Herbicidal activity and selectivity profiles of imidazole ketone-containing p-hydroxyphenylpyruvate dehydrogenase inhibitors

p-Hydroxyphenylpyruvate dehydrogenase (HPPD) is an important target in herbicide discovery. In order to discover new HPPD inhibitor-based herbicide with high activity and selectivity, the comprehensive bioevaluation of our previously synthesized imidazole ktone-containing HPPD inhibitors was conducted and the structure-activity relationship was studied. More specifically, the in vitro inhibitory activities against Arabidopsis thaliana HPPD (AtHPPD) and human HPPD (hHPPD) were studied and the selectivity profile was evaluated. Their herbicidal activities in plants were then evaluated. Some compounds showed high HPPD enzyme inhibition activities and herbicidal activities. Especially, the compounds 2E and 2G exhibited good control effect toward broadleaf weeds in winter field at the dose of 150 g/hm2. More importantly, their crop safety profiles is superior to the commercial herbicide mesotrione. In addition, compound 2P exhibited excellent selectivity (about 93 times) that is about 23-fold higher than that of mesotrione, which showing a good application potential.