Synthesis, structural peculiarities, theoretical study and biological evaluation of newly designed O-Vanillin based azomethines

Article abstract of DOI:10.1016/j.molstruc.2019.127574

Two azomethines: (E)-2-(((2-hydroxyethyl)imino)methyl)-6-methoxyphenol (1) and (E)-3-(((2-hydroxyethyl)imino)methyl)benzene-1,2-diol (2) were synthesized and characterized in solid state by FT-IR spectroscopy and single crystal X-ray crystallography, wher

Full text of DOI:10.1016/j.molstruc.2019.127574

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Synthesis, structural peculiarities, theoretical study and biological evaluation of newly
designed O-Vanillin based azomethines
Muhammad Zubair, Muhammad Sirajuddin, Kaleem Ullah, Ali Haider, Fouzia
Perveen, Ishtiaq Hussain, Saqib Ali, Muhammad Nawaz Tahir
PII:
S0022-2860(19)31683-7
DOI:
https://doi.org/10.1016/j.molstruc.2019.127574
MOLSTR 127574
Reference:
To appear in: Journal of Molecular Structure
Received Date: 26 October 2019
Revised Date: 29 November 2019
Accepted Date: 11 December 2019
Please cite this article as: M. Zubair, M. Sirajuddin, K. Ullah, A. Haider, F. Perveen, I. Hussain,
S. Ali, M.N. Tahir, Synthesis, structural peculiarities, theoretical study and biological evaluation of
newly designed O-Vanillin based azomethines, Journal of Molecular Structure (2020), doi: https://
doi.org/10.1016/j.molstruc.2019.127574.
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Graphical Abstract: Pictogram
Graphical abstract: Synopsis
The complexes interact with SS-DNA via intercalation mode of interaction resulting in
hypochromic effect and minor red shift as well as increasing the length of SS-DNA that result in
the increase in viscosity of the DNA-compound adduct formed.

Synthesis, Structural Peculiarities, Theoretical Study and Biological Evaluation of Newly
Designed O-Vanillin Based Azomethines
Muhammad Zubaira, Muhammad Sirajuddinb*, Kaleem Ullaha, Ali Haidera*, Fouzia Perveenc,
Ishtiaq Hussaind, Saqib Alia*, Muhammad Nawaz Tahire,
a Department of Chemistry, Quaid-i-Azam University, Islamabad, 45320, Pakistan
b Department of Chemistry, University of Science & Technology Bannu, 28100, Pakistan
c
Research Center for Modeling and Simulations, National University of Science and
Technology, Islamabad, Pakistan
d
Department of Pharmaceutical Science, Abbottabad University of Science and Technology,
Havelian Abbottabad, Pakistan
e Department of Physics, University of Sargodha, Sargodha, Pakistan
Corresponding Author: A.H.: ahaider@qau.edu.pk, S.A.: drsa54@hotmail.com
Abstract
Two azomethines: (E)-2-(((2-hydroxyethyl)imino)methyl)-6-methoxyphenol (1) and (E)-3-(((2-
hydroxyethyl)imino)methyl)benzene-1,2-diol (2) were synthesized and characterized in solid
state by FT-IR spectroscopy and single crystal X-ray crystallography, whereas in solution state
by NMR (1H, 13C) and GC-MS. The titled compounds exist in a zwitter ionic form with a strong
intramolecular N–H···O hydrogen bond between the NH+ and the phenolate O- as observed both
in solution states as well as in solid state. Both the compounds are stabilized in 3D network due
to C–H⋯O, N–H⋯O and O–H⋯O types of hydrogen bondings. The optimized molecular
geometries were calculated by DFT (density functional theory) with B3LYP functional with 6-
31G(d,p) basis set was used using GAUSSIAN 09 program package. The simulated geometries
showed excellent correlation with experimentally found structures. The synthesized compounds
were investigated for DNA binding interactions using UV-visible spectroscopy and viscometery
giving the intercalative mode of interaction with SS-DNA (Salmon sperm DNA). In order to
explore the binding modes of compounds with DNA, docking simulations were further
performed, that also support the aforementioned results. The compounds were also screened for
their in vitro antimicrobial activities and the results showed that their antibacterial activity is
even higher than that of the standard drug, Cefixime while their antifungal activity is lower than
the standard drug, Terbinafine. The interaction of the titled compounds with cetyl trimethy
lammonium bromide (CTAB) was investigated by conductometric method to know the critical

micelle concentration (CMC) of CTAB in the absence and presence of compounds. The
conductivity measurements revealed higher CMC value in the presence of compounds (For
compound 1 CMC = 0.003M while for compound 2 CMC = 0.0031M), proposing a stable
compound-CTAB system.
Keywords: Azomethine; Structural elucidation; Molecular docking study; DNA binding study;
Antimicrobial evaluation; DPPH activity
1. Introduction
The chemistry of azomethine (Schiff bases) is very generous in providing ligands. The numerous
amino and aldo/keto precursors available for condensation reactions leading to azomethine
compounds are almost unlimited. The systematic study of the interaction of two starting
precursors helps in defining the donor sites, binding mode and number of coordinating ligands
[1]. Azomethine based ligands play an important role in the field of inorganic chemistry, as they
readily form very stable complexes with many transition as well as main group metal ions in
various oxidation states [2-4]. They also have their applications in the field of organic synthesis,
dyes and pigments, polymer stabilizers, as catalysts and bio-medicine [5]. Of known aldehydes,
ortho-vanillin is a naturally occurring and bio-medically active compound that has been widely
used as a starting precursor for different azomethines with either mono-donor or multidentate
sites. Such ligands are considered as convenient synthetic blocks to coordinate multi-nuclear
metals such as trinuclear Gd3+[6] or trinuclear Dy3+ [7] with fascinating single molecule
magnetic properties [8, 9]. Multidentate Schiff bases are familiar to produce stable complexes,
due to coordination through various donor atoms [10]. In coordination chemistry due to their
chelating property have been considered as convenient synthetic blocks [11].
The computational chemistry is nowadays a very valuable field in understanding, interpretation
and simulation of experimental results like 1H and 13C NMR spectra [12-14] and also very useful
for simulation of X-ray geometrical parameters [15, 16]. The binding interactions of the reported
compounds are also supported by molecular docking studies. Moreover, quantum chemical
calculations are obtained for the synthesized compounds. DFT/B3LYP as function and basis set
as 6-31G (d,p) was used in gas phase to optimize the geometry of molecule.
Taking into account the importance of azomethines in different biological fields, herein we have
reported the synthesis and spectroscopic investigation of two azomethines derived from 2,3-
dihyroxybenzaldehyde (1) and o-vanillin (2). Compound 1 has also been reported by the group

