The polyhydroxylated phytosteroid ecdysterone is present in various plants (e.g. spinach). It is widely marketed as the active component of dietary supplements, due to its reported health and performance promoting effects. For evaluation of its actual bioavailability, a fast and sensitive method was developed, optimized and validated for human serum. Instrumental analysis was performed utilizing liquid chromatography-tandem mass spectrometry with positive electrospray ionization and acquisition in multiple reaction mode. Solid phase extraction and dilute-and-inject (following protein precipitation) were tested to isolate ecdysterone from human serum. Both methods were compared in the light of the preset analytical target profile. The limit of detection (LOD) and quantitation (LOQ) for ecdysterone in human serum after SPE extraction corresponded to 0.06 ng/mL and 0.14 ng/mL, respectively, meeting the requested sensitivity of the method. The assay was linear over the range of 0.10 ng/mL to 20.83 ng/mL. As expected, the sensitivity of the SPE method was better than that of the dilute-and-inject procedure, which did not allow for quantitation of all post administration serum samples. Accuracy (relative error; %) and precision (coefficient of variation; %), were both within acceptance criteria (<15%). The developed method was successfully applied to a ten week intervention study conducted in young men performing regular resistance training. Different doses of supplements containing ecdysterone from spinach extract have been administered during the study and the quantitation of ecdysterone in serum samples has been successfully conducted. Ecdysterone could be quantified in all post-administration samples using solid phase extraction (SPE) for sample pretreatment.
Keywords: Ecdysteroids; Ecdysterone; LC-MS/MS; Nutritional supplements; Serum analysis; Spinach extract.
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