Evaluation of 2-indolcarbohydrazones as potent α-glucosidase inhibitors, in silico studies and DFT based stereochemical predictions

Article abstract of DOI:10.1016/j.bioorg.2015.09.001

2-Indolcarbohydrazones 1-28 were synthesized and evaluated for their α-glucosidase inhibitory potential. A varying degree of inhibitory potential with IC₅₀ values in the range of 2.3 ± 0.11-226.4 ± 6.8 μM was observed while comparing these outcomes with the standard acarbose (IC₅₀ = 906.0±6.3μM). The stereochemistry of ten (10) randomly selected compounds (1, 3, 6, 8, 12, 18, 19, 23, 25 and 28) was predicted by Density Functional Theory (DFT). The stability of E isomer was deduced by comparing the calculated and experimental vibration modes of ν_C=O, ν_N=C and ν_CH (CH in -N=CH-R). It was observed that except compound 18, all other compounds were deduced to have E configuration while molecular modeling studies revealed the key interactions between enzyme and synthesized compounds.

Full text of DOI:10.1016/j.bioorg.2015.09.001

Accepted Manuscript
Evaluation of 2-Indolcarbohydrazones as Potent α-Glucosidase inhibitors, In
Silico Studies and DFT based Stereochemical Predictions
Muhammad Taha, Nor Hadiani Ismail, Kulsoom Javaid, Syahrul Imran, El
Hassane Anouar, Abdul Wadood, Atia-tul-Wahab, Muhammad Ali, Khalid
Mohammed Khan, Syed Muhammad Saad, Fazal Rahim, M. Iqbal Choudhary
PII:
S0045-2068(15)30016-X
DOI:
http://dx.doi.org/10.1016/j.bioorg.2015.09.001
YBIOO 1839
Reference:
Bioorganic Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
27 July 2015
3 September 2015
7 September 2015
Please cite this article as: M. Taha, N.H. Ismail, K. Javaid, S. Imran, E.H. Anouar, A. Wadood, Atia-tul-Wahab, M.
Ali, K.M. Khan, S.M. Saad, F. Rahim, M. Iqbal Choudhary, Evaluation of 2-Indolcarbohydrazones as Potent α-
Glucosidase inhibitors, In Silico Studies and DFT based Stereochemical Predictions, Bioorganic Chemistry (2015),
doi: http://dx.doi.org/10.1016/j.bioorg.2015.09.001
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Evaluation of 2-Indolcarbohydrazones as Potent -Glucosidase inhibitors, In
Silico Studies and DFT based Stereochemical Predictions
Muhammad Tahaa,b, Nor Hadiani Ismaila,b, Kulsoom Javaidc, Syahrul Imrana,b, El
Hassane Anouard, Abdul Wadoode, Atia-tul-Wahabf, Muhammad Alig, Khalid
Mohammed Khanc, Syed Muhammad Saadc, Fazal Rahimh, M. Iqbal Choudharya,f,c,i
aAtta-ur-Rahman Institute for Natural Product Discovery, Universiti Teknologi MARA (UiTM), Puncak Alam
Campus, 42300 Bandar Puncak Alam, Selangor, Malaysia
bFaculty of Applied Science UiTM, 40450 Shah Alam, Selangor, Malaysia
cH. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of
Karachi, Karachi-75270, Pakistan
dChemistry Department, College of Sciences and Humanities, Salman bin Abdulaziz University, P.O. Box 83, Al-
Kharij 11942, Saudi Arabia
eDepartment of Biohemistry, Abdul Wali Khan University Mardan, Mardan 23200, Pakistan
fDr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and
Biological Sciences, University of Karachi, Karachi-75270, Pakistan
gDepartment of Chemistry, COMSATS Institute of Information Technology, University Road, Abbottabad-22060,
KPK, Pakistan
hDepartment of Chemistry, Hazara University, Mansehra-21120, Khyber Pukhtunkhwa, Pakistan
iDepartment of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah-21412, Saudi Arabia
Abstract:
2-Indolcarbohydrazones 1-28 were synthesized and evaluated for their α-glucosidase
inhibitory potential. A varying degree of inhibitory potential with IC50 values in the
range of 2.3 ± 0.11 - 226.4 ± 6.8 µM was observed while comparing these outcomes
with the standard acarbose (IC50 = 906.0 ± 6.3 µM). The stereochemistry of ten (10)
randomly selected compounds (1, 3, 6, 8, 12, 18, 19, 23, 25 and 28) was predicted by
Density Functional Theory (DFT). The stability of E isomer was deduced by
comparing the calculated and experimental vibration modes of νC=O, νN=C and νCH
(CH in –N=CH-R). It was observed that except compound 18, all other compounds
were deduced to have E configuration while molecular modelling studies revealed the
key interactions between enzyme and synthesized compounds.
Keywords: 2-Indolcarbohydrazones, α-Glucosidase Inhibition, Structure-Activity
Relationship, Density Functional Theory (DFT), In Silico studies
Corresponding authors:
E-mail: taha_hej@yahoo.com and muhamm9000@puncakalam.uitm.edu.my, Tel: 0060193098141
1

