Cell-permeable reactive oxygen species scavenger that activates p53 through a JNK-dependent signaling pathway. Activates p21waf-1 and MDM2, represses transcription of Myc and thymidine kinase, and inhibits DNA topoisomerase IIα. Induces cell cycle arrest and exhibits cytoprotective activity towards normal cells but not cancer cells in vivo. Also exhibits broad spectrum antiviral activity in vitro.