Synthesis, molecular docking and biological evaluation of 3-arylfuran-2(5H)-ones as anti-gastric ulcer agent

Article abstract of DOI:10.1016/j.bmc.2015.05.026

3-Arylfuran-2(5H)-one derivatives show good antibacterial activity and were determined as tyrosyl-tRNA synthetase (TyrRS) inhibitors. In a systematic medicinal chemistry exploration, we demonstrated chemical opportunities to treat infections caused by Hel

Full text of DOI:10.1016/j.bmc.2015.05.026

Accepted Manuscript
Synthesis, molecular docking and biological evaluation of 3-Arylfuran-2(5H)-
ones as anti-gastric ulcer agent
Xu-Dong Wang, Wei Wei, Peng-Fei Wang, Li-Cheng Yi, Wei-Kang Shi, Yong-
Qiang Xie, Lang-Zhou Wu, Nian Tang, Liang-Song Zhu, Jia Peng, Chan Liu,
Xian-Hui Li, Shi Tang, Zhu-Ping Xiao, Hai-Liang Zhu
PII:
S0968-0896(15)00426-5
DOI:
http://dx.doi.org/10.1016/j.bmc.2015.05.026
BMC 12322
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
22 April 2015
13 May 2015
15 May 2015
Please cite this article as: Wang, X-D., Wei, W., Wang, P-F., Yi, L-C., Shi, W-K., Xie, Y-Q., Wu, L-Z., Tang, N.,
Zhu, L-S., Peng, J., Liu, C., Li, X-H., Tang, S., Xiao, Z-P., Zhu, H-L., Synthesis, molecular docking and biological
evaluation of 3-Arylfuran-2(5H)-ones as anti-gastric ulcer agent, Bioorganic & Medicinal Chemistry (2015), doi:
http://dx.doi.org/10.1016/j.bmc.2015.05.026
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Synthesis, molecular docking and biological evaluation of
3-Arylfuran-2(5H)-ones as anti-gastric ulcer agent
Xu-Dong Wang, a Wei Wei,a Peng-Fei Wang,b Li-Cheng Yi,a,c Wei-Kang Shi,a
Yong-Qiang Xie,a Lang-Zhou Wu,a Nian Tang,a Liang-Song Zhu,a Jia Peng,a Chan Liu,a
Xian-Hui Li,a Shi Tang,a Zhu-Ping Xiao,a,* and Hai-Liang Zhu a,b,*
a College of Chemistry and Chemical Engineering, Jishou University, Jishou 416000, P. R.
China
bState Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing
210093, P. R. China
c The College of Chemistry of Xiangtan University, Xiangtan 411105, P. R. China
Abstract
3-Arylfuran-2(5H)-one derivatives show good antibacterial activity and were determined
as tyrosyl-tRNA synthetase (TyrRS) inhibitors. In a systematic medicinal chemistry
exploration, we demonstrated chemical opportunities to treat infections caused by
Helecobacter pylori. Twenty 3-arylfuran-2(5H)-ones were synthesized and evaluated for
anti-H. pylori, antioxidant and anti-urease activities which are closely interconnected
with H. pylori infection. The results displayed that some of the compounds show
excellent antioxidant activity, and good anti-H. pylori and urease inhibitory activities.
Out of these compounds, 3-(3-methylphenyl)furan-2(5H)-one (b9) showed the most
potent antioxidant activity (IC50=8.2 µM) and good anti-H. pylori activity (MIC50=2.6
µg/mL), and it can be used as a good candidate for discovering novel anti-gastric ulcer
agent.
Key words: 3-Arylfuran-2(5H)-one, anti-H. pylori, antioxidant, TyrRS, gastric ulcer
treatment
* Corresponding author. Tel.: +86-743-8563911; Fax: +86-743-8563911; E-mail address: xiaozhuping2005@163.com
* Corresponding author. Tel.: +86-25-8359 2572; Fax: +86-25-83592672; E-mail address: zhuhl@nju.edu.cn
1

