text: Polyunsaturated aldehydes (PUAs) are a group of allelopathic chemicals typically associated with diatom-copepod predator-prey interactions. These compounds are classified by an aldehyde group covalently bound to long carbon chains containing two or more carbon-carbon double bonds. Examples include isomers of heptadienal, octadienal, octatrienal, and decatrienal.