N-Methyl-DL-Aspartic Acid (NMDLA) represents a racemic mixture of D and L enantiomers (NMDA; NMLA). Each enantiomer has different biological activities and different natural tissue/species abundances. Therefore, each enantiomer should be considered separately. NMDA is a widely studied neurotoxin which is an agonist of the NMDA receptor and induces brain legions. NMDA is not normally found in tissues, while NMLA can be found naturally in some bivalves.

S-Adenosyl-L-homocysteine (SAH), a potent methyltransferase inhibitor and a substrate of the s-adenosylhomocysteine hydrolase, is an amino acid derivative and an intermediator or modulator of several metabolic pathways, including the activated methyl cycle and cysteine biosynthesis. It was shown, that the plasma SAH might be a novel biomarker for the early clinical identification of cardiovascular disease. In addition, the elevated SAH in Alzheimer's brain was related to markers of disease progression and cognitive impairment.