Near-ultraviolet photolysis of l-mandelate, formation of reactive oxygen species, inactivation of phage T7 and implications on human health

Compared with ultraviolet B and C, UVA is considered to have little direct effects on biological systems. However, damaging effects of UVA on biological systems are often synergistically enhanced in the presence of sensitizers. Production of reactive oxygen species (ROS) has been implicated in the process. Several ROS have been identified but their involvement in inducing cellular damage is yet to be fully evaluated. Although membranes and proteins are affected, DNA is an important target and a variety of types of damage have been reported. Here, we present evidence that l-mandelate can act as a near UV (NUV) sensitizer, when activated by a lamp emitting 99% UVA and 1% UVB. Although evidence is available that H2O2 and a small amount of OH are produced, an alternative effect of the sensitization reaction may involve direct electron transfer. Studies have shown that NUV photolysis of mandelate can inactivate phage T7. Employment of tetrazolium blue test to detect superoxide anion may not be sufficient evidence as this agent may be reduced by alternative routes.