Yu-Qi He

Bile Acids Metabonomic Study on the CCl4- and α-Naphthylisothiocyanate-Induced Animal Models: Quantitative Analysis of 22 Bile Acids by Ultraperformance Liquid Chromatography−Mass Spectrometry

Bile acids (BAs) are crucial for the diagnosis, follow-up, and prognostics of liver and intestinal disorders and other diseases affecting BA metabolism. A rapid, simple, and sensitive analytical method is needed to demonstrate the full metabolic profile and simultaneously determine the individual BAs in biological samples. In our present study, an ultraperformance liquid chromatography-mass spectrometry (UPLC-MS) method has been established and validated for simultaneous quantitation of 22 BAs and a metabonomic study was performed based on the chemometric analysis of the serum samples from carbon tetrachloride (CCl4)- and alpha-naphthylisothiocyanate (ANIT)-induced liver failure rats. The optimal chromatographic condition was effected by UPLC (Acquity UPLC BEH column, 1.7 microm, 2.1 mm x 100 mm) using a linear gradient elution system of methanol-5 mM ammonium acetate containing 0.01% acetic acid after a simple-step deproteinization by precipitation. The separation of the 22 BAs can be finished in less than 12 min, and the concentrations of these BAs in rat serums were simultaneously determined using a selective ions monitoring mode. The method was validated with respect to repeatability (relative standard deviation < 9.78%) and accuracy (relative errors from -13.55 to 9.58%). The range of each BA was found from not detected (nd) to 8301 ng mL(-1), respectively. Furthermore, the developed method was successfully applied to the metabonomics analysis of BAs in CCl4- and ANIT-induced liver failure rats, using principle component analysis and canonical discriminant analysis. The serum samples from the two types of rat liver injury could be distinguished from each other and from the untreated animals according to the varieties of BAs. It indicated that the level of BAs could be considered as a sensitive parameter of hepatotoxicity induced by different chemical toxins. This novel metabonomics study of BAs based on the UPLC-MS profile provides not only an accurate quantitative assay of the serum concentrations of biomarkers but also a promising methodology for evaluation of liver injury.

Characterization of fifty‐one flavonoids in a Chinese herbal prescription Longdan Xiegan Decoction by high‐performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry and photodiode array detection

High-performance liquid chromatography coupled to electrospray ionization (ESI) tandem mass spectrometry and photodiode array detection (HPLC-DAD-ESI-MS(n)) was developed to identify and characterize the flavonoids in a Chinese formulated preparation, Longdan Xiegan Decoction (LXD). In total, fifty-one flavonoids (27 flavones, 10 flavanones, 7 chalcones, 5 flavonols and 2 isoflavones) were characterized. Eighteen compounds among them including a newly detected flavonoid, naringin, from the ingredient herbs, were unambiguously determined by comparing the retention times (t(R)), UV spectral data and mass fragmentation behaviors with those of the reference compounds. Another thirty-three compounds were tentatively identified by referencing to the reported data of their UV and MS spectra. The ESI-MS/MS fragmentation behavior of flavones (OMe-substituted, O-glycosides, C-glycosides), chalcones, flavonols and their appropriate characteristic pathways were proposed. In negative ion ESI-MS all the flavonoids yielded prominent [M--H](-) ions in the first order mass spectra. Fragmentation with a loss of mass of 15 Da (CH(3)), 18 Da (H(2)O), 28 Da (CO), 44 Da (CO(2)), 56 Da (2CO) and the residues of glucose and glucuronic acid observed in the MS/MS spectra were useful for aiding the structural identification of the flavonoids investigated.

Characterization of triptolide hydroxylation by cytochrome P450 in human and rat liver microsomes.

Triptolide, the primary active component of a traditional Chinese medicine Tripterygium wilfordii Hook F, has a wide range of pharmacological activities. In the present study, the metabolism of triptolide by cytochrome P450s was investigated in human and rat liver microsomes. Triptolide was converted to four metabolites (M-1, M-2, M-3, and M-4) in rat liver microsomes and three (M-2, M-3, and M-4) in human liver microsomes. All the products were identified as mono-hydroxylated triptolides by liquid chromatography-mass spectrometry (LC-MS). The studies with chemical selective inhibitors, complementary DNA-expressed human cytochrome P450s, correlation analysis, and enzyme kinetics were also conducted. The results demonstrate that CYP3A4 and CYP2C19 could be involved in the metabolism of triptolide in human liver, and that CYP3A4 was the primary isoform responsible for its hydroxylation.

