Studies on the antioxidant activity of some thiazolidinedione, imidazolidinedione and rhodanine derivatives having a flavone core

Article abstract of DOI:10.1002/bio.2667

A series of flavonyl-2,4-thiazolidinedione, imidazolidinedione and rhodanine derivatives were tested for their antioxidant activity as scavengers of oxygen free radicals. Free radical scavenging activities, including superoxide anion radical (O^-₂), hydroxyl radical (HO^?) and 2,2′-diphenyl-1-picrylhydrazyl free radical have been evaluated using chemiluminescence, electron paramagnetic resonance and spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide as a spin trap. Potassium superoxide in dimethylsulfoxide and 18-crown-6 ether were used for the production of O^-₂. Hydroxyl radical was generated using the Fenton reaction. Ten of the eleven examined compounds exhibited decrease in chemiluminescence, but there were large differences in the decrease, ranging from 16% to 89%; also, two of these compounds increased light emission by about 200%. On the contrary, all compounds tested exhibited 30-68% scavenging HO^? and 25-96% scavenging the DPPH radical respectively. Possible mechanisms are proposed to explain the results.

Full text of DOI:10.1002/bio.2667

Research article
Received: 2 January 2014,
Accepted: 18 February 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2667
Studies on the antioxidant activity of some
thiazolidinedione, imidazolidinedione and
rhodanine derivatives having a flavone core
Paweł Berczyński,a Aleksandra Kładna,b Teresa Piechowska,a Irena Kruk,a
Oya Bozdağ-Dündar,c Hassan Y. Aboul-Enein,d* Meltem Ceylan-Unlusoyc
and Rahmiye Ertanc
ABSTRACT: A series of flavonyl-2,4-thiazolidinedione, imidazolidinedione and rhodanine derivatives were tested for their
antioxidant activity as scavengers of oxygen free radicals. Free radical scavenging activities, including superoxide anion radical
¯
ꢀ
•
(O2 ), hydroxyl radical (HO ) and 2,2′-diphenyl-1-picrylhydrazyl free radical have been evaluated using chemiluminescence,
electron paramagnetic resonance and spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide as a spin trap. Potassium superoxide
¯
in dimethylsulfoxide and 18-crown-6 ether were used for the production of Oꢀ2. Hydroxyl radical was generated using the Fenton
reaction. Ten of the eleven examined compounds exhibited decrease in chemiluminescence, but there were large differences in
the decrease, ranging from 16% to 89%; also, two of these compounds increased light emission by about 200%. On the contrary,
•
•
all compounds tested exhibited 30–68% scavenging HO and 25–96% scavenging the DPPH radical respectively. Possible
mechanisms are proposed to explain the results. Copyright © 2014 John Wiley & Sons, Ltd.
Keywords: flavone derivatives; radical scavenging activity; chemiluminescence; EPR study
Introduction
Experimental
Flavonoids are a well-known class of natural compounds that
possess radical scavenging properties due to their ability to form
stable radicals (1). The reactive oxygen species (ROS)-scavenging
abilities of flavonoids give them beneficial effects, such as anti-
inflammatory, neuroprotective, cardioprotective and ultraviolet
(UV)B-protective activities (2). All these activities have been asso-
ciated with beneficial health effects (3,4). Therefore, flavonoids
are important components of the human diet. However, most
interest has been devoted to their antioxidant activity, which is
due to their ability to reduce free radical formation and to
scavenge free radicals (5). Among various ROS, superoxide anion
Chemistry
The compounds F1–F6 (8), F7 (9), F8, F10, F11 (10) and F12 (11)
