Pharmacology & Pharmacy, 2011, 2, 282-288
doi:10.4236/pp.2011.24036 Published Online October 2011 (http://www.SciRP.org/journal/pp)
Synthesis, Antioxidant and Antimicrobial
Activities of a Novel Series of Chalcones,
Pyrazolic Chalcones, and Allylic Chalcones
Tan Nhut Doan, Dao Thanh Tran
Department of Medicinal Chemistry, School of Pharmacy, University of Medicine and Pharmacy, Ho Chi Minh City, Vietnam.
Received August 17th, 2011; revised September 11th, 2011; accepted September 30th, 2011.
ABSTRACT
A new series of chalcones (4a-c) and allylicchalcones (11a-b) have been prepared by the Claisen-Schmidt condensation.
A novel series of pyrazolicchalcones (5a-c) have been synthesized by the reaction of respective chalcones (4a-c) and
hydrazine hydrate. The structures of the compounds were confirmed by spectral data (infrared spectroscopy and 1H
nuclear magnetic resonance). All of the compounds (4/5a-c and 11a-b) have been tested for their antimicrobial activi-
ties (agar disc-diffusion method) and antioxidant activities (1,1-biphenyl-2-picrylhydrazyl free radical scavenging
method). The test compounds failed to show antibacterial properties (4a-c, 5b, and 11a-b) or exhibited such properties
poorly (5a and 5c). None of the test compounds displayed antifungal properties. Of the compounds tested, compounds
5a-c and 11a-b exhibited promising antioxidant activities.
Keywords: AllylicChalcones, Antioxidant Activity, Antimicrobial Activity, PyrazolicChalcones
1. Introduction
Flavonoids comprise a large family of plant-derived poly-
phenolic compounds classified as anthocyanidins, fla-
vonols, chalcones, aurones, flavanones, isoflavones, fla-
vans, flavanonols, flavanols, and flavones differencing
from each other in their structural group arrangements
[1]. Chalcone, an important intermediate of flavonoid
synthetic pathway, has been shown to exhibit diverse
biological and pharmacological activities such as anti-
cancer, antioxidant, anti-inflammatory, antimicrobial, anti-
allergic,and antimalarial properties [2-4].
Oxidative damage which is implicated in various patho-
logical events such as cancer and aging is induced by free
radicals and reactive oxygen species [5]. Antioxidants
are the compounds that prevent such oxidative damage
due to their free radical scavenging ability [5]. In chal-
cones, such ability is attributable to phenolic-OH group
attached to the ring structure [6]. Chalcones with anti-
oxidant activity (and compounds with such activity in
general) have been demonstrated to have anticancer, anti-
cardiovascular, anti-inflammatory, and many other active-
ties [7,8]. As such, they have gained immense interest
from bioorganic and medicinal chemistry research.
Synthesized chalcones holding allylic substitutions and
pyrazolicchalcones were recently reported as potent an-
timicrobial and antioxidant agents [9-12]. In addition, the
presence of enone function in chalcones having pyrazole
moiety has been found to enhance the biological activity
[13].
Prompted by all these observations, we report herein
the synthesis, antioxidant and antimicrobial activities of
novel chalcones, pyrazolicchalcones and allylicchalcones.
2. Chemistry
In order to obtain pyrazolicchalcones 5a-c, the corre-
sponding chalcones 4a-c were prepared by the Claisen-
Schmidt condensation of respective acetophenones (1)
and benzaldehydes (2) by the known literature method
[14]. Subsequently, the corresponding pyrazolicchal-
cones 5a-c were prepared by the addition of the obtained
chalcones 4a-c to hydrazine hydrate in absolute ethanol
(Scheme 1). All of the compounds were characterized by
spectral data (infrared spectroscopy [IR] and 1H nuclear
magnetic resonance [NMR]).
The synthetic procedures and reaction conditions for
allylicchalcones 11a-b are illustrated in Scheme 2. 2-Al-
lyloxybenzaldehyde (8) was prepared by the reaction of

Synthesis, Antioxidant and Antimicrobial Activities of a Novel Series of Chalcones, 283
Pyrazolic Chalcones, and Allylic Chalcones
Scheme 1. Synthesis of the novel chalcones 4a-c and pyrazolic chalcones 5a-c.
