Diazo probe-based chemical isotope labeling assisted liquid chromatography-tandem mass spectrometry analysis for sensitive determination of amino acids in biofluids.

Amino acids are important biomolecules and contribute to essential biological processes. Liquid chromatography tandem mass spectrometry (LC-MS) now is a powerful tool for the analysis of amino acid metabolites; however, the structural similarity and polarity of amino acids can lead to the poor chromatographic retention and low detection sensitivities. In this study, we used a pair of light and heavy isotopomers of diazo probes, d0/d5-2-(diazomethyl)-N-methyl-N-phenyl-benzamide (2-DMBA/d5 -2-DMBA) to label amino acids. The paired MS probes of 2-DMBA and d5 -2-DMBA carry diazo groups that can efficiently and specifically react with the carboxyl group on free amino acid metabolites under mild conditions. Benefiting from the transfer of the 2-DMBA/d5 -2-DMBA to carboxyl group on amino acids, the ionization efficiencies of amino acids presented great enhancement during LC-MS analysis. The results suggested that the detection sensitivities of 17 amino acids increased by 9-133-fold upon 2-DMBA labeling, and the obtained limits of detection (LODs) of amino acids on-column ranged from 0.011 fmol-0.057 fmol. With the application of the developed method, we successfully achieved the sensitive and accurate detection of the 17 amino acids in microliter level of serum sample. Moreover, the contents of most amino acids were different in the serum from normal and B16F10-tumour mice, demonstrating that endogenous amino acids may play important roles in the regulation of tumors development. This developed method of chemical labeling of amino acids with diazo probes assisted LC-MS analysis provides a potentially valuable tool to investigate the relationships between amino acids metabolism and diseases.

A Comprehensive Study on the Chemical Constituents and Pharmacokinetics of Erzhi Formula and Jiawei Erzhi Formula Based on Targeted and Untargeted LC-MS Analysis.

BACKGROUND: Erzhi formula (EZF) is a traditional Chinese medicine prescription, which has been widely used in the treatment of osteoporosis and premature ovarian failure. OBJECTIVE: To enhance curative effects, the other two herbal medicines, including Spatholobi Caulis (SC) and Achyranthes bidentata Blume (ABB), were added into the original EZF formula to obtain two new Jiawei-EZF (JW-EZF) preparations. To clarify the effect of the compatibility of herbs for original formulas, the chemical constituents and bioactive compounds in vivo were detected. METHODS: An efficient and sensitive targeted and untargeted UHPLC/ESI-Q-Orbitrap MS method, together with mass defect filter and precursor ion list, was established firstly for the profiling of different EZF formulas. Furthermore, eleven absorbed compounds (apigenin, luteoloside, luteolin, oleuropein, wedelolactone, acteoside, specnuezhenide, 11-methyloleoside, ecliptasaponin A, formononetin, and ß-ecdysone) were simultaneously quantified in rat plasma. RESULTS: A total of 124, 162, and 177 compounds were identified or tentatively identified in EZF, JW-3-EZF (EZF+SC) and JW-4-EZF (EZF+SC+ABB), respectively. 110 compounds were found to be common constituents in the three formulas. Moreover, 66 prototypes were unambiguously identified in the rats' plasma after oral administration of the three formulas using the same strategy. 11 out of the 66 absorbed components were simultaneously quantitated in the pharmacokinetic (PK) study. Compared to the original EZF, the plasma AUC(0-24h) and AUC(0-∞) of apigenin, 11-methyloleoside, luteolin, luteoloside, wedelolactone, and acteoside were found to be significantly increased after oral administration of JW-3-EZF, and plasma AUC(0-24h) and AUC(0-∞) of apigenin, wedelolactone, and acteoside, were also found to be significantly increased after JW-4-EZF administration. CONCLUSION: The combined qualitative and quantitative methods were used to provide a potential approach to the characterization and quality control of the Traditional Chinese Medicine (TCM) and its preparations.

Comprehensive investigation on the metabolism of emodin both in vivo and in vitro.

Emodin is a natural anthraquinone, which displays numerous pharmacological activities, including anti-tumor, anti-inflammation and immunosuppression. However, there was no comprehensive study on its absorption, metabolism, distribution, and excretion. In order to further evaluation on the possibility of drug development of emodin, both in vivo and in vitro experiments were fulfilled in this study. The results showed that the absolute bioavailability of emodin is approximately 3.2%. Furthermore, about 56% of emodin was unabsorbed and mainly excreted into feces as prototype. The absorb constituent could be rapidly metabolized as hydroxylated and glucuronidated metabolites. Both prototype and metabolites of emodin absorbed into the body circulation were predominantly distributed in kidney. Hydroxyed metabolites were predominantly excreted via urine and feces and glucuronidated metabolites were predominantly excreted via urine and bile. CYP1A2, CYP2E1, UGT1A1, UGT1A9, and UGT2B7 played a key role in the metabolism of emodin in liver microsomes of rats. To the best of our knowledge, this is the first comprehensive study on the absorption, metabolism, distribution, and excretion of emodin, and our results could help to understand both pharmaceutical and toxicological effects of emodin greatly.

Studies on Chemical Characterization of Ginkgo Amillaria Oral Solution and Its Drug-Drug Interaction With Piceatannol 3'-O-ß-D-Glucopyranoside for Injection.

Ginkgo Amillaria oral solution (GAO) is commonly used for the treatment of cardiovascular and cerebrovascular diseases in China. Piceatannol-3'-O-ß-D-glucopyranoside for injection (PGI) is mainly used for the prevention and treatment of ischemic cerebrovascular diseases. With the spread of cerebrovascular disease, the possibility of combining the two drugs has increased; however, there is no research on the drug-drug interaction (DDI) between these two medicines. In this paper, an ultrahigh-performance liquid chromatography/quadrupole-orbitrap mass spectrometry (UHPLC/Q-Orbitrap MS) method was established to characterize the chemical constituents of GAO first; 62 compounds were identified or tentatively identified based on their retention time (RT), MS, and MS/MS data. Nine main compounds were determined by ultrahigh-performance liquid chromatography/triple quadrupole mass spectrometry (UPLC-QQQ-MS). Furthermore, incubation with liver microsomes in vitro was fulfilled; the results showed that GAO had a significant inhibitory effect on UGT1A9 and UGT2B7 (p < 0.05), and PGI was mainly metabolized by UGT1A9. The identification results of in vivo metabolites of PGI showed that PGI mainly undergoes a phase II binding reaction mediated by UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) in vivo. Therefore, pharmacokinetic studies were performed to investigate the DDI between GAO and PGI. The results showed that the AUC (p < 0.05) and T1/2 (p < 0.05) of PGI in vivo were significantly increased when administered together with GAO, whereas the CL was significantly decreased (p < 0.05). The exploration of in vitro and in vivo experiments showed that there was a DDI between GAO and PGI.