L-Dehydroascorbate efficiently degrades non-thermal plasma-induced hydrogen peroxide.

Non-thermal plasma (NTP) devices generate reactive oxygen species (ROS) and reactive nitrogen species, such as singlet oxygen (O), superoxide (O), hydroxyl radical (OH), hydrogen peroxide (HO), ozone, and nitric oxide at near-physiological temperature. In preclinical studies, NTP promotes blood coagulation, wound healing with disinfection, and selective killing of cancer cells. Although these biological effects of NTP have been widely explored, the stoichiometric quantitation of ROS in the liquid phase has not been performed in the presence of biocompatible reducing agents, which may modify the final biological effects of NTP. Here, we utilized electron paramagnetic resonance spectroscopy to quantitate OH, using a spin-trapping probe 5,5-dimethyl-1-pyrroline-N-oxide; O, using a fluorescent probe; and O and HO, using luminescent probes, after NTP exposure in the presence of antioxidants. l-ascorbate (Asc) at 50 μM concentration (physiological concentration in serum) significantly scavenged OH, whereas (-)-epigallocatechin gallate (EGCG) and α-tocopherol were also effective at performing scavenging activities at 250 μM concentrations. Asc significantly scavenged O and HO at 100 μM. l-Dehydroascorbate (DHA), an oxidized form of Asc, degraded HO, whereas it did not quench OH or O, which are sources of HO. Furthermore, EGCG efficiently scavenged NTP-induced O, O, and HO in Chelex-treated water. These results indicate that the redox cycling of Asc/DHA and metabolites of DHA are important to be considered when applying NTP to cells and tissues. Additionally, ROS-reducing compounds, such as EGCG, affect the outcome. Further studies are warranted to elucidate the interaction between ROS and biomolecules to promote the medical applications of NTP.