Rapid profiling of cytokinins using supercritical fluid chromatography coupled with tandem mass spectrometry

BACKGROUND

The determination of plant hormones is still a very challenging analytical discipline, mainly due to their low concentration in complex plant matrices. Therefore, the involvement of very sensitive high-throughput techniques is required. Cytokinins (CKs) are semi-polar basic plant hormones regulating plant growth and development. Modern methods for CK determination are currently based on ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), which enables the separation of CK isomeric forms occurring endogenously in plants. Here, ultra-high performance supercritical fluid chromatography coupled with tandem mass spectrometry (UHPSFC-MS/MS) was used for the simultaneous determination of 37 CK metabolites.

RESULTS

The chromatographic conditions were tested on three different columns with various retention mechanisms. Hybrid silica modified with 2-picolylamine was selected as the stationary phase. Several parameters such as column temperature, back pressure regulation, mobile phase composition and make-up solvent were investigated to achieve efficient separation of CK isomers and reasonable sensitivity. Compared to UHPLC-MS/MS, a 9-min chromatographic analysis using a mobile phase of supercritical CO2 and 5 mM ammonia in methanol represents a three-fold acceleration of total run time. The quantification limit of UHPSFC-MS/MS method was in the range of 0.03-0.19 fmol per injection and the method validation showed high accuracy and precision (below 15 % for most analytes). The method was finally applied to the complex plant matrix of the model plant Arabidopsis thaliana and the obtained profiles of CK metabolites were compared with the results from the conventional UHPLC-MS/MS method.

SIGNIFICANCE

The presented work offers a novel approach for quantification of endogenous CKs in plants. Compared to the conventional UHPLC-MS/MS, the total run time is shorter and the matrix effect lower for the key CK metabolites. This approach opens the opportunity to utilize UHPSFC-MS/MS instrumentation for targeted plant hormonomics including other plant hormone families.

Differential metabolism of clinically-relevant progestogens in cell lines and tissue: Implications for biological mechanisms

Steroid hormones regulate a variety of physiological processes, including reproductive function, and are widely used in hormonal therapy. Synthetic progestogens, or progestins, were designed to mimic progesterone (P₄) for use in contraception and hormonal replacement therapy in women. Medroxyprogesterone acetate (MPA) and norethisterone (NET) are the most widely used injectable contraceptives in the developing world, while other progestins such as levonorgestrel (LNG), etonogestrel (ETG) and nestorone (NES) are used in or being developed for other forms of contraception. As concerns remain about the most appropriate choice of progestin and dosage, and the associated side-effects, the mechanisms and biological effects of progestins are frequently investigated in various in vitro mammalian cell line and tissue models. However, whether progestogens are differentially metabolised in different cell types in vivo or in vitro is unknown. For nine mammalian cell lines commonly used to investigate progestogen mechanisms of action, we developed and validated an ultra-high performance supercritical fluid chromatography-tandem mass spectrometry (UHPSFC-MS/MS) protocol for simultaneously quantifying the metabolism of the above-mentioned steroids. We show for the first time that, while 50-100% of P₄ was metabolised within 24 h in all cell lines, the metabolism of the progestins is progestin- and cell line-specific. We also show that MPA and NET are significantly metabolised in human cervical tissue, but to a lesser extent than P₄. Taken together, our findings suggest that differential progestogen metabolism may play a role in cell-specific therapeutic and side-effects. Relative affinities for binding to steroid receptors as well as potencies, efficacies and biocharacters for transcriptional activity of progestins, relative to P₄, are most frequently determined using some of the cell lines investigated. Our results, however, suggest that differential metabolism of progestins and P₄ may confound these results. In particular, metabolism may under-estimate the receptor-mediated intrinsic in vitro binding and dose-response values and predicted endogenous physiological effects of P₄.

Determination of a selection of synthetic cannabinoids and metabolites in urine by UHPSFC-MS/MS and by UHPLC-MS/MS

Two different analytical techniques, ultra-high performance supercritical fluid chromatography-tandem mass spectrometry (UHPSFC-MS/MS) and reversed phase ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), were used for the determination of two synthetic cannabinoids and eleven metabolites in urine; AM-2201 N-4-OH-pentyl, AM-2233, JWH-018 N-5-OH-pentyl, JWH-018 N-pentanoic acid, JWH-073 N-4-OH-butyl, JWH-073 N-butanoic acid, JWH-122 N-5-OH-pentyl, MAM-2201, MAM-2201 N-4-OH-pentyl, RCS-4 N-5-OH-pentyl, UR-144 degradant N-pentanoic acid, UR-144 N-4-OH-pentyl, and UR-144 N-pentanoic acid. Sample preparation included a liquid-liquid extraction after deconjugation with ß-glucuronidase. The UHPSFC-MS/MS method used an Acquity UPC(2 TM) BEH column with a mobile phase consisting of CO2 and 0.3% ammonia in methanol, while the UHPLC-MS/MS method used an Acquity UPLC® BEH C18 column with a mobile phase consisting of 5 mM ammonium formate (pH 10.2) and methanol. MS/MS detection was performed with positive electrospray ionization and two multiple reaction monitoring transitions. Deuterated internal standards were used for six of the compounds. Limits of quantification (LOQs) were between 0.04 and 0.4 µg/L. Between-day relative standard deviations at concentrations ≥ LOQ were ≤20%, with biases within ±19%. Recoveries ranged from 40 to 90%. Corrected matrix effects were within 100 ± 10%, except for MAM-2201 with UHPSFC-MS/MS, and for UR-144 N-pentanoic acid and MAM-2201 N-4-OH-pentyl with UHPLC-MS/MS. Elution order obtained by UHPSFC-MS/MS was almost opposite to that obtained by UHPLC-MS/MS, making this instrument setup an interesting combination for screening and confirmation analyses in forensic cases. The UHPLC-MS/MS method has, since August 2014, been successfully used for confirmation of synthetic cannabinoids in urine samples revealing a positive immunoassay screening result. Copyright © 2015 John Wiley & Sons, Ltd.