of Tan, where it crystallized in orthorhombic crystal system with space group Pca21, however, in
our case it crystallized in monoclinic crystal system with space group C2/c [17]. Importantly, we
investigated the interaction of both compound 1 and 2 with SS-DNA, CTAB as well as their
antioxidant and antimicrobial activities has systematically been studied.
2. Materials and Methods
2.1. Synthesis
Ethanolamine, o-vanillin and 2,3-dihydroxybezaldehyde were purchased from Aldrich (USA)
and were used as received. Sodium salt of SS-DNA were obtained from Arcos and used as such.
Solvents used were purchased from Merck (Germany) and dried before use according to the
literature procedure [18].
2.2. Physical measurements
Gallenkamp (U.K.) melting point apparatus was used to find the melting point of the synthesized
compounds. FT-IR spectrum (4000-400 cm-1) was recorded on a Bruker Tensor II FT-IR
1
Spectrophotometer. H and 13C NMR spectra were recorded on a Bruker 300 MHz NMR
1
spectrometer (Switzerland), using DMSO as solvent [δ H = 2.5 ppm and 13C = 39.5 ppm].
Single crystal X-ray analysis was performed on a Bruker Kappa APEX-II CCD diffractometer
using graphite-monochromated MoKα radiation (λ = 0.71073 nm). The crystal structure was
solved by direct methods followed by final refinement on F2 with full-matrix least-squares using
SHELXL-97 [19]. The GC-MS spectra were recorded on a gas chromatograph (GC-6890N)
coupled with mass spectrometer having MSD (mass selective detector, model MS-5973). The
GC-MS was set to scan in the range of 50-250 m/z with electron impact ionization mode. DNA
interaction study was performed by using UV-1601 Shimadzu spectrophotometer. Elemental
analysis was done using a CE-440 Elemental Analyzer (Exeter Analytical, Inc).
2.3. Synthesis
(E)-2-((2-hydroxyethylimino)methyl)-6-methoxyphenol (1)
The compound 1 was synthesized by the reaction of equimolar amount of ethanolamine and o-
vanillin (2-hydroxy-3-methoxybenzaldehyde) in dry methanol using two neck flask equipped
with a magnetic stirrer and a condenser (Scheme 1). The reaction mixture was reflux for 2-3 h
and was then cooled to room temperature. The reaction mixture volume was concentrated to one
third of its original under reduced pressure and kept for crystallization at room temperature. The
light yellow crystals suitable for single crystal XRD analysis were obtained after few days.

Yield: 84%; M.P. 77-78 °C; Mol. Wt.: 195.21 g/mol; Anal. Calc. For C10H13NO3 (Found): C,
61.53 (60.92); H, 6.71 (6.74); N, 7.18 (7.10); FT-IR (ν, cm−1): 1635 (C=N), 1398 and 1540
1
(ArC=C), 3398 (free OH), 1217–1346 (Phen. C-O Str. vib.); H NMR (δ ppm): 3.77 (t, H1),
3.49 (t, H2), 4.82 (s, 1H, OH), 8.47 (s, 1H, H3, CH), 13.82 (s, 1H, H5, OH), 3.65 (s, 3H, OCH3),
6.75 (d, 1H, H7, 3J [1H, 1H] = 7.8 Hz), 6.77 (t, 1H, H8, 3J [1H, 1H] = 7.8 Hz), 7.01 (d, 1H, H9, 3J
[1H, 1H] = 7.8 Hz); 13C NMR (δ ppm): 60.6 (C1), 61.0 (C2), 167.1 (C3), 123.7 (C4), 148.8 (C5),
153.4 (C6), 118.5 (C7), 117.6 (C8), 115.0 (C9), 56.1 (C10). UV-Vis: λmax: 409nm.
(E)-3-((2-hydroxyethylimino)methyl)benzene-1,2diol (2)
Compound 2 was synthesized in similar way as compound 1, however, reaction was carried out
between equimolar concentration of ethanolamine and 2,3-dihydroxybenzaldehyde (Scheme 1).
Yield: 78%; M.P. 112-113 °C; Mol. Wt.: 181.19 g/mol; Anal. Calc.For C9H11NO3 (Found): C,
59.66 (58.98); H, 6.12 (6.08); N, 7.73 (7.74); FT-IR (ν, cm−1): 1647 (C=N), 1354 and 1503 (Ar
C=C), 3289 (free OH), 1244–1386 (Phen. C-O Str. vib.); 1H NMR (δ ppm): 3.65 (t, H1), 3.48 (t,
H2), 4.89 (s, 1H, OH), 8.93 (s, 1H, H3, CH), 13.63 (s, 1H, H5, OH), 8.43 (s, 1H, H6, OH), 6.60
3
1
3
(d, 1H, H7 , 3J [1H, 1H] = 7.5 Hz), 6.79 (t, 1H, H8 , J [1H, H] = 7.8 Hz), 6.84 (d, 1H, H9 , J
[1H, 1H]= 7.5 Hz); 13C NMR (δ ppm): 59.4 (C1), 60.9 (C2), 167.1 (C3), 122.3 (C4), 146.9 (C5),
154.5 (C6), 117.3 (C7), 117.7 (C8), 122.3 (C9); UV-Vis: λmax: 356nm and 266 nm.
Scheme 1: Synthetic procedure for designing of compound 1 and 2
2.2.1. DNA interaction studies
DNA solution was prepared by dissolving SS-DNA (20 mg) in deionized water (pH= 7.0) and
the solution was stirred for overnight. The prepared solution was stored at 4ºC. The ratio of
nucleotide to protein (N/P) of about 1.9 was obtained from the UV-absorbance at 260 and 280
nm (A260/A280 = 1.9) which indicates that DNA is free from protein [20]. The concentration of