1. Introduction
Helicobacter pylori (H. pylori), a Gram negative bacterium, plays an important role in
chronic gastritis, peptic ulcers, including gastric cancer and gastric lymphoma.1-5 H.
pylori infection leads to pathological changes in the gastric microenvironment, which are
caused by both direct and cascade effects of virulent factors. For instance, the host
immune cells (especially neutrophils) release large amounts of reactive oxygen species
(ROS), which are associated with inflammation, infiltration, activation of immune cells,
accumulation of reactive oxygen species, and oxidative DNA damage in the gastric
mucosa. 6-8
Triple therapy which consists of a proton pump inhibitor and two effective antibiotics is
commonly used for the treatment of H. pylori infection.9-10 However, the acquisition of
antibiotic resistance by H. pylori has severely weakened eradication therapy and presents
a serious problem such as allergy to antibiotics, severe complications (liver and/or kidney
dysfunction).11-12
To develop more effective and safer therapies, many substances from natural products
with
good
potency
against
H.
pylori
are
reported,
such
as
5-methoxy-3,4-dehydroxanthomegnin (a naphthoquinone from Paepalanthus latipes) 13,
epigallocatechin gallate (a major compound of Catechins)14 and 2-hydroxy-4-methoxy
benzaldehyde from Decalepis hamiltonii.15 2-Furanone framework is a part of many
natural and synthetic compounds, which possesses useful biological activities, including
anti-inflammatory and HIV-1 integrase inhibitory activities.16-22 It is to be noted that
many naturally sourced compounds with 2-furanone unit, such as Variagatic acid and
Vitamin C (Vc) (Scheme 1) were determined as efficient antioxidants, that is, compounds
2

are able to protect biomolecules from oxidative degradation, in particular through the
quenching ROS. In our group, derivatives as 3-aryl-4-aminofuran-2(5H)-ones,
3-aryl-4-acyloxyethoxyfuran-2(5H)-ones and 3-arylfuran-2(5H)-one-fluoroquinolone
hybrids have been previously reported to exhibit excellent inhibition activity against
pathogenic bacteria.23-29 However, the anti-H. pylori activity of them was not included.
Motivated by these findings and as a continuation of our ongoing efforts on the discovery
of novel chemical entities against H. pylori, twenty 3-arylfuran-2(5H)-ones were
synthesized and evaluated for anti-H. pylori, antioxidant and urease suppression activities
which are closely interconnected with the elimination of H. pylori infection.
The results diclosed that some of the compounds show excellent antioxidant activities,
compared urease inhibitory activities to that of the positive control AHA and good anti-H.
pylori activities. Both the biological evaluation and mechanism study suggested that
3-arylfuran-2(5H)-ones are good candidates for discovering novel anti-gastric ulcer
agents.
2. Materials and methods
2.1. Chemistry
All chemicals (reagent grade) were obtained from Aldrich (U.S.A) and Sinopharm
Chemical Reagent Co., Ltd (China) and used without further purification. Separation of
the compounds by column chromatography using silica gel (200-300 mesh) purchased
from Qingdao Haiyang Chemical Co.,Ltd (China). All the reactions were monitored by
thin-layer chromatography (TLC) using silica gel GF254 plates from Qingdao Haiyang
Chemical Co., Ltd (China) with an UV lamp (254 nm). Melting points were recorded on
3

1
the XT4 MP apparatus (Taike Corp., Beijing, China) and were uncorrected. H NMR
spectra were recorded using TMS as the internal standard in DMSO-d6 with a Bruker
spectrometer at 300 MHz. EI mass spectra were obtained on a Waters GCT mass
spectrometer, and elemental analyses were performed on a CHN-O-Rapid instrument and
were within 0.4 % of the theoretical values.
2.1.1. General procedure for preparation of compounds a1-a20
Compounds a1-a20 were synthesized by esterification of appropriate substituted sodium
phenylacetates with ethyl bromoacetate. Briefly, phenylacetic acid (40 mmol) and water
(20mL) were added to a round bottom flask and the pH value was adjusted to the range of
9.0 to 10.0 with 0.1M NaOH. Water was then removed under reduced pressure to give
the corresponding sodium phenylacetate, which was dissolved in 45 mL DMSO. To the
obtained solution, 4.5 mL ethyl bromoacetate was gently added, and was subsequently
stirred at room temperature for 3-4 h. The resulted mixture was poured into ice-water (50
mL), and extracted twice with 200 mL of AcOEt. The organic layer was dried over
MgSO4 followed by removal of the solvent under reduced pressure. The residue was then
purified by column chromatography on silica gel to give a1-a20 (Scheme 2) in yields of
90%-95%.
2.1.2. General procedure for preparation of compounds b1-b20
A solution of compound a (10 mmol) in dry THF (10 mL) was added to a suspension of
NaH (24 mmol) in dry THF (20 mL) in an ice cold bath, and the stirring was maintained
at room temperature for several hours (monitored by TLC). 30 mL of distilled water was
4