Scheme 2. Synthesis of the novel allylic chalcones 11a-b.
salicylaldehyde (6) and allyl bromide (7) in the presence
of potassium carbonate in anhydrous acetone. Subse-
quently, 2-hydroxy-3-allylbenzaldehyde (9) was obtained
by the Claisen thermal rearrangement [15]. The corre-
sponding allylicchalcones 11a-b were then prepared by
the Claisen-Schmidt condensation of the obtained 2-hy-
droxy-3-allylbenzaldehyde (9) and respective acetophe-
nones (10). The spectral data (IR and 1H NMR) were
used to ascertain the structures of the compounds.
3. Biology
3.1. Antimicrobial Activity
Compounds 4/5a-c and 11a-b were tested for their in
vitro antimicrobial properties against the Gram-positive
bacteria Methicillin-resistant Staphylococcus aureus
(MRSA) (ATCC 43300), Methicillin-sensitive Staphylo-
coccus aureus (MSSA) (ATCC 25923), Streptococcus
faecalis (ATCC 10541), the Gram-negative bacteria Es-
cherichia coli (ATCC 25922), Pseudomonas aeruginosa
(ATCC 27853), fungi Candida albicans (ATCC 10201)
and Candida albicans 955 using conventional agar disc-
diffusion method [16]. The minimum inhibitor concen-
trations (MICs) were determined using micro-dilution
susceptibility method [17]. Sulfamethoxazole and Keto-
conazole were the reference drugs for antibacterial and
antifungal testing respectively. The observed data on the
antimicrobial testing are presented in Tables 1-2.
3.2. Antioxidant Activity
Compounds 4/5a-c and 11a-b were assessed for antioxi-
dant activity using 1,1-biphenyl-2-picrylhydrazyl (DPPH)
radical scavenging method [18]. The observed data on
the antioxidant activity are given in Table 3.
4. Results and Discussion
We have synthesized a series of chalcones 4a-c, pyra-

Synthesis, Antioxidant and Antimicrobial Activities of a Novel Series of Chalcones, 284
Pyrazolic Chalcones, and Allylic Chalcones
zolicchalcones 5a-c and allylicchalcones 11a-b with ap-
propriate nucleophiles using the procedures presented in
Schemes 1 and 2.
4.1. Antimicrobial Activity
The results of antimicrobial testing of compounds 4/5a-c
and 11a-b are presented in Tables 1-2. The results indi-
cated that compounds 4a-c, 5b and 11a-b did not exhibit
antibacterial properties whereas compounds 5a and 5c
displayed poor antibacterial activity towards Gram-posi-
tive bacteria showing inhibitor zones between 10 and 16
mm and MIC values higher than 256 μg/ml for Strepto-
coccus faecalis and 512 μg/ml for MSSA and MRSA
compared to Sulfamethoxazole. These compounds (5a
and 5c), however, did not exhibit antibacterial activity
against Gram-negative bacteria. None of the synthesized
compounds (4/5a-c and 11a-b) showed antifungal prop-
erties.
4.2. Antioxidant Activity
The antioxidant activity of compounds 4/5a-c and 11a-b
were tested using DPPH radical scavenging method [18].
Except for compounds 4a-c which failed to show such
activity, all of the other test compounds (5a-c and 11a-b)
exhibited good antioxidant properties, with the strongest
being observed in compound 5a (Table 3). However, all
the synthesized compounds were less potent than vitamin
C as the reference. The potencies for the antioxidant ac-
tivity of the test compounds to the reference drug are in
the following order: Vitamin C > 5a-b > 5c > 11a-b.
5. Conclusions
In summary, we have synthesized a series of novel chal-
cones, pyrazolicchalcones and allylicchalcones. We have
also reported antimicrobial and antioxidant evaluations
of these compounds. All the synthesized compounds
showed poor antimicrobial properties or did not show
such properties. A good antioxidant activity was ob-
served in pyrazolicchalcones and allylicchalcones.