DNA was calculated to be 1.97 × 10-4 M via UV-Vis spectroscopy by applying Beer-Lambert
law (
SS-DNA= 6600 M-1cm-1 at 260 nm) [21] .
ε
The 0.57mM solution of each compound was prepared in 70% ethanol. During the UV visible
absorption measurements (1cm path length of cuvettes used), the concentration of SS-DNA was
varied while keeping the concentration of the compound fixed. In order to eliminate the
absorbance band of DNA, same quantity of DNA was added to both the compound and reference
solutions [22]. Prior to each measurement compound-SS-DNA solution was incubated for 25
min at room temperature.
2.2.2. Viscosity measurements
The most reliable and easiest method in defining the compound-DNA binding mode is the
viscosity measurement due to its sensitivity towards the change in DNA length as a result of
interactions with compound [23]. Herein we performed the viscosity measurements using
Ubbelohde viscometer at ambient temperature (25 ± 1 °C). The flow rate was recorded by means
of digital stopwatch, where each sample was measured in triplicate. Data of (η/ηo)1/3 was plotted
against [Compound]/[DNA] ratio. The η and ηo values represent the DNA viscosity in presence
and absence of compound, respectively [24, 25].
2.2.3. Molecular docking
For the purpose of docking simulations molecular structures of compounds 1and 2 were drawn
on MOE-2017 Window employing MOE 2017 tool, entered into MOE database and optimized to
minimum energy values employing PM3 semi-emipircal method. 3-D structure of double
stranded DNA (PDB. ID: 1D66), was extracted from the RCSB protein Data Bank [26],
imported to MOE window, optimized and protonated for further simulation. In order to perform
docking analysis, PDB coordinates of 1D66 were optimized to minimum energy employing
molecular dynamic AMBER force field and semi-empirical PM3 approaches. These coordinates
had minimum energy and stable conformation obtained through MOPAC 7.0. All water
molecules were removed from X-Ray crystal structure of DNA. The optimized structures of
compounds 1 and 2 were used for methodical conformational search at default limits with RMS
gradient of 0.041kJ mol-1 via Site Finder to find out minimum free energy sites of DNA. Finally
the scoring function was used to perform docking studies. To get the best accuracy in the binding
docking poses, 30 docking runs were carried out for each compound. The interaction energy of

both compounds 1 and 2 were calculated at every step of the simulation. Where other parameters
were set as default [27].
2.2.4. Scavenging effect on 2,2-diphenyl -1-picrylhydrazyl (DPPH)
The antioxidant study is commonly considered as the possible practice used for the treatment of
various bio-medical related infections [28]. The antioxidant study of the titled compounds was
performed using a 0.089 mM stock solution of DPPH prepared in methanol. Ascorbic acid was
used as a standard. To the 2.6 mL solution of DPPH, 0.3 mL of the compounds solutions with
concentration ranging from 0.0524 to 1.5 mg/mL were added. After 30 min of incubation, the
successive reduction in absorption band of DPPH at 517 nm was examined. Finally, to find the
percentage inhibition, the real decrease in absorption was calculated against that of the control,
ascorbic acid [29-31]. Each experiment was performed in triplicates to get the precise results.
2.2.5. Computational procedure
The Gaussian 09 program [32] was used to accomplish all the DFT calculations, by applying
B3LYP/6-31G level of theory. Moreover, Gauss view 5.0 program package was used to
construct the input files (Initial input geometry was constructed from single crystal XRD of
compound 1 and 2 ) and to plot/ visualize the theoretical results [33, 34]. Additionally, different
molecular properties such as highest occupied molecular orbital (HOMO) and lowest unoccupied
molecular orbital (LUMO), various thermodynamics properties, chemical reactivity/stability
descriptions, electronegativity, dipole moment etc. has also been reported.
2.2.6. Complex–CTAB interaction study by conductometry
The CMC value of CTAB and the effect of compound-CTAB interactions on the CMC value
were examined by means of conductometric measurements performed by conductivity meter
inolabcond 720 (WTW) calibrated with 3 M KCl solution. The effect on electrical conductivity
of compound-CTAB was monitored by keeping the compound concentration constant while
changing that of the CTAB.
2.2.7. In vitro antibacterial activity
The titled compounds were tested for their antibacterial activity against five different bacterial
strains including three Gram-positive: C. Staphylococci (Coagulase-negative staphylococci),
MRSA (Methicillin-resistant Staphylococcus aureus) and S. aureus (Staphylococcus aureus) and
two Gram-negative: E. Coli (Escherichia coli) and K. pneumoniae (Klebsiella pneumoniae)
using agar well-diffusion method [35]. DMSO and Cefixime (1 mg/mL) were used as a negative

and positive controls, respectively. Three separate petri plates of every bacterial strain were
arranged which were incubated aerobically for 24 h at 37 °C. The average diameter of the zones
of inhibition (mm) was calculated as a function of their activity.
2.2.8. In vitro antifungal activity
The antifungal activity of synthesized compounds were screened by using agar tube dilution
method against various fungal strains including A. niger, A. fumigatus, A. flavus and M. species
[36]. The screw caped test tubes which contain sabouraud dextrose agar (SDA) medium (5 mL)
were autoclaved at 120 °C for 20 min. The tubes were allowed to cool slowly at 50 °C and 67 µL
of non-solidified SDA was loaded. Then compounds (12 mg/mL in DMSO) from the stock
solution were added to make final concentration up to 0.2 mg/mL. The tubes were then allowed
to solidify in slanting position (in Laminar flow hood) at room temperature. Each tube was
inoculated with 5 mm diameter piece of inoculum from seven days old fungal culture. The media
accompanied with DMSO and Turbinafine (200 mg/mL) were used as negative and positive
controls, respectively. After 7 days incubation at 27 °C the linear growth was measured (mm).
3. Results and discussion
The desired compounds were obtained in good yields and both were crystallized in methanol.
The bulk purity of both compounds was examined by elemental analysis where the results
demonstrated good agreement with those of calculated values. The synthesized compounds
exhibited sharp melting point showing their purity. The compounds were characterized in solid
state by FT-IR spectroscopy and single crystal X-ray diffraction analysis whereas in solution by
NMR (1H and 13C) spectroscopy and GC-MS. The structural formula with the tautomeric
equilibrium for compounds 1 and 2 are shown in Scheme S1 of the supplementary data. The
Keto-enol tautomerism can proceed via enol-imine as well as keto-enamine. In order to verify the
proposed tautomers, computational study of both compounds 1 and 2 was performed. In
principle, compound 1 can directly undergo keto-enamine tautomerization to yield 1 (i), while
compound 2 can only undergo keto-enol tautomerization to yield 2 (i) as shown in Scheme S1.
The binding energies of all the analogues of compounds 1 and 2 were also computed and found
that all the analogues are comparatively less stable than the corresponding starting compounds
[37].
3.1. Mass spectrometry