combined into the solution, which was extracted twice with ethyl ether. The aqueous
phase was cooled to 0°C and then acidified with concentrated hydrochloric acid to give a
solid precipitate. After filtration and washing with water, the compound was purified by
column chromatography on silica gel, eluting with AcOEt/petroleum ether.
4-hydroxy-3-phenylfuran-2(5H)-one (b1)
1
Colorless crystal, 50%, mp 244-254 °C; H-NMR (DMSO-d6): 4.77 (s, 2H, CH2);
7.20-7.25 (m, 3H, ArH); 7.90 (d, J = 7.7 Hz, 2H, ArH); 12.90 (s, 1H, OH); EIMS m/z 175
(M+). Anal. Calcd for C10H8O3: C, 68.18; H, 4.58; Found: C, 68.50; H, 4.38.
3-(2-fluorophenyl)-4-hydroxyfuran-2(5H)-one (b2)
1
Colorless crystal, 27%, mp 192-194 °C; H-NMR (DMSO-d6): 4.81 (s, 2H, CH2);
7.19-7.25 (m, 2H, ArH); 7.33-7.40 (m, 2H, ArH); 12.64 (s, 1H, OH); EIMS m/z 193 (M+).
Anal. Calcd for C10H7FO3: C, 61.86; H, 3.63; F, 9.78; Found: C, 61.95; H, 3.58; F, 9.66.
3-(2-chlorophenyl)-4-hydroxyfuran-2(5H)-one (b3)
1
Colorless crystal, 29%, mp 197-199 °C; H-NMR (DMSO-d6): 4.82 (s, 2H, CH2);
7.29-7.40 (m, 3H, ArH); 7.48-7.53 (m, 1H, ArH); 12.57 (s, 1H, OH); EIMS m/z 209 (M+).
Anal. Calcd for C10H7ClO3: C, 57.03; H, 3.35; Cl, 16.83; Found: C, 57.11; H, 3.28; Cl,
16.79.
3-(2-methylphenyl)-4-hydroxyfuran-2(5H)-one (b4)
Colorless crystal, 42%, mp 189-191 °C; 1H-NMR (DMSO-d6): 2.36 (s, 3H, CH3); 4.85 (s,
2H, CH2); 7.35-7.42 (m, 2H, ArH); 7.62-7.67 (m, 2H, ArH); 12.61 (s, 1H, OH); EIMS
m/z 189 (M+). Anal. Calcd for C11H10O3: C, 69.46; H, 5.30; Found: C, 69.55; H, 5.21.
3-(2-(benzyloxy)phenyl)-4-hydroxyfuran-2(5H)-one (b5)
5

Colorless crystal, 38%, mp 132-134 °C; 1H-NMR (DMSO-d6): 4.75 (s, 2H, CH2); 5.10 (s,
2H, CH2); 6.96 (t, J = 7.0 Hz, 2H, ArH); 7.15-7.40 (m, 5H, ArH); 7.45 (d, J = 6.8 Hz, 2H,
ArH); 12.13 (s, 1H, OH); EIMS m/z 281 (M+). Anal. Calcd for C17H14O4: C, 72.33; H,
5.00; Found: C, 72.32; H, 5.02.
3-(3-fluorophenyl)-4-hydroxyfuran-2(5H)-one (b6)
White powder, 24%, mp 252-255 °C; 1H-NMR (DMSO-d6): 4.79 (s, 2H, CH2); 7.02-7.08
(m, 1H, ArH); 7.42 (dd, J = 14.6 Hz, J = 8.1 Hz, 1H, ArH); 7.74 (d, J = 11.3 Hz, 1H,
ArH); 7.82 (d, J = 7.86 Hz, 1H, ArH); EIMS m/z 193 (M+). Anal. Calcd for C10H7FO3: C,
61.86; H, 3.63; F, 9.78; Found: C, 61.56; H, 3.72; F, 9.81.
3-(3-chlorophenyl)-4-hydroxyfuran-2(5H)-one (b7)
White powder, 65%, mp 182-184°C; 1H-NMR (DMSO-d6): 4.79 (s, 2H, CH2); 7.26-7.30
(m, 1H, ArH); 7.41 (t, J = 7.9 Hz, 1H, ArH); 7.93 (d, J = 7.9 Hz, , 1H, ArH); EIMS m/z
209 (M+). Anal. Calcd for C10H7ClO3: C, 57.03; H, 3.35; Cl, 16.83; Found: C, 57.06; H,
3.32; Cl, 16.73.
3-(3-bromophenyl)-4-hydroxyfuran-2(5H)-one (b8)
White powder, 58%, mp 174-175 °C; 1H-NMR (DMSO-d6): 4.78 (s, 2H, CH2); 7.31-7.43
(m, 2H, ArH); 7.96 (d, J = 7.7 Hz, 1H, ArH); 8.13 (s, 1H, ArH); EIMS m/z 254 (M+).
Anal. Calcd for C10H7BrO3: C, 47.09; H, 2.77; Br, 31.33; Found: C, 47.11; H, 2.73; Br,
31.23.
3-(3-methylphenyl)-4-hydroxyfuran-2(5H)-one (b9)
Colorless crystal, 46%, mp 208-210 °C; 1H-NMR (DMSO-d6): 2.39 (s, 3H, CH3); 4.88 (s,
2H, CH2); 7.42-7.46 (m, 1H, ArH); 7.72-7.85 (m, 3H, ArH); 12.58 (s, 1H, OH); EIMS
m/z 189 (M+). Anal. Calcd for C11H10O3: C, 69.46; H, 5.30; Found: C, 69.67; H, 5.35.
6

