Properties of a furan ring-opening reaction in aqueous micellar solutions for selective sensing of mesalazine

Article abstract of DOI:10.1016/j.saa.2021.119846

A novel and efficient non-azo formation based method was developed for trace sensing of mesalazine (MES), a pharmaceutical aromatic amine. MES was simply coupled with a Meldrum's activated furan (MAF) reagent via a furan ring opening reaction to form a colored product. The intense purple colored solution was detected at 575 nm. The reaction of MES with MAF was monitored by employing ¹H NMR spectroscopy and mass spectrometry. In addition, density functional theory (DFT) was applied to optimize the structure of the colored product and its λ_max (the wavelength of maximum absorbance) in dimethyl sulfoxide and water. The colored product was considered in three possible structures, and the most possible structures in dimethyl sulfoxide and in water were identified by employing the DFT calculations. Both of the most possible structures indicated only a local excitation in their λ_max and no charge transfer was observed. However, one of the structures in dimethyl sulfoxide presented charge transfer properties occurring through N–C[dbnd]C–C moiety. A univariate optimization method was also used to attain the optimum condition for analysis. In addition, the dependence of the analytical response on the three main affecting parameters (reaction time (X₁), Triton X-100 concentration (X₂) and MAF concentration (X₃)) was identified by employing a central composite design (CCD) approach. The CCD study showed that the analytical response depends complexly on the parameters. Beer's law was obeyed within the range of 0.06–9.30 μg mL^?1 of MES (155 fold linearity) at 575 nm, under the optimum condition introduced by the CCD approach. Also, the limit of detection was obtained 0.04 μg mL^?1 of MES. The method showed precision (as relative standard deviation) and accuracy (as recovery) within the ranges of 0.6–3.2 % and 96.3–100.8%, respectively. Various organic and inorganic species, amino-pharmaceuticals, and amino acids were tested to evaluate the selectivity of the method. The selectivity of the analytical method was satisfactory. The method was successfully applied for detection of MES in various water matrices and pharmaceutical tablets.

Full text of DOI:10.1016/j.saa.2021.119846

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Properties of a furan ring-opening reaction in aqueous micellar solutions
for selective sensing of mesalazine
⇑
Leila Sabahi-Agabager, Habibollah Eskandari , Farough Nasiri, Amir Nasser Shamkhali,
Somayyeh Baghi Sefidan
Department of Chemistry, Faculty of Basic Sciences, University of Mohaghegh Ardabili, Ardabil 56199-11367, Iran
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Mesalazine is determined by
spectrophotometry using a furan
ring-opening reaction.
Mesalazine is selectively assayed
with a wide linearity range (155-
fold).
CCD study showed that absorbance is
dependent to the interactions of the
parameters.
1H NMR studies showed that the
colored product is being changed to a
cyclic isomer.
Density functional theory shows that
the colored product is excited locally.
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel and efficient non-azo formation based method was developed for trace sensing of mesalazine
(MES), a pharmaceutical aromatic amine. MES was simply coupled with a Meldrum’s activated furan
(MAF) reagent via a furan ring opening reaction to form a colored product. The intense purple colored
solution was detected at 575 nm. The reaction of MES with MAF was monitored by employing 1H
NMR spectroscopy and mass spectrometry. In addition, density functional theory (DFT) was applied to
optimize the structure of the colored product and its kmax (the wavelength of maximum absorbance)
in dimethyl sulfoxide and water. The colored product was considered in three possible structures, and
the most possible structures in dimethyl sulfoxide and in water were identified by employing the DFT
calculations. Both of the most possible structures indicated only a local excitation in their kmax and no
charge transfer was observed. However, one of the structures in dimethyl sulfoxide presented charge
transfer properties occurring through NAC@CAC moiety. A univariate optimization method was also
used to attain the optimum condition for analysis. In addition, the dependence of the analytical response
on the three main affecting parameters (reaction time (X1), Triton X-100 concentration (X2) and MAF con-
centration (X3)) was identified by employing a central composite design (CCD) approach. The CCD study
showed that the analytical response depends complexly on the parameters. Beer’s law was obeyed within
Received 24 November 2020
Received in revised form 26 February 2021
Accepted 13 April 2021
Available online 17 April 2021
Keywords:
Mesalazine
Furan ring-opening reaction
Donor-acceptor Stenhouse adducts
Central composite design
Density functional theory
the range of 0.06–9.30
introduced by the CCD approach. Also, the limit of detection was obtained 0.04
method showed precision (as relative standard deviation) and accuracy (as recovery) within the ranges
of 0.6–3.2 and 96.3–100.8%, respectively. Various organic and inorganic species, amino-
l
g mLꢁ1 of MES (155 fold linearity) at 575 nm, under the optimum condition
g mLꢁ1 of MES. The
l
%
⇑
Corresponding author.
E-mail address: heskandari@uma.ac.ir (H. Eskandari).
https://doi.org/10.1016/j.saa.2021.119846
1386-1425/Ó 2021 Elsevier B.V. All rights reserved.

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
pharmaceuticals, and amino acids were tested to evaluate the selectivity of the method. The selectivity of
the analytical method was satisfactory. The method was successfully applied for detection of MES in var-
ious water matrices and pharmaceutical tablets.
Ó 2021 Elsevier B.V. All rights reserved.
1. Introduction
naphthoquinone-4-sulfonate [37], 7-chloro-4,6-dinitrobenzofurox
ane [40] and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) [21].
The colored products during the ring opening reactions of furan
derivatives were first described by Stenhouse [1]. This type of reac-
tion was used for the assay of furfural in food products by Winkler
in 1955 [2]. In the Winkler method, furfural or hydroxymethylfur-
fural (HMF) is mixed with barbituric acid and para-toluidine to
undergo a stepwise reaction. The basic Winkler method was mod-
ified for efficient assay of furfural and HMF in various food samples
[3,4]. However, para-aminobenzoic acid was preferred more than
para-toluidine (para-toluidine is a carcinogen) [3]. Many furan
ring-opening reactions have been performed, and physical and
optical properties of their products were studied [5–15]. In 2000,
a Meldrum’s activated furan (MAF) compound reacted with some
cyclic secondary aliphatic amines to prepare a pair of products
[5]. This type of reaction was studied again (in 2014) when a
new class of T-type organic photochromic molecules named
donor–acceptor Stenhouse adducts (DASAs) were prepared [6,7].
Various donors and acceptors were employed in this type of reac-
tion [8,10,11,14,15]. Beside the studies, the analytical importance
of the reaction type was also considered when MAF was grafted
on amine-functionalized polycarbonate surfaces through DASAs
formation reaction for colorimetric sensing of secondary amines
in tetrahydrofuran (THF) [12]. Analytical assay using MAF was con-
tinued when appropriate amines were detected in THF, on solid
supports and in gas phase [9]. The first example of amine sensing
in aqueous solutions by employing this type of reaction was
reported when poly (oxa-norbornene) backbones were used. The
obtained limit of detection (LOD) for n-butylamine, diethylamine,
Development of a colorimetric procedure for MES assay having
low sample manipulation and cost, and with high sensitivity and
selectivity is very important. In addition, simple and cheap prepa-
ration of an appropriate chromogenic reagent in order to develop
an analytical method is highly desirable. Meldrum’s acid is easily
synthesized using a condensation reaction between malonic acid
and acetone in the presence of acetic anhydride and sulfuric acid
[41]. On the other hand, furfural, a well-known and cheap bypro-
duct compound prepared from the acidic process of biomass, is a
commercially available starting material for many useful syntheses
[42]. Furfural condenses safely with Meldrum’s acid in water at
70 °C in good yield to form MAF.
Through the last two decades, density functional theory (DFT)
approach has been widely used to predict and explain some phys-
ical, chemical and biological properties of materials and biomateri-
als. DFT provides low cost computations and prepares reasonable
results in comparison with the other ab initio methods [43]. Along
with the widespread applications of DFT methods, time dependent
DFT (TDDFT) approach has special importance for studying the
excited states of molecules; especially vertical electronic excita-
tions which are essentials for UV–Vis spectra [44].
The present work has studied the reaction of MES with MAF for
understanding some spectrochemical properties of the formed col-
ored product and analytical importance of the reaction. Along with
the experimental studies, DFT and TDDFT calculations have been
employed to study the vertical electronic excitations of the colored
product. The affecting parameters on MES-MAF reaction were
identified and then, the CCD method as a powerful chemometric
approach has been applied to define a mathematical equation.
According to the MES-MAF reaction in an aqueous mixture of Tri-
ton X-100 and sodium acetate, a colorimetric approach has been
developed for sensing of MES in pharmaceuticals and water sam-
ples (Scheme 1). Important features of the method such as simplic-
ity, sensitivity, selectivity, analysis time and economics have been
investigated. The method is the first applicable and efficient furan
ring-opening reaction based analytical method for assaying of a
primary aromatic amine in aqueous media. The other furan ring-
opening based methods have only been successful in detection of
secondary amines in organic or gaseous samples [9,12].
indoline and p-methoxyaniline were 10, 20, 20 and 100
l ,
g mLꢁ1
respectively [16]. A true efficient classical analytical approach for
selective sensing of an amine in aqueous solutions based on the
ring opening furan reaction has not been reported so far.
Mesalazine (MES) is a medicine which is used to cure Crohn’s
disease and inflammatory bowel disease. MES has been known as
a powerful scavenger for reactive oxygen species. Thus, it has an
important role in the pathogenesis of inflammatory bowel disease
and impairment of neutrophil function. In addition, MES inhibits
natural killer cell activity and antibody synthesis, and also affects
the cyclooxygenase and lipoxygenase pathways. It is a safe drug
with very few adverse effects and good tolerances [17,18]. Due to
its medicinal importance, MES has been assayed employing high-
performance liquid chromatography (HPLC) [19–21], electrochem-
istry [22–29], capillary electrophoresis [30,31], chemilumines-
cence [32] and spectrofluorometry [33–35]. However, the sensing
methods suffer some difficulties and limitations on selectivity
[24], sensitivity [24,32], limit of detection [19], speed of analysis
[34] and cost [19–21,30,31].
Colorimetric methods are generally simple, cheap, and are
widely accessible for quality control. However, the methods may
suffer some drawbacks and limitations on sensitivity, selectivity,
analytical time, accuracy, reproducibility, cost of the reagents and
sample manipulation protocol (including heating, cooling, control
of temperature, and extraction or clean-up steps) [36–39]. MES,
as an aromatic amine, is diazotized and then, appropriately forms
an azo dye to develop a colorimetric approach [36]. Some of the
other types of MES colorimetric methods use vanillin and Folin-
Ciocalteu reagent [36], alizarin red sulfonate and 1,2-
2. Experimental section
2.1. Apparatus
UV–vis spectra were recorded by utilizing a Shimadzu double
beam spectrophotometer model UV-1650 PC equipped with a pair
of matched quartz cells with 10.0 mm path length (Hellma). Absor-
bances were measured at 575 nm by a single beam spectropho-
tometer Jenway model 6305. Structure of appropriate
compounds were identified by 1H NMR spectroscopy (INOVA-
500) using DMSO d6 as solvent. Chemical shifts were given in
ppm (d) relative to TMS as an internal standard. Coupling constants
(J) were also reported in Hertz. Thin layer chromatography was
carried out using commercially available Merck F254 aluminum
backed silica plates. Melting points (un-corrected) were measured
with a Stuart SMP-3 apparatus. Mass spectra were recorded with
2

