Development of a CD-MEKC method for investigating the metabolism of tamoxifen by flavin-containing monooxygenases and the inhibitory effects of methimazole, nicotine and DMXAA

Yeniceli D., Deng X., Adams E., Dogrukol-Ak D., Van Schepdael A.

ELECTROPHORESIS, no.3, pp.463-470, 2013 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Publication Date: 2013
  • Doi Number: 10.1002/elps.201200356
  • Journal Name: ELECTROPHORESIS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.463-470
  • Keywords: CD-MEKC, Enzyme inhibition, Flavin-containing monooxygenase, Tamoxifen, 5,6-DIMETHYLXANTHENONE-4-ACETIC ACID DMXAA, MICELLAR ELECTROKINETIC CHROMATOGRAPHY, NONAQUEOUS CAPILLARY-ELECTROPHORESIS, DRUG-DRUG INTERACTION, GENETIC POLYMORPHISMS, DIETARY INDOLES, N-OXIDATION, IN-VITRO, FMO3, ELECTROCHROMATOGRAPHY
  • Anadolu University Affiliated: Yes

Abstract

A selective and low-cost CD-MEKC method under acidic conditions was developed for investigating the N-oxygenation of tamoxifen (TAM) by flavin-containing monooxygenases (FMOs). The inhibitory effects of methimazole (MMI), nicotine and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) on the given FMO reaction were also evaluated; 100 mM phosphate buffer (pH 8.6) was used for performing the enzymatic reaction and the separation of TAM and its metabolite tamoxifen N-oxide (TNO) was obtained with a BGE consisting of 100 mM phosphoric acid solution adjusted to pH 2.5 with triethanolamine containing 50 mM sodium taurodeoxycholate, 20 mM carboxymethyl beta-CD and 20% ACN. The proposed method was applied for the kinetics study of FMO1 using TAM as a substrate probe. A MichaelisMenten constant (Km) of 164.1 mu M was estimated from the corrected peak area of the product, TNO. The calculated value of the maximum reaction velocity (Vmax) was 3.61 mu mol/min/mu mol FMO1; 50% inhibitory concentration and inhibition constant (Ki) of MMI, the most common alternate substrate FMO inhibitor, were evaluated and the inhibitory effects of two other important FMO substrates, nicotine and DMXAA, a novel anti-tumour agent, were investigated.