 isolates of Enterobacterales including 19 isolates of E. coli. Hydrolysis of 2-fluoro-p-nitrophenyl-β-D-galactopyranoside (2-fluoro-PNPG) yielded a significantly stronger yellow coloration after a six-hour incubation period compared to hydrolysis of ONPG and PNPG, potentially allowing for a more sensitive detection of Enterobacterales. Similarly, hydrolysis of the novel substrate 2-fluoro-p-nitrophenyl-β-D-glucuronide sodium salt (2-fluoro-PNP-GUR Na) by producers of β-glucuronidase also yielded a significantly stronger yellow colouration, potentially allowing for a more sensitive detection of E. coli. The yellow chromophore 2-fluoro-PNP retained high colour intensity at reduced pH when compared to o-nitrophenol and p-nitrophenol. Both substrates potentially offer enhanced sensitivity for the detection of Enterobacterales and E. coli in environmental samples as markers of faecal pollution
Determination of Carboxypeptidase Activity in Clinical Pathogens by Gas Chromatography–Mass Spectrometry
No full textA novel method for the determination of benzoic acid has been employed to identify carboxypeptidase activities in clinically relevant pathogens. Benzoic acid was determined after chemical derivatization by gas chromatography–mass spectrometry (GC–MS). N-Benzoyl amino acid substrates were evaluated for the detection of carboxypeptidase activities in a number of clinical pathogens. Upon enzymatic hydrolysis of these substrates, benzoic acid was produced which was detected by extraction from the liquid culture supernatant, derivatization as the trimethylsilyl ester, with subsequent analysis by GC–MS. Enzymatic hydrolysis of N-benzoyl glycine was observed for S. agalactiae, M. morganii, and A. baumannii. In addition, P. fluorescens was found to hydrolyze N-benzoyl-L-glutamic acid. Although the method provides an alternative approach for determining carboxypeptidase activity, ultimately it would not be a suitable method in a clinical setting. However, the method is well-suited for identifying carboxypeptidase activities that have not been previously described or to corroborate a carboxypeptidase assay with the ninhydrin reagent
The Wittig reaction of fluorinated amides: formation of enamine and imine tautomers
No full textThe paper describes an investigation of fluorinated compounds that could be used in the synthesis of fluorinated pharmaceutical intermediates
Preparation of 23-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-1,5-dione derivatives
No full textThe 2,3-dihydro-7-methyl-1H,5H-pyrido[3,2,1-ij]quinoline-1,5-dione derivatives 9 and 10 were prepared from 3-(5,7-dimethoxy-4-methyl-2-oxo-2H- quinolin-1-yl)propionitrile (6). Cyclodehydration of the amide 8 gave 1,2-dihydro-7,9-dimethoxy-6-methylpyimido[1,2-a]quinolin-3-one (11)
Ring-opening reactions of N-aryl-1,2,3,4-tetrahydroisoquinolines: Synthesis of novel isoquino[2,1-a][3,1]benzoxazine derivatives
No full textThe aldehydes 7e and 7h were prepared by treatment of the 1,2,3,4- tetrahydroisoquinolines 5e and 5h, respectively, with N-bromosuccinimide (NBS). Basic hydrolysis of compounds 7e and 7h gave the 4bH,6H-isoquino[2,1- a][3,1]benzoxazine derivatives 9 (R=H, OMe). Heterocycle 10 was obtained from the reaction of compound 5c with NBS and isolated as the ethyl derivative 11
ChemInform Abstract: Ring-Opening Reactions of N-Aryl-1,2,3,4-tetrahydroisoquinolines: Synthesis of Novel Isoquino[2,1-a][3,1]benzoxazine Derivatives.
No full textDevelopment of an open-learning module in natural product chemistry
Get PDFThis article describes the author’s personal perspective on the design, production and delivery of an open-learning module in natural product chemistry. This 10 credit, level 6 module is delivered using three tutorial sessions and is assessed by three open-book tests. The study material is available to the students as both hard-copy and electronic copy
Preparation of some substituted imidazo[1,2-a]pyridine derivatives
No full text2-Bromopyridine derivatives 2a-2c were prepared. Compounds 2b and 2c and ammonia yielded aminopyridines 3b and 3c which were converted to imidazo[1,2-a]pyridine derivatives 4b and 4c. Compound 4b was nitrated giving the analogue 5b of metronidazole 1
Bacteria detection based on the evolution of enzyme-generated volatile organic compounds: Determination of Listeria monocytogenes in milk samples
No full textThe rapid detection of Listeria monocytogenes contamination in food is essential to prevent food-borne illness in humans. The aim of this study was to differentiate non-contaminated milk from milk contaminated with L. monocytogenes using enzyme substrates coupled with the analysis of volatile organic compounds (VOCs). The method is based on the activity of β-glucosidase and hippuricase enzymes and the detection of a specific VOC i.e. 2-nitrophenol and 3-fluoroaniline, respectively. VOCs were extracted, separated and detected by headspace-solid phase microextraction coupled to gas chromatography–mass spectrometry (HS-SPME GC–MS). This approach required the inclusion of the selective agent's cycloheximide, nalidixic acid and acriflavine HCl in the growth medium to inhibit interfering bacteria. The VOCs were liberated by L. monocytogenes provided that samples contained at least 1–1.5 × 102 CFU ml−1 of milk prior to overnight incubation. This approach shows potential for future development as a rapid method for the detection of L. monocytogenes contaminated milk
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