Comparative pharmacokinetic study of paeoniflorin after oral administration of decoction of Radix Paeoniae Rubra and Radix Paeoniae Alba in rats

An investigation was designed and conducted to compare the pharmacokinetics difference of paeoniflorin after oral administration of the extracts of Radix Paeoniae Rubra and Radix Paeoniae Alba to rats on separate occasions. Quantification of paeoniflorin in rat plasma was achieved using a simple and rapid HPLC method for pharmacokinetic study. After oral administration of decoctions of Radix Paeoniae Rubra and Radix Paeoniae Alba, paeoniflorin was absorbed and reached a maximum concentration of 3.69+/-1.46 and 1.46+/-0.29 (p<0.05)microg/ml at 1.67+/-0.43 and 0.80+/-0.35 h (p<0.05), respectively. Compared to the AUC (18.85+/-7.54 microg h/ml) after oral administration of the paeoniflorin solution, a smaller AUC (10.61+/-1.51 microg h/ml, p<0.05) and a larger AUC (24.89+/-7.41 microg h/ml) of paeoniflorin after oral administration of the decoctions of Radix Paeoniae Alba and Radix Paeoniae Rubra were obtained, respectively. There were statistically significant differences in pharmacokinetic parameters of paeoniflorin including the t(max), C(max), AUC, t(1/2), CL, and V(d) among the animals orally administered the decoctions of Radix Paeoniae Rubra and Radix Paeoniae Alba. In particular, the parameters of t(max), C(max), and AUC of paeoniflorin were remarkably increased (P<0.05, P<0.001) when oral administering paeoniflorin in the decoctions of Radix Paeoniae Rubra, but t(1/2), V(d), and CL were decreased (P<0.05 or P<0.01), in comparison of the decoction of Radix Paeoniae Alba.

Inhibition of Human Liver Cytochrome P450 by Star Fruit Juice

PURPOSE To examine the inhibitory effects of star fruit (Averrhoa carambola) juice towards seven major cytochrome P450 (CYP) isoforms and NADPH-cytochrome P450 reductase (CPR). METHODS The inhibitory effects of star fruit juice (0.5 to 5%, v/v) against the activities of seven CYP isoforms including CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6, CYP2E1, CYP3A4 and CPR were examined in human liver microsomes. To identify time-dependent inhibition, star fruit juice (2.5%, v/v) was preincubated with microsomes and a NADPH-generating system for 0-15 min, and then the extent of inhibition towards seven CYP isoforms were examined. RESULTS Star fruit juice (5.0%, v/v) was found to inhibit all the activities of CYP isoforms tested by more than 70%. Based on the half inhibition values (%, v/v), the inhibitory effects towards different CYP isoforms were in the following order: CYP2A6 (0.9) > CYP1A2 (1.4) > CYP2D6 (1.6) > CYP2E1 (2.0) > CYP2C8 (2.2) > CYP2C9 (3.0) > CYP3A4 (3.2). Time-dependent inhibition was not observed towards any of the tested CYP isoforms. In addition, star fruit juice was found not to inhibit the activity of CPR. CONCLUSIONS Star fruit juice inhibited the seven CYP isoforms tested, with the strongest inhibitory effect against CYP2A6 and the least towards CYP3A4.

Chemotaxonomic study of medicinal Taxus species with fingerprint and multivariate analysis.

Species delimitation in Taxus has been controversial and it is very difficult to distinguish yew materials by their morphological characters. In this paper, a valid HPLC fingerprinting method coupled with multivariate analysis was used to define a framework for Taxus species identification and classification. Fingerprint-based similarity was employed for a chemotaxonomic study by hierarchical clustering analysis (HCA) and principal component analysis (PCA). Based on the PCA loadings, twelve chemical constituents were selected as chemotaxonomic markers which can be used to establish a more practical classification. Finally, eight studied species could be divided into six well-supported groups and most samples can be assigned to the correct species. Additionally, twelve markers were tentatively identified by LC/MS.

Inhibition of human cytochrome P450 enzymes 3A4 and 2D6 by β-carboline alkaloids, harmine derivatives.

β‐Carboline alkaloids are the main chemical constituents of the plant Peganum harmala, while they also could be formed endogenously and found in coffee, alcoholic beverages and tobacco. Considering the fact that the possibility of herb–drug interactions has recently received great attention worldwide, the aim of the current study was to assess the potential for the metabolism‐based drug–drug interactions arising from five β‐carboline alkaloids (harmine, harmaline, harmalol, harmol and harmane) from P. harmala in vitro. With microsome incubation assays and UPLC/HPLC methods, the inhibitions on human liver CYP3A4 and CYP2D6 enzymes by those β‐carboline alkaloids were studied kinetically. Harmine, harmol and harmane exhibited noncompetitive inhibition on the activity of CYP3A4 with Ki values of 16.76, 5.13 and 1.66 μm, respectively. These β‐carboline alkaloids were also found to be both substrates and inhibitors for CYP2D6. Harmaline, harmine and harmol showed typical competitive inhibition on the activity of CYP2D6 with Ki values of 20.69, 36.48 and 47.11 μm, respectively. The inhibition of the two major CYP enzymes by those β‐carboline alkaloids suggested that changes in the pharmacokinetics of co‐administered drugs were likely to have occurred. Therefore, caution should be exercised for possible drug interactions of medicinal plants containing those β‐carboline alkaloids and CYP substrates. Copyright

