Bioactive formylpyrazole analogues: Synthesis, antimicrobial, antioxidant and molecular docking studies

Article abstract of DOI:10.14233/ajchem.2017.20562

A series of six new 3-(1-hydroxynaphthalen-2-yl)-1-aryl-1 H-pyrazole-4-carbaldehyde derivatives were synthesized by Vilsmeier-Haack reaction of phenyl hydrazones. The new compounds were characterized by spectral studies and elemental analysis. Synthesized compounds were evaluated in vitro for their antimicrobial and antioxidant susceptibilities. The results suggest that the compounds with methyl and methoxy substitutions in the aromatic ring have good in vitro antimicrobial activities and those with methyl, methoxy and no substitutions possess promising DPPH and hydroxyl free radical scavenging abilities.

Full text of DOI:10.14233/ajchem.2017.20562

Asian Journal of Chemistry; Vol. 29, No. 7 (2017), 1549-1554
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2017.20562
Bioactive Formylpyrazole Analogues: Synthesis,
Antimicrobial, Antioxidant and Molecular Docking Studies
1
2
1,*
PAVITHRA GURUNANJAPPA , VIVEK HAMSE KAMESHWAR and AJAY KUMAR KARIYAPPA
1Department of Chemistry, Yuvaraja’s College, Mysuru-570 005, India
2Department of Biotechnology, Sri Jayachamarajendra College of Engineering, Mysuru-570 006, India
*Corresponding author: E-mail: ajaykumar@ycm.uni-mysore.ac.in
Received: 2 February 2017;
Accepted: 31 March 2017;
Published online: 13 May 2017;
AJC-18391
A series of six new 3-(1-hydroxynaphthalen-2-yl)-1-aryl-1H-pyrazole-4-carbaldehyde derivatives were synthesized by Vilsmeier-Haack
reaction of phenyl hydrazones. The new compounds were characterized by spectral studies and elemental analysis. Synthesized compounds
were evaluated in vitro for their antimicrobial and antioxidant susceptibilities. The results suggest that the compounds with methyl and
methoxy substitutions in the aromatic ring have good in vitro antimicrobial activities and those with methyl, methoxy and no substitutions
possess promising DPPH and hydroxyl free radical scavenging abilities.
Keywords: Docking, Formylpyrazole, Hydrazone, Inhibition, Radical scavenging.
INTRODUCTION
H2N
R3
The emergence of new infectious diseases and increasing
resistance of microorganisms is the major cause of morbidity
and mortality [1]. Excessive ROS produced by the human
bodies result in the damage to various cell constituents that
lead to serious health problems, which were overcome by anti-
oxidants [2]. Among the nitrogen heterocycles, pyrazole core
occupies prime position in bioorganic chemistry for their
bioactive nature. Pyrazole derivatives have played a crucial
role in the field of pharmaceutical chemistry and have been
extensively used as important pharmacores in drug designing.
Designed series of pyrazoles exhibited a broad spectrum of
biological activities, few to mention that the antiproliferative
activities, anticancer and anti-inflammatory activities and
antitubercular activities [3,4].
Cl
N
R4
N
N
N
O
H3C
O
(ii)
(
i)
S
N
N
N
H
R'
(iii)
Formylpyrazole derivative
.
EXPERIMENTAL
Pyrazole and its derivatives are regarded as useful synthons
in organic synthesis for building bioactive molecules [5] and
these have significant impact on the design and development
of novel drugs [6]. Literature studies reveal that pyrazole
derivatives exhibited the antioxidant [7] analgesic [8] antiviral
[9] and anti-inflammatory properties [10]. In view of the broad
spectrum of synthetic and biological applications of pyrazoles
and in search of new potent antimicrobial and antioxidant
agents, we herein report the results of the synthesis of a series
of formylpyrazole derivatives and their antimicrobial, anti-
oxidant activities and molecular docking studies.
