• Proceedings of the PSK Conference
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• 2003.04a
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• pp.133.2-134
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• 2003

2-Methylaminoethyl-4, 4'-dimethoxy-5, 5', 6.6 -dimethylenedioxybiphenyl-2'-carboxy-2-carboxylate (DDB-S), a synthetic compound derived from DDB, has been known to protect liver against carbon tetrachloride-, D-galactosamine-, thioacetamide-, and prednisolone-induced hepatic injury in experimental animals. The metabolism of this compound has been assessed in rats by using liquid chromatography/electrospray tandem mass spectrometry (LC/MS/MS) method. (omitted)

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.902-910
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• 2012

The photodegradation characteristics of 30 pharmaceuticals were investigated by batch experiments using Ultraviolet (UV) reactor. The investigated pharmaceuticals include antibiotics, analgesics and antiarrhythmic agents etc. Tested water was prepared by simultaneously spiking 30 pharmaceuticals into pure water, and each experiment was conducted using 3 types of UV lamps. As a result, batch experiments showed that reactions of all the investigated pharmaceuticals followed pseudo-first order reaction regardless of the applied UV lamps. Among the pharmaceuticals, Cyclophosphamide, 2-Quinoxaline carboxylic acid and Clarithromycin proved to be the most UV-resistant compounds. Contrarily, Ceftiofur, Diclofenac and Ketoprofen were easily degraded by all the UV lamps. Dissolved organic carbon (DOC) concentration hardly changed although the concentration of the pharmaceuticals concentration gradually decreased with time, indicating that the degradation of parent pharmaceuticals may produce their intermediates during UV treatment.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.213.1-213.1
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• 2003

Sphingolipids and their metabolites are highly bioactive molecules that affect various cellular functions including differentiation, cellular senescence, apoptosis, and proliferation when added exogenously, or elevated intracellularly by turnover of complex sphingolipids or synthesis from de novo pathway. We are investigating the relationship of sphingolipids cycle in apoptosis early events. A new column liquid chromatography- tandem mass spectrometry (LC/MS/MS) in combination with multiple reaction monitoring (MRM) method was developed for the rapid, simultaneous and quantitative determination of unambiguous detecting sphingolipids in cells. (omitted)

• Analytical Science and Technology
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• v.36 no.1
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• pp.12-21
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• 2023

Protein glycation is vital to aging and disease. However, glycated proteins are low-abundant in plasma, rendering them difficult to identify using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Many studies have analyzed glycated peptides with high reproducibility. Here, glycated peptides in human serum were analyzed by LC-MS/MS using data-dependent acquisition (DDA) and parallel reaction monitoring (PRM). Boronic acid (BA) enrichment of in vitro glycated human serum peptides was performed. BA enrichment identified the most glycated peptides, and the glycated peptides of the more diversified proteins, excluding albumin, were analyzed. In PRM, glycated albumin PSMs were the most common, and this method exhibited the best reproducibility. The results of this study could help compare methods for identifying glycation-related biomarkers.

• Molecules and Cells
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• v.21 no.3
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• pp.381-388
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• 2006

Heat shock proteins (Hsp) 70 are a ubiquitous family of molecular chaperones involved in many cellular processes. A yeast strain, ssa1/2, with two functionally redundant cytosolic Hsp70s (SSA1 and SSA2) deleted shows thermotolerance comparable to mildly heatshocked wild type yeast, as well as increased protein synthesis and ubiquitin-proteasome protein degradation. Since mRNA abundance does not always correlate well with protein expression levels it is essential to study proteins directly. We used a gel-based approach to identify stress-responsive proteins in the ssa1/2 mutant and identified 43 differentially expressed spots. These were trypsin-digested and analyzed by nano electrospray ionization liquid chromatography tandem mass spectrometry (nESI-LC-MS/MS). A total of 22 non-redundant proteins were identified, 11 of which were confirmed by N-terminal sequencing. Nine proteins, most of which were up-regulated (2-fold or more) in the ssa1/2 mutant, proved to be stress-inducible proteins such as molecular chaperones and anti-oxidant proteins, or proteins related to carbohydrate metabolism. Interestingly, a translational factor Hyp2p up-regulated in the mutant was also found to be highly phosphorylated. These results indicate that the cytosolic Hsp70s, Ssa1p and Ssa2p, regulate an abundance of proteins mainly involved in stress responses and protein synthesis.

• Mass Spectrometry Letters
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• v.5 no.3
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• pp.84-88
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• 2014

Licoricidin isolated from Glycyrrhiza uralensis is known to have anticancer, anti-nephritic, anti-Helicobacter pylori, and antibacterial effects. In this study, a cocktail probe assay and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to investigate the modulating effect of licoricidin on cytochrome P450 (CYP) enzymes in human liver microsomes. When licoricidin was incubated at $0-25{\mu}m$ with CYP probes for 60 min at $37^{\circ}C$, it showed potent inhibitory effects on CYP2B6-catalyzed bupropion hydroxylation and CYP2C9-catalyzed diclofenac 4'-hydroxylation with half maximal inhibitory concentration ($IC_{50}$) values of 3.4 and $4.0{\mu}m$, respectively. The inhibition mode of licoricidin was revealed as competitive, dose-dependent, and non-time-dependent, and following the pattern of Lineweaver-Burk plots. The inhibitory effect of licoricidin has been confirmed in human recombinant cDNA-expressed CYP2B6 and 2C9 with $IC_{50}$ values of 4.5 and $0.73{\mu}m$, respectively. In conclusion, this study has shown the potent inhibitory effect of licoricidin on CYP2B6 and CYP2C9 activity could be important for predicting potential herb-drug interactions with substrates that mainly undergo CYP2B- and CYP2C9-mediated metabolism.

