Submitted to: Analytical Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 1999
Publication Date: N/A
Interpretive Summary: Juvenile hormones are of critical importance for insect growth and development. Thus, the use of these hormones has great potential for development of alternative strategies of pest control. However, some insects produce several different types of juvenile hormones and they are produced at different times during the life cycles of insects. Therefore, it is crucial that the different forms and the amounts of juvenile hormones produced by insects in different life stages be determined. Unfortunately, techniques used to determine these features are imprecise and do not allow for concrete identification of different hormones. To overcome these problems scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Fla., have developed a new technique to identify and quantify juvenile hormones chemically. This technique was used to identify juvenile ehormones from several insect pests including the tobacco hornworm moth, American and German cockroaches and the Caribbean fruit fly. The results have provided important information on the production of different juvenile hormones and have allowed for determination of the roles of these hormones in regulation of reproduction by these insects.
Technical Abstract: A method for identification and quantitation of insect juvenile hormones (JH) has been developed using capillary gas chromatography-ion trap mass spectroscopy. The method requires analysis using isobutane as a reagent gas for chemical ionization of analytes but does not require prior derivatization of samples or the use of selected ion monitoring, as is commonly used for mass spectral identification of JH. Analysis over a mas range of 60-350 amu allowed for identification of as little as 0.01 pmol of JH I, JH II and JH III. Quantitative analysis was based on the relative abundances of six diagnostic ions for each homolog. The ratio of diagnostic ions did not vary significantly over a range of concentrations from 2.66- 200 pg, but the intensities of these ions increased in a linear fashion with increasing amounts of analyte. The technique was used to identify and quantify the amounts of JH I, JH II and JH III secreted by individual retrocerebral complexes from adult females of the moth, Manduca sexta, maintained in tissue culture. Individual retrocerebral complexes were found to release an average of 0.03, 1.07 and 1.04 pmol of JH I, JH II and JH III per hour. No discrimination due to disparate ratios of the individual JH homologs was found when analyzing natural product samples differing in concentration by at least five fold. The use of this technique for facile, concrete identification and quantitation of biologically relevant amounts of JH and is at least as sensitive as other methods currently in use. Additionally, the ability to analyze samples without derivitization or fractionation by chromatographic methods, coupled with data acquisition over a broad mass range (60-350 amu), provides levels of accuracy and confidence greater than those of other methods.