Precocene II inhibits juvenile hormone biosynthesis by cockroach corpora allata in vitro

Abstract

BOWERS et al.¹ reported that a chromene derivative isolated from plants of the genus Ageratum interferes with the development of insects from several orders. They named the most active component of the plant extract precocene II (I), because exposure of young larval stages of test insects to the compound leads to precocious metamorphosis into unviable or moribund miniature adults. Also, exposure of adult females of several insect species causes sterility by preventing normal vitellogenic development of the oocytes, and in at least one case¹ this effect can be overcome by hormone replacement therapy with C₁₆ juvenile hormone (C₁₆JH: (II). These effects suggest that precocene II acts: antagonistically to the natural JHs which are responsible for the proper suppression of metamorphosis in larval insects², and for the activation of ovarian growth and other reproductive phenomena in adult females of most insects³. Precocenes constitute a new type of insect growth regulator, and have been referred to as ‘fourth generation insecticides’¹. We envisaged two ways a priori, in which precocene might act in the whole animal : either by blocking the biosynthesis of JHs, or by blocking the action of natural JHs, that is, their safe transport through the haemolymph followed by effective action at the various target sites. We have concentrated on one aspect of the former possibility, and have investigated whether or not active corpora allata from adult females of the cockroach Periplaneta americana are directly inhibited by exposure to precocene II in vitro.