Mendeleev
Communications
Mendeleev Commun., 2020, 30, 220–222
TiO -modified MALDI target for in vitro modeling
2
of the oxidative biotransformation of diclofenac
a,b
c
a
Alexander Yu. Gorbunov,* Konstantin A. Krasnov, Alexander A. Bardin,
b,c
a
b,c
Olga A. Keltsieva, Vladimir N. Babakov and Ekaterina P. Podolskaya
a
b
c
Research Institute of Hygiene, Occupational Pathology and Human Ecology, 188663 St. Petersburg,
Russian Federation. E-mail: gorbunov-a@inbox.ru
Institute of Analytical Instrumentation, Russian Academy of Sciences, 190103 St. Petersburg,
Russian Federation
Institute of Toxicology, 192019 St. Petersburg, Russian Federation
DOI: 10.1016/j.mencom.2020.03.030
The UV-induced photocatalytic oxidation in the presence of
TiO2 nanoparticles (UV/TiO -PCO) is a more adequate
2
approach than electrochemical oxidation to simulate the
oxidative metabolism of diclofenac based on the comparative
analysis of oxidation products using high-resolution tandem
mass spectrometry. A simple and fast high-throughput
technique is proposed for modeling the oxidative metabolism,
hv
which involves UV/TiO -PCO performed directly on a
2
MALDI target and subsequent analysis by matrix-assisted
laser desorption/ionization mass spectrometry. The ranges
and yields of diclofenac oxidation products obtained by the
MALDI target plate
TiO2 DCl
ꢀꢁꢂ
conventional bulk UV/TiO -PCO and the proposed on-target
2
version are in excellent agreement.
Keywords: titanium dioxide, photocatalysis, photooxidation, drug metabolites, MALDI MS.
The metabolic conversion of xenobiotics into reactive products,
commonly referred to as bioactivation, is a major determinant of
their unpredicted biological activities including adverse side
effects. An analysis of the oxidative metabolism of xenobiotics is
important for drug development as it allows one to predict the
potential toxicity of novel pharmacological entities.1
on-target UV/TiO -PCO followed by the direct analysis of
2
oxidation products by matrix-assisted laser desorption/ionization
mass spectrometry (MALDI MS). This technique involves the
UV irradiation of a microvolume of analyte solution on a TiO2-
covered sample spot of a MALDI target, which serves as a
common site for photocatalytic oxidation and MALDI (see
Since biotransformation analysis with the use of biological
systems (liver microsomes, hepatocytic cell lines, and laboratory
animals) is laborious and time-consuming, fast and simple
methods for the nonenzymatic in vitro modeling of oxidative
Online Supplementary Materials). The use of a TiO layer
excludes the need for organic MALDI matrices.
2
Diclofenac (1), a non-steroidal anti-inflammatory drug whose
1
0
photocatalytic degradation
bioactivation
and in vivo oxidative
2
13,14
metabolism have been developed. Although electrochemical
are well known, was used as a test compound.
oxidation is the most popular method, the UV-induced
The oxidation products of diclofenac obtained using
electrochemical oxidation,conventional photocatalytic oxidation
and the suggested on-target photocatalytic oxidation† were
analyzed and compared. The analysis of electrochemical
photocatalytic oxidation in the presence of TiO nanoparticles
2
(
UV/TiO -PCO), which is widely used for the degradation of
2
3–5
pharmaceuticals and other pollutants in wastewater, is highly
promising for the comprehensive simulation of oxidative
metabolism.
oxidation and UV/TiO -PCO products was performed using
2
6
–8
†
HPLC-MS/MS on a high-resolution FT-ICR instrument. On the
The oxidation products obtained by UV/TiO -PCO are
basis of retention times and accurate mass measurements, the
molecular structures of oxidation products were proposed
(Scheme 1, Table 1 and Online Supplementary Materials).
Diclofenac was detected as the [M – H]⁻ ion (m/z 294), and the
base peak at m/z 310 was assigned to +O products identified as
2
typically identified by mass spectrometry (MS) often coupled to
high performance liquid chromatography (HPLC), which
introduces pretreatment steps and thus slows down the overall
analytical workflow. Therefore, the development of a fast and
simple technique of UV/TiO -PCO coupled to MS for high-
monohydroxylated
derivatives
(OH-diclofenac)
2a–c
2
throughput analysis of oxidation products in multiple samples is
of considerable current importance. Several sophisticated
(Scheme 1). As minor oxidation products, polyhydroxy (2d–f,)
decarboxylated (2g–j), and quinone imine (3a–d) derivatives were
detected, as well as deep destruction products 4a–f. Compounds
approaches for the online coupling of UV/TiO -PCO to
2
electrospray ionization (ESI) MS have been suggested; they
require special instrumentation and additional materials.
Here, we present a simple, rapid, and cost-effective technique for
9
–11
†
For oxidation and analysis procedures, see Online Supplementary
Materials.
©
2020 Mendeleev Communications. Published by ELSEVIER B.V.
–
220 –
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
Babakov, Vladimir N.
