1H-Indole-3-carboxaldehyde also known as 3-formylindole or 3-indolealdehyde belongs to the class of organic compounds known as indoles. Indoles are compounds containing an indole moiety which consists of pyrrole ring fused to benzene to form 23-benzopyrrole.

Homoserine is a more reactive variant of the amino acid serine. In this variant the hydroxyl side chain contains an additional CH2 group which brings the hydroxyl group closer to its own carboxyl group allowing it to chemically react to form a five-membered ring.

2-(1-methyl-1H-imidazol-4-yl)acetic acid (2-(1-methylimidazol-4-yl)acetic acid) is a plasma histamine derivative that is a biomarker for identifying lymphangioleiomyomatosis.