4-hydroxy-3-(3-(trifluoromethyl)phenyl)furan-2(5H)-one (b10)
1
Colorless crystal, 52%, mp 178-180 °C; H-NMR (DMSO-d6): 4.82 (s, 2H, CH2);
7.56-7.65 (m, 2H, ArH); 8.23-8.30 (m, 2H, ArH); EIMS m/z 243 (M+). Anal. Calcd for
C11H7F3O3: C, 54.11; H, 2.89; F, 23.34; Found: C, 54.23; H, 2.76; F, 23.47.
3-(3-(benzyloxy)phenyl)-4-hydroxyfuran-2(5H)-one (b11)
Colorless crystal, 40%, mp 206-208 °C; 1H-NMR (DMSO-d6): 4.75 (s, 2H, CH2); 5.10 (s,
2H, CH2); 6.88 (d, 8.1 Hz, 1H, ArH); 7.25-7.47 (m, 6H, ArH); 7.53 (d, J = 8.0 Hz, 1H,
ArH); 7.61 (s, 1H, ArH); EIMS m/z 281 (M+). Anal. Calcd for C17H14O4: C, 72.33; H,
5.00; Found: C, 72.42; H, 5.09.
3-(4-fluorophenyl)-4-hydroxyfuran-2(5H)-one (b12)
Colorless crystal, 48%, mp 220-222°C; 1H-NMR (DMSO-d6): 4.79 (s, 2H, CH2); 7.58 (t,
J = 8.9 Hz, 2H, ArH); 7.89 (dd, J = 8.3 Hz, J = 5.9 Hz, 2H, ArH); 12.77 (s, 1H, OH);
EIMS m/z 193 (M+). Anal. Calcd for C10H7FO3: C, 61.86; H, 3.63; F, 9.78; Found: C,
61.84; H, 3.52; F, 9.70.
3-(4-chlorophenyl)-4-hydroxyfuran-2(5H)-one (b13)
White powder, 68%; mp 256-258 °C; 1H-NMR (DMSO-d6): 4.82 (s, 2H, CH2); 7.42-7.46
(m, 2H, ArH); 7.95-7.99 (m, 2H, ArH); 12.70 (s, 1 H, OH); EIMS m/z 209 (M+). Anal.
Calcd for C10H7ClO3: C, 57.03; H, 3.35; Cl, 16.83; Found: C, 57.06; H, 3.32; Cl, 16.73.
3-(4-bromophenyl)-4-hydroxyfuran-2(5H)-one (b14)
White powder, 60%, mp 230-232 °C; 1H-NMR (DMSO-d6): 4.77 (s, 2H, CH2); 7.56 (d, J
= 8.6 Hz, 2H, ArH); 7.90 (d, J = 8.8 Hz, 2H, ArH); 12.74 (s, 1H, OH); EIMS m/z 254
(M+). Anal. Calcd for C10H7BrO3: C, 47.09; H, 2.77; Br, 31.33; Found: C, 47.12; H, 2.73;
Br, 31.35.
7

