Diversity-oriented synthesis through gamma radiolysis: Preparation of unusual ecdysteroid derivatives activating Akt and AMPK in skeletal muscle cells

Gamma-ray radiation is a unique way to induce chemical transformations of bioactive compounds. In the present study, we pursued this approach to the diversity-oriented synthesis of analogs of 20-hydroxyecdysone (20E), an abundant ecdysteroid with a range of beneficial, non-hormonal bioactivities in mammals including humans. Gamma irradiations of aqueous solutions of 20E were conducted either in N₂- or N₂O-saturated solutions. Centrifugal partition chromatography was used to fractionate crude resulting irradiated materials using a biphasic solvent system composed of tert-butyl alcohol - ethyl acetate - water (0.45:0.9:1, v/v/v) in ascending mode. Subsequently, the products were purified by RP-HPLC. Fourteen ecdysteroids, including five new compounds, were isolated, and their structure were elucidated by 1D and 2D NMR and HRMS. Compounds 2-4, 7, 9, 12 and 15 were tested for their capacity to increase the Akt- and AMPK-phosphorylation of C2C12 murine skeletal myotubes in vitro. The compounds were similarly active on Akt as their parent compound. Stachysterone B (7) and a new ring-rearranged compound (12) were more potent than 20E in activating AMPK, indicating a stronger cytoprotective effect. Our results demonstrate the use of gamma irradiation in expanding the chemical diversity of ecdysteroids to obtain new, unusual bioactive metabolites.

Capillary electrophoresis study on the base-catalyzed formation of bioactive oxidized metabolites of 20-hydroxyecdysone

A novel capillary electrophoretic method was developed for the analysis and monitoring of the base-catalyzed autoxidation of 20-hydroxyecdysone, a worldwide used non-hormonal anabolic food supplement. An effective separation of the starting material and its bioactive oxidized derivatives was achieved by using sulfobutyl-β-cyclodextrin as selector at pH 11 and by fixing the separation voltage at +30kV. Only a dilution step was inserted before injecting the sample, taken from the crude reaction mixture, to the capillary electrophoresis instrument. The same alkaline pH was used for the analysis as for the reaction, unlike the previously reported HPLC study where sample neutralization was required prior to the measurement. Due to the very short analysis time (6min) in capillary electrophoresis, more frequent sampling and more detailed time scale analysis could be carried out. Furthermore, in contrast with the preceding HPLC results, the previously unobserved calonysterone could also be detected by capillary electrophoresis as a minor primary product. Our novel method demonstrated higher resolution than the one before. Baseline separation could be achieved and the resolution values were in the range of 1.9-7.0. The limit of detection was below 71μg/ml, the relative standard deviation values of the migration time and peak area for intra- and inter-day precision were less than 10%. The more precise, direct monitoring of the time dependency of the oxidation process is expected to have a significant impact on yield optimization initiatives to allow related pharmacological studies in the near future.