were synthesized by the Knoevenagel reaction of flavone
carboxaldehyde with thiazolidine-2,4-dione/imidazolidine-2,
4-dione/2-thioxo-imidazolidine-4-one using acetic acid/sodium
acetate mixture. Methylated compound (F9) (8) was obtained by
reacting F7 with methyl iodide in dimethylformamide/anhydrous
sodium carbonate mixture. All reagents were purchased from
E. Merck (Darmstadt, Germany) and Aldrich (Milwaukee, MI, USA).
The chemical reagents used for evaluation of antioxidant activity
were purchased from the following sources: tiron (4,5-dihydroxy-1,
3-benzene-disulfonic acid), 5,5-dimethyl-1-pyrroline oxide
(DMPO), 18-crown-6-ether (1,4,7,10,13,16)-hexaoxacyclooctane,
À
Á
¯
radical Oꢀ2 is known as an initiator of several reactions leading
to the formation of other oxygen species, such as hydrogen
peroxide (H2O2) that can be converted in the presence of
transition metal ions into a highly reactive short-lived hydroxyl
•
radical (HO ) able to cause tissue injury. In recent years,
* Correspondence to: Professor H. Y. Aboul-Enein, Pharmaceutical and
Medicinal Chemistry Department, Pharmaceutical and Drug Industries
Research Division, National Research Centre, Dokki, Cairo 12311, Egypt.
E-mail: haboulenein@yahoo.com
flavonoids as potent free radical scavengers have attracted
tremendous interest as possible therapeutics against free radical
mediated pathophysiology of several conditions, such as neuro-
degenerative and cardiovascular diseases, cancer and ageing,
caused by oxidative stress (6). The excellent free radical scavenging
(chain-breaking antioxidation) property of flavonoids is due to their
high reactivity as hydrogen or electron donors (7).
a
West Pomeranian University of Technology, Szczecin Institute of Physics,
al. Piastów 48, 70-311 Szczecin, Poland
b
Department of History of Medicine and Medical Ethics, Pomeranian Medical
University, Rybacka 1, 70-204 Szczecin, Poland
In this study, we report the in vitro antioxidant capacity
of flavonylrhodanines (F1–F6), flavonyl-thiazolidine-2,4-diones
(F7–F10), and flavonyl-imidazolidine-2,4-diones (F11, F12)
(Fig. 1) as scavengers ofOꢁ2 and HO radicals using chemilumines-
cence (CL) and electron paramagnetic resonance spectrometry
(EPR) techniques.
c
Ankara University, Faculty of Pharmacy, Department of Pharmaceutical
Chemistry, 06100 Tandoğan, Ankara, Turkey
d
Pharmaceutical and Medicinal Chemistry Department, Pharmaceutical and
Drug Industries Research Division, National Research Centre, Dokki, Cairo
12311, Egypt
Luminescence 2014
Copyright © 2014 John Wiley & Sons, Ltd.

P. Berczyński et al.
Figure 1. Chemical structures of the tested compounds (flavonyl-2,4-thiazolidinedione, imidazolidinedione and rhodanine derivatives).
Trolox (6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid from Merck
(Darmstadt, Germany); ammonium ferrous sulfate hexahydrate and
anhydrous dimethylsulfoxide (DMSO) from Aldrich (Milwaukee,
radical concentration was determined using the UV spectrum
(λmax = 251 nm, ε = 2686 29 mol/cm).
¯
The reactivity of the tested compounds towards Oꢀ2 was
•
WI, USA); 1,1-diphenyl-2-picryl hydrazyl (DPPH ), catalase from
monitored using the CL technique (13).
CL kinetics and the effect of the examined compounds (TZD
derivatives), tiron, salicylate and NBT on light intensity were
measured using an EMI9553Q photomultiplier (Photek ,East
Sussex, UK) with an S20 cathode sensitive in the range 200–
800 nm, interfaced with a computer for data acquisition and
handling. Reagents were introduced to a thermostated glass reac-
tor cell placed just before the light detector in a light-tight camera.