3-(4-methylphenyl)-4-hydroxyfuran-2(5H)-one (b15)
Colorless crystal, 37%, mp 245-247 °C; 1H-NMR (DMSO-d6): 2.34 (s, 3H, CH3); 4.77 (s,
2H, CH2); 7.17 (d, J = 8.2 Hz, 2H, ArH); 7.81 (d, J = 8.2 Hz, 2H, ArH); 12.66 (s, 1H,
OH); EIMS m/z 189 (M+). Anal. Calcd for C11H10O3: C, 69.46; H, 5.30; Found: C, 69.41;
H, 5.25.
3-(4-(benzyloxy)phenyl)-4-hydroxyfuran-2(5H)-one (b16)
1
White powder, 18%, mp 210-212 °C; H-NMR (DMSO-d6): 4.71 (s, 2H, CH2); 5.09 (s,
2H, CH2); 7.02 (d, J = 9.0 Hz, 2H, ArH); 7.25-7.50 (m, 5H, ArH); 7.85 (d, J = 9.0 Hz, 2H,
ArH); EIMS m/z 281 (M+). Anal. Calcd for C17H14O4: C, 72.33; H, 5.00; Found: C, 72.32;
H, 5.02.
3-(3,4-dichlorophenyl)-4-hydroxyfuran-2(5H)-one (b17)
Colorless crystal, 58%, mp 249-252 °C; 1H-NMR (DMSO-d6): 4.79 (s, 2H, CH2), 7.63 (d,
J = 8.6 Hz, 1H, ArH), 7.97 (d, J = 8.2 Hz, 1H, ArH), 8.19 (s, 1H, ArH); EIMS m/z 243
(M+). Anal. Calcd for C10H6Cl2O3: C, 49.01; H, 2.47; Cl, 28.93; Found: C, 49.41; H, 2.32;
Cl, 28.75.
3-(3,4-dimethoxyphenyl)-4-hydroxyfuran-2(5H)-one (b18)
Colorless crystal, 20%, mp 246-248 °C; 1H-NMR (DMSO-d6): 3.75 (s, 6H, CH3); 4.75 (s,
2H, CH2); 6.97 (d, J = 8.6 Hz, 1H, ArH); 7.50 (d, J = 8.4 Hz, 1H, ArH); 7.58 (s, 1H, ArH);
12.76 (s, 1H, OH); EIMS m/z 235 (M+). Anal. Calcd for C12H12O5: C, 61.01; H, 5.12;
Found: C, 61.20; H, 5.02.
3-(3,4-diethoxyphenyl)-4-hydroxyfuran-2(5H)-one (b19)
1
White power, 34%, mp 173-174 °C; H-NMR (DMSO-d6): 1.30-1.36 (m, 6H, CH3);
3.96-4.05 (m, 4H, CH2); 4.74 (s, 2H, CH2); 6.94 (d, J = 8.4 Hz, 1H, ArH); 7.46-7.57 (m,
8

2H, ArH); 12.56 (s, 1H, OH); EIMS m/z 263 (M+). Anal. Calcd for C14H16O5: C, 63.63; H,
6.10; Found: C, 63.50; H, 6.08.
3-(2,4-dichlorophenyl)-4-hydroxyfuran-2(5H)-one (b20)
Colorless crystal, 72%, mp 207-209 °C; 1H-NMR (DMSO-d6): 4.82 (s, 2H, CH2); 7.32 (d,
J = 8.4 Hz, 1H, ArH); 7.40-7.47 (m, 1H, ArH); 7.60-7.67 (m, 1H, ArH); 12.70 (s, 1H,
OH); EIMS m/z 243 (M+). Anal. Calcd for C10H6Cl2O3: C, 49.01; H, 2.47; Cl, 28.93;
Found: C, 49.17; H, 2.53; Cl, 28.62.
2.2. DPPH Assay for Antioxidant activity
Antioxidant activity was determined as literature.30 Briefly, 15 mg DPPH was dissolved
in 250 mL 95% ethanol. The mixture was measured with a microplate reader
(SpectraMax® Plus384 Molecular Devices, USA) at 517 nm, and the OD value should be
controlled under 1.2-1.3 to achieve reliable results. A stock solution of the synthesized
compound (1000 µg/mL) in DMSO was prepared at different concentrations. Fifty µL of
DMSO containing serially diluted compounds (Vc as control) and 200 µL of DPPH
solution were applied to 96-well plates and incubated for 30 min at 37 °C under dark
conditions. The IC50 values correspond to the concentration at which half of the DPPH• is
inhibited by the compound are presented in Table 1. The DPPH• inhibition percentage of
the samples was calculated:
Inhibition (%) = [1-(A-Ablank)/(A0-Ablank)]×100%
Where A0 is the absorbance without samples and Ablank is the absorbance of solvent,
while A is the absorbance with samples.
9

2.3. Anti-H. pylori activity
The antibacterial activity of the synthesized compounds were tested against H. pylori
(ATCC 43504, amoxicillin as positive control), which were determined by using
microdilution broth method. A stock solution of the synthesized compounds (1000
µg/mL) in DMSO were prepared and graded quantities of the test compounds were
incorporated in specified quantity of sterilized liquid medium (50% (v/v) of DMSO in
PBS). Fifty microliters of each dilution and 50 mL of suspension of the microorganism
approximate 105 cfu/mL were then dispensed into each well. The test medium and culture
conditions were following: H. pylori was grown in Brucella broth supplemented with
10% heat-inactivated horse serum for 24 h at 37 ºC under microaerobic conditions (5%
O2, 10% CO2, and 85% N2), as our previously described.31-34 The MIC50 values were
determined by observation,35 which were presented in Table 2.
2.4. Measurement of Urease Inhibitory Activity
The assay mixture, containing 25 µL (10U) of H. pylori urease and 25 µL of the test
compound, was pre-incubated for 1.5 h at room temperature in a 96-well assay plate.
Urease activity was determined by measuring ammonia production using the indophenol
method as described by Weatherburn.36
2.5. Preparation of the TyrRS and enzyme assay
S. aureus TyrRS was over-expressed in E. coli and purified to near homogeneity (~98%
as judged by SDS-PAGE) using standard purification procedures.37 TyrRS activity was
measured by aminoacylation using modifications to previously described methods.38 The
10

