Antimicrobial activity of some derivatives of triacetic lactone and their Cd(II) and Hg(II) complexes

Article abstract of DOI:10.14233/ajchem.2013.11696

Triacetic lactone derived compounds and Cd(II) and Hg(II) complexes have been synthesized, characterized and screened for biological activities. Antibacterial activity was carried out against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa

Full text of DOI:10.14233/ajchem.2013.11696

Asian Journal of Chemistry; Vol. 25, No. 2 (2013), 633-636
http://dx.doi.org/10.14233/ajchem.2013.11696
Antimicrobial Activity of Some Derivatives of Triacetic
Lactone and Their Cd(II) and Hg(II) Complexes
1,*
2
3
SAMINA SHAHID , TAHIRA MUGHAL and HAMID ULLAH SHAH
1Department of Chemistry, Queen Mary College, Empress Road, Lahore, Pakistan
2Department of Botany, Lahore College for Women University, Jail Road, Lahore, Pakistan
3Department Nutrition Science, NWFP Agriculture University, Peshawar, Pakistan
*Corresponding author: E-mail: drtahiramughal@gmail.com
(Received: 6 February 2011;
Accepted: 9 August 2012)
AJC-11944
Triacetic lactone derived compounds and Cd(II) and Hg(II) complexes have been synthesized, characterized and screened for biological
activities.Antibacterial activity was carried out against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus
pneumoniae, Bacillus subtilis, Streptococcus mutans and Sarcina lutae. In vitro antifungal activities were carried out against Trichoderma
viridis, Aspergillus flavus, Fusarium laterifum, Aspergillus fumigatus, Candida albicans, Trichophyton mentogrophytes and Microsporum
canis. The results of these studies showed that these metal complexes to be have more potential for antimicrobial activates as compared to
the ligand. Cd(II) complex is more active against the all tested bacterial and fungal strains.
Key Words: Triacetic lactone derivatives, Metal complexes, Antimicrobial.
The oxygen heterocyclic compounds such as 3-azophenyl
4-hydroxy-6-methyl-pyrane-2-one (II) have been prepared
and used as ligands for the formation of Hg(II) and Cd(II)
complexes.
INTRODUCTION
Many complexes by coordination with various metal ions
become more active than uncoordinated form. This is due to
the facts that these metals are essential for life .These metals
cause several diseases occur only when an excess or deficiency
of in vivo metals appears1-4.
EXPERIMENTAL
All the chemicals and solvents used were of analytical
grade (Merck). Mueller-Hinton agar was used; all metal(II)
salts are used as chlorides. IR spectra were recorded on a Philips
Analytical PU 9800 FTIR spectrophotometer. NMR spectra
were recorded on a Perkin-Elmer 283B spectrometer. UV-
Visible spectra were obtained in DMF on a Hitachi U-2000
double-beam spectrometer. Elemental analysis of C, H and N
were determined on a Coleman automatic analyzer. Magnetic
measurements were carried out on solid complexes using
Gouy's method. Melting points were recorded on a Gallenkamp
(UK) apparatus.
2-Pyrones and their derivatives are natural product and
their chemistry very interesting. Triacetic lactone (4-hydroxy-
6-methyl-2H-pyran-2-one) was originally prepared by previ-
ously reported reactions of triacetic lactone with electrophilic
reagents5 include bromination6 nitration acylation7 at the
3-position.
Triacetic lactone (1) and its derivatives not only have
important structural variety but also significant biological8-10
and pharmacological11,12 properties. The oxygen containing
hetrocyclic compounds especially the pyrones and their
derivatives were used for the preparation of transition metal
complexes with hetrocyclic system are studied extensively
because of their biological activates.
OH
NR2
C
OH
N
O
N
Ph
R1
OH
H3C
O
O
H3C
O
O
R1 = CH3; R2 = C2H5
H C
3
O
(I)
(II)
(III)

