Application of combined chromatographic techniques in the screening and purification of ecdysteroids

Summary Plants were found to contain ecdysteroids in concentrations in the order of 0.1% which are higher than those of the insects, and are adequate for the preparative production of ecdysteroids. A TLC screening method is elaborated for the qualitative and semiquantitative analysis of the ecdysteroid content of plants. The combined TLC method differentiates several characteristic ecdysteroids ranging from the apolar 2-deoxyecdysone to the polar 20,26-dihydroxyecdysone. A preparative purification method was developed consisting of solvent extraction, precipitation, crystallization and column liquid chromatography; these procedures permit the isolation of the main ecdysteroids in gram quantities. In some cases, droplet counter-current chromatography was also applied. Altogether, the isolation of thirteen ecdysteroids from five different plant species was accomplished by using a fast, simple and low-cost procedure, resulting in pure substances.     

Processes of dissociative electron capture by 20-hydroxyecdysone molecules

The peculiarities of dissociative electron capture by 20-hydroxyecdysone molecules with the formation of fragment negative ions were studied. In the region of high electron energies (5–10 eV), processes of skeleton bond rupture are accompanied by the elimination of H₂O and H₂ molecules. In the region of thermal energies of electrons (≈0 eV), the mass spectrum is formed mainly by the [M−nH₂O]^.− (n=1–3) and [M−H₂−nH₂O]^.− (n=0−3) ions that are generated exclusively by the rearrangement. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 709–712, April, 2000.     

Phytoecdysteroids and Other Biologically Active Compounds from Plants of the Genus <Emphasis Type="Italic">Ajuga</Emphasis>

Literature data on the structures of phytoecdysteroids and other biologically active compounds and their biological activities were reviewed. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 293–299, July–August, 2005.     

Structure and stereochemistry of novel ecdysteroids from the roots of Serratula wolffii

Three new natural ecdysteroids viz. 22‐dehydro‐20‐deoxy‐ajugasterone C (1), 1‐hydroxy‐22‐deoxy‐20,21‐didehydro‐ecdysone (2) and 22‐deoxy‐20,21‐didehydro‐ecdysone (3) were isolated from the methanol extract of the roots of Serratula wolffii. The structures of compounds 1–3 were established by various spectroscopic techniques, including one‐ and two‐dimensional NMR, circular dichroism and mass spectroscopic methods. Copyright © 2010 John Wiley & Sons, Ltd.     

Specific features of resonance electron capture mass spectra of ecdysteroid molecules

Specificity of the dissociative attachment of low-energy electrons to ecdysteroid molecules (viz., 20-hydroxyecdysone 2,3:20,22-diacetonide, 20-hydroxyecdysone 20,22-acetonide, and poststerone 2-acetate) was found, which is manifested as the formation of long-lived pseudo-molecular negative ions that appeared due to the elimination of the H₂ and H₂O molecules. These rearrangements are resulted from the formation of the system of conjugated double bonds in the ecdysteroid skeleton, stabilizing the lowest vacant molecular orbital.     

Novel ecdysteroid analogs with oxygen-containing heterocycles in the steroid skeleton

The reaction of ecdysteroids (20-hydroxyecdysone and its acetonides) with lithium in liquid ammonia gave novel analogs with an oxetane 9α,14α-oxacycle in the steroid skeleton. In aqueous alcohol solution the 9,14-oxa analogs rearrange to the more stable 9α,13α-oxa analogs through a 1,2-migration of the 18-Me group from the C-13 to the C-14 atom. Dedicated to Academician B. A. Trofimov in his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1339–1355, September, 2008.