• Mass Spectrometry Letters
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• v.12 no.1
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• pp.16-20
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• 2021

We aimed to compare the content of ginsenosides and the pharmacokinetics after the oral administration of four different ginseng products at a dose of 1 g/kg in rats. The four different ginseng products were fresh ginseng extract, red ginseng extract, white ginseng extract, and saponin enriched white ginseng extract prepared from the radix of Panax ginseng C.A. Meyer. The ginsenoside concentrations in the ginseng product and the rat plasma samples were determined using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Eight or nine ginsenosides of the 15 tested ginsenosides were detected; however, the content and total ginsenosides varied depending on the preparation method. Moreover, the content of triglycosylated ginsenosides was higher than that of diglycosylated ginsenosides, and deglycosylated ginsenosides were not present in any preparation. After the single oral administrations of four different ginseng products in rats, only four ginsenosides, such as 20(S)-ginsenosides Rb1 (GRb1), GRb2, GRc, and GRd, were detected in the rat plasma samples among the 15 ginsenosides tested. The plasma concentrations of GRb1, GRb2, GRc, and GRd were different depends on the preparation method but pharmacokinetic features of the four ginseng products were similar. In conclusion, a good correlation between the area under the concentration curve and the content of GRb1, GRb2, and GRc, but not GRd, in the ginseng products was identified and it might be the result of their higher content and intestinal biotransformation of the ginseng product.

• Journal of Ginseng Research
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• v.48 no.4
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• pp.366-372
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• 2024

Background: The biological activity and pharmacological effects of rare ginsenosides have been proven to be superior to those of the major ginsenosides, but they are rarely found in ginseng. Methods: Ginsenoside Rb1 was chemically transformed with the involvement of methanol molecules by a synthesized heterogeneous catalyst 12-HPW@MeSi, which was obtained by the immobilization of 12-phosphotungstic acid on a mesoporous silica framework. High-performance liquid chromatography coupled with mass spectrometry was used to identify the transformation products. Results: A total of 18 transformation products were obtained and identified. Methanol was found to be involved in the formation of 8 products formed by the addition of methanol molecules to the C-24 (25), C-20 (21) or C-20 (22) double bonds of the aglycone. The transformation pathways of ginsenoside Rb1 involved deglycosylation, addition, elimination, cycloaddition, and epimerization reactions. These pathways could be elucidated in terms of the stability of the generated carbenium ion. In addition, 12-HPW@MeSi was able to maintain a 60.5% conversion rate of Rb1 after 5 cycles. Conclusion: Tandem and high-resolution mass spectrometry analysis allowed rapid and accurate identification of the transformation products through the characteristic fragment ions and neutral loss. Rare ginsenosides with methoxyl groups grafted at the C-25 and C-20 positions were obtained for the first time by chemical transformation using the composite catalyst 12-HPW@MeSi, which also enabled cyclic heterogeneous transformation and facile centrifugal separation of ginsenosides. This work provides an efficient and recyclable strategy for the preparation of rare ginsenosides with the involvement of organic molecules.

• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1216-1223
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• 2016

The aim of this study was to isolate antioxidant peptides from an enzymatic hydrolysate of Spirulina platensis. A novel antioxidant peptide was obtained by ultrafiltration, gel filtration chromatography, and reverse-phase high-performance liquid chromatography, with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay used to measure the antioxidant activity, and the sequence was determined to be Pro-Asn-Asn (343.15 Da) by electrospray ionization tandem mass spectrometry. This peptide was synthesized to confirm its antioxidant properties, and it exhibited 81.44 ± 0.43% DPPH scavenging activity at 100 μg/ml, which was similar to that of glutathione (82.63 ± 0.56%). Furthermore, the superoxide anion and hydroxyl free-radical scavenging activities and the SOD activity of the peptide were 47.84 ± 0.49%, 54.01 ± 0.82%, and 12.55 ± 0.75%, respectively, at 10 mg/ml. These results indicate that S. platensis is a good source of antioxidant peptides, and that its hydrolysate may have important applications in the pharmaceutical and food industries.

• Journal of fish pathology
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• v.34 no.1
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• pp.71-80
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• 2021

Cephalexin, a semi-synthetic cephalosporin antibiotic, has long been used in fish aquaculture in various countries under legal authorization. The drug is thus widely available for use in other aquatic species except fishes like the crustacean whiteleg shrimp. This study aims to develop a sensitive method for laboratory residue studies to adopt in withdrawal period determinations. Through repeated trials from the existing methods developed for other food animal tissues, it was possible to achieve a sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. The results showed that at a concentration of 0.1 mg/kg, the recovery rate was 81.79%, and C.V. value was 8.2%, which meet the recovery rate and C.V. recommended by Codex guideline. After satisfactory validation of analytical procedures, applicability to the shrimp tissue was confirmed in experimentally cephalexin-treated whiteleg shrimp. As a result, most muscle samples were detected below the limit of quantification (0.05 mg/kg) after day 3, and most hepatopancreas samples were detected below the limit of quantification after day 14. In particular, the limit of quantification 0.05 ppm with the presently developed method suggests sufficient sensitive over the current legal maximum residue limit of 0.2 mg/kg set for fishes.