assays were performed at 37°C in a mixture containing (final concentrations) 100 mM
Tris/Cl pH 7.9, 50 mM KC1, 16 mM MgCl2, 5 mM ATP, 3 mM DTT, 4 mg/ml E. coli
MRE600 tRNA (Roche) and 10 µM L-tyrosine (0.3 µM L-[ring-3,5-3H] tyrosine
(PerkinElmer, Specific activity: 1.48-2.22 TBq/mmol), 10 µM carrier). TyrRS (0.2 nM)
was preincubated with a range of inhibitor concentrations for 10 min at room temperature
followed by the addition of pre-warmed mixture at 37°C. After specific intervals, the
reaction was terminated by adding aliquots of the reaction mix into ice-cold 7%
trichloroacetic acid and harvesting onto 0.45 mm hydrophilic Durapore filters (Millipore
Multiscreen 96-well plates) and counted by liquid scintillation. The rate of reaction in the
experiments was linear with respect to protein and time with less than 50% total tRNA
acylation. IC50s correspond to the concentration at which half of the enzyme activity is
inhibited by the compound. The results are presented in Table 1.
2.6. Protocol of docking study
The automated docking studies were carried out using AutoDock version 4.2. First,
AutoGrid component of the program pre-calculates a three-dimensional grid of
interaction energies based on the macromolecular target using the AMBER force field. A
grid box of 60×60×60 Å size (x, y, z) with a spacing of 0.375 Å and grid maps were
created to represent the catalytic active target site region where the native ligand was
embedded. Then automated docking studies were carried out to evaluate the binding free
energy of the inhibitor within the macromolecules. The genetic algorithm with local
search (GA-LS) was chosen to search for the best conformers. The parameters were set
using the software ADT (AutoDockTools package, version 1.5.4) on PC which is
11

associated with AutoDock 4.2. Default settings were used with an initial population of 50
randomly placed individuals, a maximum number of 7.5×106 energy evaluations, and a
maximum number of 2.7×104 generations. A mutation rate of 0.02 and a crossover rate of
0.8 were chosen. Results differing by less than 0.5 Ǻ in positional root-mean-square
deviation (RMSD) were clustered together and the results of the most favorable free
energy of binding were selected as the resultant complex structures.
3. Results and discussion
3.1. Chemistry
Detailed synthetic pathways to the 3-arylfuran-2(5H)-ones (b1-b20) are depicted in
Scheme 2 and the procedures were previously reported by our group. In brief, esters (a)
were prepared by esterification of the corresponding sodium phenylacetate with
2-bromoacetate. Subsequently, compounds b1-b20 were obtained via alkaline cyclization
of a1-a20 using sodium hydride in dried THF. All the final compounds were fully
characterized by elementary analysis, EIMS and 1H-NMR.
3.2. Biological Evaluation.
Antioxidant activity. Obviously, 3-arylfuran-2(5H)-ones b1-b20 is structural analogues
of Vc, and we have a concept that b1-b20 should also exhibit antioxidant activity.
Therefore, the radical scavenging activity determined by DPPH method was selected to
evaluate the antioxidant property for obtained 3-arylfuran-2(5H)-ones, and Vc was used
as control. As shown in Table 1, most 3-arylfuran-2(5H)-one derivatives exhibited good
to excellent ROS inhibitory activities, with compounds b1, b8, b9 and b15 to be noted.
12

