Differentiating isobaric steroid hormone metabolites using multi-stage tandem mass spectrometry

Comprehensive identification of steroid hormones in human urine based on liquid chromatography-high resolution mass spectrometry

Steroid hormones, structural derivatives of cyclopentanoperhydrophenanthrene, play important roles in modulation of many physiological processes. Comprehensive characterization of steroid hormones is valuable for understanding the process of human life activities and even disease diagnosis. Hitherto systematical characterization of steroid hormones has been rarely investigated. Here, we presented an integrated method for human urine analysis based on ultra-high performance liquid chromatography-high resolution mass spectrometry in data-dependent acquisition mode with the following parallel reaction monitoring mode. To process the data acquired by two scan modes, a comparative study of standards' fragmentation behaviors and diagnostic product ions (DPIs) were firstly conducted to facilitate the characterization of steroid hormones. The fragmentation behaviors, DPIs, elemental composition and double-bond equivalent were then simultaneously utilized for systematical characterization of steroid hormones in human urine. Consequently, fragmentation pathways and DPIs for all types of steroid hormones were comprehensively interpreted. It is interesting to find that dehydration is not restricted in the form of hydroxyl groups loss, elimination of the carbonyl oxygen could also generate dehydrated ions. Ultimately, a total of 80 and 107 steroidal hormones were characterized or tentatively identified in human urine of male and female, respectively. The proposed method is expected to provide valuable insights for chemical characterization in complex matrixes.

Appropriate choice of collision-induced dissociation energy for qualitative analysis of notoginsenosides based on liquid chromatography hybrid ion trap time-of-flight mass spectrometry

Liquid chromatography hybrid ion trap/time-of-flight mass spectrometry possessesd both the MS(n) ability of ion trap and the excellent resolution of a time-of-flight, and has been widely used to identify drug metabolites and determine trace multi-components for in natural products. Collision energy, one of the most important factors in acquiring MS(n) information, could be set freely in the range of 10%-400%. Herein, notoginsenosides were chosen as model compounds to build a novel methodology for the collision energy optimization. Firstly, the fragmental patterns of the representatives for the authentic standards of protopanaxadiol-type and protopanaxatriol-type notoginsenosides authentic standards were obtained based on accurate MS(2) and MS(3) measurements via liquid chromatography hybrid ion trap/time-of-flight mass spectrometry. Then the extracted ion chromatograms of characteristic product ions of notoginsenosides in Panax Notoginseng Extract, which were produced under a series of collision energies and, were compared to screen out the optimum collision energies values for MS(2) and MS(3). The results demonstrated that the qualitative capability of liquid chromatography hybrid ion trap/time-of-flight mass spectrometry was greatly influenced by collision energies, and 50% of MS(2) collision energy was found to produce the highest collision-induced dissociation efficiency for notoginsenosides. BesidesAddtionally, the highest collision-induced dissociation efficiency appeared when the collision energy was set at 75% in the MS(3) stage.

Oxidative degradation of quercetin with hydrogen peroxide using continuous-flow kinetic electrospray-ion trap-time-of-flight mass spectrometry

The time-dependent hydrogen peroxide-induced oxidative degradation of aqueous quercetin at pH 7.4 was measured using an in-house-built online continuous-flow device made of concentric capillary tubes, modified to fit a photodiode array (PDA) detector and the inlet of an electrospray ionization-ion trap-time-of-flight mass spectrometer (ESI-IT-TOF-MS). As the reaction time was increased, the deprotonated quercetin ion signal, [Q - H](-), decreased, and the formation of degradation product ions was observed. Structures for degradation product ions were proposed using higher order tandem mass spectrometry (up to MS(3)) and high mass accuracy. The determined degradation pathways included oxidation, hydroxylation, cyclic peroxylation, ring cleavage, and small molecule loss. The most intense degradation product observed was 2,4,6-trihydroxybenzoate, which was proposed to be the end point of the peroxylation pathway and the favored degradation pathway under these conditions. This pathway is believed to be the result of nucleophilic attack by hydrogen peroxide at the C2 position of quercetin. This was followed by a cross ring cyclic peroxylation event at C2-C4, which resulted in an intermediate depside that was defined by C-ring-opening due to loss of C3-OH and cleavage of the peroxy bond. Further cleavage of the depside resulted in the 2,4,6-trihydroxybenzoate. A sodiated pseudo adduct of the dimerized trihydroxybenzoate was believed to be induced under electrospray conditions. A computational study was performed to justify the position within the C-ring for both the attack by nucleophilic oxidants and the cyclic peroxylated intermediate structure.

Thermally accelerated oxidative degradation of quercetin using continuous flow kinetic electrospray-ion trap-time of flight mass spectrometry

Thermally accelerated oxidative degradation of aqueous quercetin at pH 5.9 and 7.4 was kinetically measured using an in-house built online continuous flow device made of concentric capillary tubes, modified to fit to the inlet of an electrospray ionization-ion trap-time-of-flight-mass spectrometer (ESI-IT-TOF-MS). Time-resolved mass spectral measurements ranging from 2 to 21 min were performed in the negative mode to track intermediate degradation products and to evaluate the degradation rate of the deprotonated quercetin ion, [Q-H](-). Upon heating solutions in the presence of dissolved oxygen, degradation of [Q-H](-) was observed and was accelerated by an increase in pH and temperature. Regardless of the condition, the same degradation pathways were observed. Degradation mechanisms and structures were determined using higher order tandem mass spectrometry (up to MS(3)) and high mass accuracy. The observed degradation mechanisms included oxidation, hydroxylation, and ring-cleavage by nucleophilic attack. A chalcan-trione structure formed by C-ring opening after hydroxylation at C2 was believed to be a precursor for other degradation products, formed by hydroxylation at the C2, C3, and C4 carbons from attack by nucleophilic species. This resulted in A-type and B-type ions after cross-ring cleavage of the C-ring. Based on time of appearance and signal intensity, nucleophilic attack at C3 was the preferred degradation pathway, which generated 2,4,6-trihydroxymandelate and 2,4,6-trihydroxyphenylglyoxylate ions. Overall, 23 quercetin-related ions were observed.