What is "mesotrione"

n. The herbicide ''2-(4-methyl-2-nitrobenzoyl)cyclohexane-1,3-dione''

Mesotrione is an herbicide sold under the brand names Callisto and Tenacity that was brought to market by Syngenta in 2001. It is a synthetic analog of leptospermone developed to mimic the effects of this natural herbicide. Mesotrione is a member of the class of HPPD inhibitors, which all work by inhibiting the plant enzyme 4-hydroxyphenylpyruvate dioxygenase. In plants, HPPD is necessary for carotenoid biosynthesis; carotenoids in turn protect chlorophyll from being degraded by sunlight. When an HPPD inhibitor is sprayed on a plant, it prevents carotenoid from being made, chlorophyll degrades and the plant dies.

Sales by Syngenta were more than $400 million per year in 2011 but worldwide patent rights started to expire in 2012, opening the market to generic competition.