New norfloxacin/nitric oxide donor hybrids: Synthesis and nitric oxide release measurement using a modified Griess colorimetric method

Abstract

Oximes and nitrate esters are considered as important nitric oxide (NO) donors with diverse biological activities. Herein, we report the synthesis and characterization of new oxime and nitrate ester derivatives of norfloxacin as potential NO donor hybrids with expected synergistic antimicrobial activity. The release of NO from those hybrids was measured by a modified Griess method in which p-nitroaniline was employed instead of sulfanilamide. The increased electrophilicity of the intermediate 4-nitroaniline diazonium salt accelerated the coupling process and shortened the overall assessment time. The improved detection limits and enhanced sensitivity would pave the way for the future application of this method in nitrite determination in biological or non-biological systems.

Synthesis and antimicrobial evaluation of new nitric oxide‐donating fluoroquinolone/oxime hybrids

“…Acylated derivatives of 4‐aminoacetophenone 1a , b were synthesized via reaction of p ‐aminoacetophenone with bromoacetyl bromide or 3‐bromopropionyl chloride in dichloromethane in the presence of potassium carbonates. [ 21,22 ] Preparation of compound 1c was achieved through the addition of 4‐aminoacetophenone to a mixed anhydride formed in situ via the treatment of 2‐bromopropionic acid with ethyl chloroformate in the presence of triethylamine (TEA). [ 23 ] Alkylation of ciprofloxacin or norfloxacin with haloamides 1a – c was achieved in acetonitrile in the presence of TEA to afford ketones 2a – f .…”

“…[ 23 ] Alkylation of ciprofloxacin or norfloxacin with haloamides 1a – c was achieved in acetonitrile in the presence of TEA to afford ketones 2a – f . [ 21 ] The reaction of ketones 2a – f with hydroxylamine hydrochloride or methoxyamine hydrochloride in ethanol afforded the target oximes 3a – f and O‐ methyl oximes 4a – f , respectively. [ 21,24 ] The synthesized compounds were characterized by infrared (IR), nuclear magnetic resonance (NMR), high‐resolution mass spectrometry (HRMS), and elemental microanalyses.…”

“…NO release from the target oximes 3a – f was measured by a modified Griess method. [ 21 ] NO release from the tested compounds was measured at 100 μM concentration and assessed in the stable nitrite curve, relative to that of a standard sodium nitrite solution, and calculated as the amount of NO released (mol/mol) %. As shown in Table 1, some detectable amounts of NO in the range of 6–9% (mol of NO/mol of the tested compound) were observed, albeit in much lower amounts than those obtained from the reference NaNO 2 (positive control), which could be basically explained by the solubility issues of the tested compounds in the aqueous buffer system.…”

“…The formed precipitate was filtered off while hot, washed with acetonitrile, and dried under vacuum to give compounds 2a – f . [ 21 ]…”

Design, Synthesis, In Silico and In Vitro Studies for New Nitric Oxide-Releasing Indomethacin Derivatives with 1,3,4-Oxadiazole-2-thiol Scaffold

“…To assess the capacity of new NO-IND-OXDs 8a-p to to release the nitric oxide (NO), the Griess colorimetric method was applied [137,138]. The Griess reagents consist of 0.34% (wt/v) N-(1-naphthyl)ethylenediamine (NED) solution in DMSO, 3.4% (wt/v) sulfanilamide (SULF) in 10% (wt/v) phosphoric acid and a mixture between 3.4% (wt/v) SULF and 1% (wt/v) mercuric chloride (SULF-HgCl 2 ) in 10% (wt/v) phosphoric acid.…”