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Characterization of Phyto-Constituents
Published in Rohit Dutt, Anil K. Sharma, Raj K. Keservani, Vandana Garg, Promising Drug Molecules of Natural Origin, 2020
Himangini, Faizana Fayaz, Anjali
The hyphenated technique has become revolutionary change in the identification, characterization, and quantization of herbal drugs. One of the best methods developed by combining liquid chromatography and infrared spectroscopy is known as LC-IR. LC-IR predicts the peaks of functional groups in mid-IR region which makes structure elucidation helpful. But detection technique of IR is much slower than MS or NMR. Two big tools in series may be used in these techniques are flow cell method and solvent elimination methods. Liquid chromatography-mass spectrometry (LC-MS) combines liquid chromatography with the capabilities of MS. LC-MS has very high sensitivity and selectivity for identification of mixture of separated components.
Mass Spectrometric Analysis
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
By 1960, mass spectrometry had evolved as an important tool for structure elucidation in organic chemistry. The inherent sensitivity of mass spectrometry, combined with its potential to provide molecular weight and structural information, has made it invaluable in identification studies, particularly where trace quantities are involved. Since 1961, when Henneberg used selected ion monitoring to study hydrocarbons eluting from a gas chromoto-graphic column [2], mass spectrometry has been widely used as a quantitative tool. When interfaced with a chromatographic unit, the mass spectrometer becomes a universal detector with high sensitivity and specificity. Antibiotic research has relied less on mass spectrometry than most classes of organic compounds. This is primarily due to the high molecular weights, polarity, and low volatility of many antibiotics. Compounds with these attributes are less amenable to analysis using conventional methods of sample introduction and ionization. Despite these problems, mass spectrometry has made significant contributions to the analysis of antibiotics as shown by the literature; major contributions up to 1977 have been reviewed [3,4]. Newer methods of ionization available today are capable of extracting useful structural information from nearly all antibiotics.
The Role of Epigenetics in Breast Cancer: Implications for Diagnosis, Prognosis, and Treatment
Published in Brian Leyland-Jones, Pharmacogenetics of Breast Cancer, 2020
Amy M. Dworkin, Tim H.-M. Huang, Amanda E. Toland
MassARRAY and pyrosequencing, two additional methods of detecting methylation, are currently being developed for use in clinical settings. MassARRAY is a highly sensitive technique that uses base-specific cleavage and matrix-assisted laser desorption/ionization time-to-flight mass spectrometry (MALDI-TOF MS). It is capable of detecting DNA methylation levels as low as 5%. It is suitable for testing methylation patterns on various sources, including archival tissues and laser capture microdissected specimens (1). Pyrosequencing is a locus-specific quantitative method that utilizes the detection of pyrophosphate, which is liberated from incorporated nucleotides by DNA polymerase during strand elongation. Free pyrophosphates are converted to adenosine triphosphate (ATP), which provides energy for the oxidation of luciferin to then generate light. Nucleotides are added sequentially to enable base calling. Pyrosequencing has two major advantages over MS-PCR. First, the data are actual nucleotide sequences rather than fluorescence data. Second, pyrosequencing can detect partially methylated sequences that are outside of the priming sites (30).
Steroid hormone levels in postmenopausal hysterectomised women with and without ovarian conservation: the continuous endocrine function of the ovaries
Published in Journal of Obstetrics and Gynaecology, 2023
Elsa Nunes, Eugenia Gallardo, Sara Morgado-Nunes, José Fonseca-Moutinho
Although consistent with our results, these studies used immunoassays for steroid measurements. However, concerns about specificity of these methods when steroid levels are low have led to implementation of MS-based techniques as the gold standard methodology for steroid hormone analysis. Mass spectrometry offers a unique identification profile of each of the study analytes, eliminating interferences and thus allowing greater sensitivity and specificity (Andrew and Homer 2020). In fact there are different published works about the determination of these compounds using GC-MS/MS (Hansen et al.2011, McDonald et al.2011, Caron et al.2015, Matysik and Schmitz 2015). In this work excellent limits of detection and quantitation were achieved (0.05 ng/mL for E2; 0.1 ng/mL for A and DHEA, and 0.5 ng/mL for T) using only 1 mL of sample.
Multifocal Serpiginoid Choroiditis Due to Mycobacterium Mageritense following Laparoscopic Hysterectomy in an Immunocompetent Host
Published in Ocular Immunology and Inflammation, 2023
Shrey Maheshwari, Shweta Parakh, Shrutanjoy M Das, Alok Ahuja, Shashi Nath Jha, Rupesh Agrawal, Vishali Gupta, Saurabh Luthra
MALDI-TOF MS, a novel technique for identification of microorganisms, is based on the following principle – in mass spectrometry, matrix-assisted laser desorption/ionization (MALDI) is an ionization technique that uses a laser energy absorbing matrix to create ions from large molecules with minimal fragmentation.34 MALDI methodology consists of a three-step process. First, the sample is mixed with a suitable matrix material and then applied to a metal plate. Second, a pulsed laser irradiates the sample, thereby triggering ablation and desorption of the sample and matrix material. Finally, the analyte molecules are ionized by being protonated or deprotonated in the hot plume of ablated gases, and then they can be accelerated into a Time of Flight Mass Spectrometer to analyse them.35
Untargeted metabolomics-assisted comparative cytochrome P450-dependent metabolism of fenbendazole in human and dog liver microsomes
Published in Xenobiotica, 2022
Young-Heun Jung, Dong-Cheol Lee, Jong Oh Kim, Ju-Hyun Kim
Advancements in strategies for mass spectrometry-based drug metabolism studies have evolved remarkably in recent decades (Wen and Zhu 2015). Recently, liquid chromatography–mass spectrometry (LC–MS)-based metabolomic techniques have been introduced and actively applied in drug metabolism studies (Chen et al. 2007; Meyer and Maurer 2012). The comparison of global mass spectral data between the control and in vitro or in vivo drug treatment groups enables the effective identification of drug metabolites (Kim et al. 2018a, 2018b). Multivariate analyses, such as principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA), are generally conjugated in the untargeted metabolomics approach for distinguishing between groups and for effective examination of the relative quantitative data of drug metabolites (Gromski et al. 2015; Worley and Powers 2013). Metabolomics is an excellent tool for species comparison studies of drug metabolism because of these characteristics (Kim et al. 2017, 2018c). Recently, untargeted metabolomics combined with feature-based molecular networking has become a strategy in drug metabolism studies, and the outcomes have revealed novel discoveries and insights (Le Dare et al. 2020; Quinn et al. 2017; Yu et al. 2022). Overall, the metabolomic approach is an efficient and unbiased tool for identifying drug metabolites and for metabolic comparisons between species.