6. Experimental
6.1. Chemistry
All chemicals were purchased from commercial suppliers,
and used without further purification. All solvents used
for reaction were freshly distilled from proper dehydrate-
ing agents. Melting points were determined in open cap-
illaries on a Gallenkamp Melting Point Apparatus and are
uncorrected. The purity of the compounds was checked by
thin layer chromatography (TLC) (silica gel H, n-hexane-
acetone 3:1). The IR spectra were performed on a Shi-
madzu FTIR 8101 spectrometer in potassium bromide
Table 1. Antimicrobial activity of 4/5a-c and 11a-b.
Zone of inhibition at concentration of 1024 μg/ml (mm)
Gram-positive bacteria Gram-negative bacteriaFungi
Compound
MSSA MRSA SF EC PA CA 10201 CA 955
4a - - - - - - -
4b - - - - - - -
4c - - - - - - -
5a 12 14 11 - - - -
5b - - - - - - -
5c 10 16 14 - - - -
11a - - - - - - -
11b - - - - - - -
Sulfamethoxazole34 36 38 35 33 - -
Ketoconazole - - - - - 41 39
Control (DMSO)- - - - - - -
Data represent the mean of three replicates. MSSA—Methicillin-sensitive Staphylococcus aureus(ATCC 25923); MRSA—
Methicillin-resistant Staphylococcus aureus(ATCC 43300); SF—Streptococcus faecalis (ATCC 10541); EC—Escherichia
coli (ATCC 25922); PA—Pseudomonas aeruginosa(ATCC 27853); CA 10201—Candida albicans (ATCC 10201); CA
955—Candida albicans 955; DMSO—dimethyl sulfoxide. (-) indicates “not detected”.

Synthesis, Antioxidant and Antimicrobial Activities of a Novel Series of Chalcones, 285
Pyrazolic Chalcones, and Allylic Chalcones
Table 2. Minimum inhibitor concentration (MIC), μg/ml of
5a and 5c.
Minimum inhibitor concentration (MIC) (μg/ml)
Gram-positive bacteria
Compound
MSSA MRSA SF
5a 512 512 256
5c 512 512 256
Sulfamethoxazole 4 4 4
MSSA—Methicillin-sensitive Staphylococcus aureus (ATCC 25923); MRSA—
Methicillin-resistant Staphylococcus aureus (ATCC 43300); SF—Streptoco-
ccus faecalis (ATCC 10541).
Table 3. Antioxidant property of 4/5a-c and 11a-b.
Compound % DPPH
4a 0.00
4b 0.00
4c 0.00
5a 89.64
5b 89.27
5c 77.14
11a 41.00
11b 40.90
Vitamin C* 97.92
DPPH—1,1-biphenyl-2-picrylhydrazyl. *Standard substance.
(KBr) pellets and the wave numbers were given in cm–1.
The 1H NMR spectra were run on a Bruker spectrometer
operating at 500 MHz, using deuterated chloroform
(CDCl3) as solvent and tetramethylsilane (TMS) as inter-
nal standard. All chemical shifts are reported in parts per
million (ppm) downfield relative to TMS on the δ scale.
Data are reported as follows: chemical shift, multiplicity
(s = single, d = double, t = triplet, q = quarter, m = multi-
plier, br = broad), coupling constant (Hz) and integration.
6.1.1. 2-Hydroxy-4-methoxyacetophenone
2,4-Dihydroxyacetophenone (0.1 mol), potassium car-
bonate (0.3 mol) and dimethyl sulphate (0.09 mol) in 20
ml anhydrous acetone were refluxed for 4 hours, moni-
toring by TLC with solvent system of n-hexane—acetone
(3:1). After removing potassium carbonate, the reaction
solution was evaporated in vacuo, giving solid. The solid
was filtered, washed with water, dried, and crystalized
from methanol to yield 2-hydroxy-4-methoxyacetophe0
none as gray solid with overall yield of 81%. This prod-
uct was used as the material for the synthesis of 4a.
6.1.2. 2’-Hydroxy-3,4,4’-trimethoxychalcone (4a)
2-Hydroxy-4-methoxyacetophenone (1.05 equivalence) and
3,4-dimethoxybenzaldehyde were dissolved in methanol.
