Drug Metabolism

Drug metabolites arise from the metabolic reactions of drugs; the structure of metabolites is closely related to the type of metabolic reaction and the structural properties of the parent compound.

Following metabolic conversion within the body, drugs generally undergo only partial structural modifications relative to the parent drug; the structure of the parent drug typically remains largely unchanged. Consequently, metabolites often share similar characteristic ions in mass spectrometry with the parent drug. This enables the identification of metabolites, and, in conjunction with other fragmentation patterns, allows for reasonable inferences regarding their structure.

When analysing drug metabolites, it is also necessary to compare the ProC-TOF spectra of the metabolites with the MS spectra of the synthetic compounds; the chemical structure must ultimately be confirmed using nuclear magnetic resonance (NMR) spectra. Multi-stage mass spectrometry (MSn) can also be used to directly obtain structural information on both the parent molecule and the metabolites; in this case, there is no need to prepare pure metabolites, and biological samples require only simple pre-treatment.

In the analysis and detection of drug metabolites, mass spectrometry has become the primary analytical method due to its broad applicability and high sensitivity. However, as the background matrix of drug metabolites is relatively complex, direct mass spectrometry injection has a significant impact on the ionisation efficiency of drug metabolites; therefore, during the analysis of drug metabolites, ProC-TOF can be used in tandem with chromatographic techniques possessing strong separation capabilities, such as liquid chromatography and gas chromatography.

Mass spectrometry enables the rapid, precise and ultra-trace determination of blood constituents, addressing the challenges associated with plasma component analysis, such as low concentrations, numerous constituents, difficult separation and significant inter-individual variability.

The combination of ultra-high-performance liquid chromatography (UHPLC) and mass spectrometry for the analysis of drug metabolites allows the identification of the major chemical constituents of a drug and its parent compound in animals, thereby providing a foundation for the identification of active chemical substances within the drug.

Xinyao Biotechnology offers drug metabolite analysis services to clients. Its pharmacokinetics laboratory has obtained GLP certification from the CFDA, and experimental research adheres to the guidelines of the ICH, CFDA and FDA. The company can design and conduct in vivo and in vitro pharmacokinetic studies according to client requirements, providing a comprehensive suite of pharmacokinetic evaluation and optimisation services.

To identify the metabolites in plasma, urine and faeces following administration of ‘Damp-Heat Bi’ capsules to rats, researchers utilised a Waters C18 column (2.1 mm × 50 mm, 1.7 μm) at a column temperature of 40. The mobile phase consisted of a gradient elution of 0.1% formic acid in water followed by 0.1% formic acid in acetonitrile. Ultra-high-pressure liquid chromatography–time-of-flight mass spectrometry utilises an electrospray ionisation source with detection in both positive and negative ion modes.

Analysing the metabolites of a drug within an animal’s body can provide important information for further research into the drug’s metabolites and mechanism of action, and is therefore of great significance.

ProC-TOF-MS can be coupled with other analytical methods, such as chromatography and electrophoresis, thereby further expanding the scope of mass spectrometry applications. For example, researchers have utilised ultra-high-pressure liquid chromatography–time-of-flight mass spectrometry to analyse drug metabolites in rats in order to identify the substances responsible for the drug’s therapeutic effects.