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Scheme 1. Reaction of MES with MAF.
an Agilent Technology (HP) 5973 Network Mass Selective Detector
mass spectrometer operating at an ionization potential of 70 eV.
Ultrasonic bath (Bandeline model Sonorex Digiplus DL 102H) was
used to disperse and dissolute the reagents. Rotary vacuum evap-
orator (4011 Digital, Heidolph Company, Germany) and hotplate
magnetic stirrer (Heidolph MR 3001 K) were also employed.
Standard stock solution of 500 mg mLꢁ1 of MES was prepared in
dilute hydrochloric acid. The fresh different concentrations of
DiBAF and MAF were prepared in ethanol or THF by keeping soni-
cation for 10 min. The solutions of the surfactants were prepared in
deionized water.
All analytical experiments were carried out at room tempera-
ture. All of the other solvents and materials used were purchased
from commercial suppliers and were used as received. Deionized
water was used throughout all of the appropriate dilutions.
2.2. Reagents and solutions
THF, ethanol, hydrochloric acid, sodium acetate (NaOAc),
sodium dodecyl sulfate (SDS), Triton X-100, furfural, barbituric
acid, 2-thiobarbituric acid and 1,3-dimethylbarbituric acid were
purchased from Merck (Germany). Cetylpyridinium chloride
(CPC) and MES were purchased from Loba-Chemie (India) and Alfa
Aesar (Germany), respectively.
2.3. Analytical procedure
Sample solution (7.5 mL), 150 l
L of NaOAc 2.0 mol Lꢁ1, 1.5 mL
of Triton X-100 aqueous solution (20.0%, wt/v) and 0.5 mL of MAF
solution in ethanol (4.0 ꢂ 10–2 mol Lꢁ1) were added to a 10 mL vol-
umetric flask. The reaction mixture was made up to the mark with
deionized water. The solution was allowed to stand for 10 min at
room temperature prior to absorbance measurement at 575 nm
against the appropriate blank (in the absence of MES). The net
absorbence was used to assay MES by using the appropriate cali-
bration equation.
Meldrum’s acid was synthesized according to a previously
reported procedure by a condensation reaction between acetone
and malonic acid in acetic anhydride and sulfuric acid [41]. 5-(2-
Furylmethylene)-2-thioxo-1,3-dihydropyrimidine-4,6-dione
(TBAF), 5-(2-furfurylidene)barbituric acid (BAF), 5-(furan-2-ylme
thylene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (DiBAF)
and MAF (in Scheme 2) were synthesized according to the reported
procedures [6,45,46]. Briefly, furfural (2 mmol) was added to a stir-
red aqueous solution of barbituric acid (2 mmol) or 2-
thiobarbituric acid (2 mmol). After 5 min (1 hr in case of 2-
thiobarbituric acid), the produced solids were isolated by a simple
filtration and then, were dried [45,46]. For preparation of DiBAF, an
aqueous dispersion of 1,3-dimethylbarbituric acid (10.5 mmol)
was reacted with furfural (10 mmol) at room temperature (20 °C,
2 h). In case of MAF, reaction between Meldrum’s acid (10.5 mmol)
and furfural (10 mmol) was performed at 75 °C for 2 h. The crude
DiBAF and MAF solid products were filtrated and washed with cold
deionized water. Then, the solids were dissolved in CH2Cl2 and
then, washed sequentially with a saturated aqueous solution of
NaHSO3, water, a saturated aqueous solution of NaHCO3 and brine.
Then, the organic layer was dried over CaCl2 and filtered. Finally,
the organic solvent (CH2Cl2) was evaporated to give DiBAF and
MAF as the pure bright yellow powders [6].
2.4. Sample preparations
Four tablets (equivalent to 500 mg of MES in each tablet) were
weighed and their average weight was estimated and ground to a
homogeneous fine powder in a mortar. A quantity of powder
equivalent to 100 mg of the drug was transferred to a 50 mL volu-
metric flask and dissolved in 20 mL of 0.1 mol Lꢁ1 HCl by ultrason-
ication for 30 min. The solution was filtered, and the filter paper
was washed with 10 mL of 0.1 mol Lꢁ1 HCl. The solution was added
to the filtrate and the final volume was made up to 50 mL with
deionized water [23]. After appropriate dilution, the analytical pro-
cedure was obeyed.
Tap, lake and river water samples were collected from Ardabil
tap water, Shorabil Lake and Baliqly Chay river. All of the water
samples were immediately filtered by Whatman filter paper no.
40 before use.
Scheme 2. Chemical structures of TBAF, BAF, DiBAF and MAF.
3

