Sinapaldehyde is an organic compound with the formula HO(CH3O)2C6H2CH=CHCHO. It is a derivative of cinnamaldehyde, featuring one hydroxy group and two methoxy groups as substituents. It is an intermediate in the formation of sinapyl alcohol, a lignol that is a major precursor to lignin.

Biosynthetic role

In sweetgum (Liquidambar styraciflua), sinapaldehyde arises in two steps from coniferyl aldehyde beginning with hydroxylation mediated by coniferyl aldehyde 5-hydroxylase. The diphenol is then methylated at the 5-OH by the action of caffeate O-methyltransferase. Sinapaldehyde is reduced to the alcohol by the action of dehydrogenase enzymes. In Arabidopsis thaliana, the enzyme dihydroflavonol 4-reductase uses NADP+ to reduce sinapaldehyde to sinapyl alcohol. It is found in Senra incana (Hibisceae). It is a low molecular weight phenol that is susceptible to extraction from cork stoppers into wine.