The participation of reactive oxygen species (ROS) in virus inactivation by 1,9-dimethylmethylene blue (DMMB) phototreatment in stroma-free hemoglobin (SFH) was investigated with the use of scavengers, quenchers and enhancer. Virus (R17 bacteriophage) photoinactivation by either activated monomer or dimer DMMB was suppressed by sodium azide (singlet oxygen quencher) and promoted by the substitution of H2O for deuterium oxide (D2O), which is known to prolong the lifespan of singlet oxygen. There was no or little effect of mannitol (hydroxyl radical scavenger) and superoxide dismutase (superoxide scavenger) on the photoinactivation. Similar experiments were conducted to investigate the mechanism of methemoglobin (Met-Hb) formation by the activated monomer of DMMB. There was little effect of the singlet oxygen quencher, histidine, or the enhancer, D2O, on Met-Hb formation. However, rutin, which inhibits not only singlet oxygen but also other ROS, and mannitol supressed the formation of Met-Hb by activated monomer. The addition of superoxide dismutase (SOD) did not inhibit the formation. In contrast to the activity of the DMMB monomer, that of the dimer was inhibited by histidine and enhanced by D2O. The addition of neither mannitol nor SOD affected Met-Hb formation by activated dimer. These results collectively suggest that virus photoinactivation by the activated monomer and dimer of DMMB as well as Met-Hb formation by the activated dimer proceed via a singlet oxygen mediated pathway. In contrast, singlet oxygen may play a less important role in Met-Hb formation by the activated monomer.
2001 The Pharmaceutical Society of Japan