• Mass Spectrometry Letters
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• 제9권1호
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• pp.30-36
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• 2018

A quantitation method for free amino acids in human serum was developed using a stepwise-dilution method and a bimodal cation exchange (CEX)/hydrophilic interaction liquid chromatography (HILIC)-tandem mass spectrometry system equipped with an electrospray ionization source (ESI/MS/MS). This method, which was validated using quality control samples, was optimized for enhanced selectivity and sensitivity. Dithiothreitol (DTT) was used as a reducing agent to prevent the oxidation of a serum sample ($50{\mu}L$), which was then subjected to stepwise dilution using 3, 30, and 90 volumes of acetonitrile containing 0.1% formic acid. Chromatographic separation was performed on an Imtakt Intrada Amino Acid column ($50mm{\times}3mm$, $3{\mu}m$) in mixed mode packed with CEX and HILIC ligands embedded in the stationary phase. Underivatized free amino acids were eluted and separated within 10 min. As a result of the validation, the precision and accuracy for the inter- and intraday assays were determined as 2.11-11.51% and 92.82-109.40%, respectively. The lowest limit of quantification (LLOQ) was $0.5-4.0{\mu}g/mL$ and the matrix effect was 80.22-115.93%. The proposed method was successfully applied to the quantitative analysis of free amino acids in human serum.

• 분석과학
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• 제36권6호
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• pp.281-290
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• 2023

Zidovudine is an antiretroviral agent prescribed for the prevention and treatment of human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). It is typically recommended to be used in combination with other antiretroviral drugs. Zidovudine has the potential to generate N-nitrosodimethylamine (NDMA) in the presence of dimethylamine and nitrite salt under acidic reaction conditions during the drug manufacturing process. NDMA is a potent human carcinogen that may be detected in drug substances or drug products. An analytical method was developed to determine NDMA in pharmaceuticals including zidovudine using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The analysis involved reversed-phase chromatography on a Kinetex F5 column with a mobile phase comprising water-acetonitrile mixtures. The detection of positively charged ions was conducted using atmospheric pressure chemical ionization (APCI). The calibration curve demonstrated excellent linearity (r = 0.9997) across the range of 1-50 ng/mL with a highly sensitive limit of detection (LOD) at 0.3 ng/mL. The developed method underwent thorough validation for specificity, linearity, accuracy, precision, robustness, and system suitability. This sensitive and specific analytical method was applied for detecting NDMA in zidovudine drug substance and its formulation currently available in the market, indicating its suitability for drug quality management purposes.

• BMB Reports
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• 제43권11호
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• pp.761-765
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• 2010

Salivary testosterone levels in Korean adults were quantitatively measured for the first time by liquid chromatography-electrospray-tandem mass spectrometry (LC ESI MS/MS). Salivary testosterone was separated on a multiple reaction monitoring (MRM) chromatogram within 7 min. The LC ESI MS/MS assay was validated over the linearity range of 0.01-2.00 ng/ml (r=0.99987) using testosterone-$d_3$ as an internal standard. The lower limit of quantification (LOQ) was 0.01 ng/ml. The intra- and inter-assay precisions were 1.54% to 4.09% and 0.96% to 4.29%, respectively. The mean recovery was 93.32% (range 88.43-98.05%). The validated assay was then applied to measure the salivary testosterone levels of Korean adults. In men, the salivary testosterone level collected between 9：00-11：00 am was approximately 2.8 times higher than that in women (P < 0.0001). Salivary testosterone levels in both sexes negatively correlated with age. The present assay would also be useful in measuring salivary testosterone levels in clinical laboratories.

• Mass Spectrometry Letters
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• 제12권1호
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• pp.21-25
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• 2021

We aimed to develop and validate a sensitive analytical method of nannozinone A, active metabolite of Nannochelins A extracted from the Myxobacterium Nannocytis pusilla, in mouse plasma using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Mouse plasma samples containing nannozinone A and 13C-caffeine (internal standard) were extracted using a liquid-liquid extraction (LLE) method with methyl tert-butyl ether. Standard calibration curves were linear in the concentration range of 1 - 1000 ng/mL (r2 > 0.998) with the inter- and intra-day accuracy and precision results less than 15%. LLE method gave results in the high and reproducible extraction recovery in the range of 78.00-81.08% with limited matrix effect in the range of 70.56-96.49%. The pharmacokinetics of nannozinone A after intravenous injection (5 mg/kg) and oral administration (30 mg/kg) of nannozinone A were investigated using the validated LC-MS/MS analysis of nannozinone A. The absolute oral bioavailability of nannozinone A was 8.82%. Plasma concentration of nannozinone A after the intravenous injection sharply decreased for 4 h but plasma concentration of orally administered nannozinone A showed fast distribution and slow elimination for 24 h. In conclusion, we successfully applied this newly developed sensitive LC-MS/MS analytical method of nannozinone A to the pharmacokinetic evaluation of this compound. This method can be useful for further studies on the pharmacokinetic optimization and evaluating the druggability of nannozinone A including its efficacy and toxicity.

• Mass Spectrometry Letters
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• 제2권3호
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• pp.65-68
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• 2011

The effects of column length and particle size on the efficiency of separation and characterization of phospholipids (PLs) are investigated using nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS). Since PLs are associated with cell proliferation, apoptosis, and signal transduction, it is of increasing interests in lipidomics to establish reliable analytical methods for the qualitative and quantitative profiling of PLs related to biomarker development in adult diseases. Due to the complexity of PLs, the preliminary separation of PLs is necessary prior to MS analysis. In this study, length of capillary column and the particle size of reversed phase ($C_{18}$) packing materials are varied to find a reliable condition for the high speed and high resolution separation using 8 PL standard mixtures. From experiments, it was found that a capillary column of nLC-ESI-MS-MS analysis for PL mixtures can be minimized to a 5 cm long pulled tip column packed with 3 ${\mu}m$ $C_{18}$ particles without losing resolution.