1. Introduction
Indole derivatives have found numerous pharmaceutical applications such as
anticancer [1], antioxidant [2], antibacterial [3], antidepressant [4], anxiolytic [5] as
well as anti-HIV [6] properties. Many drugs are available in the markets which
contain indole moiety as their pharmacophore such as delavirdine, a non-nucleotide
reverse-transcriptase inhibitor, used for the treatment of HIV type 1 [7], yohimbine
for the treatment of male impotency [8], oxypertine for the treatment of schizophrenia
[9], arbidol for the treatment of influenza infection [10], sumatriptan for migraine
treatment [11], ondansetron for the suppression of nausea [12], alosetron for the
treatment of irritable bowel syndrome [13] and perindopril for the treatment of
hypertension [14] etc.
Schiff base is an important pharmacophore in pharmaceutical chemistry. They exhibit
various biological activities such as antidiabetic [15-18], antioxidant [19-21],
antileishmanial [22] and analgesic [23-27] potentials etc.
α-Glucosidases (EC 3.2.1.20) are hydrolase enzymes which exist in the brush border
surface of the human intestinal cells. These enzymes are essential for the hydrolysis of
carbohydrate into glucose monomers which are absorbed into the blood stream [28].
During hydrolysis process, hydrolytic reaction takes place by splitting the bond
between the glucosidic oxygen and anomeric carbon of glucosyl residues. Glucosyl
residue is then replaced by a proton from water or an acceptor, namely an exchange
reaction between the glucosyl residue and the proton in both hydrolysis and
transglucosylation. Since α-glucosidase plays a crucial biological role in the digestion
of carbohydrates and for the processing of glycoproteins in viruses, its inhibitors are
suitable to be employed against diseases like cancers, diabetes, and HIV [29-31].
During the last two decades, various α-glucosidase inhibitors have been reported [32,
33a-i]. These inhibitors have the potential to be used for the treatment of diabetes
mellitus (DM) [34]. Indoles [35] as well as Schiff base derivatives are reported to
have excellent α-glucosidase inhibitory potentials [36].
2

Based on reported α-glucosidase inhibitory potentials of indole and Schiff bases, we
hypothesized that Schiff bases of indole might act as α-glucosidase inhibitors with the
efficacies better than indole and Schiff bases themselves independently. Therefore, we
have synthesized Schiff base derivatives of indole in order to evaluate them for their
α-glucosidase inhibitory activity in vitro.
2. Results and Discussion
2.1. Chemistry
Intermediate 1H-indole-2-carbohydrazide was obtained from methyl-1H-indole-2-
carboxylate after refluxing it with hydrazine hydrate. Corresponding hydrazide was
recrystallized from methanol and employed in second step for the preparation of 2-
indole hydrazones after condensation with various aromatic aldehydes (Scheme-1).
The crude solid products obtained so were recrystallized from methanol with
excellent yields, i.e. 78-92%. Structures of synthesized compounds (1-28) were
confirmed by various spectroscopic techniques and CHN analysis. Compounds 8 [37],
9 [38], 10 [39], 16, [40], 17 [41], 18, 22, 23, 24, 27 [42], 20, 25 [43] and 21 [44] are
known, however, rest of the compounds are new. Elemental analyses were found to be
in good agreement with the calculated values for all the compounds.
Insert scheme 1 here
2.2. DFT Predictions on E/Z Configurations
The –N=CH-R bond in 2-indolcarbohydrazone derivatives 1-28 (Scheme-1) may exist
as Z or E isomers. To determine which configuration (Z or E) exist in the current
series of compounds, the electronic energies and vibration modes νC=O, νN=C and νCH
(CH in –N=CH-R) were calculated for ten randomly selected compounds (1, 3, 6, 8,
12, 18, 19, 23, 25, and 28) at the B3LYP/6-311++G(d,p) level of theory. The
electronic and relative energies of E and Z configurations are presented in Table-1.
Results showed that E configuration is relatively more stable than Z by 8-10 kcal/mol
for compounds 1, 3, 6, 8, 12, and 19 and by 2-4 kcal/mol for compounds 23, 25 and
28. Inversely, the Z configuration of compound 18 was found more stable than E by 2
kcal/mol. The stability of the Z configuration of 18 with respect to E is explained by
3