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
2.5. Central composite design (CCD) analysis
3.2. Results of DFT studies
The MINITAB statistical package (Minitab Inc. Release 17.0)
software was employed for data analysis and corresponding dia-
gram plotting.
The possible structures of the colored product 1 obtained from
the reaction between MAF and MES were optimized by DFT
method. Accordingly,
xB97 functional with long range (LC) and
exact local exchange corrections were applied with 6–31++G
(3df,3pd) basis set [51–53]. For all calculations, the GAMESS quan-
tum chemistry program was applied [54]. After a gas phase opti-
mization, the calculations were continued in the solution using
the polarizable continuum model containing integral equation for-
malism (IEFPCM) in conjunction with the solvation model based on
density (SMD) approach in DMSO and water as solvents [55,56].
Three different structures of product 1 (Fig. 3) were considered
for the computational studies. As can be seen, A and B forms are
tautomers of each other, and A and C forms are conjugated acid-
base forms. The optimized structures of these molecules are pre-
sented in Fig. 4. After that, time dependent density functional the-
ory (TDDFT) was exerted to study the vertical excitations of the
forms [57]. Table 1 shows the complete obtained results as brief.
Also, the highest occupied molecular orbital (HOMO) and the low-
est unoccupied molecular orbital (LUMO) of these different forms
of product 1 are shown in Table 2. Further, in order to determine
the types of the electronic excitation (local or charge transfer),
the wavefunctions of these forms were analyzed by Multiwfn pro-
gram [58].
MES and sulfasalazine are two compounds containing salicylic
acid moieties. The compounds show pKas related to ACOOH acidic
groups on their salicylic acid moieties as 2.30 and 2.81 in water at
25 °C, respectively [59,60]. According to the pKas, the compounds
in aqueous solutions are present preferably as anions (salicylate).
Product 1 has a salicylic acid moiety similar to those of MES and
sulfasalazine. Thus, product 1 is strongly accepted to be present
as an anion in aqueous sodium acetate solution (form C). In addi-
tion, salicylic acid has a dissociation constant (pKa) equal to 6.6
in DMSO [61]. Thus, product 1 in DMSO is strongly accepted as
form A. On the other hand, the basic concepts of hydrogen transfer
in tautomerism predict that hydrogen transfer from nitrogen of
MES moiety to oxygen of Meldrum’s acid moiety in product 1
has low probability [62,63]. According to the statements, the most
possible forms of product 1 in DMSO and sodium acetate aqueous
solutions are form A and form C, respectively.
3. Results and discussion
3.1. Characterization of the colored product
According to previously reported results on the reaction
between MAF and amines [5–15], it is expected that the colored
compound 1 could be formed by the reaction of MES and MAF.
Fig. 1 displays the proposed mechanism for this transformation.
The reaction starts with the nucleophilic attack of MES to MAF to
form the intermediate I [47,48]. This intermediate undergoes ring
opening reaction to produce the intermediate II. Intramolecular
proton transfer in the intermediate II generates the colored pro-
duct 1. The loss of color over time can be attributed to the cycliza-
tion of the colored molecule 1 [1]. Accordingly, compound 1
undergoes intramolecular cyclization over time to produce a color-
less compound 2 [49].
Since the reaction of primary anilines and primary aliphatic
amines with MAF produces unstable and inseparable products
[6], the formation of colored compound 1 and colorless compound
2 is confirmed by examining the 1H NMR spectrum of the mixture
of MES and MAF in deuterated DMSO. For this purpose, both of the
MAF and MES were mixed together in deuterated DMSO. Then, 1H
NMR spectroscopy was carried out in the first 5 min and also after
one hour. Fig. 2b depicts some significant 1H NMR signals of the
MES-MAF mixture within the first 5 min and also after 1 h reaction.
The e, f, g, h and OH-enol signals are attributed to the colored com-
pound 1, while the i, j, k, l and m signals can be related to the col-
orless cyclic form 2 [50]. As shown in Fig. 2b, the integrals of the
NMR signals of the compound 2 within the first 5 min are negligi-
ble, but after one hour the signals associated with the compound 2
increase. These observations are consistent with the changes in the
UV–vis spectrum of the MES-MAF mixture over time. This change
in UV–vis absorption spectrum (Fig. 2a) can be attributed to the
conversion of the colored compound 1 to the colorless cyclic form
2. The formation of the expected products was also confirmed by
employing the mass spectrometric analysis (Fig. S3).
Fig. 1. The proposed mechanism for the formation of compound 1 and 2 through the reaction between MES and MAF.
4

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Fig. 2. Reaction with time: a) Absorption spectra of MES-MAF mixture after 5 and 60 min in DMSO and b) 1H NMR spectra of MES-MAF mixture after 5 and 60 min in
DMSO d6.
Fig. 3. Considered different forms of product 1.
The results obtained by the TDDFT analysis in DMSO including
the length of charge transfer (LCT) through the electronic excita-
tion from HOMO to LUMO are also reported in Table 1. The dis-
tance for charge transfer of form A is shorter than a normal C@C
bond length of this form (1.37 Å). Thus, it is concluded that excita-
tion of this form at kmax does not exhibit a charge transfer charac-
5

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Fig. 4. The optimized structures of product 1 in different forms (A–C).
Table 1
Details of TDDFT calculations results for different forms of product 1 (A–C).
Molecule
Calculated kmax (nm)
f
mg (Debye)
me (Debye)
transition
LCT (Å)
AD
BD
CD
CW
490.7
332.1
526.8
508.9
1.1511
1.0370
1.1850
1.1970
4.88
15.30
21.78
20.69
21.34
HOMO(
HOMO(
HOMO(
HOMO(
p
p
p
p
) ? LUMO(
) ? LUMO(
) ? LUMO(
) ? LUMO(
p*)
p*)
p*)
p*)
0.382
2.397
2.525
0.978
15.89
28.89
29.02
AD-CD: the results obtained for different forms of product 1 in DMSO.
CW: the results obtained for form C in water.
f is the oscillator strength; mg is dipole moment of the ground state; me is dipole moment of the excited state.
6

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Table 2
Orbital structures of HOMOs and LUMOs for different forms of product 1.
Form
HOMO
LUMO
AD
BD
CD
CW
AD-CD: the shapes of HOMOs and LUMOs obtained for different forms of product 1 in DMSO.
CW: the shape of HOMO and LUMO obtained for form C in water.
teristic and it is taken place a local
p
?
p
* excitation. However,
media (at their kmax). Also, Fig. 6 shows that in Triton X-100 solu-
tions, the colored product of MES-MAF reaction was more stable
than that of MES-DiBAF reaction. In Triton X-100 media, MAF
and DiBAF showed the same sensitivity, but less blank signal was
observed for MAF. Fig. 7a showed that the spectra of the sample
and blank solutions related to DiBAF reagent in CPC media were
the same. In CPC, MAF reacted with MES and formed a yellow col-
ored solution (a shoulder was observed in the UV–vis spectrum of
the sample and no kmax was observed). As we know, colorimetric
measurements at kmax offer some advantages on sensitivity, cali-
bration linearity and selectivity [64]. The net absorbance of the
sample solution was obtained at 431 nm in CPC media (inset graph
in Fig. 7b). The inset graph showed that the absorbance was
increasing with time (the kinetics of the MES-MAF reaction was
slow). Such the slow reaction kinetic causes limitation on the
speed of analysis.
The series of experiments compared different chromogenic
reagents and surfactants to make a decision on selecting the most
efficient chromogenic reagent and surfactant. For further experi-
ments, MAF and Triton X-100 were selected as the best chro-
mogenic reagent and surfactant, respectively.
The photoswitching reactions of the colored Stenhouse adducts
depend on the nature and composition of the solutions [6,7,42,50].
Therefore, the effect of light on MAF-MES reaction in Triton X-100
solutions was studied. Fig. 8 depicts the results of the experiments.
As can be seen, the sensitivity of the method does not depend on
the presence or absence of laboratory light during the experiments.
form B can exist in DMSO with LCT larger than C@C bond length
through NAC@CAC moiety, see Tables 1 and 2. Therefore, the
charge transfer can occur only in a form with less possibility (form
B). The shapes of HOMO and LUMO for form B in Table 2 confirm
the fact. Otherwise, in DMSO both LCTs and the shapes of HOMOs
and LUMOs in Tables 1 and 2, confirm the charge transfer property
of the excitations for form B and form C.
Beside the shapes of HOMO and LUMO in Table 2, form C shows
a LCT less than 1.37 Å (in Table 1) in water. Thus, there is not
charge transfer property for the excitation.
3.3. Study on absorption spectra
Four different reagents from the group of activated furans
(TBAF, BAF, DiBAF and MAF) were synthesized [6,45,46] and tested
for reaction with MES. Preliminary experiments showed that TBAF
and BAF could form colored products with MES, but their solubili-
ties in aqueous micellar solutions, THF and ethanol were insuffi-
cient to develop a MES sensing method. In establishment of a
spectrophotometric procedure, solubility of the reagents and prod-
ucts in the final solution is essential. Thus, TBAF and BAF were not
considered for further studies.
The other reagents (DiBAF and MAF) were also tested. The
reagents formed colored products with MES having sufficient solu-
bility in the aqueous micellar solutions, THF and ethanol. Thus,
DiBAF and MAF were considered for further investigations.
Also, the tests showed that the presence of surfactants in the
media increases the absorbance of the solutions and offers more
stability for the formed products. Figs. 5–7 display the spectra of
the solutions (sample and blank) together with time correlation
of the measured absorbances. The surfactants applied were SDS
(an anionic surfactant), Triton X-100 (a non-ionic surfactant) and
CPC (a cationic surfactant). According to the spectra in Fig. 5, it is
observed that MAF causes more sensitivity than DiBAF in SDS
3.4. Univariate optimization method
In addition to the univariate method, many chemometric meth-
ods have been applied for optimization in analytical chemistry. The
methods process some experimental results using a computer pro-
gram to predict the optimum condition. The effects of parameters
on the analytical response are presented as an equation for some of
7