• Mass Spectrometry Letters
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• 제11권4호
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• pp.113-117
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• 2020

Cytochrome P450 2J2 (CYP2J2) is a member of the cytochrome P450 superfamily, and is known to be arachidonic acid epoxygenase that mediates the formation of four bioactive regioisomers of epoxyeicosatrienoic acids (EETs). CYP2J2 is also involved in the metabolism of drugs such as albendazole, astemizole, danazol, ebastine, and terfenadine. CYP2J2 is highly expressed in the heart and cancer tissues. In this study, the inhibitory potential of ten natural products against CYP2J2 activity was evaluated using human liver microsomes and tandem mass spectrometry. Among them, bilobetin, which is a kind of biflavonoid, exhibits a strong inhibitory effect against the CYP2J2-mediated astemizole O-demethylation (IC50 = 0.73 μM) and terfenadine hydroxylation (IC50 = 0.89 μM). This result suggests that bilobetin can be used as strong CYP2J2 inhibitor in drug metabolism study.

• Mass Spectrometry Letters
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• 제11권2호
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• pp.30-35
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• 2020

Schisandra chinensis is a traditional herbal medicine that is widely spread in Korea, Japan, and China. The fruits of S. chinensis Bailon, known as omija in Korea, have traditionally been used for the treatment of coughs, fatigues, and insomnia. Up to now, there have been several reports for the identification of major lignan compounds and their quantitation in S. chinensis extracts. To the best of our knowledge, however, there is no report on the analysis of lignans in omija wine and omija cheong (sugared omija or omija sugar syrup). In the present study, seven dibenzocyclooctadiene lignans (gomisin A, gomisin B, gomisin C, gomisin N, schisandrin, deoxyschisandrin, and wuweizisu C) in omija wine and omija cheong were analyzed and quantitated using liquid chromatography-tandem mass spectrometry. Among seven lignans, pharmacologically active gomisin A, schisandrin, and deoxyschisandrin, which are major components in fruits of S. chinensis, were the most abundant lignans in omija wine and cheong. The content of lignan in omija wine was in the order: schisandrin > gomisin A > deoxyschisandrin > gomisin N > gomisin B > gomisin C > wuweizisu C. The concentration of deoxyschisandrin and gomisin N in omija wine was approximately 2.0- and 6.0-fold higher than for omija cheong. Additionally, this study provided a systematic identification of lignans in omija wine and cheong and indicated that the omija wine and cheong might be of value for their dietary application.

• Mass Spectrometry Letters
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• 제10권1호
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• pp.18-26
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• 2019

We developed a bioanalytical method for simultaneous determination of nine NBOMe derivatives (25H-NBOMe, 25B-NBOMe, 25E-NBOMe, 25N-NBOMe, 25C-NBOH, 25I-NBOH, 25B-NBF, 25C-NBF, and 25I-NBF) in human plasma using liquid chromatography tandem mass spectrometry (LC-MS/MS). Human plasma samples were pre-treated using solid-phase extraction. Separation was achieved on a C18 column under gradient elution using a mobile phase containing 0.1% formic acid in acetonitrile and 0.1% formic acid in water at a flow rate of 0.3 mL/min. Mass detection was performed in the positive ion mode using multiple reaction monitoring. The calibration range was 1-100 ng/mL for all quantitative analytes, with a correlation coefficient greater than 0.99. The intra- and inter-day precision and accuracy varied from 0.85 to 6.92% and from 90.19 to 108.69%, respectively. The recovery ranged from 86.36 to 118.52%, and the matrix effects ranged from 27.09 to 99.72%. The stability was acceptable in various conditions. The LC-MS/MS method was validated for linearity, accuracy, precision, matrix effects, recovery and stability in accordance with the FDA guidance. The proposed method is suitable for reliable and robust routine screening and analysis of nine NBOMe derivatives in forensic field.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
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• pp.212.1-212.1
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• 2002

• Natural Product Sciences
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• 제23권2호
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• pp.84-91
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• 2017

This study proposes a sensitive and selective liquid chromatography-electrospray ionization tandem mass spectrometry method of efficiently assessing the quality of a traditional herbal medicine called Yeonggyechulgam-tang (YGCGT). The following compounds 1 - 11, namely, liquiritin apioside (1), liquiritin (2), liquiritigene (3), coumarin (4), cinnamic acid (5), cinnamaldehyde (6), glycyrrhizin (7), atractylenolide III (8), atractylenolide II (9), atractylenolide I (10), and pachymic acid (11) were separated on a UPLC BEH $C_{18}$ column ($2.1{\times}100mm$, $1.7{\mu}m$) at a column temperature of $45^{\circ}C$ eluted with a gradient condition of 0.1% (v/v) formic acid in distilled water and acetonitrile. The correlation coefficient of the calibration curve of the eleven constituents was ${\geq}0.9936$. The limits of detection and quantification of the compounds 1 - 11 were 0.06 - 4.73 ng/mL and 0.17-14.20 ng/mL, respectively. Using this analytical method, the compound 11 in lyophilized YGCGT decoction extract was not detected, while the compounds 1 - 10 were detected 0.13-166.43 mg/g.