A rapid assay for angiotensin-converting enzyme activity using ultra-performance liquid chromatography-mass spectrometry

Angiotensin-converting enzyme (ACE) plays an important role in the renin-angiotensin system and ACE activity is usually assayed in vitro by monitoring the transformation from a substrate to the product catalyzed by ACE. A rapid and sensitive analysis method or ACE activity by quantifying simultaneously the substrate hippuryl-histidyl-leucine and its product hippuric acid using an ultra-performance liquid chromatography coupled with electrospray ionization-mass spectrometry (UPLC-MS) was first developed and applied to assay the inhibitory activities against ACE of several natural phenolic compounds. The established UPLC-MS method showed obvious advantages over the conventional HPLC analysis in shortened running time (3.5 min), lower limit of detection (5 pg) and limit of quantification (18 pg), and high selectivity aided by MS detection in selected ion monitoring (SIM) mode. Among the six natural products screened, five compounds, caffeic acid, caffeoyl acetate, ferulic acid, chlorogenic acid and resveratrol indicated potent in vitro ACE inhibitory activity with IC(50) values of 2.527 +/- 0.032, 3.129 +/- 0.016, 10.898 +/- 0.430, 15.076 +/- 1.211 and 6.359 +/- 0.086 mm, respectively. A structure-activity relationship estimation suggested that the number and the situation of the hydroxyls on the benzene rings and the acrylic acid groups may play the most predominant role in their ACE inhibitory activity.

Taxane's Substituents at C3′ Affect Its Regioselective Metabolism: Different in Vitro Metabolism of Cephalomannine and Paclitaxel

To investigate how taxanes substituents at C3′ affect its metabolism, we compared the metabolism of cephalomannine and paclitaxel, a pair of analogs that differ slightly at the C3′ position. After cephalomannine was incubated with human liver microsomes in an NADPH-generating system, two monohydroxylated metabolites (M1 and M2) were detected by liquid chromatography/tandem mass spectrometry. C4″ (M1) and C6α (M2) were proposed as the possible hydroxylation sites, and the structure of M1 was confirmed by 1H NMR. Chemical inhibition studies and assays with recombinant human cytochromes P450 (P450s) indicated that 4″-hydroxycephalomannine was generated predominantly by CYP3A4 and 6α-hydroxycephalomannine by CYP2C8. The overall biotransformation rate between paclitaxel and cephalomannine differed slightly (184 vs. 145 pmol/min/mg), but the average ratio of metabolites hydroxylated at the C13 side chain to C6α for paclitaxel and cephalomannine varied significantly (15:85 vs. 64:36) in five human liver samples. Compared with paclitaxel, the major hydroxylation site transferred from C6α to C4″, and the main metabolizing P450 changed from CYP2C8 to CYP3A4 for cephalomannine. In the incubation system with rat or minipig liver microsomes, only 4″-hydroxycephalomannine was detected, and its formation was inhibited by CYP3A inhibitors. Molecular docking by AutoDock suggested that cephalomannine adopted an orientation in favor of 4″-hydroxylation, whereas paclitaxel adopted an orientation favoring 3′-p-hydroxylation. Kinetic studies showed that CYP3A4 catalyzed cephalomannine more efficiently than paclitaxel due to an increased Vm. Our results demonstrate that relatively minor modification of taxane at C3′ has major consequence on the metabolism.

Identification of metabolites of adonifoline, a hepatotoxic pyrrolizidine alkaloid, by liquid chromatography/tandem and high‐resolution mass spectrometry

Hepatotoxic pyrrolizidine alkaloid (HPA)-containing plants have always been a threat to human and livestock health worldwide. Adonifoline, a main HPA in Senecio scandens Buch.-Ham. ex D. Don (Qianli guang), was used officially as an infusion in cases of oral and pharyngeal infections in China. In this study in vivo metabolism of adonifoline was studied for the first time by identifying the metabolites of adonifoline present in bile, urine and feces of rats using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS(n)) (ion trap) as well as liquid chromatography/electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS) (quadrupole-time of flight). In total 19 metabolites were identified and, among them, retronecine-N-oxides were confirmed by matching their fragmentation patterns with their fully characterized synthetic compounds. These metabolites are all involved in both phase I and phase II metabolic processes and the principal in vivo metabolism pathways of adonifoline were proposed.