The MS spectra of compounds 1 and 2 are shown in Figures S1 and S2 while their mass
fragmentation pathways are shown in Schemes S2 and S3 of the supplementary data,
respectively. In the mass spectra of both the compounds the parent peaks (molecular ion peak)
appeared at m/z = 195 and 181, respectively. The fragments with m/z value 178 and 164 are due
to the loss of hydroxyl group from compound 1 and 2, respectively. Furthermore, the molecular
ion peaks go through two other key fragmentation path ways with m/z= 164 and 150 in
compound 1 while m/z = 150 and 136 in compound 2. The fragment of m/z = 164 of compound
1 and m/z = 150 of compound 2 experiences cleavage to give ion peak at m/z = 122 and 109,
respectively, by the elimination of C2H3N group. This fragment of both the compound yields
same fragment m/z = 92 by elimination of methoxy (OCH3) and (OH) groups from compound 1
and 2, respectively. This fragment of m/z = 92 of both the compounds undergoes two
fragmentation patterns resulting in m/z = 77 and m/z = 65. The former ion peak can be attributed
to the phenyl radical ion, while the latter by elimination of CH2 group via another rout can gives
ion peak at m/z = 51.
3.2. Spectroscopic analysis
3.2.1. FT-IR spectroscopy
The detailed FT-IR data for the both the compounds are given in the experimental section. Both
the compounds exhibited strong bands in the region of 3500-3200 cm-1 attributed to the inter-
and intramolecular hydrogen bonded hydroxyl groups which is further supported by the single
crystal data. A strong band attributable to azomethine group (C=N) was observed at 1635 cm−1
and 1647 cm−1, while the stretching vibration of phenolic C-O band appeared at 1205-1357 and
1244-1386 cm−1 in compound 1 and 2, respectively [38]. Furthermore, for both compounds the
stretching vibrations of aliphatic and aromatic C-H group were observed 2914, 3040 cm−1 and
2940, 3001 cm−1, respectively.
3.2.2. 1H and 13C NMR spectroscopy
The detailed NMR data for the both the compounds are given in experimental section. The
formation of the synthesized compounds 1 and 2 was confirmed by the appearance of a sharp
singlet of azomethine proton (N=CH) at 8.47 ppm and 8.93 ppm, respectively. For compound 1,
one of the hydroxyl proton attached to C-1 appeared as a singlet at 4.82 ppm while the other
hydroxyl OH attached to the C-5 of the benzene ring appeared at 13.82 ppm. For compound 2,
OH protons attached to C-1 and C-5 appeared around 4.89 and 8.65 ppm, respectively. The

downfield shift of –OH proton attached to aromatic ring (C-5) is due to intramolecular N-H···O
hydrogen bonding which is also observed in solid state from single crystal analysis. The
formation of the compounds 1 and 2 was further confirmed by 13C NMR giving the peak at 167.1
and 154.5 ppm of the azomethine carbon (C-6). The remaining peaks are found at the positions
as calculated by incremental methods as given in the experimental section [39]. The
1
experimental and simulated H and 13C NMR chemical shift (DMSO) values of compounds 1
and 2 are reported in Table S1. A good agreement is found in the experimental and simulated
chemical shift values.
3.2.3. Single crystal X-ray diffraction study
The crystallographic data and structure refinements parameters are summarized in Table 1 while
the various bond lengths and bond angles are given in Tables 2 and 3, respectively. Figures 1
and 2 describe the perspective view of compounds 1 and 2, respectively. A monoclinic crystal
system with space group of C2/c was observed for the both the compounds. Also both the
compounds form zwitter ion with the hydrogen of the nearby hydroxyl group and as a result the
H of the OH group is transferred from oxygen to nitrogen making a 6-membered stable ring. The
stability of the 6-membered ring is due to the strong intramolecular N–H⋯O hydrogen bond as
shown in their structures [17]. The bond lengths and angles are within normal ranges [40] (Allen
et al., 1987). The N1=C8 [1.289(2) Å] and N1–C8 [1.457(2)Å] bond distances are comparable to
these found in similar Schiff base compounds as reported earlier [17, 41, 42]. In the crystal
structures, O3–H3···O1 (Table 4) intermolecular hydrogen bonds formed between the hydroxy
and oxygen of phenolate link the molecules into a 3-dimension wave type supramolecular chain
structure as shown in Figures S3 and S4 of the supplementary data, respectively. The intra- and
inter-molecular H-bondings present in both compounds are shown in Figures S5 and S6 of the
supplementary data.
Tables 1-4
Figures 1-2
3.3. Absorption spectral features of DNA-compound binding
UV-Vis absorption spectroscopy is an effective method for studying the DNA-compound
interaction and examining the binding mode of compound with DNA. In this method the
absorption spectra of free compound and that of compound-DNA are compared to monitor the
changes in the absorbance as well as in the peak shifting. In case of intercalation mode of

binding, the compound intercalate into the DNA base pairs where the π orbital of the base pairs
of DNA interacts with the π* orbital of the intercalated aromatic chromophore, therefore,
reducing the π→π* transition energy and causes bathochromic shift. Additionally hypochromism
is observed because of the partially filled electrons in π orbital of intercalated compound that
reduces the probabilities of transition and accompanying in the hypochromism. Therefore,
hypochromism when coupled with bathochromism the intercalation mode of binding between
compound-DNA occurs [43].
The compounds reported in the manuscript are small organic molecules for which DNA is the
easy target as mentioned in the literature. Moreover these compounds are structurally analogue to
compounds binding to DNA via various mode of interaction [44]. Figures 3 and 4 demonstrate
the absorption spectra of the investigated compounds in the absence (a) and presence (b-m) of
SS-DNA. For free compound 1 there exists one strong peak at about 409 nm while for compound
2, two peaks were observed at 356 nm and 266 nm. With incremental addition of DNA, the
absorption bands exhibit hypochromism and small bathochromism (red shift) of about 4 nm. All
these observations give a clue that the synthesized compounds bind with DNA via an
intercalative binding mode [45]. Furthermore, the extent of compound-DNA interaction was
evaluated in term of binding constant (K) that was determine using the intercept-to-slope ratio of
Ao/(A-Ao) vs.1/[DNA] plots. The observed values of binding constant for the investigated
compounds are 1.7 × 104 M-1 and 1.36 × 104 M-1, respectively. The spontaneity of the DNA-
compound adduct formation process was evaluated from the negative value of Gibbs free energy
(ꢀG) using the equation [46]:
ꢀG = - RTlnK
Here R = 8.314 Jmol-1K-1 and T = 298 K. The values of ꢀG calculated for the screened
compounds are -24.13 kJ mol-1 and -23.58 kJ mol-1.
Figures 3-4
3.4. Viscosity measurements
Viscosity or hydrodynamic measurements response to the change in length of DNA during
interactions with compounds, therefore, it is considered as most simplest and more reliable
method to describe the interaction mode of DNA-compound [47]. During the intercalative mode
of binding, DNA lengthens due to the accumulation of compound between the base pairs
resulting in the increase in viscosity. However, if DNA undergoes groove mode of binding with

compound, kink or bend in the DNA helix is produced that results in the decrease of DNA length
and hence the viscosity either decreases or remain unaffected [48]. Figure 5 describes the effect
of increasing concentration ratio of compound-DNA upon the relative viscosity of the DNA. It
can be clearly evidenced from the figure that during the compound-DNA adduct formation the
viscosity of the DNA increased showing intercalative mode of binding. The viscosity results
completely support the UV-Vis absorption findings discussed in section 3.3.
Figure 5
3.5. Structural analysis DNA binding by molecular docking
Molecular docking is a simulation technique used to express the “best-fit” binding orientation of
a compound under study with a specific macromolecule like DNA. It further describes the
anticipated structure of intermolecular complex system formed by the interaction of two or more
molecules [27]. DNA can bind to a compound via different possible mutual conformations and
are commonly referred as its binding modes [49]. In order to support our experimental results of
compound-DNA binding docking simulations were performed.
Pose view analysis of best and stable conformations the compounds 1 and 2 (Figure 6a and 6c)
and showed that both compounds interacted with via intercalation binding mode between stacked
base pairs of double helical DNA. An acute looks over 2D ligplot (Figure 6b and 6d) depicted
that compound 2 developed four hydrogen bonds i.e., one between H-atom of hydroxyl group
and N-atom of adenine (DA-A6), second and third hydrogen bond between H atom of -OH on
compound 2 with N-atom of another adenine (DA-A5), fourth hydrogen bond between H-atom
of hydroxyl group and O-atom of guanine (DG-A3). Compound 1 intercalated via three
hydrogen bonds; one hydrogen bond is formed between H-atom of hydroxyl group on compound
1 and O- atom of guanine (DG-A3), second bond was developed between H-atom of hydroxyl
group and O-atom of guanine DG (A4), third hydrogen bond was constructed between O-atom of
hydroxyl on compound 1 and H-atom of guanine DG (A3).Greater number of hydrogen bonds in
compound 2 contributed to its greater binding strength with 1D66 (Table 5).
Several electronic and steric descriptors for compound 1 and 2 were calculated (Table 6)
respectively. EHOMO and ELUMO that describes electron donating and accepting character of a
compound also determine the energetic dependency of binding a compound with
macromolecules. A compound will be considered as electron-donating if the EHOMO value
increase whereas it will be considered as electron-accepting its ELUMO value decreases [31].

Steric parameters for docked conformation i.e., partition coefficient (log P) and Molar
refractivity (MR) were also calculated and they exhibited inverse correlation with binding
constant Kb (Table 6). SlogP is illustrative of steric interactions and hydrophobicity of the
molecule while MR gives extent of polarizability of a small molecule. Both of these descriptors
exhibited converse correlation with binding strength (Kb) of the compound 1 and 2. Hydrophobic
surface area (Vsurf) is considered as another important steric descriptor calculated which revealed
greater value of Vsurf for compound 2, therefore greater overlapping of compound 2 with electron
rich DNA resulted in its higher Kb with 1D66.
Figure 6
Tables 5-6
3.6. DPPH scavenging activity
The stable DPPH free radical scavenging model has been widely applied to efficiently determine
the antioxidant activities. The potential antioxidant activity of compounds 1 and 2 were
evaluated by DPPH radical-scavenging assay, whereby DPPH free radicals were applied in the
rapid analysis of the antioxidants, and while scavenging these radicals, the antioxidants donate
hydrogen and a stable 1, 1-diphenyl-2-picrylhydrazine (DPPH-H) molecule is formed. The
DPPH radical generally gives a strong absorption band at 517 nm due to extensive delocalization
of free electron [50]. However, this band disappears due to non-availability of free electron by
abstracting hydrogen radical from the interacting compound [51]. The variation produced is a
key factor that defines the antioxidant potential of tested compound. Both compounds were
tested for their potential antioxidant activities by the interaction of fixed concentration of DPPH
solution with varying concentrations of compound 1 and 2 The percentage inhibition was
calculated by using the Eq.
% Inhibition of DPPH = Ao – As / Ao× 100
Where Ao and As in equation are the absorbance of DPPH in the absence and presence of the test
compound, respectively.
The inhibition of DPPH by the tested compounds in contrast to ascorbic acid (standard
antioxidant) has been shown in Figure 7. The plot between percentage inhibition and
concentration clearly shows that with increase in the concentration of tested compounds,
percentage inhibition increases, where maximum inhibition of DPPH free radical was observed
at a concentration of about 52 µg/mL. The test compounds have scavenging activity of 36 % to

52 % for 1 and 38% to 54% for 2 within the investigated range due to the donation of H from
OH group and a stable DPPH-H molecule was formed. In compound 1 the most probable
chances of H atom abstraction is from the OH group attached to C-1 as the H of the other OH
attached to C-5 of aromatic ring is involved in strong intramolecular H-bonding with N atom
resulting in the formation of stable 6-membered ring. While in compound 2 there are total 3 OH
groups in which one is involved in intramolecular H-bonding with N atom (the one attached to
C-5 of aromatic ring) while the other two (one attached to C-1 and other attached to C-6 of
aromatic ring) may influence the anti-oxidant activity. Also the anti-oxidant activity of
compound 2 is slightly higher than that of compound 1.
Figure 7
3.7. Computational structure analysis by DFT studies
The geometries of synthesized compounds were optimized by B3LYP method of DFT with
default convergence criteria and without any constraints. DFT considers electronic structure of a
molecule for theoretical investigations through a quantum mechanical approach. The various
parameters like maximum charge distribution, HOMO-LUMO energy gap and energies, dipole
moment, ionization potential, electronegativity, electron affinity, global hardness and UV-visible
analysis were calculated from the optimized geometry. For understanding the electronic
structures of our compounds and its possibilities of interaction with different biological
macromolecules like DNA these theoretical results interpretation are helpful. B3LYP Global
hybrid [52] method was selected for the calculation purposes in order to get accurate non-
bonding interactions that are responsible for crystal structure stability. From the calculations of
optimized structure it can be concluded that both compounds have planar geometry which favors
intercalation mode. The calculated bond angles and lengths (Table 7) correlated well with the
experimental data obtained by single crystal X-ray diffraction analysis. However, slight
deviations observed can be explained on the basis of the fact that DFT calculations used
isolated molecules in gaseous phase while the single crystal X-ray analysis was performed on the
solid phase of the compounds [53].
Table 7
3.7.1. Frontier molecular orbital (FMO) analysis
Pictorial representation of the charge distributions on the optimized molecule geometry and
HOMO-LUMO orbitals are shown in Figure S7 of the supplementary data, while different

computational parameters of the optimized molecule are given in Table 9. The optimized
structures of both compounds 1 and 2 have shown planner geometry; so, probably both
compounds interact with DNA base pairs via intercalative mode of interaction. Furthermore,
oxygen atom of hydroxyl group (OH) has high electron density, so it has the probability to form
a hydrogen bond with DNA base pairs. While the hydrogen atom of OH group is electron
deficient, so it has the tendency to form a hydrogen bond by accepting an electron pair from
DNA base pairs.
Parameters like molecule softness/hardness, chemical reactivity and stability can be evaluated
with the HOMOs and LUMOs which are also known as frontier molecular orbitals (FMOs) [54].
Ionization potential and electron affinity has a direct dependence on the energies of FMOs as
these are the electron donating and accepting orbitals of a molecule. Importantly the difference in
energy between HOMO and LUMO depicts the energy gap and hence can affect the chemical
reactivity of the compound. Lower the energy gap between HOMO and LUMO, more the
compound will be reactive or in other words less stable [52, 55, 56]. Difference in energy of
HOMO and LUMO decides the softness/hardness of the compound. When the energy difference
is higher it shows more hardness in the respective compound and vice versa. For both
compounds, the calculated HOMO and LUMO energy, energy gap, ionization potential, electron
affinity (A), electronic chemical potential (ꢁ), electronegativity (χ), molecular softness (S) and
hardness (η), and electrophilicity index (ω) are given in the Table 8. The calculated energy gap,
and smaller value of hardness, while higher value of dipole moment depicted the reactive nature
of both compounds [57]. In addition, electronic absorption spectra for compounds 1 and 2 in gas
phase were calculated using the Time-Dependent Self Consistent Field (TD- SCF) method by
using the optimized structure in ethanol as solvent with the same level of theory. The simulated
UV-visible absorption maxima (λmax) values, theoretical electronic excitation energies and
oscillator strengths are depicted in Table S2. As can be clear from Table S2, the simulated
absorption maxima values for the compounds 1 and 2 are found to be 302.71 and 306.53 nm,
respectively. The oscillator strength f has no dimension and tells about the strength of an
electronic transition. The maximum absorption at 302.71 (compound 1) and 306.53 (compound
2) nm, respectively is assigned to the transition from HOMO to LUMO molecular orbital.
Table 8
3.8. CTAB-complex interaction study

Surfactant can be possibly used as a drug carriers because of its potential behavior of
establishing soluble environment even for very poorly soluble drugs, and hence increases the
bioavailability together with reducing the hostile effect of the drugs [58]. Each surfactant form
micelles at different concentrations called its CMC value, which changes by the interaction of
surfactant with drugs. Now when a drug is administered with a surfactant, the CMC value either
increases representing good bioavailability of drug upon dilution or it decreases/remains constant
representing low bioavailability of drug.
Herein, we studied the CTAB-compounds interactions via conductometric method. In order to
emphasize the CTAB-compound study through their specific conductance, 1 mM solutions of
compound 1 and 2 were prepared in methanol and interacted with varying concentration of
CTAB i.e. ranging from 0 to 7 mM. Initially the specific conductance of compound solutions
increases with increase in CTAB concentration till a point called as inflection point was observed
and hereafter CTAB monomers tend to form micelle and the conductance is mainly due to free
Br¯ ions (Figure 8) [59]. Generally free ions (CTAB+ and Br-) formed in the solution are
responsible for the sharp increase in conductance in the pre-micellar concentration region while
comparative decrease in the increase rate of conductance in post-micellar region is because of the
micelle formation from the available free ions. However, on interaction of compound molecules,
the repulsion between the positive charges of N atom of CTAB+ monomers decreases by
reducing its charge density hence increases the CMC value.
For compound 1 while interacting with CTAB system CMC value is found to be 0.003M
whereas the value is 0.0031M when compound 2 interacts with CTAB (Figure 8). CMC value
for compounds-CTAB system is comparatively higher than the reported free CTAB value
(0.0009 M) [60]. This increase in CMC value indicates strong interaction of compounds with the
surfactant (CTAB) that might results in higher bioavailability of the compounds in biological
system.
Gibbs free energy of micellization (ꢀGm) was calculated using the equation:
ꢀGm = 2.303(1+β) RTlogXcmc
β = 1-α (β = degree of the counter ion binding)
α = S2/S1(α = degree of dissociation or ionization, calculated before and after CMC from the
ratio of plots)

S1 and S2 are slopes of conductivity–concentration plots before and after CMC. It is taken in
mole fractions called as Xcmc which in aqueous solution can be calculated as:
Xcmc = cmc/55.55
For compound 1 and 2 ꢀGm value is found to be -36 kJ mol-1 and -34 kJ mol-1, respectively,
where its negative value indicates spontaneous solubilization of the compounds in surfactant
micelles system.
Figure 8
3.9. In vitro antibacterial activity
The agar well diffusion method was used to carry out the in vitro antibacterial activity against
five different bacterial strains: C. Staphylococci, MRSA, S. Aureus, E. Coli and K. Pneumoniae.
The zone inhibition (mm) of both the compounds was measured against their activity (Table 10).
Both compounds showed good anti-bacterial activity and is comparable to that of standard. The
anti-bacterial activity was higher against G+ve (S. aureus) bacteria than against G -ve bacteria.
The antibacterial activity and inhibition zone around the tested compounds can be caused by
their bactericide effects or their bacteriostatic effects [25].
Table 10
3.10. In vitro antifungal activity
The agar well diffusion protocol was used to carry out the antifungal activity against four
different strains of fungi and is summarized in Table 10. Terbinafine and DMSO were used as
positive and negative controls, respectively. The zone of inhibition for both compounds was
measured as a function of their activity. Percentage inhibition value was evaluated by following
formula:
Compound 1 has shown maximum inhibition of 79% against M. species fungal strain while
compound 2 has shown maximum inhibition of 69% against A. niger. Overall both the
compounds have shown good inhibition against all the tested fungal strains.
Table 10
Conclusions
The titled Schiff bases derived from 2,3-dihyroxybenzaldehyde (1) and o-vanillin (2) were
synthesized and characterized by various analytical techniques. Crystallographic data of the