To the above mixture, potassium hydroxide (3 equiva-
lence) was added in portions to give a blood-red solution.
The reaction mixture was stirred at room temperature for
32 hours, during which 2’-hydroxy-3,4,4’-trimethoxy-
chalcone (4a) precipitated as the potassium salt. The re-
action mixture was poured into cold 1N hydrochloride
acid (HCl) solution and was further added concentrated
HCl (c-HCl) until the solution became acidic. The result-
ing precipitate was filtered, washed with water, and
crystalized from methanol to give product 4a as crystals.
Yield 61%. Light yellow solid, melting point (mp):
170˚C, IR (KBr), ν (cm–1): 1633 (C=O), 1564 (C=C aryl),
1126 (C-O). 1H-NMR (500 MHz, CDCl3):
 13.50 (s, 1
H, Ar-OH), 7.85 - 7.82 (d, J = 15.5 Hz, 1 H, Hβ), 7.84 -
7.82 (d, J = 8 Hz, 1 H, H6’), 7.44 - 7.41 (d, J = 15.5 Hz,
1H, Hα), 7.25 - 7.23 (d, J = 2 Hz, 8.5 Hz, 1H, H6), 7.16 (d,
J = 2 Hz, 1H, H3’), 6.91 - 6.89 (d, J = 8 Hz, 1H, H5), 6.49
- 6.47 (d, J = 2.5 Hz, 8.5 Hz, 1H, H5’), 6.47 (s, J = 2 Hz,
1H, H2), 3.96 (s, 3H, Ar-OCH3), 3.93 (s, 3H, Ar-OCH3),
3.85 (s, 3H, Ar-OCH3).
6.1.3. 4’-Nitro-4-dimethylaminochalcone (4b)
4-Nitroacetophenone (1.05 equivalence) and 4-dimethy-
laminobenzaldehyde were dissolved in methanol. To the
above mixture, potassium hydroxide (3 equivalence) was
added in portions to give a blood-red solution. The reac-
tion mixture was stirred at room temperature for 32 hours,
during which 4’-nitro-4-dimethylaminochalcone (4b) pre-
cipitated as the potassium salt. The reaction mixture was
poured into cold 1N-HCl solution and was further added
c-HCl until the solution became acidic. The resulting
precipitate was filtered, washed with water, and crystal-
ized from methanol to give product 4b as crystals. Yield
79%. Light yellow solid, mp: 206˚C, IR (KBr), ν (cm–1):
1647 (C=O), 1518 (C=C aryl), 1258 (C-O). 1H-NMR
(500 MHz, CDCl3):  7.93 - 7.90 (d, J = 15 Hz, 1H, Hβ),
7.93 - 7.91 (d, J = 1.5 Hz, 7.5 Hz, 1H, H6), 7.58 - 7.55 (d,
J = 8 Hz, 2H, H2’, H6’), 7.47 - 7.44 (d, J = 15 Hz, 1H, Hα),
7.47 - 7.44 (t, 1H, H4), 7.02 - 7.00 (d, J = 8 Hz, 1H, H3),
6.93 - 6.90 (t, 1H, H4’), 6.71 - 6.69 (d, J = 2 Hz, 8 Hz, 2H,
H3, H5), 3.05 (s, 6H, 2 × CH3).
6.1.4. 2’-Hydroxy-2,4-dimethoxychalcone (4c)
2-Hydroxyacetophenone (1.05 equivalence) and 2,4-di-
methoxybenzaldehyde were dissolved in methanol. To
the above mixture, potassium hydroxide (3 equivalence)
was added in portions to give a blood-red solution. The
reaction mixture was stirred at room temperature for 20

Synthesis, Antioxidant and Antimicrobial Activities of a Novel Series of Chalcones, 286
Pyrazolic Chalcones, and Allylic Chalcones
hours, during which 2’-hydroxy-2,4-dimethoxychalcone
(4c) precipitated as the potassium salt. The reaction mix-
ture was poured into cold 1N-HCl solution and was fur-
ther added c-HCl until the solution became acidic. The
resulting precipitate was filtered, washed with water, and
crystalized from methanol to give product 4c as crystals.