Reagents and chemicals used were procured from
commercial sources (Merck Chemicals, India;Aldrich, India)
and used without any further purification. Melting points were
determined by an open capillaries tube method and are unco-
1
rrected. H NMR and 13C NMR spectra obtained using an
Agilent (400 MHz) and (100 MHz) NMR spectrometer, respec-
tively using CDCl3 as solvent. Mass spectra were obtained on
Mass Lynx SCN781 spectrometer in TOF mode. The elemental
analyses were done using a Thermo Finnigan Flash EA 1112
CHNS analyzer. Thin layer chromatography (TLC) was carried

1550 Gurunanjappa et al.
Asian J. Chem.
out on aluminum sheets coated in Merck Kieselgel silica gel
60, eluting with ethyl acetate: hexane (1:4 v/v). The spots were
visualized under UV light.
2-Acetyl-1-hydroxy naphthol (1) reacted with phenyl-
hydrazine hydrochlorides, 2(a-f) in the presence of sodium
acetate to produce hydrazones, 3(a-f). Compounds, 3(a-f)
yielded formylpyrazoles, 4(a-f) in good yields by Vilsmeier-
Hack reaction (Fig. 1).
Vilsmeier-Haack reagent, a solution of hydrazones (3a-f)
(0.001 mol) in 5 mL DMF was added to it and the mixture
was stirred for 6 h at 60-65 °C. The progress of the reaction
was monitored by TLC. After completion, the mixture was
poured into ice cold water and then neutralized with NaHCO3.
The precipitated products were collected and purified by
crystallization from methanol to give compounds 4(a-f).
3-(1-Hydroxynaphthalen-2-yl)-1-phenyl-1H-pyrazole-
4-carbaldehyde (4a): Yield 86 %, m.p. 147-148 °C; IR: 3228,
1
1668 cm-1; H NMR: 11.125 (s, 1H, CHO), 10.263 (s, 1H,
OH), 8.574 (s, 1H, pyrazole-H), 7.412-8.438 (m, 11H, Ar-H);
13C NMR: 119.3 (1C), 119.5 (3C), 123.3 (2C), 125.5 (1C),
125.8 (2C), 127.3 (1C), 127.5 (2C), 128.4 (2C), 129.9 (3C),
132.6 (1C), 153.0 (1C), 184.31(1C); MS m/z: 314 (M+), 313
(M-1, 100 %); Anal. calcd. for C20H14N2O2 %: C, 76.42; H,
4.49; N, 8.91; Found: C, 76.71; H, 4.24; N, 8.68.
3-(1-Hydroxynaphthalen-2-yl)-1-(3-methylphenyl)-
1H-pyrazole-4-carbaldehyde (4b): Yield 80 %, m.p. 136-
137 °C; IR: 3247, 1662 cm-1; 1H NMR: 11.092 (s, 1H, CHO),
10.268 (s, 1H, OH), 8.711 (s, 1H, pyrazole-H), 7.721-8.506
(m, 10H,Ar-H), 1.243 (s, 3H, CH3);13C NMR: 22.3 (1C), 117.2
(2C), 119.7 (1C), 123.6 (2C), 124.4 (1C), 126.7 (1C), 127.1
(2C), 127.5 (1C), 127.9 (2C), 128.1 (1C), 128.6 (1C), 129.4
(2C), 132.7 (1C), 134.5 (1C), 152.1 (1C), 183.1 (1C); MS m/z:
329 (MH+); Anal. calcd. for C21H16N2O2 %: C, 76.81; H, 4.91;
N, 8.53; Found: C, 76.59; H, 4.63; N, 8.87.
Fig. 1. Reaction path for synthesis of formylpyrazoles 4(a-f)
Synthesis of hydrazones 3(a-f): A series of new hydrazones
were synthesized by a known procedure [11], 1-(1-hydroxy-
naphthalen-2-yl)ethanone (1) (0.001 mol) in 15 mL ethyl alcohol
was added to a solution of phenylhydrazine hydrochlorides
2(a-f) (0.001 mol) and sodium acetate (0.01 mol) in water
and the mixture was heated at 90-95 °C for 3 h. After comp-
letion of reaction, it was allowed to cool to room temperature,
precipitated hydrazones were collected and purified by crysta-
llization from methanol to give the compounds 3(a-f).
