Synthesis and antioxidant and antibacterial activities of metal-based schiff bases of nicotinoyl, isonicotinoyl and benzoyl hydrazides

Article abstract of DOI:10.14233/ajchem.2013.13495

A series of 15 metal based [Cu(II), Co(II) and Ni(II)] complexes have been synthesized with novel N'-[-(5-hydroxy-2-nitrophenyl)- methylidene]pyridine-4- carbohydrazide (L¹), N'-[-1-(2,5-dihydroxyphenyl)ethylidene]pyridine- 3-carbohydrazide (L<

Full text of DOI:10.14233/ajchem.2013.13495

Asian Journal of Chemistry; Vol. 25, No. 5 (2013), 2593-2596
http://dx.doi.org/10.14233/ajchem.2013.13495
Synthesis and Antioxidant and Antibacterial Activities of Metal-Based
Schiff Bases of Nicotinoyl, Isonicotinoyl and Benzoyl Hydrazides
1
1,*
1
1
2
3
4
1
M. HUSSAIN , Z. SHAFIQ , A. HUSSAIN , M. YAQUB , S. ARSHAD , M. ASHRAF , B.H. ABBASI and H.B. AHMAD
1Department of Chemistry, Bahauddin Zakariya University, Multan, Pakistan
2College of Conventional Medicine, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
3Department of Biochemistry and Biotechnology, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
4Department of Biotechnology, Quaid-e-Azam University, Islamabad, Pakistan
*Corresponding author: Fax: +92 61 9210138; Tel: +92 61 9210085; E-mail: z_shafiq@yahoo.com
(Received: 21 January 2012;
Accepted: 15 November 2012)
AJC-12409
A series of 15 metal based [Cu(II), Co(II) and Ni(II)] complexes have been synthesized with novel N'-[-(5-hydroxy-2-nitrophenyl)-
methylidene]pyridine-4-carbohydrazide (L1), N'-[-1-(2,5-dihydroxyphenyl)ethylidene]pyridine-3-carbohydrazide (L2), N'-[-1-(5-chloro-
2-hydroxphenyl)ethylidene]pyridine-3-carbohydrazide (L3), N'-[-1-(5-chloro-2-hydroxyphenyl)ethylidene]pyridine-4-carbohydrazide (L4)
and N'-[-1-(2, 5-dihydroxyphenyl)ethylidene]-3-hydroxybenzohydrazide (L5) Schiff bases and screened for antioxidant and cytotoxic
activities. All these complexes exhibited strong antioxidant activity against DPPH radical. Antibacterial activity assay exhibited MIC50
values of these compounds comparable to standard drugs for both Gram-positive and Gram-negative bacteria.
Key Words:Antibacterial activity, Antioxidant, Benzoyl hydrazides, Nicotinoyl hydrazides, Isonicotinoyl hydrazides, Schiff Bases.
a Bruker-300 MHz NMR spectrophotometer. UV-visible spectra
were obtained in DMSO on a Hitachi U-2000 spectrophotometer.
Conductance of the metal complexes was determined in DMSO
on a Hitachi (Japan) YSI-32 model conductometer. Melting
points were recorded on a Fischer Johns melting point apparatus
and are uncorrected. The complexes were analyzed for their
metal contents by EDTA titration.
INTRODUCTION
Hydrazides have received a considerable attention due to
their biological activity as tuberculostatic1, antibacterial2 and
anticancer agents3. They have also been used in analytical
chemistry as chelating agents4. Recently, a series of novel
diflunisal hydrazide-hydrazone derivatives have demonstrated
significant antimicrobial5 activity. Hydrazide-hydrazones
exhibited antibacterial6, anticonvulsant7 and antitubercular8
activities. Very recently, we have reported the synthesis, anti-
oxidant and cytotoxic activities9 of some novel hydrazide-
hydrazone Schiff bases and their [Cu(II), Co(II), Ni(II), Mn(II)
and Zn(II)] complexes.
In the present studies, several new compounds have been
synthesized to evaluate the effects of carbonyl compounds on
the bioactivity of isoniazid, nicotinic acid hydrazide and
3-hydroxy benzoic acid hydrazide and the effect of metals
like Ni(II), Co(II) and Cu(II) on the antioxidant activity of
these compounds. The synthesis, antioxidant and antibacterial
activity of hydrazide derivatives is therefore reported.
