Fold change in plasmid pOX38 conjugation frequency from E. coli RZ211 under ciprofloxacin (1/2 the MIC) and several antioxidants (0.1 mM) exposure. Control, no exposure to antibiotic; CIP, ciprofloxacin; EDA, edaravone; NAC, N-acetylcysteine; pCA, p-coumaric acid. Three independent replicates were performed. The data are means and SD. *, P ≤ 0.05; **, P ≤ 0.01.