3,4-Dihydroxyphenylacetaldehyde (also known as Protocatechuatealdehyde, Benzeneacetaldehyde, 3,4-dihydroxy-, 2-(3,4-dihydroxyphenyl)ethanal, (3,4-dihydroxyphenyl)acetaldehyde, DHPAA aldehyde, Dopal, GTPL6632, 3,4-Dihydroxybenzeneacetaldehyde, 3,4-dihydroxy-Benzeneacetaldehyde or HY-121252A) is a neurotoxin substance of the phenol class.