634 Shahid et al.
Asian J. Chem.
Preparation of L1
obtained from the Main Microbiology Laboratory of Mayo
Hospital, Lahore.
3-Azophenyl-4-hydroxy-6-methyl-pyran-2-one (II):
Benzene diazonium chloride (50 mL) was added to triacetic
lactone (10 g) dissolved in 10 % aqueous solution of sodium
carbonate (200 mL) at 50 ºC. After 1 h, the reaction mixture
was acidified with acetic acid. The resulting yellow precipi-
tate was filtered, dried and crystallized from ethanol as yellow
solid.
Test samples of metal complexes were dissolved in sterile
DMSO to serve as stock solution. Different concentrations
were prepared from the stock solution of the metal complexes.
Sabouraud dextrose was used to grow the fungal strains in test
tube. All media took in the tubes, after sterilization the100 µL
metal complexes added into non solidified media. Each tube
was inoculated with 105 (CFU)/mL-1 fungal spore suspensions
of 7 days old culture of fungi. Kept all the tubes at optimum
temperature of 28-30 ºC for growth for 7-10 days. DMSO
was used as control as negative control and ketoconazole,
econazole, nystatin, amphotericin, clotrimazole and miconazole
used as positive control. After the incubation for 7-10 days
the test tubes with no visible growth of the microorganism
was taken to represent the zone of inhibition of the test sample
which was expressed in µg/mL. The test was carried out in
triplicate and their means were recorded.
Preparation of L2
3-2-Methyl Iminoethyl) 4-hydroxy 6-methyl-pyran-2-
one (III): Dehydroacetic acid (10 g) was treated with
ethylamine (70 %, 12 mL) and heated on a steam bath for
30-40 min. Reaction mixture on cooling gave yellow solid
product. This on recrystallization from n-hexane gave light
yellow product.
General method for the preparation of metal complexes
(1-4): A solution of corresponding metal(II) salt (0.01 M) in
ethanol (20 mL) was added to a solution of appropriate ligand
(0.02 M) in alcohol and finally with ether. Then the products
were dried. The solid products were obtained immediately in
most of the cases; otherwise the reaction mixture was concen-
trated to get the products10.
RESULTS AND DISCUSSION
The ligands L1 and L2 were prepared by reported
method13. The structural determinations of these synthesized
ligands were done with the help of UV, IR, 1H NMR and their
elemental analysis data.
Antimicrobial activity: The synthesized ligands L1 and
L2 and their Cd(II) and Hg(II) complexes (1-4) were screened
in vitro for their antibacterial activity against Staphylococcus
aureus, Escherichia coli, Pseudomonas aeruginosa, Strepto-
coccus pneumoniae, Bacillus subtilis, Streptococcus mutans
and Sarcina lutae bacterial strains (Collected from Mayo
Hospital Lahore) by using the agar well diffusion method13.
Nutrient agar media was used for antibacterial activity. Nutrient
broth media was used to grow the culture media. 10 mL of
broth were inoculated with test strains of bacteria in all culture
tubes. Mixed the 0.6 mL of broth culture in 60 mL of the
molten agar media, mixed well and poured in Petri dishes.
After solidifying, 3 mm holes are cut by using the sterile cork
borer. Test samples of metal complexes were dissolved in sterile
DMSO to serve as stock solution. Different concentrations
were prepared from the stock solution of the metal complexes.
100 µL of the metal complexes were poured in these holes of
all concentration. The minimum inhibitory concentration was
determined using the agar well diffusion technique by pre-
paring concentration containing 10, 25, 50 and 100 µg/mL of
the compounds14.
Due to the excellent chelating properties of oxygen
hetrocyclic compounds, the derivatives of triacetic lactone (I),
4-hydroxy-6-methyl-3-azophenyl-2H-pyrane-2-one (II), 3-(2-
methyl imino ethyl) 4-hydroxy-6-methyl-2H-pyran-2-one (III)
have been prepared and used as ligand for the formation of
Hg(II) and Cd(II) complexes.
A solution of the appropriate ligand on treatment with
Cd(II) or Hg(II) salt in ethanolic or methanolic solvent in
presence of sodium carbonate gave the respective complexes
in appreciable yields. In order to ensure the completion of the
reaction, the reaction mixture was also heated on steam bath
and then cooled to get the products.
All reactions preceded smoothly and resulted in the for-
mation of coloured products .The products are stable towards
air and moisture. Triacetic lactone and its derivatives show
sharp melting points. While complexes are in soluble in water
but show appreciable solubility in DMF and DMSO but are
sparingly soluble or even insoluble in other solvents such as
ethanol, methanol, chloroform, ether, acetone and carbon
disulphide.
DMSO was used as negative control. Other wells were
supplemented with reference compound i.e., ampicillin,
amoxicillin, levofloxacin, tetracycline, vancomycin and
ciprofloxacin as positive control.All the antibacterial activities
were carried out in triplicate and their means are recorded.
Antifungal activity of plants extract was determined by
the agar tube dilution method13. Seven fungal strains were
slected for antifungal strains. Trichoderma viridis (FCBP# 642)
(T. viridis) Aspergillus flavus (FCBP# 647) (A. flavusi),
Fusarium laterifum (FCBP# 624) (F. laterifum), Aspergillus
fumigatus (FCBP# 474) (A. fumigatus) Candida albicans
(FCBP# 478) (C. albicans) were obtained from the Department
of Mycology and Plant Patholgy, University of the Punjab,
Quaid-e-Azam Campus, Lahore. Two identified fungal strains
trichophyton mentogrophytes and microsporum canis were
The polydentate nature of ligands provides a number of
sites for coordination. However, in the basic medium, all this
ligands are invariably expected to lose the proton of -OH at
4-position to produce the anion which provides the preferential
point for the attachment of the ring. However, the coordination
of the oxygen of the carbonyl group at the 2-position cannot
be ruled out.
IR Spectroscopy:The tentative structures assigned to the
metals complexes (1-4) are supported by infrared spectra of
ligands and complexes are compared. Ligands gave a strong
band due to OH group 3114-3100 cm-1. In all the complexes,
the absence of characteristic band of -OH group indicates the
participation of phenolic oxygen in bonding with metal ions15.
No change is observed in the absorption of carbonyl group
(1700-1730) stretching.

