Identification of DMS as an endogenous antioxidant that declines with aging. (A) The levels of DMSO in PC12 cells were measured by HPLC after treatment of H2O2 (250 μm)/DMS (1 mm) for 12 h (n = 6, Student's t‐test, ## P < 0.01 vs. control, **P < 0.01 vs. H2O2). (B) PC12 cells were transfected with MsrA shRNA or control shRNA before the treatment of DMS (1 mm). And then, the DMSO contents were evaluate after H2O2 (250 μm) treatment for 12 h (n = 6, Student's t‐test, ## P < 0.01 vs. control, **P < 0.01 vs. H2O2). (C) The levels of DMS in different tissues of adult rat (brain, heart, and blood) were detected by GC‐MS assay, which were shown in a histogram (n = 6). (D)The tissues of different species (rat brain, mouse brain, and whole body of Drosophila or Caenorhabditis elegans) were also detected (n = 6). (E) The DMS levels in adult and aged rat samples were measured by SPME‐GC‐MS method (n = 6, **P < 0.01 vs. adult, Student's t‐test).