3beta-hydroxy-9beta-pimara-7,15-diene-19,6beta-olide + NAD(P)+ momilactone A + NAD(P)H + H+
The rice phytoalexin momilactone A is a diterpenoid secondary metabolite that is involved in the defense mechanism of the plant. Momilactone A is produced in response to attack by a pathogen through the perception of elicitor signal molecules such as chitinoligosaccharide, or after exposure to UV irradiation.