2-[1-(2-Phenylhydrazono)ethyl]naphthalen-1-ol (3a):
Yield 90 %, m.p. 162-163 °C; 1H NMR: 10.108 (s, 1H, OH),
8.112 (s, 1H, NH), 6.213-7.712 (m, 11H, Ar-H), 3.108 (s, 3H,
CH3), 1.932 (s, 3H, CH3).
3-(1-Hydroxynaphthalen-2-yl)-1-(2,4-dimethylphenyl)-
1H-pyrazole-4-carbaldehyde (4c): Yield 85 %, m.p. 140-141
1
°C; IR: 3247, 1665 cm-1; H NMR: 11.011 (s, 1H, CHO),
10.275 (s, 1H, OH), 8.699 (s, 1H, pyrazole-H), 7.696-8.495
(m, 9H,Ar-H), 2.134 (s, 6H, CH3);13C NMR (CDCl3, 100 MHz)
δ: 18.1 (1C), 18.8 (1C), 118.3 (1C), 119.2 (1C), 121.5 (2C),
122.4 (1C), 124.1 (1C), 124.5 (2C), 125.2 (3C), 127.5 (1C), 127.6
(1C), 128.4 (1C), 131.2 (3C), 134.5 (1C), 152.1 (1C), 181.3
(1C); MS m/z: 343 (MH+); Anal. calcd. for C22H18N2O2 %: C,
77.17; H, 5.30; N, 8.18; Found: C, 77.35; H, 5.14; N, 8.36.
1-(4-Chlorophenyl)-3-(1-hydroxynaphthalen-2-yl)-1H-
pyrazole-4-carbaldehyde (4d): Yield 81 %, m.p. 180-182 °C;
IR: 3215, 1681 cm-1; 1H NMR: 11.103 (s, 1H, CHO), 10.274
(s, 1H, OH), 8.569 (s, 1H, pyrazole-H), 7.486-8.328 (m, 10H,
Ar-H);13C NMR (CDCl3, 100 MHz) δ: 116.4 (1C), 118.7 (1C),
121.5 (2C), 122.4 (2C), 124.5 (1C), 126.1 (2C), 126.9 (1C),
127.5 (1C), 130.1 (2C), 131.2 (1C), 132.4 (1C), 132.9 (1C),
135.5 (2C), 154.8 (1C), 180.1 (1C); MS m/z: 349 (MH+, 35Cl),
351 (MH++2, 37Cl);Anal. calcd. for C20H13ClN2O2 %: C, 68.87;
H, 3.76; N, 8.03; Found: C, 68.61; H, 3.91; N, 8.28.
2-[1-(2-(m-Tolyl)hydrazono)ethyl]naphthalen-1-ol
(3b): Yield 76 %, m.p. 154-155 °C; 1H NMR: 10.113 (s, 1H,
OH), 8.512 (s, 1H, NH), 6.910-8.128 (m, 10H, Ar-H), 3.108
(s, 3H, CH3), 2.326 (s, 3H, CH3).
2-[1-(2-(2,4-Dimethylphenyl)hydrazono)ethyl]naph-
1
thalen-1-ol (3c): Yield 85 %, m.p. 160-161 °C; H NMR:
10.096 (s, 1H, OH), 8.586 (s, 1H, NH), 6.986-8.110 (m, 9H,
Ar-H), 3.008 (s, 3H, CH3), 2.330 (s, 6H, CH3).
2-[1-(2-(4-Chlorophenyl)hydrazono)ethyl]naphthalen-
1-ol (3d) [11]: Yield 82 %, m.p. 174-175 °C; 1H NMR: 10.121
(s, 1H, OH), 8.482 (s, 1H, NH), 7.026-8.412 (m, 10H, Ar-H),
2.382 (s, 3H, CH3).
2-[1-(2-(4-Methoxyphenyl)hydrazono)ethyl]naphthalen-
1-ol (3e): Yield 78 %, m.p. 168-170 °C; 1H NMR: 10.116 (s,
1H, OH), 8.522 (s, 1H, NH), 7.246-8.186 (m, 10H, Ar-H),
3.848 (s, 3H, OCH3), 2.980 (s, 3H, CH3).