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Fig. 6. Absorption spectra of the manipulated MES containing solutions in Triton X-
Fig. 5. Absorption spectra of the manipulated MES containing solutions in SDS
100 media using a) DiBAF and b) MAF. Condition: chromogenic reagent 1.0 mmol
media using a) DiBAF and b) MAF. Condition: chromogenic reagent 1.0 mmol Lꢁ1
,
Lꢁ1, Triton X-100 1.0% (wt/v), MES 20.00
l
g mLꢁ1, THF 10% (v/v) and NaOAc
SDS 1.0% (wt/v), MES 20.00 l .
g mLꢁ1, THF 10% (v/v) and NaOAc 0.02 mol Lꢁ1
0.02 mol Lꢁ1
.
NaOAc as the major constituent in the final solution not only
normalizes matrix of the solution but also controls the pH of the
solution. The concentration of NaOAc was varied and the sensitiv-
ity was investigated. The obtained results in Fig. 9c show that
0.030 mol Lꢁ1 of NaOAc caused the best sensitivity. Thus,
0.030 mol Lꢁ1 of NaOAc was chosen for the next optimization
steps.
THF has been used as co-solvent in preparation of the stock
solution of MAF. Thus, THF is present in the final solution prior
to the measurement of absorbance. Ethanol as a common water
miscible solvent was also examined in the preparation of the
MAF stock solution. Different volumes of ethanol or THF were
added to the final solution, separately, while the final concentra-
tion of MAF was constant (2.0 mmol Lꢁ1). The results have been
shown in Fig. 10a. The results show that the sensitivity is inversely
dependent on the volume of the organic solvent added. The results
also reveal that ethanol offers more sensitivity against THF. Thus,
the lowest possible volume of ethanol (0.5 mL) was selected for
further experiments.
the chemometric approaches. In this research, both the central
composite design (CCD) optimization method and the univariate
method were used to optimize the condition of the MES detection
system. The results obtained by the univariate method prepared
some information about the relationship between the sensitivity
and the effective parameters. Also, the results of the univariate
optimization method were applied to define the ranges of the
parameters that must be considered during applying the CCD opti-
mization method. The univariate optimization method was applied
step by step. Every experiment was performed three times. The
absorbance was monitored at 575 nm when concentration of Tri-
ton X-100 as the solubilizing and stabilizing agent was varied.
The results of the experiment are shown in Fig. 9a. As can be seen,
the best sensitivity was obtained when Triton X-100 had a concen-
tration of 2.0% (wt/v). Thus, 2.0% (wt/v) was selected as the opti-
mum concentration of Triton X-100.
The concentration of MAF was changed and absorbance was
detected. The results in Fig. 9b show the dependency of absorbance
on the MAF concentration. The results show that the optimal con-
The reaction period between MAF and MES was changed and
absorbance was monitored. The results of the study are given in
centration of MAF was 2.0 mmol Lꢁ1
.
8

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Fig. 7. Absorption spectra of the manipulated MES containing solutions in CPC
media using a) DiBAF and b) MAF. Condition: chromogenic reagent 1.0 mmol Lꢁ1
,
CPC 1.0% (wt/v), MES 20.00 l .
g mLꢁ1, THF 10% (v/v) and NaOAc 0.02 mol Lꢁ1
Fig. 9. Effect of: a) Triton X-100, b) MAF and c) NaOAc on the sensitivity of the
method. Condition for (a): MES 17.5 l
g mLꢁ1, NaOAc 0.04 mol Lꢁ1, MAF 1.5 mmol
Lꢁ1, THF 10% (v/v) and reaction period of 6 min. Conditions were consecutively
changed for the study of the other parameters according to the univariate
optimization method.
Fig. 10b. As seen, the greatest sensitivity has been attained after
10 min.
A 10 min reaction period was considered and the effect of ionic
strength was investigated. The results in Fig. 10c showed that the
lowest ionic strengths caused the greatest sensitivity.
3.5. CCD method for studying MES-MAF reaction
In order to evaluate the dependence of absorbance on the
affecting factors and to understand how the parameters interact
with each other, the CCD chemometric method was applied. The
modeling was established for three factors involving five levels
[65].
Fig. 8. Effect of light on the absorbance of the solution. Condition: MAF 0.5 mmol
Lꢁ1, Triton X-100 1.0% (wt/v), MES 10.00
0.01 mol Lꢁ1 at room temperature.
l
g mLꢁ1, THF 10% (v/v) and NaOAc
The involved factors with the true and encoded quantities at
diverse levels are shown in Table S1. A fixed concentration of
9

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
the lack of fit is insignificant. The value of determination coefficient
(R2 = 0.8585) also indicated that the fitting is well. Finally, based on
ANOVA, the reliability of the model was concluded. According to
Equation (1), X1, X2 and X3 factors linearly affect the response. Also,
the squares of X1 and X2 are significant. In addition, it was found
that the interactions of X1, X2, and X3 with each other affect the
response. Three-dimensional response surfaces in Fig. 11 clearly
illustrate the obtained outcomes. CCD predicted the optimal values
of time, and Triton X-100 and MAF concentrations. They were
10.0 min, 3.0% (wt/v) and 2 ꢂ 10-3 mol L-1, respectively.
MES at the concentration of 8.75 l
g mLꢁ1 was selected and two
series of experiments were conducted. Initially, the univariate opti-
mization condition was applied. The measured absorbance was 0.
710 0.034 (n = 8). Also, some measurements were conducted
when the condition proposed by the CCD method was applied.
The measured absorbance was 0.890 0.031 (n = 8). The paired
t-test at 95% confidence interval confirmed the presence of a signif-
icant difference between the means of the both results. Thus, the
condition proposed by the CCD method was selected to be
employed in the subsequent experiments.
3.6. Analytical characteristics
The optimized condition (obtained by the CCD approach) was
applied and important analytical features of the method were eval-
uated. Initially, different concentrations of MES were prepared, the
procedure was obeyed and the absorbance of the solutions was
measured at 575 nm. A linear calibration plot was obtained within
the wide range of 0.06–9.30
To obtain the precision and accuracy of the method, different
concentrations of MES at 0.70, 1.00 and 8.40
g mLꢁ1 were tested.
g mLꢁ1 of MES
l
g mLꢁ1 (Fig. S4).
l
Also, the reproducibility of the method for 1.00
l
was investigated.
The minimum concentration of MES that can be detected (LOD)
is another important analytical index. LOD was obtained
0.04
l
g mLꢁ1 of MES when ten times repetitive analysis of blank
was performed. The important analytical characteristics of the
method are given in Table 5. Therefore, the satisfactory efficiency
of the MES sensing approach is validated.
3.7. Selectivity of the method
The effects of different species on the detection of MES were
investigated under optimum experimental conditions when the
other species were added individually. MES concentration was
2.00
l
g mLꢁ1 in all of the experiments. A specie was considered
as an interferent when it caused ꢃ 5% error on the MES concentra-
tion. The results in Table 6 indicated that the frequently added
cations, anions and organic chemicals did not interfere at 200-
fold (wt/wt) ratio. In addition, some pharmaceutical amines such
as procaine, procainamide, metoclopramide, sulfamethazine and
dapsone were also tested. The results showed that the pharmaceu-
tical amines did not cause considerable interferences on the MES
detection.
Fig. 10. Effect of: a) Co-solvent, b) Reaction period and c) NaCl on the sensitivity of
the method. Condition for (a): MES 17.5
l
g mLꢁ1, NaOAc 0.03 mol Lꢁ1, MAF
2.0 mmol Lꢁ1, Triton X-100 2.0% (wt/v) and reaction period of 6 min. Conditions
were consecutively changed for the study of the other parameters according to the
univariate optimization method.
MES (8.75 mg mLꢁ1) was used through all the experiments. Table S2
lists the CCD matrix in 39 experimental runs for these variables
and responses. The results of the analysis of variance (ANOVA)
and P-values by the CCD optimization procedure are presented in
Tables 3 and 4. The polynomial equation which describes the
absorbance of the solution in terms of significant variables is:
3.8. Sample analysis
Various pharmaceutical samples and three different water sam-
ples were tested to evaluate the applicability of the MES detection
method. In the analysis of water samples, 5.0 mL of the water sam-
ples (after filtration with Whatman filter paper no. 40) were
employed. The results of the study are reported in Table 7. MES
was not found in the water samples. Thereafter, the water samples
were spiked with two different concentrations of MES (1.0 and
5.0 mg mLꢁ1) and were analyzed (n = 6) according to the analytical
procedure. The obtained recoveries and relative standard devia-
A ¼ Constant ꢁ b1X1 þ b2X2 þ b3X3 ꢁ b11X2 ꢁ b22X2
1
2
þ b12X1X2 ꢁ b13X1X3‘ þ b23X2X3
ð1Þ
The ANOVA results in Tables 3 and 4 revealed that the model is
highly significant. The good predictability of the model shows that
10