Preparation of L1: To a hot stirred solution of isoniazid
(1.37 g, 0.01 mol) in ethanol (15 mL), 2-nitro-5-hydroxy-
benzaldehyde (1.67 g, 0.01 mol) was added. The resultant
mixture was heated under reflux. The reaction was monitored
through TLC.After one hour reflux precipitates were obtained.
The reaction mixture was further heated for ca. 0.5 h. After
completion of reaction, the mixture was cooled at room
temperature. The solid was collected by suction filtration. The
pink coloured precipitates were washed with hot ethanol,
filtered and dried.
Preparation of L2: To a hot stirred solution of 2,5-
dihydroxyacetophenone (1.52 g, 0.01 mol) in ethanol (25 mL)
nicotinic acid hydrazide (1.37 g, 0.01 mol), was added. The
resultant mixture was then heated under reflux. The reaction
was monitored through TLC. After 0.5 h, a solid product
began to form. The reaction mixture was refluxed about 7-8 h.
After the completion of reaction, the mixture was cooled at
room temperature. The solid was collected by suction filtration.
EXPERIMENTAL
Solvents used were of analytical grade and all metals (II)
were used as chloride salts. IR spectra were recorded on 8400-
FTIR spectrophotometer using KBr disc and NMR spectra on

2594 Hussain et al.
Asian J. Chem.
The yellow coloured precipitates were washed with hot
ethanol, filtered and dried.
N'-[1-(5-Chloro-2-hydroxyphenyl)ethylidene]pyri-
dine-4-carbohydrazide (L4): Yield 76%, m.p. 216-218 ºC;
IR (KBr, νmax, cm-1): 3348 (OH), 3205 (-NH-), 1670 (>C=O),
Preparation of L3: To a hot stirred solution of 5-chloro-
2-hydroxyacetophenone (1.71 g, 0.01 mol) in ethanol (25 mL),
nicotinic acid hydrazide (1.37 g, 0.01 mol) was added. The
resultant mixture was heated under reflux. The reaction was
monitored through TLC. After half an hour, a solid product
began to form. The reaction mixture was refluxed for 7-8 h.
After completion of the reaction, the mixture was cooled at
room temperature. The solid was collected by suction filtration.
The light yellow coloured precipitates were washed with hot
ethanol, filtered and dried.
1
1605, (C=N), H NMR (DMSO) δ: 3.38 (s, 3H, CH3-C=N),
6.96 (d, J = 9.0 Hz, 1H, C12-H), 7.36 (dd, J = 2.4 & 9.0 Hz,
1H, C13-H), 7.67 (d, J = 2.4 Hz, 1H, C15-H), 7.85 (d, J = 5.7
Hz, 2H, C3-H, C5-H), 8.80 (d, J = 5.7 Hz, 2H, C2-H, C6-H),
11.70 (s, 1H, NH-CO), 13.29 (br, 1H, C11-OH) ppm; EIMS
(m/z) = 289 (M+), 274, 167, 125, 106, 78, 51.
N'-[1-(2,5-Dihydroxyphenyl)ethylidene]-3-hydroxy-
benzohydrazide (L5):Yield 79 %, m.p. 204-206 ºC; IR (KBr,
νmax, cm-1): 3358 (OH), 3207 (-NH-), 1650 (>C=O), 1590,
(>C=N-); 1H NMR (DMSO) δ: 3.39 (s, 3H, CH3-C=N), 6.70
(m, 2H, C12-H, C13-H), 6.98 (m, 2H, C6-H, C15-H), 7.30 (m,
3H, C2-H, C3-H, C4-H), 8.95 (s, 1H, C14-OH), 9.83 (s, 1H,
C5-OH), 11.23 (s, 1H, NH-CO), 12.61 (s, 1H, C11-OH) ppm;
EIMS (m/z) = 286 (M+), 271, 148, 121, 160, 93, 65.
Preparation of L4: To a hot stirred solution of 5-chloro-
2-hydroxyacetophenone (1.71 g, 0.01 mol) in ethanol (25 mL),
isoniazid (1.37 g, 0.01 mol) was added. The resultant mixture
was heated under reflux. The reaction was monitored through
TLC. After half an hour a solid product began to form. The
reaction mixture was refluxed for 7-8 h. After the completion
of reaction, the mixture was cooled at room temperature. The
solid was collected by suction filtration. The off white coloured
precipitates were washed with hot ethanol, filtered and dried.