Vol. 25, No. 2 (2013)
Antimicrobial Activity of Some Derivatives of Triacetic Lactone and Their Cd(II) and Hg(II) Complexes 635
The C=N stretching bands are observed in 1652-1698 and
1434-1432 peaks at 2884-2847 and 722-720 fit very well in
the expected ranged of the C-H in all complexes and also
showed strong band of C-N in 1575-1576. Two new bands
were observed at 688-667 and 564-550 for all metal complexes,
which did not exist in the spectrum of the free ligand. It could
be sign to ν(M-O) and ν(M-N)15. The inferred band assign-
ment though its nitrogen and oxygen atoms. The presence of
broad at 3600-3200 cm-1 in the same complexes is attributed to
the -OH of the coordinated with water molecules15. According
to the above data suggests the ligands behaved as bidentate
towards all metals. On the basis of analytical data and spectro-
scopic evidence, the molecular formula proposed for the comp-
lexes in general is M:L (1:2).
showed highest activity against, S. aureus, E. coli and S. mutans
while it showed moderate bactericidal activity against B.
subtilis and Sarcina lutae (Table-3). The results obtained for
the antibacterial potential of Hg(II)(L1)2 were also good against
B. subtilis and S. lutae. The bacterialcidal activity of Cd(II)(L1)2
showed poor result against all the bacterial strains except S.
aureus. The result of Cd(II)(L2)2 activity also very poor result
as compared to ligands activity even (Table-3).
TABLE-1
ZONE OF INHIBITION OF LIGANDS (CONTROL STUDY)
Zone of inhibition (mm)
Bacterial
strains
L1
12
11
9
12
11
10
10
L2
13
14
12
11
10
10
12
S. aureus
E. coli
The electronic spectra of ligands and complexes in DMSO
are also studied. The solutions of each complex were noted.
The λmax for each complex were noted. The λmax of complexes
are compared with λmax of the respective ligands. The shift in
the λmax confirms the formation of metals complexes.
P. aeruginosa
S. pneumoniae
B. subtilis
S. lutae
S. mutans
TABLE-2
ZONE OF INHIBITION OF LIGANDS (CONTROL STUDY)
Zone of inhibition in mm
Bacterial strains
L1
10
13
12
10
08
12
13
L2
13
15
12
14
17
15
11
A. flavus
F. laterifum
A. fumigatus
C. albicans
T. mentogrophytes
M. canis
T. viridis
TABLE-3
ZONE OF INHIBITION OF METAL COMPLEXES OF L1 AND L2
Ph
Zone of inhibition (mm)
Bacterial strains
Hg(II)(L1)2 Cd(II)(L1)2 Hg(II)(L2)2 Cd(II)(L2)2
S. aureus
E. coli
34
28
22
38
45
23
45
32
20
15
12
32
12
13
45
45
29
35
36
38
47
30
17
22
15
10
10
20
P. aeruginosa
S. pneumoniae
B. subtilis
S. lutae
Ph
S. mutans
where M= Hg(II) and Cd(II)
The Hg(L2)2 showed highest activity against, A. flavus,
C. albicans and T. viridis while it showed moderate bacteri-
cidal activity against F. laterifum, A. fumigatus, T. mentogrophytes
and M. canis. The results obtained for the antifungal potential
of Hg(II)(L1)2 were very enhancing against A. flavus, F. laterifum
and C. albicans (Table-4).
NMR: On comparing the 1H NMR spectra of complexes
with ligands in DMSO-d6 using TMS as internal standard. The
enolic OH signal observed at 16.5-16.6 ppm in the spectra17
of L1 and L2 ligands, disappeared on complex formation confir-
ming that the bonding of metal (II) ion to the ligands take
place through a proton displacement from the enolic OH group.
A new signal observed in spectra of complexes at 3.6-3.77 is
not present in the spectra of free ligands can be assigned H2O
molecules associated with complex formation20. The data
TABLE-4
ZONE OF INHIBITION OF METAL COMPLEXES OF L1 AND L2
Zone of inhibition (mm)
Bacterial strains
Hg(II)(L1)2 Cd(II)(L1)2 Hg(II)(L2)2 Cd(II)(L2)2
1
A. flavus
43
36
23
46
25
23
48
23
34
25
32
32
22
22
46
48
24
45
26
28
27
20
37
32
25
20
20
32
obtained from H NMR of the complexes are in accordance
F. laterifum
A. fumigatus
C. albicans
T. mentogrophytes
M. canis
with the results obtained from IR spectra. This is the sporting
the mode of bonding between the metal (II) ion and (L1 and
L2) ligands.
The zone of inhibition of L1 and L2 as control study
against all test bacterial strains (Tables 1 and 2). The Hg(L2)2
T. viridis