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Table 3
Table 5
Analysis of variance for the experiments in Table S2.
Analytical characteristics of MES assay method.
Source
DFa
AdjMSb
Fc
Pd
Slope of calibration curve
0.128
Model
Blocks
Linear
Square
10
1
3
3
3
27
18
10
38
0.8585
0.157415
0.028042
0.430996
0.043242
0.039551
0.004259
0.005324
0.006544
–
24.05
4.29
65.86
6.61
6.04
–
2.17
–
–
0.000
0.048
0.000
0.002
0.003
–
0.199
–
–
Intercept of calibration equation
0.006
0.9981
0.04
Square of correlation coefficient (R2)
Limit of detection (
Linear dynamic range (
l
g mLꢁ1
l
)
g mLꢁ1
)
0.06–9.30
Interaction
Residual error
Lack-of-fit
Pure error
Total
Repeatability (RSD%)a:
0.70
1.00
8.40
l
g mLꢁ1
l
l
3.2
2.5
0.6
g mLꢁ1
g mLꢁ1
Recoverya:
0.70
R2
–
–
–
l
1.00
8.40
g mLꢁ1
l
l
96.3
98.9
100.8
a
b
c
g mLꢁ1
g mLꢁ1
Degree of freedom;
Adjusted mean of squares;
F test;
Reproducibility (RSD%)b:
1.00
g mLꢁ1
Recoveryb:
1.00
g mLꢁ1
d
Probability value.
l
3.5
l
100.6
Table 4
Analysis of variance (coded coefficients).
Amounts are standard deviations.
a
For 8 replicate measurements;
Term
Coefficient
SE Coefficienta
T-valueb
P-valuec
b
For 7 day period;
Constant
X1
X2
0.4281
0.0233
0.0166
0.0155
0.0155
0.0166
0.0152
0.0152
0.0202
0.0202
0.0202
18.35
ꢁ0.60
8.41
11.25
ꢁ2.97
ꢁ3.12
ꢁ1.85
2.10
0.000
0.556
0.000
0.000
0.006
0.004
0.075
0.045
0.031
0.007
ꢁ0.0099
0.1302
Table 6
Influence of foreign species on the detection of 2.0 l
g mLꢁ1 MES.
X3
0.1741
X1X1
X2X2
X3X3
X1X2
X1X3
X2X3
ꢁ0.0492
ꢁ0.0473
ꢁ0.0281
0.0425
Foreign species
(Wtspecies/
WtMES
)
Mg(II), Ca(II), Ni(II), Fe(III), K(I), Na(I), Cl-, SO42-, H2PO4- , NO3ꢁ,
Serine, Glycine, Alanine, Methionine, Glutamic acid,
Leucine, Asparagine, Sucrose, Citrate, Procaine,
Procainamide, Metoclopramide
Sulfamethazine, Glucose
200a
ꢁ0.0459
ꢁ2.27
0.0592
2.93
a
b
c
Standard error;
t-statistics;
Probability value.
200
100
50
L-Cysteine
Dapsone
a
The maximum tested concentration. The ratio did not show any interference in
the mentioned level.
tions (RSDs) were in the ranges of 96.0–105.0 % and 1.9–5.2%,
respectively (Table 7). Different pharmaceutical tablets were also
analyzed. The results in Table 8 show satisfactory accuracy and
reproducibility of the method. The recovery of the method was
in the range of 99.3–102.3 %.
Table 7
Detection of MES in water samples.
Sample
MES, mg mLꢁ1 (n = 6)
Recovery, %
3.9. Comparison with the other spectroscopic MES sensing methods
Taken
Found
Tap water
–
NDa
–
The characteristics of the simple MES sensing method should be
compared with some of the previously reported methods to define
its analytical efficiency. The efficiency of the presented method has
been compared with some spectroscopic methods in Table 9. The
methods show some limitations on cost [21,37,40], simplicity
(condition must be precisely controlled) [36,66], LOD [37,40,66]
and linear dynamic range (LDR) [21,40]. The presented method
can be easily employed in a general laboratory for MES detection
in pharmaceutical and polluted water samples. In this method,
1.00
5.00
0.96 0.05
5.16 0.12
NDa
1.02 0.03
5.11 0.17
NDa
96.0
103.2
River water
Lake water
–
1.00
5.00
–
102.0
102.2
–
1.00
5.00
–
1.03 0.02
5.25 0.18
103.0
105.0
a
Non-determinable; Amounts are standard deviations.
Fig. 11. Three-dimensional (3D) response surfaces obtained based on the model for optimization of chemical variables.
11