Reagents were injected through polyethylene pipes with the aid of
semiautomatic syringes. The cuvette was exhausted using a B-169
vacuum system (Büchi, Flawill, Switzerland). All measurements
bovine liver and p-nitroblue-tetrazolium chloride (NBT) from
Sigma-Aldrich GmbH (Sternheim, Germany); and potassium
superoxide from Fluka (Buchs, Switzerland). Other reagents were
obtained from POCH (Gliwice, Poland). They were of analytical
grade and were prepared fresh daily. The flavonyl-2,4-
thiazolidindione, imidazolidinedione and rhodanine derivatives
(TZD compounds) were dissolved in DMSO, which was suitable
for dissolving both water-soluble and water-insoluble reagents.
¯
Superoxide anion radical ðOꢀ2Þ was prepared from KO2 according
to the method described by Valentine et al. (12). 18-Crown-6 ether
(60 mg) was dissolved in 10 mL dry DMSO, and then 7 mg KO2 was
added quickly to avoid contact with air humidity. The mixture of
reagents was stirred for 1 h to give a pale yellow solution of
¯
were carried out at 295 1 K. The CL signal from the Oꢀ2 /DMSO
system or that influenced by the tested compounds was recorded
as the kinetic curve of the CL decay. The CL intensity was used to
determine the reactivity of the tested compounds and their
reactivity was compared with those well known in the
subject literature as inhibitors of Oꢁ2 radicals. The quenching
¯
10 mmol/L superoxide anion radical. The Oꢀ2 concentrated solution
could be stored at 255 K for weeks without major decomposition.
¯
For CL experiments, Oꢀ2 was used as a 1 mmol/L solution. The
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Copyright © 2014 John Wiley & Sons, Ltd.
Luminescence 2014

Antioxidant activity of some heterocyclic compounds with flavone core
activity was calculated as ratio Q(%) = [(Io – I)/Io] ꢂ 100%, where
¯
reaction of Oꢀ2 produced in DMSO (13). The emission spectrum
was found to have four bands with maxima at 480 nm, 580 nm,
640 nm and 700 nm. The CL bands at 640 nm and 700 nm were
described to the vibrational component (0,0),(1,0) transition in
O2 (1Δg) dimole (18,19):
Io is the light intensity measured in the absence of an inhibitor
and I is the light intensity measured in the presence of the
¯
inhibitor. Because addition of DMSO to the Oꢀ2 /DMSO system
caused a short-lasting small “flash” followed by a small increase
in the CL, this reaction was considered as the control reaction.
Hydroxyl radical scavenging activity was evaluated using the
Haber Weiss/Fenton reactions as a source of the radical (14,15)
as follows:
ꢀ
ꢀ
ꢁ
2 O2 1Δg Þ→2 O2 3Σgꢁ þ hν
1
where Δg and 3Σꢁg are the first excited state and the ground
state of the O2 molecule, respectively. The band at 580 nm can
be attributed to the same transition but with a vibrational
quantum number of (1,0), whereas the band at 480 nm corre-
sponds to the simultaneous transition in the O2 dimole:
H2O2 þ FeðIIÞ → HOꢀ þ FeðIIIÞ þ HOꢁ
FeðIIÞ þ HOꢀ → FeðIIIÞ þ HOꢁ
H2O2 þ HOꢀ → HOOꢀ þ H2O
ꢀ
ꢀ
ꢀ
ꢁ
O2 1Δg Þ O2 1Σgþ Þ→2 O2 3Σgꢁ þ hν
and EPR conjugated with the spin-trapping technique using
DMPO as a spin trap (16).
with a quantum number of (0,0). The spectra were presented in a
recent paper (13). Based on the spectroscopic and literature
data the following reactions may be responsible for the 1O2
generation (18,20).
The Fenton reaction mixtures in the sample cell contained the
following reagents at the indicated final concentrations (in the
final volume of 2 mL): ammonium ferrous sulfate (0.0625 mmol/L),
sodium trifluoroacetate buffer (0.02 mmol/L, pH 6.15), H2O2
(0.5mmol/L), DMPO (25 mmol/L).The reaction was started by addi-
tion of the Fe(II) ion. The mixture was placed in the EPR cavity
using a quartz flat cell within ꢀan optical path length of 0.25 mm.