636 Shahid et al.
Asian J. Chem.
TABLE-5
MIC VALUE OF DIFFERENT ANTIBIOTICS (POSITIVE CONTROL)
MIC (µg/mL)
Bacterial strains
Ampicillin
Amoxicillin
Levofloxacin
Tetracyclin
Vancomycin
Ciprofloxacin
S. aureus
10
10
–
50
80
50
–
50
–
100
150
–
20
5.0
10
30
50
–
20
–
1.0
5.0
–
5.0
–
5.0
1.0
5.0
5.0
–
E. coli
P. aeruginosa
S. pneumoniae
B. subtilis
S. lutae
–
250
100
50
50
–
–
1.0
10
5.0
S. mutans
30
10
TABLE-6
MIC VALUE OF DIFFERENT ANTIBIOTICS (POSITIVE CONTROL)
MIC (µg/mL)
Bacterial strains
Ketoconazole
Econazole
Nystatin
Amphotericin
Clotrimazole
Miconazole
500
A. flavus
15
–
250
–
50
250
10
50
10
50
–
50
–
–
100
–
20
10
100
50
–
100
–
250
50
–
100
500
500
250
100
–
F. laterifum
A. fumigatus
C. albicans
T. mentogrophytes
M. canis
100
250
100
50
50
T. viridis
30
–
–
500
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