S-Adenosyl-DL-methionine (SAMe) is a synthetic analog of the naturally occurring coenzyme S-adenosyl-L-methionine, a key methyl donor in biological methylation reactions. Chemically, it is a sulfonium salt with the formula C₁₅H₂₂N₆O₅S, commonly supplied as a white to off-white powder with approximately 80% purity for laboratory and pharmaceutical use.

In research, SAMe is utilized as a reagent in biochemical studies of transmethylation processes, including DNA methylation, histone modification, and the synthesis of neurotransmitters such as serotonin and dopamine. It serves as an intermediate in the production of pharmaceutical compounds and as a catalyst in enzymatic assays related to epigenetics and metabolism.

Additionally, due to its role in methylation and cellular health, S-Adenosyl-DL-methionine is incorporated into dietary supplements for supporting mental health (e.g., depression via mood regulation), joint health (e.g., osteoarthritis by promoting cartilage repair and reducing inflammation), and liver function (e.g., detoxification in conditions like cholestasis and cirrhosis). Its use in therapeutic contexts should be under medical supervision.