¯
Oꢀ2→1O2 þ electron
(1)
(2)
(3)
¯
¯
Oꢀ2 þ O2→Oꢀ4
À
Á
The spin-trapped DMPO ꢁ OH signal was analyzed 1 min after
the addition ammonium ferrous sulfate on a standard EPR
spectrometer operating at 9.3GHz with 100 kHz modulation of
the steady magnetic field. Tested TZD derivatives were dissolved
in DMSO because of insolubility in water and were added before
the Fe ion.
¯
¯
¯
Oꢀ4 þ Oꢀ2→ 1O2 þ Oꢀ2
2
2Oꢀ2 þ 2ðCH3Þ2SO→1O2 þ ðCH3Þ SO2 þ CH3SOðCH2Þꢁ þ OHꢁ (4)
¯
2
À
2
1O2 → 1O2 Þ2→2 3O2 þ light
(5)
•
The ability to scavenge HO was calculated using the follow-
Singlet oxygen dimoles (1O2)2 emit ultraweak CL during their
radiative deactivation to the ground state (3O2).
ing formula:
¯
Fig. 2 presents the CL kinetics detected from the Oꢀ2 /DMPO
Rð%Þ ¼ ½ðHo–HÞ=Hoꢃ ꢂ 100%
system alone (blank) (curve 1), and in the presence of well-known
¯
inhibitors of Oꢀ2 -Tiron (curve 6) and NBT (curve 5), and in the
where Ho and H represent the relative height of the second peak
in the EPR spectrum of the spin-adduct from the blank (DMSO)
and in the presence of a sample dissolved in an appropriate
amount of DMSO, respectively.
presence of representative compounds F7 and F10 (curves 4 and
3, respectively). Tiron and NBT showed high responses against
¯
Oꢀ2 and 1O2, which was in good agreement with the literature data
•
DPPH scavenging activity was measured according to the
(21). Compound F7, similarly as compounds F1–F6, F8, F11 and F12
(kinetics not shown) represented antiradical properties. Com-
pounds F9 and F10 enhanced the maximal intensity of CL. The
method given by Nanjo et al. (17), except for the DMSO as a
solvent instead of ethanol. The DMSO solution of each sample
(100 μL) or DMSO itself as a control was added to 100 μL of
2,2′-diphenyl-1-picrylhydrazyl (DPPH) dissolved in DMSO. After
mixing for 10 s, the solution was introduced into flat cell, and DPPH
signal was detected 2 min later. The scavenging ratio was calcu-
lated using the following equation R(%) = [(Ho – H)/Ho] ꢂ 100%,
where Ho and H are the relative heights of the third peak
in the EPR spectrum of the DPPH radical in the absence
of a tested compound and in the presence of the com-
pound, respectively.
¯
Oꢀ2 scavenging ratios of the TZD derivatives were examined and
compared to that of Tiron and NBT as shown in Fig. 3. The results
¯
indicated that the Oꢀ2 -dependent light emission was quenched by
flavones F1–F8, F11 and F12 varying from 16% to 89% at concen-
tration of 1 mmol/L. The majority of the compounds exhibited the
¯
Oꢀ2 scavenging activity at least equal with that monitored specifi-
cally for these radical scavengers Tiron and NBT (at the same
concentration) or higher activity. It is noteworthy that the absolute
¯
second order rate constant interaction between Oꢀ2 and Tiron was
determined as 5 ꢂ 108 L/mol per s (22). This means that the tested
¯
Results and discussion
TZD derivatives in the reaction with Oꢀ2 could serve as efficient
reducing agents or as a proton source (7):
Superoxide anion radical scavenging capacity
¯
-
¯
ꢀ
•
Oꢀ2 þ TZDðNHÞ → TZDðNꢀÞ þ HO2 H–atom transfer
(6)
(7)
The shorter half-life of HO and O2 in aqueous solution makes
them difficult to measure and only a few techniques can be
utilized. In our laboratory, the Oꢀ2 antiradical measurement of
several pharmaceuticals and plant extracts showing antioxidant
activity have been carried out based on CL accompanying the
HOꢁ2 þ ðCH3Þ2SO → OHꢁ þ ðCH3Þ2SO2
¯
À
Á
¯
-
Oꢀ2 þ TZDðN-CH3Þ → TZD N-CH2 þ HOꢀ2 proton transfer (8)
Luminescence 2014
Copyright © 2014 John Wiley & Sons, Ltd.