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
Table 8
Analysis of MES in pharmaceutical preparations.
Sample
Amount, mg tabletꢁ1 (n = 4)
Taken
Recovery, %
Found
Sample 1a
Sample 2b
Sample 3c
500
500
500
497
511
505
2
6
9
99.4
102.2
101.0
Amounts are standard deviations.
a
Tablet (500 mg); Iran hormone company; average mass of each tablet was 0.657 g.
Tablet (500 mg); Chemidarou company; average mass of each tablet was 0.773 g.
Tablet (500 mg); Arya company; average mass of each tablet was 0.698 g.
b
c
Table 9
Comparison of the MES analytical method with the other spectroscopic methods.
Characteristics of method
kmax, nm
LDRa, mg mLꢁ1
LODb, mg mLꢁ1
Samples
Ref.
Colorimetry-uses DPPH radical
517
655
510
395
600
470
500
659
487d
575
0.4–3
1–30
1–15
2–30
15–98
2–22
0.32–4.6
5–150
0.076–19.9
0.06–9.3
–
Tablet
Tablet
Tablet
Tablet
Tablet
Tablet
Urine
Tablet
[21]
[36]
[36]
[36]
[37]
[37]
[40]
[66]
[67]
Colorimetry-uses Folin-Ciocalteu reagent
Colorimetry-uses a Diazo-coupling reaction
Colorimetry-uses a Schiff base formation reaction
Colorimetry-uses ARS reagent
0.004
0.006
0.021
4.92
0.56
0.3
1.48
0.02
0.04
Colorimetry-uses NQS reagent
Colorimetry-uses 7-Chloro-4,6-dinitrobenzofuroxane
Colorimetry-FIAc- uses o-coumaric acid
Fluorimetry-uses N/P-doped carbon dots
Colorimetry-uses MAF reagent
Tablet, Blood
Tablet, Water
This work
a
b
c
Linear dynamic range;
Limit of detection; DPPH: 1,1-Diphenyl-2-picrylhydrazyl; ARS: Alizarin red sulfonate; NQS: 1,2-Naphthoquinone-4-sulfonate;
Flow injection analysis;
Emission wavelength.
d
MAF is employed as a chromogenic reagent. MAF can be simply
prepared from furfural (a biomass derived reagent) as a starting
material.
The developed method showed a wide calibration range for
mesalazine. In addition, the method revealed high selectivity for
mesalazine against some common ions, biologically active materi-
als and pharmaceutical amines. MES was determined in different
water matrices and pharmaceutical samples using the analytical
method. The method is the first applicable sensing method for an
amine in aqueous solutions based on a furan ring-opening reaction.
4. Conclusions
Easy preparation of a chromogenic reagent from the natural
compounds for developing an analytical method is an advantage.
A simple, sensitive and selective colorimetric method was devel-
oped for MES sensing based on the coupling of MES with MAF.
The major reagent in the preparation of MAF was furfural (a bio-
mass derived reagent). The obtained NMR spectra at different
times revealed that the colored product was being converted to a
colorless isomer. The optimum condition obtained by the univari-
ate optimization method was employed to attain the best sensitiv-
ity. Besides applying the univariate method, the CCD method was
employed to obtain the dependency of the method sensitivity on
the affecting parameters. The CCD model was employed to discuss
the effects of the reaction parameters on the sensitivity of the
method. The study revealed that the response has been linearly
dependent to the concentrations of Triton X-100 and MAF. Further-
more, squares of the reaction period and Triton X-100 had negative
effects on the response. Also, the analytical response was depen-
dent on X1 X2, X1 X3 and X2 X3. The efficiencies of the optimum
conditions attributed to the CCD and univariate methods were
compared with each other and the optimum condition proposed
by the CCD method was chosen due to greater sensitivity.
DFT calculations were employed on three possible structures
attributed to the colored product. Neutral and anionic forms are
the most possible structures in DMSO and aqueous solutions,
respectively. TDDFT calculations indicated that the most possible
forms in the studied media are locally excited at their kmax. How-
ever, the TDDFT calculations on the other neutral form in DMSO
predicted that charge transfer is taken place through NAC@CAC
moiety.
CRediT authorship contribution statement
Leila Sabahi-Agabager: Conceptualization, Methodology, Visu-
alization, Investigation, Writing - original draft, Writing - review &
editing. Habibollah Eskandari: Project administration, Supervi-
sion, Data curation, Validation, Writing - review & editing. Farough
Nasiri: Project administration, Supervision, Writing - review &
editing. Amir Nasser Shamkhali: Data curation, Methodology,
Software, Writing - review & editing. Somayyeh Baghi Sefidan:
Data curation, Methodology, Software, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgements
The authors wish to acknowledge support of this work by the
University of Mohaghegh Ardabili and the Iran National Science
Foundation (INSF) [grant Number 96004838].
Appendix A. Supplementary material
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.saa.2021.119846.
12