Preparation of L5: To a hot stirred solution of 2,5-
dihydroxyacetophenone (1.52 g, 0.01 mol) in ethanol (25 mL),
3-hydroxybenzoichydrazide (1.52 g, 0.01 mol) was added. The
resultant mixture was then heated under reflux. The reaction
was monitored through TLC.After half an hour a solid product
began to form. The reaction mixture was refluxed for 7-8 h.
After completion of the reaction, the mixture was cooled at
room temperature. The solid was collected by suction filtration.
The dark yellow coloured precipitates were washed with hot
ethanol, filtered and dried.
Preparation of metal (II) complexes
Nickel(II) complex of L1: Nickel(II) chloride hexahydrate
(1 mmol, 0.237 g) in ethanol (10 mL) was added to a magneti-
cally stirred solution of L1 (2 mmol, 0.572 g) in 1,4-dioxane
(25 mL). The mixture was refluxed for 2 h. Light yellow
precipitates of the respective metal complex were formed after
volume reduction by evaporation. The precipitates were filtered
while hot, washed with ethanol and dried over silica gel in
vacuum desiccators. All other complexes (2-15) were synthe-
sized following the same method using the respective metal
salts as chloride and ligands (L1-L5).
N'-[-(5-Hydroxy-2-nitrophenyl)methylidene]pyridine-
4-carbohydrazide (L1):Yield 80 %, m.p. 290-292 ºC; IR (KBr,
νmax, cm-1): 3361 (NH), 1660 (>C=O), 1590 (-HC=N-), 1340,
1300 (-NO2); 1H NMR (DMSO) δ: 6.99 (dd, J = 2.7 & 9.0 Hz,
1H, C12-H), 7.49 (d, J = 2.7 Hz, 1H, C14-H), 7.86 (d, J = 5.7
Hz, 2H, C3-H, C5-H), 8.09 (d, J = 9.0 Hz, 1H, C11-H), 8.80 (d,
J = 5.7 Hz, 2H, C2-H, C6-H), 8.99 (s, 1H, N=C-H), 11.16 (s,
1H, NH-CO), 12.44 (br, C13-OH) ppm; EIMS (m/z) = 286 (M+),
269, 240, 121, 106, 51.
N'-[1-(2,5-Dihydroxyphenyl)ethylidene]pyridine-3-
carbohydrazide (L2):Yield 78 %, m.p. 204-206 ºC; IR (KBr,
νmax, cm-1): 3365 (OH), 3310 (NH), 1652 (>C=O), 1590,
(-N=C<), 1H NMR (DMSO) δ: 2.49 (s, 3H, CH3-C=N), 6.73
(m, 2H, C12-H, C13-H), 6.99 (d, J = 1.8 Hz, 1H, C15-H), 7.62
(dd, J = 7.8 & 5.1 Hz, 1H, C5-H), 8.32 (d, J =7.8 Hz, 1H,
C4-H), 8.80 (d, J = 5.1 Hz, 1H, C6-H), 8.97 (br, C14-OH), 9.09
(s, 1H, C2-H), 11.52 (s, 1H, NH-CO), 12.48 (br, C11-OH) ppm;
EIMS (m/z) = 271 (M+), 254, 150, 106, 78, 51.
N'-[1-(5-Chloro-2-hydroxphenyl)ethylidene]pyridine-
3-carbohydrazide (L3):Yield 82 %, m.p. 160-162 ºC; IR (KBr,
νmax, cm-1): 3361 (OH), 3220 (-NH-), 1648 (>C=O), 1600,
(-C=N-); 1H NMR. (DMSO) ƒÔ: 2.51 (s, 3H, CH3-C=N),
6.96 (d, J = 8.7 Hz, 1H, C12-H), 7.35 (dd, J = 2.4 & 8.7 Hz,
1H, C13-H), 7.59 (dd, J = 4.8 & 7.8 Hz, 1H, C5-H), 7.67 (d,
J = 2.4 Hz, 1H, C15-H), 8.29 (d, J = 7.8 Hz, 1H, C4-H), 8.79
(d, J = 4.8 Hz, 1H, C6-H), 9.09 (s, 1H, C2-H), 11.65 (s, 1H,
NH-CO), 13.35 (br, 1H, C11-OH) ppm; EIMS (m/z) = 289
(M+), 272, 121, 106, 78, 51.