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P. Berczyński et al.
Hydroxyl radical scavenging capacity
180
160
140
120
100
80
The hydroxyl radical as a short-lived (t1/2 ≈ 10ꢁ 9s) species would
be detected using the EPR spectroscopy in combination with the
spin-trapping method, i.e., the radical addition to a spin trap. The
method is based on the formation of a stable free radical by
reacting covalently with a trap with an unstable free radical.
Nitrones, e.g., DMPO are the spin traps most commonly used.
Using this method and the Fenton reaction as a generator of
•
HO (14,15), we examined reactivity of TZD derivatives towards
60
the radical (Fig. 4). The hydroxyl radical trapped by DMPO gives
a spin-adduct for which the EPR spectrum shows four-splitted
lines with an intensity ratio 1: 2: 2: 1 and hyperfine splitting
40
20
constant of aN ¼ aβ ¼ 14:9 G. The parameters we measured
H
0
are consistent with those values for the DMPO ꢁ OH spin adduct
reported by other authors (16). All examined TZD derivatives were
able to decrease the EPR signal amplitude of the DMPO ꢁ OH spin
adduct at least by 30% (ranging from 25% to 68%) at concentra-
tion of 2.5 mmolL-1 (Fig. 4). The scavenging effects exhibited by
compounds F1, F2, F4, F7, F8 and F11 are significantly higher
than an inhibition of the signal found for positive control
salicylate. A salicylate concentration of 3.5 mmol/L exhibited
20
40
60
80
100
120
140
160
180
Figure 2. Scavenging effect of the representative compounds F7 (curve 4) and
¯
F10 (curve 3) and reference Oꢀ2 inhibitors Tiron (curve 6) and p-nitroblue-tetrazo-
¯
lium chloride (curve 5) on the CL intensity recorded from 1 mmol/L Oꢀ2 in DMSO af-
¯
ter adding DMSO (0.5 mL) (curve 2) (control). Curve 1 represents blank (Oꢀ2/DMSO).
Reaction mixtures contained (1 mmol/L) of the flavonyl-2,4-thiazolidinedione,
imidazolidinedione and rhodanine derivatives or reference inhibitors. An arrow
indicates the moment of the compounds dissolved in 0.5 mL DMSO or 0.5 mL of
DMSO addition. Denotations of the examined compounds are given in Fig. 1. CL,
chemiluminescence; DMSO, dimethylsulfoxide.
•
the HO scavenging ratio equal to about 40%, although the rate
•
constant for the salicylate reaction with HO was reported to be
high 1.2 ꢂ 1010 L/mol per s (24). We checked the specificity of
•
the Fenton reaction as a generator of HO by the addition of
100
catalase (19,900 U/mg) from bovine liver, an enzyme decomposing
H2O2. Catalase at a concentration of 180 μg/L prevented the
appearance of any EPR signal.
80
60
The ERP spin-trapping method used for estimating the ability
•
of the tested compounds to scavenge HO is the technique
40
routinely applied for detection of short-lived oxygen species.
The hydroxyl radical exhibits the high reactivity with ethanol
(20); therefore, addition of this compound should have an
influence on the DMPO-OH spin adduct formation. Indeed, the
presence of 4.9 mol/L ethanol in the Fenton–DMPO reaction
caused inhibition of the EPR signal amplitude by about 75%,
and resulted in the appearance of a new six-line spectrum due
to trapping of the α-hydroxyethyl radical (16) (data not shown).