Yield 59%. Light yellow solid, mp: 111˚C, IR (KBr), ν
(cm–1): 1637 (C=O), 1558 (C=C aryl), 1170 (C-O). 1H-
NMR (500 MHz, CDCl3):
 13.10 (s, 1H, Ar-OH), 8.14 -
8.22 (d, J = 15.4 Hz, 1H, Hβ), 7.90 - 7.94 (d, J = 8.2 Hz,
1H, H6’), 7.64 - 7.75 (d, J = 15.4, 1H, Hα), 7.58 - 7.62 (d,
J = 8.6 Hz, 1H, H6), 7.44 - 7.52 (m, J = 8 Hz, 1H, H4’),
6.99 - 7.03 (d, J = 8.6 Hz, 1H, H5’), 6.93 - 6.97 (d, J = 8.4
Hz, 1H, H3’), 6.55 - 6.59 (d, J = 7.6 Hz, 1H, H5), 6.5 (ds,
J = 1.4 Hz, 1H, H3), 3.93 (s, 3H, Ar-OCH3), 3.87 (s, 3H,
Ar-OCH3).
6.1.5. 2-(5-(3,4-Dimethoxyphenyl)-4,5-dihydro-1H-
pyrazol-3-yl)-5-methoxyphenol (5a)
2’-Hydroxy-3,4,4’-trimethoxychalcone (4a, 2 mmol) was
dissolved in 100 ml absolute ethanol. To this mixture,
hydrazine hydrate (4 mmol) was added dropwise at room
temperature. The reaction mixture was refluxed for 7
hours, monitoring by TLC with solvent system of n-
hexane-acetone (3:1). The reaction mixture was cooled in
ice bath. The resulting white solid was filtered and wash-
ed with cold water. The filtrate was extracted with ether
and evaporated in vacuo yielding more solid. The solid
was collected and crystalized from ethanol to yield 2-(5-
(3,4-dimethoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl)-5-
methoxyphenol (5a). White solid, mp: 115˚C, IR (KBr),
ν (cm–1): 3336 (N-H), 1591 (C=N), 1155 (C-O). 1H-
NMR (500 MHz, CDCl3):
 11.19 (s, 1H, Ar-OH), 7.07 -
7.06 (d, J = 8.5 Hz, 1H, H6’), 6.93 - 6.92 (s, J = 1 Hz, 8
Hz, 1H, H2”), 6.90 - 6.88 (d, J =1.5 Hz, 8 Hz, 1H, H5”),
6.84 - 6.82 (d, J = 8.5 Hz, 1H, H6”), 6.56 (s, J = 1.5 Hz,
1H, H3’), 6.46 - 6.44 (d, J = 2.5 Hz, 8 Hz, 1H, H5’), 5.87
(s, 1H, NH), 4.82 - 4.78 (t, 1H, H3), 3.87 (s, 6H, 2 × Ar-
OCH3), 3.81 (s, 3H, Ar-OCH3), 3.52 - 3.47 (q, 1H, H4β),
3.09 - 3.05 (q, 1H, H4α).
6.1.6. N,N-Dimethyl-4-(3-(4-nitrophenyl)-4,5-
dihydro-1H-pyrazol-5-yl)-benzenamin (5b)
4’-Nitro-4-dimethylaminochalcone (4b, 2 mmol) was dis-
solved in 100 ml absolute ethanol. To this mixture, hydra-
zine hydrate (4 mmol) was added dropwise at room tem-
perature. The reaction mixture was refluxed for 7 hours,
monitoring by TLC with solvent system of n-hexane-
acetone (3:1). The reaction mixture was cooled in ice
bath. The resulting white solid was filtered and washed
with cold water. The filtrate was extracted with ether and
evaporated in vacuo yielding more solid. The solid was
collected and crystalized from ethanol to yield N,N-di-
methyl-4-(3-(4-nitrophenyl)-4,5-dihydro-1H-pyrazol-5-
yl)-benzenamin (5b). White solid, mp: 154˚C - 154.7˚C,
IR (KBr), ν (cm–1): 3334 (N-H), 1614 (C=N). 1H-NMR
(500 MHz, CDCl3):
 8.22 - 8.20 (d, J = 2 Hz, 9 Hz, 2H,
H3’, H4’), 7.78 - 7.76 (d, J = 1.5 Hz, 9 Hz, 2H, H2’, H6’),
7.21 - 7.19 (d, J = 8.5 Hz, 2H, H2”, H6”), 6.71 - 6.69 (d, J =
2 Hz, 9 Hz, 2H, H3”, H4”), 6.19 (s, 1H, NH), 4.95 - 4.92 (t,
1H, H3), 3.45-3.39 (dd, 1H, H4), 2.94 (s, 6H, 2 × CH3).