On the whole, modification at the phenyl with electron donating group seemed to be
beneficial to antioxidant activity (CF3 < F < Cl < Br < H < CH3, b10 vs b6 vs b7 vs b8
vs b9). The substituent group on benzyl ring at the 3-positionion were stronger
antioxidant activity than those with the 2- and 4-positionion. For instance, compounds b4
and b15 showed 5.6 and 1.5-folds weaker antioxidant activity (IC50 = 45.6 µM and IC50 =
12.3 µM) than compound b9, with an IC50 value of 8.2 µM. Out of these compounds, b9
bearing 3-methylphenyl group is the most active, which showed even more potency than
Vc (IC50 = 12.1 µM).
Anti-H. pylori activity. All synthesized compounds were tested for antibacterial
activities against H. pylori by using amoxicillin as control. The MIC50s of these
compounds are presented in Table 1. The results revealed that some of the compounds
exhibited good antibacterial activities, such as compound b1 (MIC50 = 4.7 µg/mL), b2
(MIC50 = 2.7 µg/mL), and b9 (MIC50 = 2.6 µg/mL). Out of the synthetic compounds,
compound b4 (MIC50 = 1.5 µg/mL) displayed the best activity against H. pylori, and
showed a potency compared to that of amoxicillin (MIC50 = 0.8 µg/mL). It is important to
note that compound b9 not only showed excellent antioxidant activity but also exhibited
significant antibacterial activity.
Urease Inhibitory Activity.
It is well known that H. pylori urease is an etiological factor of gastritis and peptic
ulcer,39 which catalyzes the hydrolysis of urea to ammonia and carbon dioxide. High
concentration of ammonia arising from these reactions leads to an increase in pH, which
13

permits H. pylori to endure the acidic environment of the stomach during colonization.
The continuously produced ammonia was confidently considered to enhance the
permeability of gastric mucosa and to have toxicity to parietal cell. Therefore, people
infected by H. pylori are exposed to a high risk for chronic atrophic gastritis, peptic ulcer
and urolithiasis. Thus the strategies based on urease inhibition are now essential lines of
treatment for H. pylori infection. In order to completely study the potential role of the
3-arylfuran-2(5H)-ones against H. pylori, all the synthetic compounds were further
screened for their urease inhibitory potential and the results were listed in Table 2. It was
found that most of the compounds showed moderate activity, and compound b16 showed
the most potency (IC50 = 10.5 0.3 µM). It is to be noted that compound b9 (IC50 =
31.1 0.7 µM) has comparable activity to the positive control AHA (IC50 = 27.6 2.5 µM).
These discoveries suggested that 3-arylfuran-2(5H)-ones do not show significant potency,
and therefore do not use as urease inhibitors. However, urease inhibitory capacity will
synergize the antioxidant and antibacterial activities of 3-arylfuran-2(5H)-ones for
treatment of H. pylori infections.
TyrRS assay.
TyrRS assay was conducted to study the structure-activity relationship profiles and to
confirm antibacterial mechanisms of 3-arylfuran-2(5H)-ones. The observed data showed
that most of the selected compounds (b1, b2, b4-b10, b15, b16) displayed good activity,
and compound b4 was the most potent with IC50 of 0.6 0.04 µM. Both replacements of
the 2-CH3 or 3-CH3 with electron-withdrawing groups (fluoro, chloro, bromo,
trifluoromethyl) and with bulky group (benzyloxy) lead to a decrease of activity,
14

indicating that CH3 might hydrophobically interact or not typically hydrogen bond with
the active site of the TyrRS enzyme and a bulky group might not be tolerated. In
comparison with b4, movement of the methyl group to 3-position or 4-position results in
a significant decrease in potency.
3.3. Protocol of docking study.
In order to further explore the mechanism of inhibition, the molecular docking study was
performed based on the TyrRS complex structure (1jij.pdb).40 The 3D structure of
enzyme revealed that the most potent inhibitor b4 is located at the active site of TyrRS,
and 2-methylphenyl moiety of compound b4 is oriented towards the entrance cavity (Fig.
1), which is coordinated by Gln174, Gln190, Asp195, Gly193, Val191 and Cys37
residues (Fig. 2). In the binding model, the 2-CH3 is firmly bound to the active site,
through a strong C–H···N hydrogen bond (H···N distance of 2.585 Å) to the N atom of
Gly193 residues and a strong O–H···S hydrogen bond (H···S distance of 1.737 Å) to the
S atom of Cys37 and these strong interactions may explain its excellent inhibitory
activity. Thus, shift of 2-CH3 group to 3- or 4-position will decrease the potency, which is
consistent with the experimental data. The 3-, 5- and 6-H of the benzene ring moiety form
four hydrogen-bonds with Val191, Gln190 and Gln174 residues through C-H···O and
C-H···N hydrogen bonds (1.313Å, 2.142 Å and 2.634). The docking model also show
that three hydrogen-bonding interactions anchor the furanone-ring moiety to the active
site by O–H···O, C-H···N and N–H···O hydrogen bonds (2.871Å, 3.915Å and 2.802 Å).
4. Conclusitions
15