In turn, the addition of catalase (a key enzyme playing a part in
the decomposition of H2O2) at the concentration of 150 μg/mL
20
0
-20
-40
Figure 3. Superoxide radical scavenging activity of the flavonyl-2,4-
thiazolidinedione, imidazolidinedione and rhodanine derivatives (F1–F12), Tiron
¯
and NBT (1 mmol/L) monitored using the chemiluminescence from 1 mmol/L O2ꢀ
arising in DMSO. Temperature 295 K. The remaining conditions are reported in
Experimental section. NBT, p-nitroblue-tetrazolium chloride.
80
70
60
50
40
30
20
10
¯
Depending on the nature of products arising from Oꢀ2 in reac-
tions 6 and 8, consistent with the CL mechanism, it is likely that
reaction 6 was responsible for the scavenging of Oꢀ2 and reaction
8 might be responsible for an increase of the light emission
observed for compounds F9 and F10 as follows (21,23):
¯
À
Á
¯
2 HOꢀ2 → 1O2 þ H2O2
k ≈ 106L=mol=s
(9)
0
F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 SA
À
Á
¯
1
HOꢀ2 þ Oꢀ2 → H2O2 þ O2
k ≈ 8:5 ꢂ 107L=mol=s
(10)
Figure 4. The inhibitory effect of the flavonyl-2,4-thiazolidinedione, imidazolidinedione
and rhodanine derivatives (F1–F12) and SA (2.5mmol/L) exerted on the 5,5-dimethyl-
1-pyrroline oxide-OH spin adduct formation. Measurement conditions are reported in
the Experimental section. The electron paramagnetic resonance spectrometry
settings were microwave power 20mW, modulation amplitude 0.5G, time constant
0.3 s and receiver gain 4 ꢂ 104. Temperature 295 K. SA, salicylate.
The structural feature of TZD derivatives provides the conjuga-
tion between the D-ring and B-ring or A-ring, and contributes to
the stabilization of the products arising from TZD transformation.
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Luminescence 2014

Antioxidant activity of some heterocyclic compounds with flavone core
completely eliminated the spectrum. These findings further
120
100
80
60
40
20
0
•
indicate that H2O2 was the necessary reagent for HO generation
by the Fenton reaction, and confirm that the observed EPR
•
spectrum is attributed to the HO ꢁ DMPO reaction.
As one of the modes of action in antioxidants is chelating metal
ions, such as Fe(II)/Fe(III) and Cu(I)/Cu(II) involved in the conversion
¯
of Oꢀ2 and H2O2 into HO in the Fenton reaction (14,15), we
•
examined if TZD derivatives were able to form complexes with
Fe ions under our experimental conditions. We found, using
UV-visible spectrophotometry, that the compounds tested
might not exert their antioxidant effects through binding Fe(II)
and Fe(III) ions (data not shown). These findings are consistent
with those of Linxiang and co-workers (25).
F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 AA Trolox
Figure 6. Scavenging effect of the tested flavonyl-2,4-thiazolidinedione,
imidazolidinedione and rhodanine derivatives, AA and Trolox (1.25 mmol/L) on free
radical 2,2′-diphenyl-1-picrylhydrazyl in ethanol (75%, v/v)/dimethylsulfoxide
(25%, v/v) solution. Denotations of the examined compounds are given in Fig. 1.
Measurement conditions are reported in the Experimental section. The electron
paramagnetic resonance spectrometry settings were microwave power 20 mW,
modulation amplitude 0.2 G, time constant 0.2 s and receiver gain 3.2 ꢂ 104.
Temperature 295 K. AA, ascorbic acid.
The hydroxyl radical is one of the strongest oxidizing agents
able to react with the first encountered biomolecule in vivo
(21,26). The species is involved in several reactions, such as adding
to a double bond, e.g., in the benzene molecule, reaction with
hydrogen-containing molecules resulting in H-abstraction, and the
•
rapid electron transfer reaction. The mutagenic capacities of HO
and pathophysiological implications have been extensively
•
studied (27,28). Therefore, a study on the inhibition of HO
As seen from Fig. 5 only ascorbic acid, Trolox and compound
F4 reacted rapidly with the DPPH , reaching a steady state in less
than 2 min. The remaining compounds reacted more slowly with
the radical.
and the search for compounds as good antioxidants, particu-
larly of natural origin, have attracted attention as agents to
prevent against oxidative stress.