6.1.7. 2-(5-(2,4-Dimethoxyphenyl)-4,5-dihydro-
1H-pyrazol-3-yl)-phenol (5c)
2’-Hydroxy-2,4-dimethoxychalcone (4c, 2 mmol) was dis-
solved in 100 ml absolute ethanol. To this mixture, hy-
drazine hydrate (4 mmol) was added dropwise at room
temperature. The reaction mixture was refluxed for 7
hours, monitoring by TLC with solvent system of n-
hexane-acetone (3:1). The reaction mixture was cooled in
ice bath. The resulting white solid was filtered and
washed with cold water. The filtrate was extracted with
ether and evaporated in vacuo yielding more solid. The
solid was collected and crystalized from ethanol to yield
2-(5-(2,4-dimethoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl)-
phenol (5c). White solid, mp: 154˚C - 154.7˚C, IR (KBr),
ν (cm–1): 3327 (N-H), 1591 (C=N), 1153 (C-O). 1H- NMR
(500 MHz, CDCl3):
 11.09 (s, 1H, Ar-OH), 7.24 - 7.18
(m, 3H, H3’, H4’, H6’), 6.99 - 6.97 (d, J = 1Hz, 8 Hz, 1H,
H6”), 6.87 - 6.84 (t, J = 8.5 Hz, 1H, H5’), 6.47 (sb, 1H, NH),
6.47 - 6.44 (m, 2H, H3”, H5”), 5.13 - 5.09 (t, 1H, H3), 3.82
(s, 3H, Ar-OCH3), 3.79 (s, 3H, Ar-OCH3), 3.50 - 3.45 (q,
1H, H4β), 3.08 - 3.03 (q, 1H, H4α).
6.1.8. 2-Allyloxybenzaldehyde (8)
To a solution of salicylaldehyde (6, 0.1 mol) and allyl
bromide (7, 0.11 mol) in anhydrous acetone (30 ml), po-
tassium carbonate (0.12 mol) was added. The reaction
mixture was refluxed for 3 hours. At the completion of
the reaction (monitoring by TLC with solvent system of
n-hexane-acetone 3:1), the resulting mixture was cooled
to room temperature and poured into water (150 ml). The
aqueous phase was then extracted with dichloromethane.
The obtained extract was washed with 5% sodium hy-
droxide (NaOH) solution and water. The organic phase
was dried over anhydrous magnesium sulfate and con-
centrated under reduced pressure. After distillation under
reduced pressure, 2-allyloxybenzaldehyde (8) was ob-
tained as a yellow liquid. Yield 87%, boiling point (bp):
273.5˚C/760 mmHg. 1H-NMR (500 MHz, CDCl3):
 4.75
(dd, J = 5.0 Hz, 1.6 Hz, 2H), 5.13 - 5.43 (m, 2H), 5.4 -
5.9 (m, 1H), 6.65 - 8.12 (m, 4H), 10.62 (s, 1H).
6.1.9. 2-Hydroxy-3-allylbenzaldehyde (9)
14 g of 2-allyloxybenzaldehyde (8) was heated in a sealed
tube. After 12 hours, the rearrangement was complete.