Twenty 3-arylfuran-2(5H)-ones were prepared and tested for their anti-H. pylori,
antioxidant and urease inhibitory activities. Among the compounds, compound b9,
3-(3-methylphenyl)furan-2(5H)-one, showed the most potent antioxidant activity (8.2 µM)
and good anti-H. pylori activity (2.6 µg/mL) with a compared urease inhibitory activity to
that of AHA. These observations indicate that compound b9 would be a potential
candidate for further modification to treat the H. pylori infection. All in all, the most
obtained 3-arylfuran-2(5H)-ones are weak or inactive urease inhibitors. The TyrRS assays
disclosed that the compound exhibits good activity against H. pylori also shows good
activity against TyrRS. Molecular docking revealed that compound b4, the most potent
enzyme inhibitor, well docked into TyrRS active site. Several interactions anchoring the
ligand to the active site of the enzyme tightly might explain its excellent inhibitory
activity.
Acknowledgements
The work was financed by grants from National Natural Science Foundation (grant No.
81273382) of China, by a Project supported by Hunan Provincial Natural Science
Foundation of China (grant No. 2015JJ2116), by aid program (Environment and Energy
Materials and deep processing of mineral resources in Wuling Mountain ) for Science and
Technology Innovative Research Team in Higher Educational Instituions of Hunan
Province, by aid program from Science and Technology Innovative Research Team in
Jishou University for Improving Drug-like Properties of Active Components from
Medicinal Plants in Wulin Montains.
16

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20

Scheme 1 The structure of Variagatic acid, Vitamin C and 3-Arylfuran-2(5H)-one
Scheme 2 Synthetic route of 3-arylfuran-2(5H)-ones
21

Table 1 Inhibitory activity of the synthetic compounds for its anti-H. pylori activity and
antioxidant activity.
Structure
Anti-H.
Antioxidant
pylori
activity
activity
Compound
MIC50
(µg/mL)
4.7
R1
R2
R3
IC50 (µM)
H
F
H
H
H
H
H
H
H
H
H
H
H
H
H
F
13.5
>100
>100
45.6
>100
23.5
16.5
11.2
8.2
b1
b2
2.7
Cl
CH3
OBn
H
H
36.7
1.5
b3
H
b4
H
13.8
>100
36.7
24.5
2.6
b5
F
b6
H
Cl
Br
CH3
CF3
OBn
H
b7
H
b8
H
b9
H
28.2
31.7
>100
49.3
61.3
110
b10
b11
b12
b13
b14
H
31.5
27.7
18.5
16.8
H
H
H
Cl
Br
H
H
22

H
H
H
H
CH3
OBn
Cl
15.2
52.1
>100
46.2
72.5
>100
---
12.3
34
b15
b16
H
Cl
28.7
20.4
23.4
>100
12.1
---
b17
H
OMe
OEt
H
OMe
OEt
Cl
b18
H
b19
Cl
---
---
b20
---
---
Vc
---
---
0.8
Amoxicillin
Table 2. In vitro inhibitory activity data of the synthesized compounds against Urease
and TyrRS.
IC50 (µM)
entry
Urease
89 1.5
75 2.6
68 2.2
65 1.9
50 2.1
62 6.1
45.3 1.4
81.8 1.7
31.1 0.7
TyrRS
5.6 0.03
1.9 0.07
---
b1
b2
b3
b4
b5
b6
b7
b8
b9
0.6 0.04
2.5 0.05
27.8 0.11
15.4 0.06
13.1 0.21
1.1 0.04
23

64.4 1.5
77.5 0.8
40.6 2.1
>100
17.5 0.14
b10
b11
b12
b13
b14
b15
b16
b17
b18
b19
b20
I
---
---
---
>100
---
>100
8.6 0.06
30 0.21
---
10.5 0.3
>100
36.5 0.9
91.7 1.5
>100
---
---
---
---
0.10 0.03
---
27.6 2.5
AHA
I,
3-(4-hydroxyphenyl)-4-(2-morpholinoethoxy)furan-2(5H)-one;
AHA,
acetohydroxamic acid.
24

Fig. 1 Binding mode of compound b4 with TyrRS. The enzyme is shown as surface;
while b4 docked structures are shown as sticks. This figure was made using PyMol.
Fig. 2 Binding mode of compound b4 with TyrRS from S. aureus. For clarity, only
interacting residues were labeled. Hydrogen bonding interactions are shown in dash. This
figure was made using PyMol.
25

Synthesis, molecular docking and biological evaluation of
3-Arylfuran-2(5H)-ones as anti-gastric ulcer agent
Xu-Dong Wang, Wei Wei, Peng-Fei Wang, Li-Cheng Yi, Wei-Kang Shi, Yong-Qiang
Xie, Lang-Zhou Wu, Nian Tang, Liang-Song Zhu, Jia Peng, Chan Liu, Xian-Hui Li, Shi
Tang, Zhu-Ping Xiao, and Hai-Liang Zhu
26