•
As indicated in the Experimental section, the antiradical
activity was evaluated from the plot of the percentage DPPH
•
2,2′-Diphenyl-1-picrylhydrazyl radical scavenging activity
remaining when the kinetics reached a steady state. Fig. 6
presents these data. Among the compounds examined, F4 was
the most potent in the DPPH scavenging, reaching about 90%
The ability of the tested compounds to exhaust their hydrogen
donating activity was detected using DPPH radical. This com-
pound as a stable free radical is able to abstract the hydrogen
atom directly or via an electron transfer process (29–31). A typical
EPR spectrum of DPPH monitored in DMSO is presented in Fig. 5.
The spectrum measured is very similar to that reported by
•
effect. The remaining TZD derivatives presented the antiradical
efficiency ranging from 27% to 56% being lower than that of
ascorbic acid and Trolox.
•
It is commonly accepted that the ability of antioxidants to
scavenge the DPPH belongs to their hydrogen-donating ability
other authors (30). All tested TZD derivatives were able to
decrease the EPR signal from the DPPH radical due to its
•
•
or an electron process (28,31). The data reported in Fig. 5
showed that reactions of the tested derivatives are biphasic,
similar to the reference antioxidants used in this study namely
ascorbic acid and Trolox. The reduction of the DPPH radical
was successfully used for the primary characterization of
total antioxidant activity of several biologically important com-
pounds (17,29,30,32).
reduction. We compared the influence of TZD derivatives on
the EPR spectrum of DPPH to the behavior of the well-known
radical scavengers, ascorbic acid and vitamin E analog, Trolox.
•
100
80
60
40
20
0
Conclusions
The findings in the present study revealed promising flavone
derivatives with outstanding oxygen free radicals scavenging
property. The preliminary TZD derivatives evaluation indicated
that 10 of the 12 examined compounds exhibited significant
¯
direct scavenging activities towards Oꢀ2, and all compounds were
•
effective as HO scavengers. This property is important with
regard to the participation of ROS in cell damage under
oxidative stress. In addition, TZD derivatives were found to be
•
effective as reducing agents in the reaction with DPPH . The
0
2
4
6
8
10
Time (min)
design of flavone-based drugs against ROS and the primary
screening of their antioxidant capacity constitutes a promising
direction for novel anticancer pharmaceutical drugs, long-term
prevention against neurodegenerative pathologies or natural
product, such as antioxidants for use in, for example, food
preservatives.
Figure 5. The disappearance of the 2,2′-diphenyl-1-picrylhydrazyl radical as a
function of time in the presence of flavonyl-2,4-thiazolidinedione,
imidazolidinedione and rhodanine derivatives, Trolox and AA (1.25 mmol/L). The
reaction contained ethanol (75%, v/v) and dimethylsulfoxide (25%, v/v). AA,
ascorbic acid.
Luminescence 2014
Copyright © 2014 John Wiley & Sons, Ltd.
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P. Berczyński et al.
16. Finkenstein E, Rosek GM, Rauckamn EJ. Spin trapping of superoxide and
hydroxyl radical: practical aspects. Arch Biochem Biophys 1980;200:1–16.
17. Nanjo F, Goto K, Seto R, Suzuki M, Sakai M, Hara Y. Scavenging
effects of tea catechins and their derivatives on 1,1-diphenyl-2-
picrylhydrazyl radical. Free Radic Biol Med 1966;21:895–952.
18. Khan AU, Kasha M. Chemiluminescence arising from simultaneous
transition in pairs of singlet oxygen molecules. J Am Chem Soc
1970;92:3293–300.
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