Synthesis, Antioxidant and Antimicrobial Activities of a Novel Series of Chalcones, 287
Pyrazolic Chalcones, and Allylic Chalcones
The reaction was cooled to room temperature and diluted
with 50 ml diethyl ether. The diluted solution was then
extracted with 10% NaOH. The alkaline extract was
added 10% HCl until the solution became slightly acidic
(pH 6). The above solution was then extracted with di-
ethyl ether. The ethereal extract was dried with anhy-
drous magnesium sulfate and was concentrated in vacuo.
The oily residue was distilled under reduced pressure to
get 2-hydroxy-3-allylbenzaldehyde (9) as a light yellow
liquid. Yield 72.8% (10.2 g), bp: 243.5˚C/760 mmHg.
1H-NMR (500 MHz, CDCl3):
 11.30 (s, 1H, Ar-OH),
9.85 (s, 1H, CHO), 7.41 - 7.39 (m, 2H, H4, H6), 6.97 -
6.94 (t, 1H, H5), 6.03 - 5.95 (m, 1H, H2’), 5.12 - 5.08 (m,
2H, =CH2), 3.44 - 3.41 (d, 1H, H1’). Compound 9 was
used as the material for the synthesis of compounds
11a-b.
6.1.10. 2’-Hydroxy-5’-methyl-2-hydroxy-3-
allylchalcone (11a)
2-Hydroxy-5-methylacetophenone (1.05 equivalence) and
2-hydroxy-3-allylbenzaldehyde (9) were dissolved in me-
thanol. To the above mixture, potassium hydroxide (3
equivalence) was added in portions to give a blood-red
solution. The reaction mixture was stirred at room tem-
perature for 52 hours, during which 2’-hydroxy-5’-me-
thyl-2-hydroxy-3-allylchalcone (11a) precipitated as the
potassium salt. The reaction mixture was poured into
cold 1N-HCl solution and was further added c-HCl until
the solution became acidic. The resulting precipitate was
filtered, washed with water, and crystalized from metha-
nol to give product 11a as crystals. Yield 40%. Light
purple solid, mp: 156˚C, IR (KBr), ν (cm–1): 1706 (C=O),
1559 (C=C aryl), 1166 (C-O). 1H-NMR (500 MHz,
CDCl3):
 12.65 (s, 1H, Ar-OH), 8.20 - 8.17 (d, J = 15.5
Hz, 1H, Hβ), 7.71 - 7.68 (d, J = 15.5, 1H, Hα), 7.66 (s, 1H,
H6), 7.51 - 7.49 (d, J = 1 Hz, 7.5 Hz, 1H, H6’), 7.28 (s, J
= 2 Hz, 1H, H2’), 7.16 - 7.14 (d, J = 1 Hz, 7.5 Hz, 1H,
H4), 7.04 - 7.02 (d, J = 1 Hz, 8 Hz, 1H, H3’), 6.91 - 6.88
(t, 1H, H5’), 6.89 - 6.87 (d, J = 8.5 Hz, 1H, H4’), 6.03 -
5.95 (m, 1H, H2”), 5.16 - 5.12 (m, 2H, =CH2), 3.42 - 3.41
(d, 1H, H1”), 2.30 (s, 3H, Ar-CH3).
6.1.11. 4’-Nitro-2-hydroxy-3-allylchalcone (11b)
4’-Nitroacetophenone (1.05 equivalence) and 2-hydroxy-
3-allylbenzaldehyde (9) were dissolved in methanol. To
the above mixture, potassium hydroxide (3 equivalence)
was added in portions to give a blood-red solution. The
reaction mixture was stirred at room temperature for 50
hours, during which 4’-nitro-2-hydroxy-3-allylchalcone
(11b) precipitated as the potassium salt. The reaction
mixture was poured into cold 1N-HCl solution and was
further added c-HCl until the solution became acidic. The
resulting precipitate was filtered, washed with water, and
crystalized from methanol to give product 11b as crystals.
