The antioxidant activities of five alkylresorcinol (AR) homologs with alkyl chains of 1, 3, 5 6 and 12 carbon atoms were studied using molecular and cellular assays for superoxide anions (O2.-). The effect of ARs as superoxide anion scavengers was assessed using the photochemical reaction of spontaneous photo-reduced flavin re-oxidation. In this system, ARs reaction with O2.- produced dye derivatives, as C6- and C12-AR prevented the O2.--induced conversion of nitroblue tetrazolium into formazan in AR-containing mixtures. The influence of ARs on soxS gene expression and bacterial cell viability was studied with the luminescent Escherichia coli K12 MG1655 psoxS'::luxCDABE-AmpR strain, showing low basal light emission. This increased significantly during paraquatinduced oxidative stress as a consequence of the simultaneous transcription of soxS-gene and lux-gene fusion. ARs with alkyl chains containing 5-12 carbon atoms at concentrations of 0.1-1.0 μM weakly induced soxS-gene expression, whereas 1-10 mM repressed it. This respectively increased or decreased the bacterial cell resistance to O2.- -related oxidative stress. AR derivatives lost their protective activity from reactions with superoxide anions, which required increased soxS gene expression for cell viability. These results show the dual nature of ARs, which possess direct antioxidant properties and the ability to indirectly regulate the activity of cellular antioxidative defense mechanisms.