2-[1-(2-(2,4-Dinitrophenyl)hydrazono)ethyl]naphthalen-
1-ol (3f): Yield 83 %, m.p. 210-211 °C; 1H NMR: 10.230 (s,
1H, OH), 8.543 (s, 1H, NH), 7.556-8.236 (m, 9H,Ar-H), 2.982
(s, 3H, CH3).
3-(1-Hydroxynaphthalen-2-yl)-1-(4-methoxyphenyl)-
1H-pyrazole-4-carbaldehyde (4e): Yield 86 %, m.p. 155-157
1
°C; IR: 3232, 1675 cm-1; H NMR: 11.017 (s, 1H, CHO),
10.279 (s, 1H, OH), 8.592 (s, 1H, pyrazole-H), 7.387-8.463
(m, 10H, Ar-H), 3.128 (s, 3H, OCH3); 13C NMR: 55.1 (1C),
116.2 (2C), 117.5 (1C), 119.2 (1C), 121.1 (1C), 122.4 (2C),
125.1 (1C), 126.8 (2C), 127.1 (1C), 127.8 (2C), 129.8 (1C),
132.9 (2C), 133.2 (1C), 152.4 (1C), 154.5 (1C), 183.2 (1C);
MS m/z: 345 (MH+);Anal. calcd. for C21H16N2O3 %: C, 73.24;
H, 4.68; N, 8.13; Found: C, 73.57; H, 4.42; N, 8.36.
Synthesis of 3-(1-hydroxynaphthalen-2-yl)-1-aryl-1H-
pyrazole-4-carbaldehydes 4(a-f). Drop-wise addition of POCl3
(1.2 mL) to a cold DMF (10 mL) in a reaction flask produces
3-(1-Hydroxynaphthalen-2-yl)-1-(2,4-dinitrophenyl)-
1H-pyrazole-4-carbaldehyde (4f): Yield 80 %, m.p. 198-199

Vol. 29, No. 7 (2017)
Synthesis and Studies of Bioactive Formylpyrazole Analogues 1551
1
°C; IR: 3243, 1678 cm-1; H NMR: 11.115 (s, 1H, CHO),
10.271 (s, 1H, OH), 8.594 (s, 1H, pyrazole-H), 7.439-8.573
(m, 9H, Ar-H).13C NMR: 116.1 (1C), 119.6 (1C), 120.8 (1C),
120.6 (1C), 121.8 (2C), 123.7 (1C), 125.2 (2C), 126.5 (1C),
127.1 (2C), 129.2 (1C), 134.1 (1C), 134.6 (1C), 136.2 (1C),
137.2 (1C), 142.5 (1C), 152.1 (1C), 182.3 (1C); MS m/z: 345
(MH+); Anal. calcd. for C21H16N2O3 %: C, 73.24; H, 4.68; N,
8.13; Found: C, 73.52; H, 4.42; N, 8.35.
The mixture was shaken vigorously and allowed to stand for
20 min at room temperature. The absorbance was read against
blank at 517 nm in an ELICO SL 159 UV-visible spectrophoto-
meter. The free radical scavenging potential was calculated as
a percentage (I %) of DPPH decolouration using the equation:
A0 − A1
I (%) of scavenging =
×100
A0
Antimicrobial activity: Antimicrobial activities of the
synthesized compounds were determined as minimum inhibi-
tory concentrations (MIC’s) by broth dilution technique [7].
The nutrient broth, which contains logarithmic serially two-
fold diluted amount of compounds 3(a-f) and 4(a-f) and control
was inoculated with approximately 5 × 105 cfu of actively
dividing bacteria cells. The cultures were incubated for 24 h
at 37 °C for bacterial and 72 h at 37 °C for fungal stains and
the growth was monitored visually. The tests were conducted
in triplicates against bacterial pathogens Escherichia coli,
Pseudomonas aeruginosa, Staphylococcus aureus and against
fungal stains Aspergillus nigar, Aspergillus flavus and Candila
albicans. Ciprofloxacin and nystatin were used as positive
controls against bacterial and fungal species, respectively;
methanol was used as solvent control. The results are expressed
as a mean standard deviation (SD) (Table-1).
A0 is the absorbance of the control without test compounds;
A1 is the absorbance of test compounds. The experiments were
performed in triplicate; the results were expressed as a mean
standard deviation (SD) (Table-2).