the formation of hydrogen bonding (2.37 Å) between the oxygen atom of the furan
and NH of amide (Figure 1S).
The stability of E configuration was confirmed by comparing the calculated and
experimental vibration modes of νC=O, νN=C and νCH (CH in –N=CH-R) (Table-1).
Except compound 18, the variations of vibrational modes ΔνC=O (ΔνN=C) between the
calculated and experimental values vary from 1 to 11 cm-1 (1 to 13 cm-1) and 12 to 29
cm-1 (0 to 27 cm-1) for E and Z configurations, respectively. The variation modes
obtained with E configuration are closer to the experimental values than Z
configuration. Instead, for compound 18 the vibrational modes of Z configuration are
closer to the experimental value. These variations are not sufficient to distinguish
between Z and E configurations (small variation). However, the large variations
between the E and Z configurations were obtained for νCH (CH in –N=CH-R)
vibration modes. Except for compound 18, a variation of 1-21 cm-1 was observed for
E configuration for the selected compounds, while for Z configuration the variation
varies 99 to 125 cm-1. These results are in good agreement with electronic energies
obtained above. Therefore, for all selected compounds (except 18), the
stereochemistry of –N=CH- is E configuration. Based on these results, we compared
the νCH (CH in –N=CH-R) of all other compounds (2, 4, 5, 7, 9-11, 13-17, 20-22, 24,
26, and 27) and they were found to be in the range of 2905-2942. Hence, they are
predicted to have E configuration.
Insert Table 1 here
2.3. α-Glucosidase Inhibition and SAR Analysis
α-Glucosidase inhibitory activity of indole hydrazones 1-28 were evaluated by using
α-glucosidase enzyme isolated from Saccharomyces cerevisiae (yeast) and p-
nitrophenyl-α-D-glucopyranoside as standard substrate [33i]; the IC50 values of all
screened compounds 1-28 are shown in Table 2.
Insert Table 2 here
4

Out of twenty-eight (28) synthesized compounds 1-28, fourteen (14) compounds
displayed potent inhibitory potentials against α-glucosidase with the IC50 values in the
range of 2.3 to 226.4 µM, in comparison to the standard, acarbose (IC50 = 906 ± 6.3
µM). Compound 1 was found to be the most potent inhibitor of α-glucosidase enzyme
with the IC50 value of 2.3 ± 0.11 µM. Compounds 19, 27, 4, 2, 13, 14 and 6
demonstrated commanding potential of inhibition (10-34 folds) than the standard
inhibitor, while compounds 3, 8, 11, 9, and 7 showed five to eight (5-8) folds better
activity than the standard acarbose. However, compounds 5, 12, 15-18, 20-26, and 28
did not show any activity (Table-2).
Structure-activity relationship (SAR) analysis indicated that α-glucosidase inhibitory
activity of this class of compounds is mainly dependent upon the variation of
substituents on the aromatic side chains, derived from aldehydes, of the 1H-indole-2-
carbohydrazones.Compound 1 (IC50 = 2.3 ± 0.11 µM) showed highest α-glucosidase
inhibition among the synthesized library of compounds. It was found to be 400 times
more potent than the standard acarbose. This suggests that the presence of three
hydroxyl groups at 3′,4′,5′-position has made this compound such a potent lead
molecule that could be employed for further investigations leading to in vivo and
toxicity analysis. On the other hand compound 2 having 2′,4′,6′ trihydroxy showed
almost twenty-two (22) folds lesser activity than compound 1. This depicts that any
alteration in the position of substituents on aromatic ring influences greatly the
inhibition.
This finding was further endorsed when dihydroxy analogues 4 (IC50 = 41.0 ± 4.96
µM), a 3,4-dihydroxy and 6 (IC50 = 86.5 ± 0.98 µM µM), a 2,3-dihydroxy, were
compared. Furthermore, when analogues, 4 and 6, were compared with those of 3 and
7 as well as 5; it clearly showed that position of substituents have greatly shaped the
inhibitions. Activity potentials were improved broadly when one of the hydroxyl
groups in dihydroxy analogues (3-7) was substituted with methoxy group. For
example, in 3 where a hydroxyl group at position 5 was replaced with a methoxy
group (13), the activity of compound 13 was seen to be improved almost three folds.
However, compounds 8 (3-methoxy analogue) and 11 (4-methoxy analogue) were
found less active when compared with compound 4 (3,4-dihydroxy analogue), this
finding was contrary to what was explained vide supra. This might be due to the fact
5

