Novaluron

Novaluron, or (±)-1--3-(2,6-difluorobenzoyl)urea, is a chemical with pesticide properties, belonging to the class of insecticides called insect growth regulators. It is a benzoylphenyl urea developed by Makhteshim-Agan Industries Ltd.. In the United States, the compound has been used on food crops, including apples, potatoes, brassicas, ornamentals and cotton.Patents and registrations have been approved or are ongoing in several other countries throughout Europe, Asia, Africa and South America, as well as Australia. The US Environmental Protection Agency and the Canadian Pest Management Regulatory Agency consider novaluron to pose low risk to the environment and non-target organisms, and value it an important option for integrated pest management that should decrease reliance on organophosphorus, carbamate and pyrethroid insecticides. Novaluron, or (±)-1--3-(2,6-difluorobenzoyl)urea, is a chemical with pesticide properties, belonging to the class of insecticides called insect growth regulators. It is a benzoylphenyl urea developed by Makhteshim-Agan Industries Ltd.. In the United States, the compound has been used on food crops, including apples, potatoes, brassicas, ornamentals and cotton.Patents and registrations have been approved or are ongoing in several other countries throughout Europe, Asia, Africa and South America, as well as Australia. The US Environmental Protection Agency and the Canadian Pest Management Regulatory Agency consider novaluron to pose low risk to the environment and non-target organisms, and value it an important option for integrated pest management that should decrease reliance on organophosphorus, carbamate and pyrethroid insecticides. In the European Union, a registration application was filed in 2001, but in 2007 there was still no definitive agreement regarding the legal status of novaluron. Member states of the European Union were allowed to award temporary permits for products based on novaluron. On April 4, 2012, a decision was disclosed which discontinued permits for the use of novaluron, to be executed on October 3.The development of the legal status of novaluron in the United States is condensed in the timeline below. Novaluron can be synthesized in a four-step reaction process. First, 2-chloro-4-nitrophenol is converted into chloro-4-aminophenol through a reduction reaction. After this first step, an addition reaction with perfluoro-vinyl-perfluoro-methyl ether is conducted to synthesize 3-chloro-4-aniline. The next step in the process is the production of 2,6-difluorobenzoyl isocyanate in an acylation reaction using 2,6-difluorobenzamide and oxalyl dichloride. The final part of the synthesis of novaluron is an addition reaction with 3-chloro-4-aniline. The exact mode of action of novaluron has not been extensively researched, but the general mechanisms and effects common to benzoylphenyl ureas apply. The compound inhibits chitin formation, targeting specifically larval insect stages that actively synthesize chitin. The adults of non-target species are seldom affected.Benzoylphenyl ureas, including novaluron, do not inhibit chitin synthesis in cell free systems or block the chitin biosynthetic pathway in intact larvae. The precise biochemical activity of these compounds, that gives them their insecticidal activity, has not yet been elucidated. The most likely hypothesis is that benzoylphenyl ureas interrupt the in vivo synthesis and transport of specific proteins required for assemblage of polymeric chitin. After oral administration in rats, novaluron treated with chlorophenyl-14C, only about 6-7% of the administered dose was absorbed after a single low dose (2 mg per kilogram bodyweight). A single high dose (1000 mg per kilogram bodyweight) caused an absorption that was 10-fold less. In another experiment novaluron caused an absorption of approximately 20%, but this number may be an overestimate due to cleavage of novaluron in the gastrointestinal tract. Through whole-body autoradiography it was demonstrated that the concentrations of radioactivity were highest in the kidneys, liver, fat tissues, pancreas and in the mesenteric lymph nodes, while the lowest concentrations appeared to be in the thymus, eyes, brain, testes, bone, muscles and blood. In a study of absorption, distribution, metabolism (biotransformation) and excretion of novaluron, rats received radioactively labeled novaluron orally. The absorbed novaluron was metabolized and 14 and 15 components were detected in the urine and bile respectively. The main metabolic pathway was cleavage of the urea bridge between the chlorophenyl- and difluorophenylgroups. The products of this reaction are 2,6-difluorobenzoic acid and 3-chloro-4-(1,1,2-trifluoro-2-trifluoromethoxyethoxy) aniline. Most of the radioactivity consisted of unchanged novaluron. The parent compound was also the major component present in extracts from fat, liver and kidneys. The proposed metabolic pathway is shown in the adjacent image. Benzoylphenyl ureas have provided consistently good results when applied properly against certain susceptible pests. Novaluron in particular has been shown to have insecticidal activity against several important pests. Bioactivity of novaluron is usually much greater than that of insecticides diflubenzuron and teflubenzuron and the compound is at least as active as other insecticides from its developmental generation, for example chlorofluazuron and lufenuron.In comparison to other benzoylphenyl ureas, novaluron demonstrates improved contact toxicity, while the probable mechanism of action remains the same. Novaluron has been shown to be highly active against a number of common pests, such as the Colorado potato beetle (Leptinotarsa decemlineata), whiteflies, the African Cotton Leafworm (spodoptera littoralis) and the cotton bollworm. Organisms that are closely related to these animals seem to share this susceptibility to the compound. A notable exception to this is a study evaluating the efficacy of various insecticides on the stem borers Diatraea saccharalis and Eoreuma loftini, in which the results seemed to indicate that these organisms were not susceptible to novaluron. The Joint FAO/WHO Meeting on Pesticide Residues (JMPR) concluded that novaluron is unlikely to be carcinogenic to humans. Furthermore, it concluded that it is not a developmental toxicant. The organization established an ADI (Acceptable Daily Ingestion) of 0-0.01 mg/kg of body weight, because of the NOAEL (No Observed Adverse Effect Level) of 1.1 mg/kg of body weight per day for erythrocyte damage and secondary splenic and liver changes. This was established in a 2-year study in rats.