Two simple chromenes with anti-JH activity have been isolated and identified from the bedding plant Ageratum houstoianum. By contact and fumigation these compounds induce precocious metamorphosis and sterilization in several hemipteran species of insects. Certain holometabolous species are sterilized, forced into diapause, or both. Each of these biological actions is equivalent to removal of the corpora allata, which produce the JH's, and is reversible by treatment with exogenous JH. Thus, the action of these compounds is to stop the production or depress the titer of the JH's. To our knowledge, this is the first discovery of anti-JH, and we hope it will guide the way to the emergence of a fourth generation of safe and insect-specific pesticides.

https://science.sciencemag.org/content/sci/193/4253/542.full.pdf

Discovery of insect anti-juvenile hormones in plants.?2U

Publisher Summary This chapter discusses the juvenile hormones (JH). The JH, a family of acyclic sesquiterpenoids, are essential to insect development and reproduction. This chapter examines the new compounds that have been added to the family. Recent structural elucidation of the hemolymph transport and catabolic proteins is examined. Molecular biology surrounding the long-sought JH receptor and potential candidates are discussed. The juvenile hormones, a family of acyclic sesquiterpenoids, are essential to insect development and reproduction. This family of hormones has been extensively studied because of its central role in regulating development and value as an insect pest control agent. Recent advances have been made in the areas of chemistry, biosynthesis, transport, catabolism, and biological roles the hormones play in the immature insect. Two common features characterize the naturally occurring JHs: their site of synthesis, the corpora allata (CA), and their farnesoid structure.

The Juvenile Hormones

Publisher Summary This chapter discusses the structure and regulation of the corpus allatum. The corpora allata (CA) are endocrine glands in the posterior regions of the head, or in rare instances in the thorax, which are closely associated with the stomatogastric nervous system. This chapter focuses on the regulation of the CA. It also describes the embryology, innervations, and the relationships of the structure, particularly the ultrastructure, to its synthetic activity. The characteristic shape of the CA is ovoid to round but they may be elongate as in large larvae and adults of Libellula depressa. The size of the glands is frequently about the diameter of the aorta or smaller; however, there is much variation among species and even within a species, size differs with age, sex, polymorphism, and the activity cycle of the glands. Although only one type of glandular cell occurs in the CA, there are a variety of types of CA with respect to the number of cells per gland and the relative size of the cells. The CA are surrounded by a continuous noncellular basal lamina, roughly 0.1-1 μ m thick. This material occasionally projects between two glandular cells into the interior of the gland, forming trabeculae that may accompany nerves and trachea.

Structure and Regulation of the Corpus Allatum

The term insect growth regulator (IGR) was designed to describe a new class of bio-rational compounds. Through greater selectivity of action these compounds appear to fit the requirements for third generation pesticides, such as the absence of undesirable effects on man, wildlife, and the environment and compatibility with modern insect pest management principles. Although the majority of new com­ pounds in this class are the result of research on insect juvenile hormones, the general term IGR would also accommodate compounds with a different mode of action. The scope of this review, however, is restricted to those IGRs that produce only or primarily juvenile hormone-type responses. The nomenclature of the chemi­ cals and mixtures with JH activity has given rise to much confusion, and terms such as synthetic JH have occasionally been misused. The terms juvenoid, JH mimic, JH analog (JHA), etc all describe the general class of compounds fairly well. In this review we will use the term juvenile hormone (JH) for the natural hormones, IGR when compounds are used with an intention to control pests, and on occasion JHA for less defined situations. IGR, JH, and JHA may therefore occasionally be used for the same compound. Less than ten years have elapsed since the chemical structure of the first insect juvenile hormone (JH I) was elucidated in 1967. This was followed by the positive identification of two closely related structures (JH II and JH III, see Table I). Their presence in various combinations was subsequently proven in various insects, pri­ marily Lepidoptera (82). Schmialek in 1961 ( 180) was the first to elucidate the JH active isoprenoids farnesol and farnesal in excrement of Tenebrio molitor. The low specific activity of these structures made it unlikely, however, that these were actual hormones. It is remarkable that Bowers, Thompson & Uebel ( 18) synthesized the compound that later became known as JH III as early as 1 965, recognized its biological activity, and suggested that it had characteristics of a hormone. Industrial and federal involvement started a great flood of chemical analogs of the juvenile

Insect Growth Regulators with Juvenile Hormone Activity

Biologists in the early part of the 20th century believed that since the secondary sexual characteristics of insects were unaffected by castration, insects did not secrete hormones. This view was challenged by the conclusive experiments of Stephan Kopec in 1917, who showed by surgical maneuver, that insect metamorphosis was under the hormonal control of the brain. Over the next half- century, significant discoveries in insect endocrinology were made by such pioneers as Wigglesworth, Bodenstein, Fukuda, and Williams, among others (see review by Granger and Bollenbacher 1981). The classical scheme that was developed by these scientists was that a hormone from the brain, now known as prothracicotropic hormone (PTTH), stimulated the prothoracic glands to release a molting hormone (ecdysteroid), which caused either molting or metamorphosis depending upon the stage of the insect, and in particular, on whether a third hormone, juvenile hormone (JH), was present.

Insect growth regulators

Some years ago we reviewed the status of the insect juvenile hormone (JH) and its isolation.1 Since then two noteworthy contributions toward purification of the hormone have appeared.2' In all these purification attempts adult male Cecropia silk moths4 proved to be an invaluable source material. The first nearly pure hormone preparation was isolated in 1965.1 We obtained it from Cecropia oil (second batch) and characterized it by means of a gas-liquid chromatographic (GLC) analysis in conjunction with an ultrasensitive argon ionization systemA The hormonal activity was located exclusively in the two major peaks B and E. Both these substances had a specific activity of the same magnitude as the original preparation. They were retained on neopentyl glycol adipate (NGA) columns at ratios of 1.60 and 1.29 relative to methyl stearate. Only one contamination, peak H, was apparent, which amounted to less than 10 per cent of the total peak area. Thus our 3 X 105-fold enriched preparation was at least 90 per cent pure. A host of subsidiary gas chromatographic peaks (A,D, etc.) were artifacts that resulted from reactions of the active compounds in the analytical system. These substances were produced even though the hormonal preparations had been injected with a Hamilton syringe directly onto the packed glass columns, but they were more plentiful in the fractions that had been previously submitted to a GLC separation and collected after passage through the brass detector cell. Since the same pyrolytic products were formed whether they were derived from compound B or compound E, the two hormonally active compounds had to be closely related structurally. We have now processed a new (third) batch of Cecropia oil by a five-step purification sequence similar to that applied to the second batch. These steps w-ere: (I) molecular distillation at -1 mTorr and 1000C; (II) separation from acidic products formed; (III) leaching with cold aqueous methanol; (IV) SiO2 chromatography; and (V) A1203 chromatography. One modification had been made in step IV in which an improved silica gel system was substituted for the zinc carbonate sy-stem6 previously used. This resulted in eliminating compound H. In the Galleria N-lX test, fractions of the final preparation again exhibited a potrency of some 3 X 105 JH units per milligram (Table 1). Our GLC unit wsas perfected by construction of a metal-free injector and a glass effluent splitter. As a result, the hormone preparation could be processed through the system without contacting any metal. From then on, much simplified chromatograms have been recorded (Fig. 1). The GLC analysis of the biologically most active fractions of the pure preparation revealed that they were composed of only two substances: compounds B and E (Table 1). When the

Jane H. Ko

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The two juvenile hormones from the cecropia silk moth.