that the position of hydroxyl group that contributes significant interactions with
enzyme active site is lost. On the other hand, when both 3,4-dihydroxyls are replaced
with 3,4-dimethoxy groups (compound 16), the activity is completely vanished.
Similarly compound 15 was found to be inactive when 3,5-dihydroxyl substitutions
(compound 7) were converted into 3,5-dimethoxy substitutions such as in 15.
Among the mono-hydroxy analogues, compound 10 having 2-hydroxyl substitution
showed very potent activity, as compared to its analogue 9 having 4-hydroxl
substituent, which indicates that 2-hydroxyl group better interacts with enzyme active
site. Compound 13, a 2-hydroxy-5-methoxy analogue, was found to be the second
most active inhibitor amongst the mono-hydroxyl analogues. This finding
corroborated our assumption that 2-hydroxy position is important for potent inhibitory
potentials in mono hydroxyl analogues. More interestingly, compound 12 with 3-
bromo-4-hydroxy substituents showed no activity which may be due to the bulk of
bromine atom that it has introduced in the molecular structure which possibly
hindered the H-bond interaction of this compound with the enzyme.
Compound 14, 3-hydroxy-2-iodo-4-methoxy analogue, showed 50 times more activity
than the standard drug. When we compared compound 11 with compound 14, we
found that iodine substitution at position 2 improves the activity almost 3 folds.
Compounds 19, a 3-fluoro-4-bromo analogue, (IC50 = 26.6 ± 0.80 µM) and 27, a 4-
chloro analogue, (IC50 = 32.1 ± 3.05 µM) also showed very potent activities when
compared with standard.
Molecular Docking Calculations
MOE docking program was used to analyze the binding modes of the ligands with the
protein molecule. To find the correct conformations of the ligands and to obtain
minimum energy structures, ligands were allowed to be flexible. The default
parameters of MOE-Dock program were used for the molecular docking of the
ligands. The top ranked pose of each compound was selected on the basis of docking
score (S) for further analysis. At the end of docking, the best conformations on the
6

basis of score were analyzed for hydrogen bonding/π-π interactions. It was observed
in the docking studies that the substituent groups of the compounds are involved in
bonding especially as compared to the rest of the body of compounds. Analysis of the
predicted binding conformations showed that the compounds in which the electron
rich substituents have such positions where the delocalization of their electronic
density is restricted are more active than others. For example the most active
compound 1 (IC50 = 2.3 ± 0.11 µM) showed better interactions through the three
adjacent OH groups located on aromatic ring as shown in Figure 1a. In this
compound the three OH groups are located over the three adjacent C atoms of the
aromatic ring and thus the delocalization of their electronic density over the ring is
highly restricted. Due the concentrated electronic density over these groups they
interact with various important residues of target protein, i.e. Arg 439, Asp 214 and
Glu 276. The imidazole moiety of this compound also interacts with Phe 157. In
compound 2 the three OH groups occupy alternate C atoms of the ring and their
electronic density have some space to delocalize over the ring. Due to slightly
dispersed electronic density of these groups compound 2 showed poor interactions
with the residues of protein i.e. Asp 349, His 279 as shown in Figure 1b.
Figure 1 insert here
The docking study revealed that the interaction mode of these compounds may
depend on the electron rich nature of the substituted groups, their number and
positions. As the number of OH groups goes on decreasing from three to two in
compounds 3, 4, 5, 6, 7 and to one in compounds 9, 10, their interactions also go on
decreasing. However, the compounds in which the OH groups are at adjacent position
such as compound 4 competes with compound 2 having three OH but at alternate
7

positions. The interaction mode of compound 4 is shown in Figure 2a. In our series
of compounds, the other compounds giving good results are the compounds having
halogen groups over the substituted aromatic ring. Compound 19 having Br and F
showed three interactions with the residues Arg 212, Asp 349 and Phe 298 as shown
in Figure 2b. The binding mode analysis of inactive compounds clearly verified the
reason of inactivity. These compounds do not make any remarkable interactions with
the surrounding amino acid residues.
Figure 2 insert here
Conclusion
In this study, we identified new class of highly potent α-glucosidase inhibitors.
Further to this, we found that only those hydroxyl derivatives (di- and tri-) such as 1,
4, and 6 showed potent activities which had vicinal hydroxyl positions. In
monohydroxy derivatives, activity depends on the position of hydroxyl group such as
2-OH > 4-OH. The halogenated compounds showed a good activity. We also
determined the configuration of stereoisomers (E/Z). It was found that only compound
18 has Z configuration due to hydrogen bonding.
8