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
determination in pharmaceutical dosage forms, Rev. de Cienc. Farm. Basica e
References
Apl.
43
(1)
(2007)
97–103,
https://doi.org/10.1590/S1516-
93322007000100012.
[1] R.F.A. Gomes, J.A.S. Coelho, C.A.M. Afonso, Synthesis and Applications of
Stenhouse Salts and Derivatives, Chem. Eur. J. 24 (37) (2018) 9170–9186,
https://doi.org/10.1002/chem.201705851.
[2] O. Winkler, Beitrag zum Nachweis und zur Bestimmung von
Oxymethylfurfurol in Honig und Kunsthonig, Z Lebensm Unters Forsch. 102
(3) (1955) 161–167, https://doi.org/10.1007/BF01683776.
[3] K. CASTOLDI, M.I. MILANI, E.L. ROSSINI, L. PEZZA, H.R. PEZZA, Flow injection
analysis of 5-(hydroxymethyl)-2-furaldehyde in honey by a modified Winkler
method, Anal. Sci. 32 (4) (2016) 413–417, https://doi.org/10.2116/
analsci.32.413.
[4] M.I. Milani, E.L. Rossini, K. Castoldi, L. Pezza, H.R. Pezza, Paper platform for
reflectometric determination of furfural and hydroxymethylfurfural in
sugarcane liquor, Microchem. J. 133 (2017) 286–292, https://doi.org/
10.1016/j.microc.2017.03.046.
[22] A.B. Teradale, S.D. Lamani, P.S. Ganesh, B.E.K. Swamy, S.N. Das, CTAB
immobilized carbon paste electrode for the determination of mesalazine: A
cyclic voltammetric method, Sens. Biosensing Res. 15 (2017) 53–59, https://
doi.org/10.1016/j.sbsr.2017.08.001.
ˇ
´
[23] M. Štepánková, R. Šelešovská, L. Janíková, J. Chylková, Voltammetric
determination of mesalazine in pharmaceutical preparations and biological
samples using boron-doped diamond electrode, Chem PAP 71 (8) (2017)
1419–1427, https://doi.org/10.1007/s11696-017-0135-6.
[24] A. Akkaya, C. Altug, N. Pazarlioglu, E. Dinckaya, Determination of 5-
Aminosalicylic Acid by Catalase-Peroxidase Based Biosensor, Electroynalysis
(N.Y.N.Y.) 21 (16) (2009) 1805–1810, https://doi.org/10.1002/elan.200904606.
[25] N. Nataraj, S.K. Krishnan, T.-W. Chen, S.-M. Chen, B.-S. Lou, Ni-Doped ZrO 2
nanoparticles decorated MW-CNT nanocomposite for the highly sensitive
electrochemical detection of 5-amino salicylic acid, Analyst. 146 (2) (2021)
664–673, https://doi.org/10.1039/D0AN01507E.
[26] S. Ebrahimi, A. Afkhami, T. Madrakian, Enhanced electrochemical responses at
supramolecularly modified graphene: Simultaneous determination of
sulphasalazine and its metabolite 5-aminosalicylic acid, J. Electroanal. Chem.
838 (2019) 186–194, https://doi.org/10.1016/j.jelechem.2019.03.001.
[27] T.S. Kanna Sharma, K.-Y. Hwa, A. Santhan, A. Ganguly, Synthesis of novel three-
dimensional flower-like cerium vanadate anchored on graphitic carbon nitride
as an efficient electrocatalyst for real-time monitoring of mesalazine in
biological and water samples, Sens. Actuators B Chem. 331 (2021) 129413,
https://doi.org/10.1016/j.snb.2020.129413.
[28] J. Vinoth Kumar, T. Kokulnathan, S.-M. Chen, T.-W. Chen, A.M. Elgorban, M.S.
Elshikh, N. Marraiki, E.R. Nagarajan, Two-dimensional copper tungstate
nanosheets: application toward the electrochemical detection of mesalazine,
ACS Sustain. Chem. Eng. 7 (22) (2019) 18279–18287, https://doi.org/10.1021/
acssuschemeng.9b02171.
[29] B. Nigovic´, A. Mornar, E. Brusac, M.-L. Jelicic, Selective sensor for simultaneous
determination of mesalazine and folic acid using chitosan coated carbon
nanotubes functionalized with amino groups, J. Electroanal. Chem. 851 (2019)
113450, https://doi.org/10.1016/j.jelechem.2019.113450.
ˇ
ˇ
ˇ
[5] P. Šafár, F. Povazanec, N. Prónayová, P. Baran, G. Kickelbick, J. Kozíšek, M. Breza,
Dichotomy in the Ring Opening Reaction of 5-[(2-Furyl) methylidene]-2, 2-
dimethyl-1, 3-dioxane-4, 6-dione with Cyclic Secondary Amines, Collect.
Czech. Chem. Commun. 65 (12) (2000) 1911–1938, https://doi.org/10.1135/
cccc20001911.
[6] S. Helmy, S. Oh, F.A. Leibfarth, C.J. Hawker, J. Read de Alaniz, Design and
synthesis of donor–acceptor stenhouse adducts: a visible light photoswitch
derived from furfural, J. Org. Chem. 79 (2014) 11316–11329, https://doi.org/
10.1021/jo502206g.
[7] S. Helmy, F.A. Leibfarth, S. Oh, J.E. Poelma, C.J. Hawker, J. Read de Alaniz,
Photoswitching using visible light:
molecules, JACS 136 (23)
10.1021/ja503016b.
a
new class of organic photochromic
(2014) 8169–8172, https://doi.org/
[8] J.R. Hemmer, Z.A. Page, K.D. Clark, F. Stricker, N.D. Dolinski, C.J. Hawker, J. Read
de Alaniz, Controlling Dark Equilibria and Enhancing Donor-Acceptor
Stenhouse Adduct Photoswitching Properties through Carbon Acid Design,
JACS. 140 (33) (2018) 10425–10429, https://doi.org/10.1021/jacs.8b06067.
[9] Y.J. Diaz, Z.A. Page, A.S. Knight, N.J. Treat, J.R. Hemmer, C.J. Hawker, J. Read de
Alaniz, A versatile and highly selective colorimetric sensor for the detection of
amines, Chem. Eur. J. 23 (15) (2017) 3562–3566, https://doi.org/10.1002/
chem.201700368.
[10] R. Saha, A. Devaraj, S. Bhattacharyya, S. Das, E. Zangrando, P.S. Mukherjee,
Unusual Behavior of Donor-Acceptor Stenhouse Adducts in Confined Space of a
Water-Soluble PdII8 Molecular Vessel, JACS. 141 (21) (2019) 8638–8645,
https://doi.org/10.1021/jacs.9b03924.
[11] Y.-D. Cai, T.-Y. Chen, X.Q. Chen, X. Bao, Multiresponsive Donor-Acceptor
Stenhouse Adduct: Opportunities Arise from a Diamine Donor, Org. Lett. 21
(18) (2019) 7445–7449, https://doi.org/10.1021/acs.orglett.9b02753.
[12] S. Singh, P. Mai, J. Borowiec, Y. Zhang, Y. Lei, A. Schober, Donor–acceptor
Stenhouse adduct-grafted polycarbonate surfaces: selectivity of the reaction
for secondary amine on surface, R. Soc. Open Sci. 5 (7) (2018) 180207, https://
doi.org/10.1098/rsos.180207.
ˇ
ˇ ´
[30] R. Gotti, R. Pomponio, C. Bertucci, V. Cavrini, Determination of 5-aminosalicylic
acid related impurities by micellar electrokinetic chromatography with an ion-
pair reagent, J. Chromatogr. A. 916 (1-2) (2001) 175–183, https://doi.org/
10.1016/S0021-9673(00)01097-9.
ˇ
´
[31] K. Maráková, J. Pieštansky, P. Mikuš, Determination of drugs for Crohn’s
disease treatment in pharmaceuticals by capillary electrophoresis hyphenated
with tandem mass spectrometry, Chromatographia 80 (4) (2017) 537–546,
https://doi.org/10.1007/s10337-016-3213-y.
[32] E.J. Llorent-Martínez, P. Ortega-Barrales, M.L. Fernández de Córdova, A. Ruiz-
Medina, Development of an automated chemiluminescence flow-through
sensor for the determination of 5-aminosalicylic acid in pharmaceuticals: a
comparative study between sequential and multicommutated flow
techniques, Anal. Bioanal. Chem. 394 (3) (2009) 845–853, https://doi.org/
10.1007/s00216-009-2757-1.
[33] A.A. Elbashir, F. Altayib Alasha Abdalla, H.Y. Aboul-Enein, Host–guest inclusion
complex of mesalazine and b-cyclodextrin and spectrofluorometric
determination of mesalazine, Luminescence 30 (4) (2015) 444–450, https://
doi.org/10.1002/bio.v30.410.1002/bio.2758.
[34] A.A. Elbashir, F.A.A. Abdalla, H.Y. Aboul-Enein, Supramolecular interaction of
18-crown-6 ether with mesalazine and spectrofluorimetric determination of
mesalazine in pharmaceutical formulations, Luminescence 30 (8) (2015)
1250–1256, https://doi.org/10.1002/bio.2888.
[35] F.-L. Cui, L.-X. Qin, F. Li, H.-X. Luo, Synchronous fluorescence determination
and molecular modeling of 5-Aminosalicylic acid (5-ASA) interacted with
human serum albumin, J. Mol. Model. 14 (12) (2008) 1111–1117, https://doi.
org/10.1007/s00894-008-0352-6.
[36] B.S. Chandra, S.S. Bhogela, M. Shaik, C.S. Vadlamudi, M. Chappa, N.S. Maddirala,
Simple and sensitive spectrophotometric methods for the analysis of
mesalamine in bulk and tablet dosage forms, Quim. Nova. 34 (2011) 1068–
1073, https://doi.org/10.1590/S0100-40422011000600026.
[37] F. Alasha Abdalla, A. Elbashir, Development and Validation of
spectrophotometric methods for the determination of mesalazine in
pharmaceutical formulation, Med. Chem. 4 (2014) 361–366, https://doi.org/
10.4172/2161-0444.1000166.
[13] A. Balamurugan, H.-i. Lee,
A visible light responsive on–off polymeric
photoswitch for the colorimetric detection of nerve agent mimics in solution
and in the vapor phase, Macromolecules 49 (7) (2016) 2568–2574, https://doi.
org/10.1021/acs.macromol.6b00309.
[14] G. Noirbent, Y. Xu, A.-H. Bonardi, S. Duval, D. Gigmes, J. Lalevée, F. Dumur, New
Donor-Acceptor Stenhouse Adducts as Visible and Near Infrared Light
Polymerization Photoinitiators, Molecules 25 (2020) 2317, https://doi.org/
10.3390/molecules25102317.
[15] Q. Yan, C. Li, S. Wang, Z. Lin, Q. Yan, D. Cao, Visible light responsive donor-
acceptor
stenhouse
adducts
with
indoline-tri/tetra-phenylethylene
chromophore: synthesis, aggregation-induced emission, photochromism and
solvent dependence effect, Dyes Pigm. 178 (2020) 108352, https://doi.org/
10.1016/j.dyepig.2020.108352.
[16] Q. Chen, Y.J. Diaz, M.C. Hawker, M.R. Martinez, Z.A. Page, S. Xiao-An Zhang, C.J.
Hawker, J. Read de Alaniz, Stable Activated Furan and Donor-Acceptor
Stenhouse Adduct Polymer Conjugates as Chemical and Thermal Sensors,
Macromolecules 52 (11) (2019) 4370–4375, https://doi.org/10.1021/
acs.macromol.9b00533.
[17] N. Shahabadi, S.M. Fili, Molecular modeling and multispectroscopic studies of
the interaction of mesalamine with bovine serum albumin, Spectrochim. Acta
A
Mol. Biomol. Spectrosc. 118 (2014) 422–429, https://doi.org/10.1016/j.
saa.2013.08.110.
[38] S.B. Sefidan, H. Eskandari, A.N. Shamkhali, Rapid colorimetric flow injection
sensing of hypochlorite by functionalized graphene quantum dots, Sens.
[18] A. Pandith, G. Hazra, H.-S. Kim, A new fluorogenic sensing platform for salicylic
acid derivatives based on
deficient and electron-rich aromatics, Spectrochim. Acta
p
-
p
and NH-
p
interactions between electron-
Mol. Biomol.
Actuators
B
Chem. 275 (2018) 339–349, https://doi.org/10.1016/j.
A
snb.2018.08.023.
Spectrosc. 178 (2017) 151–159, https://doi.org/10.1016/j.saa.2017.01.053.
[39] S.B. Sefidan, H. Eskandari, Sensitive assay of pharmaceutical amines in
environmental samples and formulations by oxygenated graphene quantum
dots, Measurement 132 (2019) 292–302, https://doi.org/10.1016/j.
measurement.2018.09.063.
[40] S.Y. Garmonov, Z.C. Nguyen, I.F. Mingazetdinov, L.M. Yusupova, N.S. Shitova, R.
N. Ismailova, V.F. Sopin, Spectrophotometric determination of mesalazine in
urine for assessing the acetylation phenotype in vivo in humans, Pharm. Chem.
J. 45 (12) (2012) 757–760, https://doi.org/10.1007/s11094-012-0719-y.
[41] N.J. Thumar, M.P. Patel, Synthesis, characterization, and antimicrobial
evaluation of carbostyril derivatives of 1H-pyrazole, Saudi Pharm. J. 19 (2)
(2011) 75–83, https://doi.org/10.1016/j.jsps.2011.01.005.
[19] E. Pastorini, M. Locatelli, P. Simoni, G. Roda, E. Roda, A. Roda, Development and
validation of
a HPLC-ESI-MS/MS method for the determination of 5-
aminosalicylic acid and its major metabolite N-acetyl-5-aminosalicylic acid
in human plasma, J. Chromatogr. B. 872 (1-2) (2008) 99–106, https://doi.org/
10.1016/j.jchromb.2008.07.026.
ˇ
ˇ
[20] M. Nobilis, Z. Vybíralová, K. Sládková, M. Lísa, M. Holcapek, J. Kvetina, High-
performance liquid-chromatographic determination of 5-aminosalicylic acid
and its metabolites in blood plasma, J. Chromatogr. A. 1119 (1-2) (2006) 299–
308, https://doi.org/10.1016/j.chroma.2006.01.058.
[21] J.A. Rafael, J.R. Jabor, R. Casagrande, S.R. Georgetti, M.d.F. Borin, M.J.V. Fonseca,
Validation of HPLC, DPPHꢀ and nitrosation methods for mesalamine
13

