Ecdysteroids examples

Figure 7.15 Some ecdysteroid examples. Makisterone A is used by some insects, including Apis mellifera arui Drosophila melanogaster, and by crabs and is a phytoecdysteroid in Podocarpus trees arui the wild flower Lychnis flos-cuculi (ragged robin). Ecdysone 22-palmitate is an example of a storage product found in insect ovaries arui eggs. Ajugasterone C is an example of a phytoecdysteroidfrom the Labiatae, Compositae and Verbenaceae, but also identified in an Anthozoa (corals and sea anemones)...

LC-NMR can be used to identify natural products in crnde plant extracts that usually consist of complex mixtnres. The crnde natural product extracts normally contain a great nnmber of closely related and difficult-to-separate compounds. The classical separation approach may become very tedious and time-consuming. The directly conpled HPLC-NMR presents an efficient separation techniqne together with a powerfnl spectroscopic method to speed up the identification process. LC-NMR has been nsed extensively for characterization of natnral prodncts. More recently, the combination of LC-NMR and LC-MS has been further developed in this field. Eor example, Wilson et al. have nsed combined on-flow NMR and electrospray ionization MS to characterize ecdysteroids in extracts of silene otites. After reversed-phase HPLC nsing D2O in acetonitrile-dj and UV detection, the LC flow was split 95 5 for the simnl-taneous detection by NMR and MS. The peaks of interest were analyzed by stop-flow NMR to give better quality spectra for structural assignment. 

The first application of LC-NMR-MS to natural products analysis was presented in 1999 [37]. The additional mass spectroscopic information allowed the identification of a further ecdysteroid in an extract of Silene otides which could not be identified by LC-NMR alone [24], Further applications of this double hyphenation dealt with the identification of napthodianthrones [38] and flavone glycosides [38,39] in natural products extracts. Taking the hyphenated technique one step further, the suitability of an integrated LC-UV-IR-NMR-MS system for natural products analysis has been assessed [40] - again using ecdysteroids as an example. Such systems still suffer from different requirements of the individual detectors (mainly in terms of sensitivity). However, the results obtained are promising. 

Figure 11 Examples of compounds which antagonise ecdysteroid action in the...

Scheme 3). A clone of cells from the midge Cbironomus tentans was found to be resistant to the effects of ecdysteroids because they metabolized 20-hydroxyecdysone rapidly. The initial oxidation product was 20,26-dihydroxyecdysone, but this was oxidized further to 20-hydroxy-26-oxo-ecdysone (21). This aldehyde (21) then formed a tautomeric equilibrium mixture of two cyclic hemiacetals (22) and (23), which were separable, isolated, and their structures determined (Scheme 3) with the use of acetonides (Section 4.03.3.6).32 These are the first examples of ecdysteroids with side-chain hemiacetals. Although 20,26-dihydroxyecdysterone still... 

An example for the separation of ecdysteroids with HP-RPC systems was published by Louden et al.119 and related to the separation of an ecdysteroids extract from the plant Lychnis flos-cuculi (Caryopyllaceae). These authors used an analytical 4.6 mm x 100 mm 5 pm C18 silica column with isocratic elution (eluent ACN and DzO 99.8% isotopic purity 20 80 v/v) at 1.0 ml min 1 and DAD between 190 and 360nm. This study also explored the application of HPLC—NMR spectroscopy and HPLC—NMR spectroscopy—MS to these ecdys-teroid-containing plant extracts, showing the advantages and limitations of the use of complex multiply hyphenated detection systems, which incorporate detectors of differing sensitivities. 

Finally, since many natural product compounds have been investigated with various chromatographic modes and detection techniques, a selection of examples has been summarized in this chapter. This information has been compiled in the form of tables for well-researched classes of secondary metabolites selected from the major subgroups of isoprenoids (mono-, sesqui-, di-, and triterpenes iridoids and secoiridoids carotenoids saponins and ecdysteroids), of phenolics (coumarins, flavonoids, and isoflavonoids), and of alkaloids. 

Our present meagre understanding of normal endocrine processes in invertebrates makes the assessment of chemical endocrine disruption in the field difficult (LeBlanc 1999). Steroid roles differ between species and sometimes sexes, and their influence may vary at different developmental stages. In most studies of invertebrates, endocrine disruption appears to involve androgenization rather than oestrogenic effects (see Box 7.2). Arthropods (crustaceans and insects), annelids and molluscs use ecdysteroids, terpenoids and vertebratelike sex steroids for endocrine control. For example, the ecdysteroid ecdysone is naturally converted to 20-hydroxyecdysone (Fig. 7.10), which induces moulting (ecdysis) in both insect larvae and crustaceans. 

There are several reports that cHH can inhibit the ecdysteroid synthesis by YO in vitro but that MIH cannot act as a cHH by increasing glucose concentration (see for example [108]). It was probably this multifunctionality of cHH that led to it being mistaken for MIH in certain instances. Why should cHH duplicate the role of another hormone during the moult cycle The definitive answer to this question is still not known but specific receptors for cHH (along with MIH-specific receptors) have been demonstrated, by classical membrane binding studies, to be present on the YOs of intermoult brachyuran crabs [84]. Unlike cHH, radiolabelled MIH binds only to membrane preparations of YOs and not... 

We will discuss some of our comparative sterol metabolism studies and provide specific examples to illustrate some of these unusual variations in steroid utilization and metabolism in insects, and to show how this information is useful in predicting differences in ecdysteroid biosynthesis in certain species. We will also point out instances in which these variations in neutral sterol metabolism can be related to phylogenetic relationships between species. 

The Isolation and Identification of free ecdysteroids from Manduca and insects in general has not been too difficult, because we had partition systems that effectively separated free ecdysteroids from their impurities. For example, from processing 130 g of pupae, the ecdysteroids which partition into the butanol phase are now present in only 413 mg of residue (Fig. 3). This material could be further purified by column and thin-layer chromatography and countercurrent distribution. On the other hand, the ecdysteroid conjugates are present in 3.74 g of residue that is water-soluble which presents additional obstacles to further purification. The nature of the conjugation or the impurities present quite often prevented successful column or thin-layer chromatography of the conjugates. More recently, however, a method was described for the separation of... 

Y et, another example of the pleiotropic nature of ecdysteroids has been characterized in a mosquito (Anopheles gambiae, Pondeville et al. 2008). Males of this arthropod transfer significant amounts of 20E to females during mating. Since 20E is a female... 

Cultured and wild-caught crustaceans (especially shrimp) comprise one of the world s most valuable food commodities. As future protein resources become even scarcer, the intensification of aquaculture and fisheries activities is bound to increase. Research will become even more important in these areas (see Chap. 25). For example, manipulation of the MIH/ecdysteroid hormone axis is an obvious example of increasing growth rates. Attraction pheromones have the possibility of luring desired food species into traps. This mechanism could also be used for the control of invasive species pests (Hardege et al. 2002). 

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