Experimental
4.1. Material and methods
NMR experiments were performed on Bruker FT NMR 500 MHz. IR experiments
were performed on Perkin Elmer FT-IR and UV on the Perkin Elmer Lamda 35 UV-
VIS Spectrometer. CHN analysis was performed on a Carlo Erba Strumentazion-
Mod-1106, Italy. Electron impact mass spectra (EI MS) were recorded on a Finnigan
MAT-311A, Germany. Thin layer chromatography (TLC) was performed on pre-
coated silica gel aluminum plates (Kieselgel 60, 254, E. Merck, Germany).
Chromatograms were visualized by UV at 254 and 365 nm. Chemicals are Substrate:
p-Nitrophenyl-α- D-glucopyranoside. Lot # (BCBD7865V) CAS #3767-28-0 Sigma
Aldrich and Enzyme: α-Glucosidase from Saccharomyces cerevisiae recombinant,
G0660-750UN CAS9001-42-7 Sigma Aldrich.
4.2. Assay for α-Glucosidase Inhibitory Activity
Assay Protocol of α-Glucosidase
The 135 µL of 50 mM phosphate saline buffer pH (6.8) was added in the 96-well
plate and 20 µl of test sample with 70% DMSO added into the wells. The solution of
Enzyme 20 µL was added into the wells, and incubated the plate for 15 minutes.
After incubation pre- read of the plate was taken by the spectra max. Afterward 25 µL
of the substrate (pNPG) was added and a reading was taken on spectra max at 400
NM for 30 minutes. The normal reading is taken and the percent inhibition was
calculated.
4.2.1 Synthesis of 1H-indole-2-carbohydrazide
The methyl 1H-indole-2-carboxylate (10 g, 57.14 mmol) was refluxed with the
mixture of hydrazine hydrate (10 mL) and methanol (25 mL) for 6 hours. The excess
hydrazine hydrate and methanol was evaporated to afford crude product which was
recrystallized by methanol to produce pure 1H-indole-2-carbohydrazide with 92%
(9.2g, 52.57mmol) yield.
4.2.2. The optimization and frequency calculations of the ground states of Z and E
configurations of compounds 1, 3, 6, 8, 12, 18, 19, 23, 25, and 28 of 2-
9

