Homocystine is the double-bonded form of homocysteine but it occurs only transiently before being converted to the harmless cystathionine via a vitamin B6-dependent enzyme. Increasing evidence supports a role for an elevation of homocysteine in schizophrenia.

2-Acetylnaphthalene is a fragrance, anticonvulsant, and antimicrobial agent. It has an onion type flavor and a sulfurous type odor.

3-Methyl-2-oxovaleric acid is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. 3-Methyl-2-oxovaleric acid is a neurotoxin an acidogen and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues.