EPR characteristics of free radicals in DOPA–melanin–moxifloxacin complexes at ambient level of UVA radiation

EPR studies pointed out that o-semiquinone free radicals with g-values 2.0038–2.0040 take part in moxifloxacin–melanin complex formation. The process contributed to increase in free radicals concentration in nonirradiated complexes. This effect was observed for the complexes with 1 × 10−4 M, 1 × 10−3 M and 4 × 10−3 M drug concentrations. UV irradiation contributed to decrease in free radicals concentration in DOPA–melanin complexes with moxifloxacin, besides the complexes with the drug concentration of 1 × 10−4 M. The strongest decrease was observed for DOPA–melanin–moxifloxacin complexes with the drug concentration of 1 × 10−3 M. Homogeneous broadening of EPR lines, strong dipolar interactions and slow spin–lattice relaxation processes characterized all the tested melanin samples.