indolcarbohydrazone derivatives have been performed at the B3LYP/6-311++G(d,p)
level of theory [45]. The minima were confirmed by the absence of imaginary
frequencies. The vibrational modes were calculated at the same level of theory and
scaled by 0.9679 [46]. All calculations were carried out using Gaussian09 package
[47].
4.2.3 General procedure for the synthesis 1H-Indole-2-carbohydrazones
1H-Indole-2-carbohydrazones were synthesized by refluxing in methanol a mixture of
1 mmol each 1H-indole-2-carbohydrazide with different arylaldehydes catalyzed by
acetic acid for 3 h. The progress of reaction was monitored by TLC. After completion
of reaction, the solvent was evaporated by vacuum to afford crude products which
were further recrystallized in methanol and got pure product in good to excellent
yields.
4.3.1. (E)-N'-(3,4,5-Trihydroxybenzylidene)-1H-indole-2-carbohydrazide (1)
Yield: 82%. m.p. 254-256 °C; Gray crystals; UV (MeOH) λmax(nm) 339.43; IR (KBr):
3304 cm-1 (OH-str), 3270 cm-1 (2oamine N-H Str), 3072 cm-1 (Ar CH str), 1674 cm-1
(C=N), 1630 cm-1 (C=O), 1600 cm-1 (Ar C=C), 1533 cm-1 (N-H Bend), 1321 cm-1 (C-
N str), 1125 cm-1 (C-O str). 1H NMR (500 MHz, DMSO-d6):  11.74 (s, 2H, 2xNH),
11.10 (s, 2H, 2xOH), 10.50 (s,1H, OH), 8.16 (s, 1H, ArCH=N), 7.67 (d, 1H, J = 8.0
Hz, H-4), 7.47 ( d, 1H, J = 8.0 Hz, H-7), 7.26 (s, 1H, H-3), 7.23 (t, 1H, J = 7.5 Hz, H-
5), 7.09 (t, 1H, J = 8.5 Hz, H-6), 6.72 (s, 2H, H-6′, H-2′);13C NMR (125 MHz,
DMSO-d6):  157.40, 146.60, 146.10, 146.10, 139.70, 138.30, 138.10, 131.10,
129.20, 121.60, 120.40, 119.60, 114.80, 111.10, 108.60, 108.60; Anal. Calcd for
C16H13N3O4, C = 61.72, H = 4.20, N = 13.51, Found C = 61.73, H = 4.21, N = 13.50;
EI MS m/z (% rel. abund.): 311 (M+ ,40), 10 (293) 144 (100), 116 (20), 75 (10).
4.3.2. (E)-N'-(2,4,6-Trihydroxybenzylidene)-1H-indole-2-carbohydrazide (2)
°
Yield: 85%. m.p. 256-258 C; Brown crystals; UV (MeOH) λmax(nm) 346.62; IR
(KBr): 3380 cm-1 (OH-str), 3326 cm-1 (2oamine N-H Str), 1642 cm-1 (C=O), 1615 cm-1
(Ar C=C), 1581 cm-1 (N-H Bend), 1259 cm-1 (C-N str), 1160 cm-1 (C-O str). 1H NMR
(500 MHz, DMSO-d6):  11.97 (s, 1H, NH), 11.77 (s, 1H, NH), 11.14 (s, 1H, OH),
9.92 (s, 2H, 2xOH), 8.80 (s, 1H, ArCH=N), 7.68 (d, 1H, J = 8.0 Hz, H-4), 7.48 (d,
10

1H, J = 8.0 Hz, H-7), 7.27 (s, 1H, H-3), 7.24 (t, 1H, J = 7.0 Hz, H-5), 7.09 (t, 1H, J =
13
7.5 Hz, H-6), 5.86 (s, 2H, H-3′, H-5′); C NMR (125 MHz, DMSO-d6): 163.80,
163.80, 163.20, 157.40, 143.60, 139.60, 138.70, 131.20, 121.60, 120.60, 119.50,
114.60, 111.10, 106.50, 96.20, 96.20; Anal. Calcd for C16H13N3O4, C = 61.72, H =
4.20, N = 13.51, Found C = 61.71, H = 4.20, N = 13.49; EI MS m/z (% rel. abund.):
311. (M+ ,30), 293 (12) 144 (100), 116 (15), 75 (12).
4.3.3. (E)-N'-(2,5-Dihydroxybenzylidene)-1H-indole-2-carbohydrazide (3)
Yield: 78%. m.p. 278-279 °C; Beige powder; UV (MeOH) λmax(nm) 321; IR(KBr):
3507 cm-1 (OH-str), 3346 cm-1 (2°amine N-H Str), 3050 cm-1 (Ar CH str), 1663 cm-1
(C=N), 1617 cm-1(Ar C=C), 1546 cm-1 (N-H Bend), 1307-1274 cm-1 (C-N str), 1147
1
cm-1 (C-O str). H NMR (500 MHz, DMSO-d6):  12.05 (s, 1H, NH), 11.81 (s, 1H,
NH), 10.33 (s, 1H, OH), 9.06 (s, 1H, OH), 8.58 (s, 1H, ArCH=N), 7.69 (d, 1H, J = 8.0
Hz, H-4), 7.48 (d, 1H, J = 8.0 Hz, H-7), 7.32 (s, 1H, H-3), 7.25 (t, 1H, J = 7.5 Hz, H-
5), 7.10 (t, 1H, J = 7.0 Hz, H-6), 7.03 (s, 1H, H-6′), 6.78-6.72 (m, 2H, H-4′,H-3′); 13C
NMR (125 MHz, DMSO-d6): 157.30, 153.20, 151.40, 146.10, 139.70, 138.40,
131.20, 121.60, 120.30, 120.10, 119.70, 119.60, 119.40, 116.20, 114.80, 111.10;
Anal. Calcd for C16H13N3O3, C = 65.08, H = 4.44, N = 14.23, Found C = 65.06, H =
4.43, N = 14.24; EI MS m/z (% rel. abund.): 295. (M+ ,27), 277 (12), 144 (100), 116
(20), 75(10).
4.3.4. (E)-N'-(3,4-Dihydroxybenzylidene)-1H-indole-2-carbohydrazide (4)
Yield: 84%. m.p. 234-237 °C; Dark brown crystals; UV (MeOH) λmax(nm) 339; IR
(KBr): 3412cm-1 (OH-str), 3253 cm-1 (2° amine N-H Str), 3043 cm-1 (Ar CH str), 1630
cm-1 (C=O), 1557cm-1 (N-H Bend), 1250cm-1 (C-N str), 1111cm-1 (C-O str).1H NMR
(500 MHz, DMSO-d6):  11.74 (s, 1H, NH), 11.69 (s, 1H, NH), 9.41 (s, 2H, 2xOH),
8.26 (s, 1H, ArCH=N), 7.67 (d, 1H, J = 8.0 Hz, H-4), 7.48 ( d, 1H, J = 8.5 Hz, H-7),
7.27 (s, 2H, H-3,H-2′), 7.23 (t, 1H, J = 7.5 Hz, H-5), 7.08 (t, 1H, J = 7.5 Hz, H-6),
13
6.98 (d, 1H, J = 8.0 Hz, H-5′), 6.82 (d, 1H, J = 8.0 Hz, H-6′); C NMR (125 MHz,
DMSO-d6): 157.50, 149.40, 146.70, 146.30, 139.40, 138.20, 131.20, 131.20,
123.40, 121.60, 120.40, 119.40, 117.20, 116.10, 114.80, 111.20; Anal. Calcd for
C16H13N3O3, C = 65.08, H = 4.44, N = 14.23, Found C = 65.07, H = 4.44, N = 14.23;
EI MS m/z (% rel. abund.): 295 (M+ ,50), 277 (14), 144 (100), 116 (24), 75(6).
11

