Diflubenzuron, chitin biosynthesis

The well-known insecticidal benzoyl phenyl ureas (BPUs), exemplified by diflubenzuron, are chitin biosynthesis disrupters, but at an uncharacterized site distinct from chitin synthase (2), Figure 1. The related bridge-cyclized oxazoline chemistries from DuPont and Yashima, represented by etoxazole, are also commercial or near-conunercial insecticides with the same mechanism of action (5), Figure 1. 

Chitin synthesis in wing pads of 1-day-old fifth-instar larvae of Locusta is stimulated in vitro by 20-hydroxyecdysone and makisterone A 88), This chitin biosynthesis system requires integrity of the microtubular system and the chitin-synthetase complex. Chitin synthesis can be inhibited in this test system by azadirachtin as well as by colcemid, a microtubular poison, or by diflubenzuron, a chitin synthetase inhibitor. It is also of interest to note that RH5849 stimulates chitin synthesis in wing discs of Plodia interpunctella 89). 

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