Hydroxyl radical scavenging assay: Hydoxyl radical
scavenging ability of compounds 3(a-f) and 4(a-f) was perfor-
med by known method [14]. Mixture of phosphate buffer (0.1
mL), 2-deoxyribose (0.2 mL), test solution (25, 50, 75 and
100 µg/mL), H2O2 ((0.1 mL, 10 mM), ascorbic acid ((0.1 mL,
1 mM), EDTA (0.1 mL) and FeCl3 ((0.01 mL, 100 mM) was
incubated at 37°C for 60 min. Thereafter, the reaction was
arrested by adding cold trichlroacetic acid (1 mL, 2.8 %) and
thiobarbituric acid (1 mL, 1 % in 0.05 N NaOH) in boiling
water for 15 min and, absorbance was measured at 535 nm.
Butylated hydroxyanisole (BHA) was used as positive control.
Experiments were performed in triplicates and results are
expressed as I % standard deviations (Table-3).
DPPH radical scavenging assay: 1,1-Diphenylpicryl-
hydrazyl (DPPH) radical scavenging ability of the 3(a-f) and
4(a-f) was performed by Blois method [12,13]. 1 mL of DPPH
solution (0.1mM in 95 % methanol) was mixed with different
aliquots of test samples (25, 50, 75 and 100 µg/mL) in methanol.
Molecular docking studies: The co-ordinates of superoxide
dismutase (SOD), catalase (CAT), oxidoreductase (OXD) and
tyrosinase (TYr) from Bacillus megaterium were retrieved from
Brookhaven Protein Data Bank, with those PDB id's are 1CB4,
TABLE-1
MINIMUM INHIBITORY CONCENTRATION (MIC’s) OF COMPOUNDS 3(a-f) AND 4(a-f) (µg/mL*)
Compound
S. aureus
E. coli
P. aeruginosa
A. niger
A. flavus
C. albicans
3a
3b
3c
3d
3e
3f
4a
4b
50 0.35
50 0.15
25 0.66
50 0.36
75 0.20
100 0.25
50 0.26
25 0.50
12.5 0.30
100 0.36
25 0.30
50 0.15
25 0.40
–
50 0.17
25 0.11
12.5 0.51
50 0.25
100 0.45
50 0.26
25 0.30
25 0.35
12.5 0.47
50 0.32
6.25 0.45
75 0.30
25 0.30
–
50 0.05
12.5 0.15
12.5 0.20
25 0.26
50 0.40
50 0.25
25 0.30
25 0.25
25 0.30
75 0.15
12.5 0.41
50 0.45
12.5 0.26
–
50 0.50
25 0.21
12.5 0.61
50 0.57
75 0.65
50 0.50
50 0.56
25 0.56
12.5 0.60
50 0.82
25 0.57
75 0.56
–
25 0.50
50 0.26
50 0.36
25 0.75
100 1.06
50 0.65
50 0.36
50 0.60
25 0.76
75 0.72
12.5 0.62
50 0.60
–
50 0.30
50 0.32
50 0.56
75 0.42
50 0.72
100 0.60
50 0.55
25 0.81
50 0.75
50 0.36
25 0.60
75 0.71
–
4c
4d
4e
4f
Ciprofloxacin
Nystatin
25 0.25
25 0.21
50 0.96
*Values are mean SD of three replicates.
TABLE-2
DPPH RADICAL SCAVENGING ACTIVITY OF COMPOUNDS 4(a-f) AT
DIFFERENT CONCENTRATIONS IN METHANOL (MEASURED IN %)*
Compounds
25 (µg/mL)
26.98 0.66
26.91 0.20
23.65 0.49
21.02 0.40
31.19 0.68
20.32 0.90
26.87 0.24
50 (µg/mL)
33.43 0.60
31.88 1.39
29.95 0.95
28.76 0.82
37.02 0.49
25.84 0.90
31.54 0.68
75 (µg/mL)
37.25 0.54
36.53 1.04
32.76 0.60
32.43 0.58
43.96 0.49
30.71 0.60
36.09 1.22
100 (µg/mL)
4a
4b
4c
4d
4e
4f
46.54 0.90
47.41 0.72
39.87 0.62
36.43 0.55
49.45 0.67
34.18 0.71
45.32 0.70
Ascorbic acida
*Values are mean SD of three replicates; aUsed as positive control

1552 Gurunanjappa et al.
Asian J. Chem.