L1
L2
L3
L4
L5
X = N,
Y = CH,
R = H,
R1 = NO2,
R2 = OH
R2 = OH
R2 = Cl
X = CH, Y = N,
X = CH, Y = N,
R = CH3, R1 = OH,
R = CH3, R1 = OH,
R = CH3, R1 = OH,
X = N,
Y = CH,
R2 = Cl
X = CH, Y = C-OH, R = CH3, R1 = OH,
R2 = OH
Structure of transition metal(II) complexes
DPPH radical scavenging activity: The stable 1,1-
diphenyl-2-picrylhydrazyl radical (DPPH) was used for the
determination of antioxidant activity as given10. Diffrent concen-
trations of compounds in DMSO (or a suitable solvent) were
added at an equal volume (5 µL) to 95 µL of 100 µM methanolic
DPPH in a total volume of 100 µL in 96-well plates. The contents
were mixed and incubated at 37 ºC for 0.5 h. The absorbance
was measured at 517 nm. Propyl gallate and 3-t-butyl-4-
hydroxyanisole (t-BHT) were used as standard antioxidants.
The experiments were carried out in triplicates. IC50 value
denotes the concentration of the sample which is required to

Vol. 25, No. 5 (2013) Synthesis and BiologicalActivities of Metal-Based Schiff Bases of Nicotinoyl, Isonicotinoyl and Benzoyl Hydrazides 2595
scavenge 50 % of DPPH free radicals. The activity was deter-
mined by the following formula and IC50 was were calculated
using EZ-Fit 5 Perrella Scientific Inc. Amherst USA software,
Per cent scavenging activity = [100 – (Abs of test compound /
Abs of control) × 100]
L3 were prepared by refluxing equimolar (0.01 mol) quantities
of nicotinic acid hydrozide with 2,5-dihydroxy acetophenone
and 5-chloro-2-hydroxy acetophenone, respectively in enthanol.
This Schiff base L5 was prepared by refluxing equimolar (0.01
mol) quantity of 3-hydroxy benzoic hydrazide with 2,5-
dihydroxy acetophenone in ethanol. The precipitates formed
were collected by suction filtration, washed with hot ethanol
and dried. The purity of the products was checked on TLC
plates and the spots were visualized under UV light at 250
and 360 nm. The structures of all the synthesized bases were
established through IR, Mass spectrum and 1H NMR and micro
analytical data.
The Schiff bases were further used for the complexation
reaction with Ni(II), Co(II) and Cu(II) metal ions.All the metal
complexes (1-15) of the Schiff bases were stable in air and
decomposed above 190 ºC (Table-1). These were prepared by
the stoichiometric reaction of the corresponding metal(II)
chlorides with the Schiff base ligands in a molar ratio of 1:2.
All the metal complexes are solid and intensely colored. They
are insoluble in common organic solvents such as acetone,
chloroform methanol and ethanol but soluble in DMSO and
DMF. All the chelates exhibited high value of molar conduc-
tance (35.8-116 Ω-1 cm2 mol-1) determined in DMSO which
showed their ionic and electrolyte nature.
Antibacterial activity: Antibacterial activity was per-
formed in sterile 96-wells microplates under aseptic environ-
ments11. The method is based on the principle that microbial
cell number increases as the microbial growth proceeds in the
log phase of growth which results in increased absorbance of
broth medium. Four Gram-negative (Shigella sonnei, Escheri-
chia coli, Pseudomonas aeruginosa and Salmonella typhi) and
two Gram-positive bacteria (Bacillus subtilis, Staphylococcus
aureus) were included in the study. The organisms were main-
tained on stock culture agar. The test samples with suitable
solvent and dilution were pipetted into wells (20 µg/well).
Overnight maintained fresh bacterial cultures after suitable
dilution with fresh nutrient broth were poured into wells (180
µL). The initial absorbance of the culture was strictly maintained
between 0.12-0.19 at 540 nm. The total volume in each well
was kept to 200 µL. The incubation was done at 37 ºC for 16-
24 h with lid on the microplate. The absorbance was measured
at 540 nm using Synergy HT BioTekR USA microplate reader,
before and after incubation and the difference was noted as an
index of bacterial growth. The percent inhibition was calculated
using the formula:
IR spectra of ligands (L1-L5) showed the absence of bands
at 1725-1735 cm-1 due to carbonyl (-C=O) of aldehyde and
ketones and at 3420-3440 cm-1 due to -NH2 stretching vibrations
and instead a new band appeared at 1605-1590 cm-1 assigned12
to the azomethine (C=N) linkage. This suggested that amino
and aldehyde moieties of the starting materials have been
converted into their corresponding Schiff bases. The (C=O)
of amide frequency was present at 1648-1675 cm-1. A compa-
rison of the IR spectra of Schiff bases to the starting material
indicated that Schiff base linkage (C=N) have been formed.
