o-Coumaric acid is a hydroxycinnamic acid, an organic compound that is a hydroxy derivative of cinnamic acid. There are three isomers of coumaric acids â o-coumaric acid, m-coumaric acid, and p-coumaric acid â that differ by the position of the hydroxy substitution of the phenyl group.
o-Coumaric acid can be found in vinegar.
In some plants such as Melilotus species, o-coumaric acid is produced directly from cinnamic acid by the enzyme trans-cinnamate 2-monooxygenase.
2-Coumarate reductase is an enzyme that converts o-coumaric acid to melilotic acid using reduced nicotinamide adenine dinucleotide (NADH). This enzyme participates in phenylalanine metabolism.