Asymmetric dimethylarginine
Asymmetric dimethylarginine (ADMA) is a naturally occurring chemical found in blood plasma. It is a metabolic by-product of continual protein modification processes in the cytoplasm of all human cells consisting of an arginine core with two methyl groups on one of the side-chain nitrogen atoms.
Source: Wikipedia — Asymmetric dimethylarginine (CC BY-SA 4.0)