Ecdysteroids plants

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. 

Ecdysteroids. Ecdysteroids can be isolated from many species of the annual kingdom that belong to the phyla Protomia, e.g., insects, worms, and arthropods, as well as a variety of different plant species. Ecdysteroids include the molting hormones, however, nnl all the over 60 ecdysteroids that have been isolated are active hormones. Ecdysteroids from animals... 

Two main hypotheses have been put forward to account for the occurrence of ecdysteroids in the plant world. The first is that PEs have a hormonal role within the plant, but there is very little hard evidence in support of this hypothesis (reviewed in [26]). Alternatively, PEs participate in the defence of plants against non-adapted phytophagous invertebrates. Deterrent effects of 20E on non-adapted insect species are... 

Recently, it has been demonstrated that ecdysteroid accumulation in spinach is inducible by mechanical [50] or insect [51] damage to roots. Evidence was further provided for the involvement of jasmonates in the induction of de novo ecdysteroid synthesis. Also, short- and long-term labelling of 20E from [2-14C]mevalonic acid in spinach demonstrate that ecdysteroids are metabolically stable in this species, which fits much better with a role in plant defence, rather than a phytohormonal role [52], Most recently, it has been demonstrated that root predation by the fungus gnat Bradysia impatiens results in elevated ecdysteroid levels in spinach and a significant reduction in larval establishment of B. impatiens [53],... 

Definitive assessment of the contribution of PEs to the deterrence of invertebrate predators must await the comparison of the susceptiblity of genetic lines of the same plant species which differ in their ecdysteroid levels and/or profiles [26],... 

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... 

The ecdysteroid antagonists identified to date are all of rather low potency This may be a consequence of them all being plant natural products, which the plant is able to produce in high concentrations at low cost to itself [231],... 

D. Louden, A. Handley, R. Lafont, S.Taylor, I. Sinclair, E. Lenz,T. Orton, and I. D. Wilson, HPLC analysis of ecdysteroids in plant extracts using superheated deuterium oxide with multiple on-line spectroscopic analysis (UV, IR, IH NMR, and US), Anal. Chem. 74 (2002), 288-294. 

Adler, J.H. and Grebenok, R.J. (1999) Occurrence, biosynthesis, and putative role of ecdysteroids in plants. Crit. Rev. Biochem. Mol. Biol., 34,253-64. 

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