Ecdysteroids phytoecdysteroids

Formation of Cholesterol Formation of Other Plant Sterols Biological Activity of Plants Sterols Progestans in Plants and from Animals Progestagens from Insects Ecdysteroids Phytoecdysteroids Chemotaxis in Fungi Cucurbitacins... 

Meng Y, Whiting P, Sik V, Rees HH, Dinan L (2001) Limnantheoside C (20-hydroxyecdysone 3-0-beta-D-glucopyranosyl-[1 3]-beta-D-xylopyranoside), a phytoecdysteroid from seeds of Limnanthes alba (Limnanthaceae). Zeitschrift fur Naturforschung 56 988-994 Sarker SD, Girault JP, Lafont R, Dinan L (1997) Ecdysteroid xylosides from Limnanthes douglasii. Phytochemistry 44 513-521... 

It has been recognised for some time that certain insect species have the ability to perceive ecdysteroids [38,116,117], This is probably a general phenomenon for many phytophagous insect species, which would encounter phytoecdysteroids in their diets [26], Only recently have more extensive electrophysiological studies on ecdysteroid taste receptor cells been performed [40,118], but very little is currently known about their specificity [119], This will clearly be an important area for future research, if ecdysteroids (or their analogues) are to be developed further as crop protection agents. 

Elbrecht et al. [167] reported that the iridoid glucoside 8-0-acetylharpagide (8-7), isolated from Ajuga reptans, possessed ecdysteroid agonist activity. Unfortunately, A. reptans is also a rich source of phytoecdysteroids and it is now clear that 8-0-acetylharpagide, per se, possesses no agonistic activity [168],... 

Ecdysteroids are generally regarded as not being able to penetrate insect cuticle readily [179], However, the rice stem borer, C. suppressalis, has a thin cuticle which allows ecdysteroids to penetrate when ligated last instar larvae are dipped into a methanolic solution of the test compound for 5 s [180], The proportion of pupated abdomina are assessed after 48 h. This assay is less sensitive than the Calliphora bioassay, but is easier to perform. Its main application has been in screening plant extracts for the presence of phytoecdysteroids [74],... 

Taken together these data indicate that different insect species are susceptible to ecdysteroid analogues to differing extents. This may go some way to explaining why phytoecdysteroid-containing plant species possess different ecdysteroid profiles. 

Antagonists of vertebrate steroid receptors are proving experimentally and therapeutically very significant [220-222], It has been known that certain plants contain ecdysteroid receptor agonists (phytoecdysteroids) for over 30 years It seemed reasonable to assume that plants might also contain compounds which could antagonise the action of ecdysteroids. With the advent of simple, reliable bioassays, it became appropriate to search for such compounds. In the intervening years we have screened... 

There are many well-established methods for separation and structure determination of ecdysteroids.20 27 A newly described method is two-dimensional thin-layer chromatography. It has been used to separate complex mixtures of phytoecdysteroids. Silica plates were developed first with toluene—acetone—ethanol—25% aqueous ammonia (100 140 32 9 v/v) and then developed in the other direction with chloroform—methanol—benzene (25 5 3 v/v)48... 

Effects of ecdysteroids in plants. The discovery that insect hormones occur in plants (31, 32) was a real surprise for endocrinologists. In the meantime more than 100 different phytoecdysteroids have been detected (6). Some of them are identical with insect ecdysteroids, some are unique to plant systems. According to Lafont and Horn (6) phytoecdysteroids have been found in most embryo-phytes, mainly ferns, gymnosperms and angiosperms. Their occurrence in thallophytes has not been reported. The concentration of ecdysteroids in plants may reach or even surpass 1 % of dry weight. Thus ecdysteroids represent the most widespread and quantitatively most abundant family of steroidal animal hormones. 

The variability of structures among phytoecdysteroids led to the discrimination between true ecdysteroids and ecdysteroid-related compounds (6 see above). It should be pointed out that these definitions are based on chemical structures and do not discrimi-... 

In some arthropods (for this hormone is shared with other classes besides insects), the series are not hydroxylated at C-25. Many crustaceans use 20-hydroxyecdysone as moulting hormone, others use ponasterone A (Figure 7.14). Ecdysteroids have also been found in plants. These phytoecdysteroids are widely distributed in the plant... 

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