A comparison13 of the IR spectra of the Schiff bases (L1-
L5) and their metal(II) complexes (1-15) indicated that the
ligands are coordinated to the metal atoms mainly in two ways,
thus the ligand acting in a bidentate manner (Table-1). The
band appearing at 1605-1590 cm-1 due to azomethine group
was shifted to a lower frequency ca. 5-20 cm-1 indicating the
participation of the azomethine N in the complexation with
Inhibition (%) = 100 × (X – Y) / X
where X is absorbance in control with bacterial culture andY
is absorbance in test sample. Results are mean of triplicate (n
= 3, mean sem). Gentamycin and ampicilin were taken as
standard. Minimum inhibitory concentration (MIC) was measured
with suitable dilutions and results were calculated using EZ-
Fit 5 Perrella Scientific Inc. Amherst USA software and data
expressed as MIC50.
RESULTS AND DISCUSSION
The Schiff bases L1, L4 were prepared by refluxing
equimolar (0.01 mol) quantities of isoniazid and the respective
carbonyl compound, 5-hydroxy-2-nitrobenzaldehyde 5-
chloro-2-hydroxy acetophenone in ethanol. Schiff bases L2,
TABLE-1
PHYSICAL AND ANALYTICAL DATA OF THE METAL(II) COMPLEXES (1-15)
Decom.
temp. (ºC)
Compd. No.
Metal complex/m.f. (m.w.)
IR (cm–1)
λmax (nm)
1
2
[Ni(L1)2(H2O)2]Cl2; C26H24N8O10NiCl2 [737.70]
[Co(L1)2(H2O)2]Cl2; C26H24N8O10CoCl2 [737.93]
[Cu(L1)2(H2O)2]Cl2; C26H24N8O10CuCl2 [742.546]
[Ni(L2)2(H2O)2]Cl2; C28H30N6O8NiCl2 [707.70]
[Co(L2)2(H2O)2]Cl2; C28H30N6O8CoCl2 [707.933]
[Cu(L2)2(H2O)2]Cl2; C28H30N6O8CuCl2 [712.546]
[Ni(L3)2(H2O)2]Cl2; C28H28N6O6NiCl4 [743.70]
[Co(L3)2(H2O)2]Cl2; C28H28N6O6CoCl4 [743.933]
[Cu(L3)2(H2O)2]Cl2; C28H28N6O6CuCl4 [748.546]
[Ni(L4)2(H2O)2]Cl2; C28H28N6O6NiCl4 [743.70]
[Co(L4)2(H2O)2]Cl2; C28H28N6O6CoCl4 [743.93]
[Cu(L4)2(H2O)2]Cl2; C28H28N6O6CuCl4 [748.546]
[Ni(L5)2(H2O)2]Cl2; C30H32N4O10NiCl2 [737.70]
[Co(L5)2(H2O)2]Cl2; C30H32N4O10CoCl2 [737.933]
[Cu(L5)2(H2O)2]Cl2; C30H32N4O10CuCl2 [742.546]
215
224
219
234
227
224
197
188
192
242
238
227
234
240
231
578
552
497
493
523
489
561
677
530
601
457
483
652
511
489
1643 (CO), 1582 (C=N), 525 (M-O), 423 (M-N)
1647 (CO), 1579 (C=N), 533 (M-O), 440 (M-N)
1641 (CO), 1581 (C=N), 537 (M-O), 432 (M-N)
1641 (CO), 1577 (C=N), 540 (M-O), 438 (M-N)
1643 (CO), 1583 (C=N), 541 (M-O), 432 (M-N)
1645 (CO), 1582 (C=N), 533 (M-O), 440 (M-N)
1637 (CO), 1592 (C=N), 534 (M-O), 442 (M-N)
1638 (CO), 1595 (C=N), 540 (M-O), 437 (M-N)
1640 (CO), 1594 (C=N), 537 (M-O), 438 (M-N)
1655 (CO), 1600 (C=N), 534 (M-O), 440 (M-N)
1657 (CO), 1592 (C=N), 527 (M-O), 433 (M-N)
1657 (CO), 1597 (C=N), 530 (M-O), 433 (M-N)
1641 (CO), 1585 (C=N), 541 (M-O), 440 (M-N)
1638 (CO), 1585 (C=N), 537 (M-O), 441 (M-N)
1638 (CO), 1583 (C=N), 540 (M-O), 437 (M-N)
3
4
5
6
7
8
9
10
11
12
13
14
15

2596 Hussain et al.
Asian J. Chem.