4.3.5. (E)-N'-(2,4-Dihydroxybenzylidene)-1H-indole-2-carbohydrazide (5)
Yield: 85%. m.p. 280-282 °C; Orange micro crystals; UV (MeOH) λmax(nm) 342; IR
(KBr): 3416 cm-1 (OH-str), 3268 cm-1 (2° amine N-H Str), 1630 cm-1 (C=O), 1602 cm-
1
1
(Ar C=C), 1555 cm-1 (N-H Bend), 1233 cm-1 (C-N str), 1078 cm-1 (C-O str). H
NMR (500 MHz, DMSO-d6):  12.00 (s, 1H, NH), 11.78 (s, 2H, 2×OH), 11.40 (s,
1H, NH), 8.51 (s, 1H, ArCH=N), 7.68 (d, 1H, J = 8.0 Hz, H-4), 7.48 (d, 1H, J = 8.5
Hz, H-7), 7.36 (d, 1H, J = 8.5 Hz, H-6′), 7.28 (s, 1H, H-3), 7.24 (t, 1H, J = 7.0 Hz, H-
5), 7.10 (t, 1H, J = 7.5 Hz, H-6), 6.39 (d, 1H, J = 8.5 Hz, H-5′), 6.34 (d, 1H, J = 1.5
Hz, H-3′); 13C NMR (125 MHz, DMSO-d6): 162.20, 162.10, 157.40, 146.30,
139.60, 138.40, 133.50, 131.10, 121.40, 120.30, 119.60, 114.80, 111.30, 111.10,
108.40, 103.60; Anal. Calcd for C16H13N3O3, C = 65.08, H = 4.44, N = 14.23, Found
C = 65.08, H = 4.45, N = 14.26, EI MS m/z (% rel. abund.): 295 (M+ ,30), 277 (18)
144 (100), 116 (30), 75 (16).
4.3.6. (E)-N'-(2,3-Dihydroxybenzylidene)-1H-indole-2-carbohydrazide (6)
Yield: 86%. m.p. 224-227 °C; Gray crystals; UV (MeOH) λmax(nm) 326; IR (KBr):
3420 cm-1 (OH-str), 3268 cm-1 (2° amine N-H Str), 1609 cm-1 (Ar C=C), 1555 cm-1
(N-H Bend), 1237 cm-1 (C-N str). 1H NMR (500 MHz, DMSO-d6):  11.85 (br. s, 2H,
2×NH), 10.60 (s, 2H, 2xOH), 8.61 (s, 1H, ArCH=N), 7.70 (d, 1H, J = 8.0 Hz, H-4),
7.49 (d, 1H, J = 8.5 Hz, H-7), 7.33 ( s, 1H, H-3), 7.26 (t, 1H, J = 7.0 Hz, H-5), 7.10 (t,
1H, J = 7.5 Hz, H-6), 7.02 (d, 1H, J = 8.0 Hz, H-6′), 6.88 (d, 1H, J = 8.0 Hz, H-4′),
13
6.78 (t, 1H, J = 7.0 Hz, H-5′); C NMR (125 MHz, DMSO-d6): 157.40, 151.60,
145.80, 145.70, 139.20, 138.10, 131.80, 124.60, 122.60, 121.60, 120.20, 119.60,
119.50, 19.20, 114.50, 111.00; Anal. Calcd for C16H13N3O3, C = 65.08, H = 4.44, N =
14.23, Found C = 65.05, H = 4.42, N = 14.24; EI MS m/z (% rel. abund.): 295 (M+ ,
30), 277 (25), 144 (100), 116 (22), 75 (20).
4.3.7. (E)-N'-(3,5-Dihydroxybenzylidene)-1H-indole-2-carbohydrazide (7)
Yield: 81%. m.p. 200-202 °C; Light brown crystals; UV (MeOH) λmax(nm) 325; IR
(KBr): 3346 cm-1 (OH-str), 3290 cm-1 (2° amine N-H Str), 3072 cm-1 (Ar CH str),
1624 cm-1 (C=O), 1588 cm-1 (N-H Bend),1159 cm-1 (C-O str).1H NMR (500 MHz,
DMSO-d6):  11.82 (s, 1H, NH), 11.78 (s, 1H, NH), 9.56 (s, 2H, 2×OH), 8.24 (s, 1H,
12

