High Performance Liquid Chromatography/Electrochemistry/High Resolution Electrospray Ionization‐Mass Spectrometry (HPLC/EC/HR ESI‐MS) Characterization of Selected Cytokinins Oxidation Products

Abstract

Electrochemistry combined with mass spectrometry represents an emerging analytical technique used to study the oxidation pathway of various drugs and in vivo occurring compounds, continuously showing a capability to generate many known metabolites or new oxidation products. An on‐line HPLC/EC/HR ESI‐MS method had been used to investigate the oxidation of selected cytokinin compounds. This setup allowed rapid identification and general structure elucidation of the obtained products. An electrochemical oxidation of isopentenyladenine resulted in five products, including hydroxylated and dehydrogenated products, which correlates very well with its in vivo metabolism. Electrochemical conversion of trans‐zeatin revealed six products, with two dehydrogenation products corresponding to its in vivo occurring metabolites. cis‐Zeatin oxidation in the electrochemical cell gave rise to eight products, resembling similarity to trans‐zeatin oxidation. All three compounds underwent a complete turnover mainly through two oxidation reactions occurring in the electrochemical celldehydrogenation and a less typical aliphatic hydroxylation. The resulting products are in correlation with their known in vivo metabolism.

Sample transformation in online separations: how chemical conversion advances analytical technology

“…With regard to drug metabolism studies, the EC can be placed either before or after the LC separation. One application demonstrating the utility of LC-EC-MS was to first separate cytokinins by LC and subsequently study the oxidation products of selected cytokinins to MS. 158 Several studies demonstrated the use of EC to simulate both phase I and phase II human metabolism. 159,160 Phase I metabolism was simulated by EC-based oxidation while phase II was simulated by the addition of glutathione for follow-up reactions.…”

Efficient and Selective Enrichment of Ultratrace Cytokinins in Plant Samples by Magnetic Perhydroxy-Cucurbit[8]uril Microspheres

“…It is very difficult to accurately determine CKs in plant samples due to the complex matrix and the extremely low concentration level of pmol/g, sensitive analytical methods including efficient sample preparation methods and accurate determination methods are required for the analysis of these analytes . Various extraction methods such as affinity purification, adsorption-based separation, hydrophobic adsorbant, monolith column, and magnetic separation , have been developed to enrich trace CKs from complex matrix, but their selectivity to CKs is still a big challenge. Some analytical techniques including immunoassays, electroanalysis, capillary electrophoresis, liquid chromatography, , high/ultra performance liquid chromatography (HPLC/UPLC) coupled to different detectors, i.e., mass spectrometry (MS), have been developed for quantification of CKs.…”

“…Various extraction methods such as affinity purification, adsorption-based separation, hydrophobic adsorbant, monolith column, and magnetic separation , have been developed to enrich trace CKs from complex matrix, but their selectivity to CKs is still a big challenge. Some analytical techniques including immunoassays, electroanalysis, capillary electrophoresis, liquid chromatography, , high/ultra performance liquid chromatography (HPLC/UPLC) coupled to different detectors, i.e., mass spectrometry (MS), have been developed for quantification of CKs. Compared with other methods, HPLC–MS and UPLC–MS/MS are the most powerful techniques because of its good resolution separation, sensitivity, and identification of CKs from plant samples.…”