The Sesquiterpene Caulerpenyne from Caulerpa spp. is a Lipoxygenase Inhibitor

Many algae contain secondary metabolites with the potential to gain importance as pharmaceutically active secretions. Caulerpa racemosa var. cylindracea and Caulerpa prolifera are very abundant on the Mediterranean coastlines. The methanolic extracts of C. racemosa and C. prolifera were tested for inhibitory effects on soybean lipoxygenase. The extract of C. prolifera showed potent inhibitory effect in a lipoxygenase enzyme activity assay. HPLC comparison revealed that C. racemosa extract contained less caulerpenyne, the major secondary metabolite of both algae. In accordance with these findings, purified caulerpenyne inhibited lipoxygenase with an IC₅₀ of 5.1 μM. The enzyme kinetic studies indicated that both K _M and V _max decreased from 0.041 to 0.019 mM and 312.5 to 151.5 U mL⁻¹ in the presence of 5 μM caulerpenyne, revealing an un-competitive type of inhibition kinetics. The major secondary metabolite of Caulerpa species, caulerpenyne, is thus a novel lipoxygenase inhibitor that can be easily obtained in high quantities from the abundant algae.