Investigation of isomeric transformations of chlorogenic acid in buffers and biological matrixes by ultraperformance liquid chromatography coupled with hybrid quadrupole/ion mobility/orthogonal acceleration time-of-flight mass spectrometry.
ABSTRACT Ultraperformance liquid chromatography coupled with hybrid quadrupole/ion mobility/orthogonal acceleration time-of-flight (oa-TOF) mass spectrometry (UPLC-IM-MS) was used to study the isomeric transformations of trans-5-caffeoylquinic acid, an extremely active compound present in multiple vegetables, fruits, and beverages. The UPLC/oa-TOF MS results proved that in phosphate buffer (pH 7.4), plasma, or urine sample, trans-5-caffeoylquinic acid first isomerizes to trans-4-caffeoylquinic acid and then to trans-3-caffeoylquinic acid by intramolecular acyl migration. When exposed to UV light, trans-3-, -4-, and -5-caffeoylquinic acids undergo cis/trans isomerization to form cis isomers. The isomerization was solely dependent on the pH of the matrix, as well as the incubation temperature, and was independent of metabolic enzymes. UPLC-IM-MS results revealed that a reversible cis/trans isomerization of caffeoylquinic acids could also be induced by the electric field in an electrospray source. Thus, understanding the possible role of electric field-induced isomerization of caffeoylquinic acids may help lessen the confusion between gas phase phenomena and liquid state chemistry when applying IM-MS analysis. The comprehensive understanding of caffeoylquinic acid isomerization transformations is crucial for the appropriate handling of samples and interpretation of experimental data.
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ABSTRACT: The need for rapid, sensitive and effective identification and quantitation of drugs and metabolites to accelerate drug discovery and development has given MS its central position in drug metabolism and pharmacokinetic research. This review attempts to orient the readers with respect to hybrid Q-TOF MS, which enables accurate mass measurement and generates information-rich datasets. The key properties of the Q-TOF MS system, including mass accuracy, resolution, scan speed and dynamic range, are herein discussed. Developments on tandem separation techniques (e.g., UHPLC(®) and ion mobility spectrometry), data acquisition and data-mining methods (e.g., mass defect, product/neutral loss, isotope pattern filters and background subtraction) that facilitate qualitative and quantitative analysis are then examined. The performance and versatility of LC-Q-TOF MS are thoroughly illustrated by its applications in metabolite identification and quantitative bioanalysis. Future perspectives are also discussed.Bioanalysis 05/2012; 4(8):937-59. DOI:10.4155/bio.12.43 · 3.03 Impact Factor
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ABSTRACT: 5-O-Caffeoylquinic acid (5-CQA) is one of the major bioactive ingredients in some Chinese herbal injections. Occasional anaphylaxis has been reported for these injections during their clinical use, possibly caused by reactive metabolites of 5-CQA. This study aimed at characterizing the bioactivation pathway(s) of 5-CQA and the metabolic enzyme(s) involved. After incubating 5-CQA with GSH and NADPH-supplemented human liver microsomes, two types of GSH conjugates were characterized: one was M1-1 from the 1,4-addition of GSH to ortho-benzoquinone intermediate; the other was M2-1 and M2-2 from the 1,4-addition of GSH directly to the α,β-unsaturated carbonyl group of the parent. The formation of M1-1 was cytochrome P450 (P450)-mediated, with 3A4 and 2E1 as the principal catalyzing enzymes, whereas the formation of M2-1 and M2-2 was independent of NADPH and could be accelerated by cytosolic glutathione transferase. In the presence of cumene hydroperoxide, M1-1 formation increased 6-fold, indicating that 5-CQA can also be bioactivated by P450 peroxidase under oxidizing conditions. Furthermore, M1-1 could be formed by myeloperoxidase in activated human leukocytes, implying that 5-CQA bioactivation is more likely to occur under inflammatory conditions. This finding was supported by experiments on lipopolysaccharide-induced inflammatory rats, where a greater amount of M1-1 was detected. In S-adenosyl methionine- and GSH-supplemented human S9 incubations, M1-1 formation decreased by 80% but increased after tolcapone-inhibited catechol-O-methyltransferase (COMT) activity. In summary, the high reactivities of the ortho-benzoquinone metabolite and α,β-unsaturated carbonyl group of 5-CQA to nucleophiles have been demonstrated. Different pathological situations and COMT activities in patients may alter the bioactivation extent of 5-CQA.Drug metabolism and disposition: the biological fate of chemicals 05/2012; 40(8):1628-40. DOI:10.1124/dmd.112.045641 · 3.33 Impact Factor
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ABSTRACT: Three isomers of mono-caffeoylquinic acid, specifically, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid and 5-O-caffeoylquinic acid, were successfully isolated from a crude extract of tobacco (Nicotiana tobaccum L.) wastes using continuous resin-based pre-separation and preparative high-performance liquid chromatography (HPLC). The extract of tobacco wastes was continuously pre-separated by resin-based columns packed with D101 and XAD-4, yielding total mono-caffeoylquinic acids with a purity of 67.71% and a recovery rate of 90.06%. Variables affecting resolution and productivity of three mono-caffeoylquinic acid isomers in preparative HPLC (i.e. mobile-phase composition, pH, flow rate and loading amount) were studied. The optimum chromatographic conditions were determined to be a mobile phase consisting of 15% (v/v) methanol and aqueous acetic acid with a pH of 4.5, a flow rate of 4.0 mL/min, a loading amount of 4 mL and a detection wavelength of 360 nm. From 300 mg of loading sample, 56.3 mg of 3-O-caffeoylquinic acid, 92.8 mg of 5-O-caffeoylquinic acid and 73.1 mg of 4-O-caffeoylquinic acid were obtained in a single run, each with a purity of over 98% by HPLC. The structures of the isolated compounds were elucidated by ESI-MS, (1) H-NMR and (13) C-NMR spectral data.Journal of Separation Science 06/2012; 35(10-11):1379-87. DOI:10.1002/jssc.201101055 · 2.59 Impact Factor