Affiliations 

  • 1 Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia
  • 2 Usains Biomics Laboratory Testing Services Sdn. Bhd., Universiti Sains Malaysia, Minden 11800, Penang, Malaysia
  • 3 Institute for Research in Molecular Medicine, Universiti Sains Malaysia, Minden 11800, Penang, Malaysia. Electronic address: mervynliew@usm.my
  • 4 Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia. Electronic address: niksoriani@usm.my
PMID: 32416571 DOI: 10.1016/j.jchromb.2020.122148

Abstract

Screening for potential drug-drug interaction (DDI) or herb-drug interaction (HDI) using in vitro cytochrome P450 inhibition (IVCI) assays requires robust analytical methods with high sensitivity and reproducibility. Utilization of liquid chromatography-mass spectrometry (LC-MS) for analyte quantification is often hampered by the presence of non-volatile IVCI sample buffer constituents that often results in ion suppression. In this study, to enable screening of drug interactions involving tamoxifen (TAM) metabolism using IVCI-LC-MS/MS, a liquid-liquid extraction (LLE) method was developed and optimized for sample clean-up. Utilization of chloroform as extraction solvent and adjustment of sample pH to 11 was found to result in satisfactory recovery (>70%) and low ion suppression (<19%). A LC-MS/MS method was subsequently developed and validated for simultaneous quantification of major TAM metabolites, such as N-desmethyltamoxifen (NDT), endoxifen (EDF) and 4-hydroxytamoxifen (HTF) to enable IVCI sample analysis. Satisfactory separation of E-/Z-isomers of endoxifen with peak resolution (Rs) of 1.9 was achieved. Accuracy and precision of the method was verified within the linear range of 0-50 ng/mL for NDT, 0-25 ng/mL for HTF and 0-25 ng/mL for EDF (E/Z isomers). Inhibitory potency (IC50, Ki and mode of inhibition) of known CYP inhibitors and Strobilanthes crispus extract was then evaluated using the validated method. In summary, the results demonstrated applicability of the developed LLE and validated LC-MS/MS method for in vitro screening of DDI and HDI involving TAM metabolism.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.