P. aureginosa
TABLE-3
ANTIBACTERIAL ACTIVITY OF METAL(II) COMPLEXES (MEAN SEM, n =3)
Antibacterial activity MIC50 (µg/mL)
Compd. No.
S. aureus
B. subtilis
S. typhi
E. coli
S. sonnei
2
13.92 0.14
12.33 0.09
–
–
–
12.32 0.11
11.66 0.02
–
13.09 0.12
11.29 0.12
–
3
13.43 0.15
14.76 0.09
–
12.38 0.22
–
12.26 0.31
13.18 0.16
10.36 0.13
11.66 0.14
13.02 0.32
–
11.76 0.22
–
6
–
–
7
–
13.66 0.11
14.06 0.38
12.12 0.60
12.29 0.26
12.86 0.02
11.21 0.31
10.85 0.16
–
12.07 0.01
13.32 0.16
11.62 0.38
12.03 0.08
–
8
12.66 0.15
12.68 0.11
13.23 0.93
–
9.42 0.12
10.69 0.06
12.21 0.08
11.78 0.24
–
12.39 0.25
9.29 0.02
11.32 0.13
14.33 0.33
–
11.57 0.21
–
9.31 0.18
11.98 0.13
9
12
15
Gentamycin
Ampicilin
10.89 0.11
12.33 0.15
the metal ion. The band at 1648-1675 cm-1 assigned to the
(-C=O) group is also shifted to lower frequency by ca. 5-20
cm-1 which is indicative of the involvement of the carbonyl
group of hydrazide moiety in the coordination. Further conclu-
sive evidence of the coordination of these Schiff bases with
the metal ions was shown by the appearance of week low
frequency new bands at 455-433 and 540-525 cm-1. These are
assigned14 to the metal nitrogen (M-N) and metal oxygen
(M-O) vibrations, respectively and were observed in the spectra
of the metal complexes and not in the spectra of the uncomp-
lexed Schiff bases, thus confirming the participation of O and
N atoms in the coordination. All of the data established the
fact that a conjugate chelate formed by ligand enolization exists
in these complexes.
The NMR spectra of ligands were determined in DMSO.
The 1H NMR spectral data are reported along with the possible
assignments.All the protons were found to be in their expected
regions15. The conclusions drawn from these studies lend further
support to the mode of bonding discussed in their IR spectra.
It was also observed that DMSO did not have any coordinating
effect on the spectra of ligands or their metal complexes.
Antioxidant and antibacterial activities: Compounds
13 and 15 showed maximum antioxidant activity against the
free radical DPPH with lowest IC50 values, even lower than
the control (Table-2). These results suggest highest antioxidant
activity of these compounds. Compounds 3, 9, 12 possess
antioxidant activity slightly higer than that of standard 3-t-
butyl-4-hydroxyanisole and propyl gallate (compare IC50
values with that of standard) and are also good as antioxidant.
However, compounds 8, 11 had higher IC50 values than that of
control and possess low antioxidant activities (ca. 65-70 %
activity).
When the antibacterial activities of these compounds were
carried out with two gram positive and four gram negative
bacteria, only selected compounds exhibited antibacterial
activity. Lowest the MIC50 value, highest is the antibacterial
activity. Compounds 3, 8, 9, 12 and 15 possessed MIC50 values
close to the standard drugs gentamycin and ampicilin (Table-
3). These compounds were active against both gram positive
and gram negative bacteria. These results suggest the potential
of these molecules as antibacterial agents and screening against
large clinical isolates is suggested for further work.
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1
42.86 2.13
23.84 1.25
87.33 2.45
48.23 1.65
18.67 1.57
46.31 1.87
58.27 1.12
70.37 1.42
79.71 1.65
37.37 1.11
65.06 1.24
72.61 1.46
82.58 1.43
18.93 0.79
89.33 1.98
91.89 1.96
93.18 1.17
–
–
2
3
98.77 2.21
–
4
5
–
–
6
7
227.45 4.96
161.12 2.68
71.25 2.06
–
151.91 3.12
70.33 1.13
22.17 0.95
–
8
9
10
11
12
13
14
15
3-t-BHA
Propyl gallate
16.75 0.72
44.12 2.31
32.21 0.83
Data is given both as percent activity and as IC50 (µM) of active
compounds.