It is a derivative of phenylacetaldehyde and occurs as a white solid at room temperature.

[2] 4-Hydroxyphenylacetaldehyde is produced from the metabolism of tyramine by monoamine oxidase (MAO) enzymes in humans and the tyramine oxidase (tynA) enzyme in Escherichia coli.

[3][4] In both species, it is subsequently metabolized into 4-hydroxyphenylacetate by aldehyde dehydrogenase (ALDH) enzymes in humans and the phenylacetaldehyde dehydrogenase (feaB) enzyme in E.

[3][4][5] The condensation of 4-hydroxyphenylacetaldehyde and dopamine is a key step in the biosynthesis of benzylisoquinoline alkaloids.

These natural products include berberine and morphine.