Yield 45%. Light purple solid, mp: 180˚C, IR (KBr), ν
(cm–1): 1651 (C=O), 1573 (C=C aryl), 1170 (C-O). 1H-
NMR (500 MHz, CDCl3):  8.28 - 8.26 (d, J = 8.5 Hz,
2H, H3, H4), 8.141 - 8.11 (d, J = 16 Hz, 1H, Hβ), 8.08 -
8.06 (d, J = 8.5 Hz, 2H, H2, H6), 7.53 - 7.49 (d, J = 16 Hz,
1H, Hα), 7.47 - 7.45 (s, J = 8 Hz, 1H, H6’), 7.15 - 7.13 (d,
J = 7.5 Hz, 1H, H4’), 6.88 - 6.86 (t, 1H, H5’), 5.98 - 5.93
(m, 1H, H2”), 5.12 - 5.07 (m, 2H, =CH2), 3.39-3.38 (d,
1H, H1”).
6.2. Biological Evaluation
6.2.1. Antimicrobial Testing
Compounds 4/5a-c and 11a-b were evaluated for their in
vitro antimicrobial activity by agar disc-diffusion method
[16]. Stock solutions of test compounds were diluted in
dimethyl sulfoxide (DMSO) (1%) to give a final concen-
tration of 1024 μg/ml. The DMSO (1%) alone was used
as a control. Sterile filter paper discs (6 mm diameter)
moistened with the test compound solution were care-
fully placed on the agar culture plates which had been
previously inoculated separately with the microorgan-
isms. The plates were incubated at 37˚C for 24 hours (in
the case of bacteria) or 48 hours (in the case of fungi).
After incubation, growth was surveyed by measuring the
diameter of the growth inhibition zones. All determina-
tions were made in triplicate for each compound. Aver-
age of three independent readings for each compound
was recorded. The results are given in Table 1.
MIC was defined as the lowest concentration of com-
pound required for a complete inhibition of inoculated
bacteria or fungi after incubation time. Sulfamethoxazole
and Ketoconazole were used as reference agents for an-
tibacterial and antifungal activities respectively. The MICs
of the test compounds were determined using micro-
dilution method [17]. The test compounds, Sulfameth-
oxazole and Ketoconazole were dissolved in DMSO (1%)
to give a concentration of 1024 μg/ml; and two-fold dilu-
tion of the solution was prepared (512, 256, 128, 64, 32,
16, 8, and 4 μg/ml). The microorganism suspensions
were inoculated to the corresponding wells. The plates
were incubated at 37˚C for 24 hours (in the case of bac-
teria) or 48 hours (in the case of fungi). The MIC values
are displayed in Table 2.
6.2.2. Antioxidant Testing
Compounds 4/5a-c and 11a-b were tested for antioxidant
activity by DPPH radical scavenging method [18]. The
nitrogen centered stable free radical DPPH has been in
widespread use in spectrophotometric studies to charac-
terize antioxidants [19]. This is based on the fact that the
odd electron in the DPPH free radical gives a strong ab-

Synthesis, Antioxidant and Antimicrobial Activities of a Novel Series of Chalcones,
Pyrazolic Chalcones, and Allylic Chalcones
288
sorption maximum at λ 517 nm, which is purple in color
[18]. A radical scavenging antioxidant reacts with DPPH
stable free radical, resulting in the decolorization which
is stoichiometric with respect to the number of electrons
captured [18]. The change on the absorbance produced in
this reaction is used to measure antioxidant properties
[18].
Stock solutions of different compounds (1 mM) were
mixed with 0.5 ml of 0.3 mMDPPH in methanol. Final
volume was adjusted to 3 ml. Reaction mixtures were
variously shaken and allowed to react for 30 minutes in
the dark at room temperature. Absorbance values were
measured at 517 nm using anultraviolet-visible (UV-VIS)
spectrophotometer. 0.5 ml of 0.3 mM DPPH diluted in
2.5 ml of methanol was used as control. Absorbance was
converted to % antioxidant activity using the following
equation: S (%) = 100 (A0 – AS)/A0 where A0 is the ab-
sorbance of the control (containing all reagents except
the test compound) and AS represents absorbance of the
test compound. Results were compared with activity of
vitamin C which was used as the standard. The data are
summarized in Table 3.
7. Authors’ Disclosures of Potential Conflicts
of Interest
The authors indicated no potential conflicts of interest.
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