investigated compounds show that both the compounds crystallized in the monoclinic crystal
system with space group C2/c and exhibited strong intramolecular N–H⋯O hydrogen bond
resulting in the formation of stable 6-membered ring. The geometric parameters obtained from
DFT studies and spectroscopic properties obtained from experimental data showed excellent
correlation with each others. The interaction of the titled compounds with DNA was investigated
by UV-visible spectroscopy and viscometry showing the intercalative mode of interaction.
Moreover, the interaction of the compounds with CTAB is characterized by higher CMC and
negative ꢀG values which indicates good bioavailability and spontaneous solubilization of
compounds. The antibacterial and antifungal evaluation of compounds exhibit relatively good
results as compared to standard drugs, cefixime and terbinafine, respectively.
Acknowledgement
S. Ali is thankful to Quaid-i-Azam University Islamabad Pakistan for financial support (URF
2019).
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Table 1: Crystal data and structure refinement parameters for compound 1 and 2
Parameters
Compound 1
C10H13NO3/195.21
296(2)
Compound 2
C9H11NO3/181.19
296(2)
Formula/molecular weight
Temperature/K
Crystal system/Space group
Monoclinic/C2/c
Monoclinic/C2/c
17.118(3),7.3373(10),
15.989(2)
a, b, c/Å
24.618(4), 5.0167(7), 31.985(5)
α, β, γ /°
V/Å3
90, 101.612(6), 90
3869.3(11)
16
90, 116.472(7), 90
1797.7(5)
Z
8
ρcalcg/cm3
1.340
1.339
ꢀ/mm-1
0.099
0.101
F(000)
1664.0
768.0
Crystal dimension/mm3
0.39 × 0.22 × 0.20
MoKα (λ = 0.71073)
0.42 × 0.32 × 0.28
MoKα (λ = 0.71073)
5.316 to 51.972
Radiation
2θ range for data collection/° 4.66 to 52
-29 ≤ h ≤ 30, -6 ≤ k ≤ 5, -30 ≤ l -14 ≤ h ≤ 20, -8 ≤ k ≤ 9, -19 ≤
Index ranges
≤ 39
l ≤ 17
Reflections collected
Independent reflections
11702
5028
3802 [Rint = 0.0493, Rsigma = 1760 [Rint = 0.0517, Rsigma
=
0.0647]
0.0620]
Data/restraints/parameters
S on F2
3802/0/257
1760/0/120
1.039
1.032
Final R indexes [I>=2σ (I)]
R1 = 0.0538, wR2 = 0.1410
R1 = 0.0494, wR2 = 0.1318
R1 = 0.0661, wR2 = 0.1479
0.22/-0.19
Final R indexes [all data]
R1 = 0.0899, wR2 = 0.1606
Largest diff. peak/hole / e Å-3 0.41/-0.30
CCDC# 1888257
1888256

Table 2: Selected bond lengths (Å) for Compounds 1 and 2
Compound 1
Atom-Atom
O1-C1
O2-C2
O2-C7
O3-C10
N1-C8
N1-C9
C1-C6
C1-C2
C2-C3
C3-C4
C4-C5
C5-C6
C6-C8
C9-C10
Length/Å
1.280(3)
1.367(3)
1.425(3)
1.417(3)
1.292(3)
1.463(3)
1.433(3)
1.446(3)
1.364(3)
1.405(4)
1.354(3)
1.423(4)
1.412(3)
1.514(3)
Atom-Atom
O4-C11
Length/Å
1.354(3)
1.365(3)
1.426(3)
1.415(3)
1.254(3)
1.468(3)
1.393(3)
1.411(3)
1.375(3)
1.384(4)
1.375(4)
1.405(4)
1.460(3)
1.487(4)
O5-C12
O5-C17
O6-C20
N2-C18
N2-C19
C11-C16
C11-C12
C12-C13
C13-C14
C14-C15
C15-C16
C16-C18
C19-C20
Compound 2
O1-C1
O2-C2
O3-C9
N1-C7
N1-C8
C1-C2
C1-C6
1.3001(18)
1.367(2)
1.401(2)
1.289(2)
1.457(2)
1.427(2)
1.430(2)
C2-C3
C3-C4
C4-C5
C5-C6
C6-C7
C8-C9
1.368(2)
1.406(3)
1.352(3)
1.422(2)
1.416(2)
1.510(3)

Table 3: Selected bond angles (˚) for compounds 1 and 2
Compound 1
Atom-Atom-Atom
C2-O2-C7
C8-N1-C9
O1-C1-C6
O1-C1-C2
C6-C1-C2
C3-C2-O2
C3-C2-C1
O2-C2-C1
C2-C3-C4
C5-C4-C3
C4-C5-C6
C8-C6-C5
N1-C8-C6
N1-C9-C10
O3-C10-C9
Angle/˚
117.4(2)
125.0(2)
122.4(2)
121.6(2)
116.0(2)
125.5(2)
121.1(2)
113.4(2)
121.6(2)
119.9(2)
120.7(2)
119.1(2)
124.7(2)
112.04(18)
112.90(19)
Atom-Atom-Atom
C12-O5-C17
C18-N2-C19
O4-C11-C16
O4-C11-C12
C16-C11-C12
O5-C12-C13
O5-C12-C11
C13-C12-C11
C12-C13-C14
C15-C14-C13
C14-C15-C16
C11-C16-C15
N2-C18-C16
N2-C19-C20
O6-C20-C19
Angle/˚
117.2(2)
119.3(3)
122.7(2)
117.8(2)
119.5(2)
125.9(2)
114.6(2)
119.5(2)
120.8(2)
120.4(2)
119.9(3)
119.8(2)
122.8(3)
113.4(2)
111.6(2)
Compound 2
C7-N1-C8
O1-C1-C2
O1-C1-C6
C2-C1-C6
O2-C2-C3
O2-C2-C1
C3-C2-C1
124.40(15)
120.62(14)
122.79(14)
116.58(14)
119.53(15)
119.07(14)
121.40(15)
C5- C4-C3
C4- C5-C6
C7- C6-C5
C7- C6-C1
C5- C6-C1
N1- C7-C6
N1- C8-C9
119.56(17)
121.15(17)
119.25(16)
120.65(15)
120.10(16)
125.14(16)
111.51(15)

