Cytosine

Cytosine is one of the four nucleobases of DNA and RNA, released into biofluids during nucleic-acid turnover, cell renewal, and salivary epithelial shedding. As a salivary metabolite it contributes to the nucleotide-metabolism fraction of the metabolome, reflecting tissue turnover and cellular proliferation rates. Its concentration provides background context for the purine and pyrimidine catabolites used to assess cellular stress and oxidative DNA damage.