Cinnamaldehyde is the organic compound that gives cinnamon its flavor and odor. This pale yellow, viscous liquid occurs naturally in the bark of cinnamon trees and other species of the genus Cinnamomum. The essential oil of cinnamon bark is about 90% cinnamaldehyde. Several methods of laboratory synthesis exist, but cinnamaldehyde is most economically obtained from the steam distillation of the oil of cinnamon bark. The compound can be prepared from related compounds such as cinnamyl alcohol, but the first synthesis from unrelated compounds was the aldol condensation of benzaldehyde and acetaldehyde. Cinnamaldehyde occurs widely, and closely related compounds give rise to lignin. All such compounds are biosynthesized starting from phenylalanine, which undergoes conversion. Cinnamoyl-CoA reductase is an enzyme responsible for the production of cinnamoyl-CoA from cinnamaldehyde.