aclonifen

Aclonifen is a diphenyl ether herbicide which has been used in agriculture since the 1980s. Its mode of action has been uncertain, with evidence suggesting it might interfere with carotenoid biosynthesis or inhibit the enzyme protoporphyrinogen oxidase (PPO). Both mechanisms could result in the observed whole-plant effect of bleaching (removal of leaf colour) and the compound includes chemical features (a nitro group attached to a diphenyl ether) that are known to result in PPO effects, as seen with acifluorfen, for example. In 2020, further research revealed that aclonifen has a different and novel mode of action, targeting solanesyl diphosphate synthase which would also cause bleaching.

==History== The nitrophenyl ethers are a well-known class of herbicides, the oldest member of which was nitrofen, invented by Rohm & Haas and first registered for sale in 1964. This area of chemistry became very competitive, with the Mobil Oil Corporation's filing in 1969 and grant in 1974 of a patent to the structural analog with a COOCH3 group adjacent to the nitro group of nitrofen. This product, bifenox, was launched in 1981. Meanwhile, Rohm & Haas introduced acifluorfen (as its sodium salt) in 1980. It had much improved properties including a wider spectrum of herbicidal effect and good safety to soybean crops. The first patent for this material was published in December 1975,