C2-C3-C4
121.20(16)
O3- C9-C8
108.42(15)
Table 4: Hydrogen-bond lengths and bond angles (Å,˚) for compounds 1 and 2
D-H···A
d(D-H)/Å
d(H-A)/Å
Compound 1
1.91
d(D-A)/Å
D-H-A/°
O3-H3A···O11
N1-H1···O1
N1-H1···O11
C8-H8···O4
C9-H9B···O11
O6-H6···O32
N2-H2···O4
0.82
0.86
0.86
0.93
0.97
0.82
0.86
2.722(2)
2.630(2)
3.108(3)
3.450(3)
3.132(3)
2.875(2)
2.630(3)
169.8
134.2
119.9
160.7
110.7
156.6
133.3
1.96
2.59
2.56
2.65
2.10
1.96
Compound 2
2.33
O2-H2··· O1
O2- H2··· O11
O3- H3A··· O12
N1- H1··· O1
C7- H7··· O33
C8- H8B··· O24
0.82
0.82
0.82
0.86
0.93
0.97
2.7543(16)
2.7304(17)
2.7336(18)
2.6658(17)
3.361(2)
112.7
144.0
170.0
133.5
162.0
163.0
2.02
1.92
2.00
2.46
2.65
3.591(3)
Symmetry transformations used to generate equivalent atoms in compound 1: (1) 1/2-X,1/2-Y,-Z; (2) -1/2+X,1/2+Y,+Z
Symmetry transformations used to generate equivalent atoms in compound 2: (1) 1/2-X,-1/2-Y,1-Z; (2) -X,-Y,1-Z; (3) -X,1-Y,1-Z; (4) +X,-
Y,1/2+Z

Table 5: Binding constant (Kb), Gibbs free energies (∆G) and electronic descriptors of
compounds 1 and 2 calculated from molecular docking analysis
Binding Parameter
Kb (M-1)
Compound 1
6.5 × 101
-10.37
Compound 2
9.92× 102
-17.05
∆G (kJmol-1)
Table 6: Electronic descriptors of compounds 1 and 2 calculated from molecular docking
analysis
Comp.
Electronic descriptors
#
EHOMO
(kJ mol-1)
-37.18
ELUMO
(kJ mol-1)
-2.60
EIP
(kJ mol-1)
37.18
Eele
(kJ mol-1)
Evander
(kJ mol-1)
0.00
Etot
(kJ mol-1)
-1166828.69
-1228896.86
-2198895.92
-238328254.88
1
2
-40.02
-2.79
2.36
0.00
Steric descriptors
SlogP
Comp. #
Hf
MR
Vsurf
194.8
195.6
-99.630
-98.547
0.6940
5.4354
4.9318
1
2
0.5090

Table 7: Comparison of experimental and simulated geometric parameters of compounds 1 and 2
Bond lengths (Å)
Bond angles (º)
Experimental
Parameters Experimental Calculated
Parameters
Calculated
Compound 1
O1-C1
O2-C2
1.280(3)
1.367(3)
1.425(3)
1.417(3)
1.292(3)
1.463(3)
1.354(3)
1.365(3)
1.426(3)
1.415(3)
1.254(3)
1.468(3)
1.283
1.371
1.417
1.434
1.280
1.447
1.345
1.342
1.432
1.390
1.269
1.456
C2-O2-C7
C8-N1-C9
117.4(2)
125.0(2)
122.4(2)
121.6(2)
116.0(2)
125.5(2)
117.2(2)
119.3(3)
122.7(2)
117.8(2)
119.5(2)
125.9(2)
117.6
125.4
122.8
121.9
116.4
125.1
117.4
119.5
122.9
117.6
119.1
125.8
O2-C7
O1-C1-C6
O3-C10
N1-C8
O1-C1-C2
C6-C1-C2
N1-C9
C3-C2-O2
O4-C11
O5-C12
O5-C17
O6-C20
N2-C18
N2-C19
C12-O5-C17
C18-N2-C19
O4-C11-C16
O4-C11-C12
C16-C11-C12
O5-C12-C13
Compound 2
O1-C1
O2-C2
O3-C9
N1-C7
N1-C8
C1-C2
C1-C6
C2-C3
C3-C4
C4-C5
C5-C6
C6-C7
C8-C9
1.300(18)
1.367(2)
1.401(2)
1.289(2)
1.457(2)
1.427(2)
1.430(2)
1.368(2)
1.406(3)
1.352(3)
1.422(2)
1.468(3)
1.510(3)
1.302
1.348
1.426
1.279
1.440
1.453
1.417
1.368
1.413
1.340
1.441
1.45
C7-N1-C8
O1-C1-C2
O1-C1-C6
C2-C1-C6
O2-C2-C3
O2-C2-C1
C3-C2-C1
C2-C3-C4
N1- C7-C6
N1- C8-C9
O3- C9-C8
C5- C4-C3
C4- C5-C6
124.40(15)
120.62(14)
122.79(14)
116.58(14)
119.53(15)
119.07(14)
121.40(15)
121.20(16)
125.14(16)
111.51(15)
108.42(15)
119.56(17)
121.15(17)
124.45
120.55
122.80
116.51
119.55
118.00
121.44
121.23
125.18
111.55
108.44
119.60
121.18
1.50

Table 8: Calculated physical parameters of compounds 1 and 2
Physical properties
EHOMO (eV)
ELUMO (eV)
∆E = EHOMO-ELUMO (eV)
I.P (eV)
Compound 1
-5.71
Compound 2
-5.605
-0.952
4.653
-1.306
4.404
5.71
5.605
E.A (eV)
1.306
0.952
Χ (eV)
3.508
3.278
η (eV)
2.202
2.326
S (eV-1)
0.227
0.215
ꢀ (eV)
ω (eV-1)
-3.508
-3.508
1.68
-3.278
-3.278
5.89
Dipole moment (Debye)
Table 9: Antibacterial activity data for compounds 1 and 2
Pathogen used→
Comp ↓
S. aureus
E. coli
C-negative
K. pneumonia
MRSA
staphylococci
Zone of inhibition in mm (Mean ± standard deviation)
1
2
28.52 ± 0.46 16.43 ± 1.03 19.08 ± 1.0
26.72 ± 0.41 19.23 ± 1.05 21.08 ± 1.02
22.23 ± 0.62 18.04 ± 0.07 15.09 ± 0.82
23.85 ± 1.31 14.71 ± 0.54
20.75 ± 1.01 16.71 ± 0.34
Cefixime
20.92 ± 1.04
13.4 ± 0.09
Table 10: Antifungal activity data for compounds 1 and 2
Pathogens used →
Comp ↓
A. niger
A. fumigates
A. flavus
M. species
Zone of inhibitation in mm (Mean ± standard deviation)
1
62 ± 1.14
69 ± 0.53
46± 1.18
38 ± 0.49
56± 0.96
61 ± 0.76
76± 1.86
65 ± 0.71
2
Terbinafine
100± 0
100± 0
100± 0
100± 0