Interaction of cinnamaldehyde (a sensitizer in fragrance) with protein.

Formation of a cinnamaldehyde-protein conjugate in the skin by reaction of cinnamaldehyde with nucleophilic groups in proteins is considered to be responsible for the observed immunogenicity. The kinetics of the reaction of bovine serum albumin with cinnamaldehyde in aqueous solution at 30 degrees C have been investigated, and the rate of formation of conjugate over the pH range 6.4-10.5 showed a first-order dependence on cinnamaldehyde concentration. The cinnamaldehyde binding sites on the protein appeared mostly or exclusively to be the thiol groups of cysteine residues.