Previous reports have reported the existence of DMS in blood circulation of mammals (Blom et al., 1988; Miekisch et al., 2001). We firstly quantified the amount of endogenous DMS in different organisms by gas chromatography (GC)–mass spectrometry (MS). After being concentrated by solid‐phase microextraction (SPME), DMS was separated by GC followed by identification with MS (Fig. S8). The levels of DMS were 1.14 ± 0.24 nmol g−1 wet tissue (at about 1 μm) in rat brain, 2.42 ± 0.09 nmol g−1 wet tissue (at about 2 μm) in rat heart, and 1.09 ± 0.11 nmol g−1 wet tissue (at about 1 μm) in mice brain (Fig. 6A), respectively. The level of DMS in C. elegans and Drosophila was 0.19 ± 0.04 nmol g−1 wet tissue and 0.19 ± 0.02 nmol g−1 wet tissue, respectively (Fig. 6B), which was much lower in the tissues of mice and rats. More interesting, in aged group (20 months), the concentrations of DMS in brain and heart tissues of rats were significantly decreased from 1.17 ± 0.14 nmol g−1 to 0.64 ± 0.04 nmol g−1 (brain cortex) and from 2.53 ± 0.12 to 1.44 ± 0.07 nmol g−1 (heart), respectively (P < 0.01, Fig. 6C).