L. Sabahi-Agabager, H. Eskandari, F. Nasiri et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 258 (2021) 119846
[42] J.R. Hemmer, S.O. Poelma, N. Treat, Z.A. Page, N.D. Dolinski, Y.J. Diaz, W.
Tomlinson, K.D. Clark, J.P. Hooper, C. Hawker, J. Read de Alaniz, Tunable visible
and near infrared photoswitches, JACS 138 (42) (2016) 13960–13966, https://
doi.org/10.1021/jacs.6b07434.
[43] F. Jensen, Introduction to computational chemistry, second ed., John wiley &
sons, West Sussex, 2007.
[44] C.A. Ullrich, Time-dependent density-functional theory: concepts and
applications, OUP Oxford, New York, 2011.
[45] A. Pałasz, A Green Approach to the Synthesis of Fused Uracils: Pyrano [2, 3-d]
pyrimidines.‘On-Water’One-Pot Synthesis by Domino Knoevenagel/Diels-
Alder Reactions, Synthesis 2010 (2010) 4021–4032, https://doi.org/10.1055/
s-0030-1258292.
[55] B. Mennucci, R. Cammi, J. Tomasi, Excited states and solvatochromic shifts
within
a nonequilibrium solvation approach: A new formulation of the
integral equation formalism method at the self-consistent field, configuration
interaction, and multiconfiguration self-consistent field level, J. Chem. Phys.
109 (7) (1998) 2798–2807, https://doi.org/10.1063/1.476878.
[56] A.V. Marenich, C.J. Cramer, D.G. Truhlar, Universal solvation model based on
solute electron density and on a continuum model of the solvent defined by
the bulk dielectric constant and atomic surface tensions, J. Phys. Chem. B. 113
(18) (2009) 6378–6396, https://doi.org/10.1021/jp810292n.
[57] F. Furche, R. Ahlrichs, Adiabatic time-dependent density functional methods
for excited state properties, J. Chem. Phys. 117 (16) (2002) 7433–7447, https://
doi.org/10.1063/1.1508368.
[46] M.L. Deb, P.J. Bhuyan, Uncatalysed Knoevenagel condensation in aqueous
medium at room temperature, Tetrahedron Lett. 46 (38) (2005) 6453–6456,
https://doi.org/10.1016/j.tetlet.2005.07.111.
[47] C. Verrier, S. Moebs-Sanchez, Y. Queneau, F. Popowycz, The Piancatelli reaction
and its variants: recent applications to high added-value chemicals and
biomass valorization, Org. Biomol. Chem. 16 (5) (2018) 676–687, https://doi.
org/10.1039/C7OB02962D.
[48] O. Nieto Faza, C. Silva Lopez, R. Álvarez, Á.R. de, Lera, Theoretical study of the
electrocyclic ring closure of hydroxypentadienyl cations, Chem. Eur. J. 10
(2004) 4324–4333, https://doi.org/10.1002/chem.200400037.
[49] N. Mallo, A. Tron, J. Andréasson, J.B. Harper, L.S. Jacob, N.D. McClenaghan, G.
Jonusauskas, J.E. Beves, Hydrogen-bonding donor-acceptor Stenhouse adducts,
ChemPhotoChem (2020), https://doi.org/10.1002/cptc.201900295.
[50] N. Mallo, P.T. Brown, H. Iranmanesh, T.S.C. MacDonald, M.J. Teusner, J.B.
Harper, G.E. Ball, J.E. Beves, Photochromic switching behaviour of donor–
acceptor Stenhouse adducts in organic solvents, ChemComm. 52 (93) (2016)
13576–13579, https://doi.org/10.1039/C6CC08079K.
[58] T. Lu, F. Chen, Multiwfn: a multifunctional wavefunction analyzer, J. Comput.
Chem. 33 (5) (2012) 580–592, https://doi.org/10.1002/jcc.22885.
[59] D.L. French, J.W. Mauger, Evaluation of the physicochemical properties and
dissolution characteristics of mesalamine: relevance to controlled intestinal
drug delivery, Pharm. Res. 10 (1993) 1285–1290, https://doi.org/10.1023/
A:1018909527659.
[60] K. Box, C. Bevan, J. Comer, A. Hill, R. Allen, D. Reynolds, High-throughput
measurement of p K a values in a mixed-buffer linear pH gradient system,
Anal. Chem. 75 (4) (2003) 883–892, https://doi.org/10.1021/ac020329y.
[61] I.M. Kolthoff, M.K. Chantooni, Substituent effects on dissociation of benzoic
acids and heteroconjugation of benzoates with p-bromophenol in acetonitrile,
N, N-dimethylformamide, and dimethyl sulfoxide. Intramolecular hydrogen
bonding in o-hydroxybenzoic acids and their anions, JACS. 93 (16) (1971)
3843–3849, https://doi.org/10.1021/ja00745a001.
[62] P.J. Taylor, G. van der Zwan, L. Antonov, Tautomerism: Introduction, history,
and recent developments in experimental and theoretical methods, in: L.
Antonov (Ed.), Tautomerism: methods and theories, Wiley-VCH Verlag GmbH
& Co. KGaA, Weinheim, 2014, pp. 1–24.
[51] J.-D. Chai, M. Head-Gordon, Systematic optimization of long-range corrected
hybrid density functionals, J. Chem. Phys. 128 (8) (2008) 084106, https://doi.
org/10.1063/1.2834918.
[63] A.D. Dubonosov, V.A. Bren, V.I. Minkin, Enolimine-Ketoenamine Tautomerism
for Chemosensing, in: L. Antonov (Ed.), Tautomerism: Concepts and
[52] H. Iikura, T. Tsuneda, T. Yanai, K. Hirao, A long-range correction scheme for
generalized-gradient-approximation exchange functionals, J. Chem. Phys. 115
(8) (2001) 3540–3544, https://doi.org/10.1063/1.1383587.
[53] M.M. Francl, W.J. Pietro, W.J. Hehre, J.S. Binkley, M.S. Gordon, D.J. DeFrees, J.A.
Pople, Self-consistent molecular orbital methods. XXIII. A polarization-type
basis set for second-row elements, J. Chem. Phys. 77 (7) (1982) 3654–3665,
https://doi.org/10.1063/1.444267.
[54] M.W. Schmidt, K.K. Baldridge, J.A. Boatz, S.T. Elbert, M.S. Gordon, J.H. Jensen, S.
Koseki, N. Matsunaga, K.A. Nguyen, S. Su, T.L. Windus, M. Dupuis, J.A.
Montgomery, General atomic and molecular electronic structure system, J.
Comput. Chem. 14 (11) (1993) 1347–1363, https://doi.org/10.1002/
jcc.540141112.
Applications in Science and Technology, Wiley-VCH Verlag GmbH
KGaA, Weinheim, 2016, pp. 229–251.
[64] D.A. Skoog, D.M. West, F.J. Holler, S.R. Crouch, Fundamentals of Analytical
Chemistry, ninth ed., Cengage Learning, Belmont, 2013.
[65] D.C. Montgomery, Design and analysis of experiments, ninth ed., John wiley &
sons, Hoboken, 2017.
[66] H. Hadi, Continuous flow injection spectrophotometric determination of
mesalazine in pharmaceutical forms, Syst. Rev. Pharm. 12 (2021) 202–208,
https://doi.org/10.31838/srp.2021.2.25.
[67] Y. Hu, Y. Wang, R. Guan, C. Zhang, X. Shao, Q. Yue, Construction of a ratio
fluorescence assay of 5-aminosalicylic acid based on its aggregation induced
emission with blue emitting N/P-codoped carbon dots, RSC Adv. 11 (12) (2021)
6607–6613, https://doi.org/10.1039/D0RA10258J.
& Co.
14