TABLE-3
HYDROXYL RADICAL SCAVENGING ACTIVITY OF COMPOUNDS 4(a-f) AT
DIFFERENT CONCENTRATIONS IN METHANOL (MEASURED IN %)*
Compounds
25 (µg/mL)
8.04 0.65
9.13 0.80
6.87 0.39
4.87 0.92
11.43 0.77
4.92 0.95
7.11 0.24
50 (µg/mL)
13.43 0.98
13.96 1.06
11.96 0.85
9.76 0.32
15.12 0.23
10.75 0.56
12.98 0.38
75 (µg/mL)
23.13 0.88
24.85 0.89
22.04 0.47
17.53 0.71
27.81 0.78
15.76 0.74
22.65 0.20
100 (µg/mL)
4a
4b
4c
4d
4e
4f
32.93 0.69
33.51 0.36
32.21 0.76
28.97 0.73
35.43 0.56
22.42 1.14
32.98 0.71
Butylated hydroxyanisoleb
* Values are mean SD of three replicates; b Used as positive control
2CAG, 1MBT and 3NM8, respectively. Compounds were drawn
using Maestro 2D sketcher and energy to minimize was computed
by OPLS 2005. Proteins prepared by retrieving into Maestro 9.3
platform (Schrödinger, Inc.) and their structures were corrected
by Prime software module of Schrödinger. Water molecules
which are from SOD, CAT, OXD and TYr were removed beyond
5 Å from the hetero atom. Water molecules are important in
aiding the interaction between the receptor and ligands was
optimized during protein pepwizard. Necessary bonds, bond
orders, hybridization, explicit hydrogens and charges were
automated. OPLS 2005 force field applied to the protein to
restrained minimization and RMSD of 0.30 Å was set to converge
heavy atoms during the pre-processing of protein before starting
docking. Using Extra-precision (XP) docking and scoring, each
compound was docked into the receptor grid of radii 20 Å and
docking calculation were a judge based on the Glide score.
Preliminary studies show that the compounds (4a), (4b)
and (4e) showed remarkable radical scavenging activity in
comparison with the standard. It is anticipated that, this might
be attributed to the presence of -CH3 and -OCH3 substituent.
While rest of the series of compounds shows lesser activities.
Preliminary studies on hydroxyl radical scavenging activities
shows that compounds (4a), (4b) and (4e) possesses promising
radical scavenging activity in compared with the standard
butylated hydroxyanisole.
Molecular docking has been carried out to design novel
potential leads. A total of six validated potential leads are
suggested from the in vitro studies. Comparative investigation
is based on docking score with that of the reported inhibitors.
Compounds (4d) and (4f) of parental nucleus, imparted a
specific geometrical space around the Cu-Zn binding loop.
Among which activity of SOD gets exuberated during the
process followed by catalase [15].Activity of Cu-ZnSOD has
studied based on protein engineering to increase activity by
modifying the electrostatic environment of the active site.
Strong binding of compound at Cu-Zn domain of SOD causes
increases in antioxidant activity of SOD and reduce oxidative
stress [16].
Binding modes of compound (4c) showed the better pose
with docking and glide score determined and those that retain
interactions with Cys55 residing at Cu-Zn loop of the SOD.
Compound (3e) showed binding with His61, His78, Lys134
(Fig. 2). Compound (3c) showed π-π stacking with Phe140,
His54 and hydrogen bond with water of CAT (Fig. 3A). Com-
pounds (4a), (4c), (4d) and (4e) showed better binding with
OXD (Arg327 and Ile45), SOD, CAT andTYr (Lys47B), respec-
tively. Among them, (4c) showed binding with Cys55 resided
at Zn153 of SOD (Fig. 2B); (4a) showed maximum interaction
with His54, Phe140 and Tyr337 of CAT (Fig. 3B). Among all
the designed series, (4d) and (4e) showed very tight binding
with CAT (Fig. 5A and Fig. 5B) and tyrosinase from Bacillus
megaterium, respectively (Fig. 4B).
