Nitrification Inhibitors from the Root Tissues of Brachiaria humidicola, a Tropical Grass

Abstract

Nitrification inhibitory activity was found in root tissue extracts of Brachiaria humidicola, a tropical pasture grass. Two active inhibitory compounds were isolated by activity-guided fractionation, using recombinant Nitrosomonas europaea containing luxAB genes derived from the bioluminescent marine gram-negative bacterium Vibrio harveyi. The compounds were identified as methyl-p-coumarate and methyl ferulate, respectively. Their nitrification inhibitory properties were confirmed in chemically synthesized preparations of each. The IC₅₀ values of chemically synthesized preparations were 19.5 and 4.4 μM, respectively. The ethyl, propyl, and butyl esters of p-coumaric and ferulic acids inhibited nitrification, whereas the free acid forms did not show inhibitory activity. Keywords: Brachiaria humidicola; nitrification inhibitor; methyl ferulate; methyl-p-coumarate