Results of docking analyses showed that, among the desi-
gned series, compounds (4c) and (4e) have strong interaction
with amino acid Tyr267A,Ala44A and Tyr267B of tyrosinase.
QikProp modules provide ranges of molecular predicting
properties for comparing select molecule with known drugs
(17]. Therefore, it is concluded from docking studies, com-
pounds (4a), (4b) and (4e) might act as a good antioxidant
compounds and are suitable candidates to be carried forward
as a potential lead for targeting various diseases affected by
free radicals.
RESULTS AND DISCUSSION
Elucidation of structure of the synthesized compounds
were obtained by 1H NMR, 13C NMR, Mass spectral studies
and elemental analyses. Compounds 4(a-f) showed sharp and
strong absorption bands at 1671-1662 cm-1 due to C=O str.
and broad bands at 3247-3215 cm-1 due to O-H str. in their IR
1
spectra. In H NMR spectra, 4(a-f) showed a singlet at δ
11.092-11.125 ppm for -CHO proton, singlet at δ 10.263-
10.279 ppm for phenolic -OH proton, absence of signals due
to -NH proton of its precursor 3(a-f) confirms the structure. In
13C NMR spectra, signals obtained at δ 180.1-184.3 ppm, δ
133.2-134.5 ppm, δ 116.4-119.7 ppm and δ 129.4-135.5 ppm
were due to -CHO carbon, newly formed pyrazole ring C-3,
C-4 and C-5 carbons, respectively. All compounds showed
M+1 ion molecular mass peak as a base peak. Further, all
synthesized compounds showed satisfactory CHN analysis
data when compared with the theoretically calculated values.
The preliminary studies show that all the compounds
possess moderate to good bacterial inhibition. Among series,
good activity was observed for compounds (3c) against E. coli
and A. niger; (3e) against E. coli, A. flavus and C. albicans.
Moderate inhibition was shown by compounds; (3a) and (4c)
against A. flavus and C. albicans; (4b) against S. aureus and
E. coli; (4a) and (4c) against A. flavus and C. albicans; (3b),
(4e) against P. aeruginosa and A. niger; and (3b), (4a) against
E. coli and C. albicans; and (3c)againstS. aureus and P. aeruginosa
organisms. Compounds (3e) and (4f) showed lesser activity
against all the test strains.

Vol. 29, No. 7 (2017)
Synthesis and Studies of Bioactive Formylpyrazole Analogues 1553
Fig. 2. Molecular interaction of SOD (PDB ID: 1CB4) with (3e) (A) and (4c) (B)
Polar
Unspecified residue
Water
Hydration site
Hydration site (displaced)
Charged (negative)
Charged (positive)
Glycine
Hydrophobic
Metal
Distance
Salt bridge
Solvent exposure
H-bond (backbone)
H-bond (side chain)
Metal coordination
π−π stacking
Fig. 3. Molecular interaction of catalase (PDB ID: 2CAG) with (3c) (A) and (4a) (B)
Fig. 4. Molecular interaction of tyrosinase (PDB ID: 3NM8) with (I3c) (A) and (4e) (B)

1554 Gurunanjappa et al.
Asian J. Chem.
Fig. 5. Molecular secondary structure (A) and electrostatic interactions (B) of catalase with (4d)
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Conclusion
The designed and synthesized series of novel formylpyra-
zoles were evaluated for their antimicrobial and antioxidant
activities. Preliminary studies of the synthesized series, com-
pounds (4c) and (4e) shows potent antimicrobial activities.
Compounds (4a), (4b) and (4e) possess significant antioxidant
activity in both DPPH and hydroxyl radical scavenging assays.
In silico results are also concordant with in vitro results.
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ACKNOWLEDGEMENTS
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The authors acknowledge to University with Potential for
Excellence (UPE) and University of Mysore for the laboratory
facilities. One of the authors, G. Pavithra is grateful to the
UGC for awarding NON-NET Fellowship (Order No. DV9/
192/NON-NETFS/2013-14, Dated 11-11-2013).
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