ArCH=N), 7.68 (d, 1H, J = 7.5 Hz, H-7), 7.48 ( d, 1H, J = 8.0 Hz, H-4), 7.29 (s, 1H,
H-3), 7.24 (t, 1H, J = 7.5 Hz, H-5), 7.10 (t, 1H, J = 7.5 Hz, H-6), 6.64 (s, 2H, H-6′, H-
13
2′), 6.28 (s, 1H, H-4′); C NMR (125 MHz, DMSO-d6): 161.20, 161.20, 157.20,
146.10, 139.10, 138.70, 136.40, 131.20, 121.10, 120.60, 119.90, 114.80, 111.30,
108.20, 108.20, 105.40; Anal. Calcd for C16H13N3O3, C = 65.08, H = 4.44, N = 14.23,
Found C = 65.06, H = 4.45, N = 14.25; EI MS m/z (% rel. abund.): 295 (M+ ,50), 277
(18) ,144 (100), 116 (24), 75(6).
4.3.8. (E)-N'-(4-Hydroxy-3-methoxybenzylidene)-1H-indole-2-carbohydrazide (8)
Yield: 83%. m.p. 146-149 °C; Beige crystals; UV (MeOH) λmax(nm) 338; IR (KBr):
3355 cm-1 (OH-str), 3260 cm-1 (2° amine N-H Str), 1635 cm-1 (C=O), 1591 cm-1 (Ar
1
C=C), 1282 cm-1 (C-N str), 1031 cm-1 (C-O str). H NMR (500 MHz, DMSO-d6): 
11.76 (s, 1H, NH), 11.74 (s, 1H, NH), 9.60 (s, 1H, OH), 8.35 (s, 1H, ArCH=N), 7.68
(d, 1H, J = 8.0 Hz, H-4), 7.48 ( d, 1H, J = 8.0 Hz, H-7), 7.35 (s, 1H, J = 1.0 Hz, H-2′),
7.30 (s, 1H, H-3), 7.24 (t, 1H, J = 7.0 Hz, H-5), 7.13 (d, 1H, J = 7.5 Hz, H-5′), 7.08 (t,
1H, J = 7.5 Hz, H-6), 6.87 (d, 1H, J = 8.0 Hz, H-6′), 3.85 (s, 3H, OCH3 ); 13C NMR
(125 MHz, DMSO-d6): 157.50, 151.10, 149.20, 146.70, 139.70, 138.40, 131.20,
130.80, 122.80, 121.60, 120.60, 119.60, 117.00, 114.80, 112.20, 111.10, 56.20; Anal.
Calcd for C17H15N3O3, C = 66.01, H = 4.89, N = 13.58, Found C = 66.02, H = 4.88, N
= 13.57; EI MS m/z (% rel. abund.): 309 (M+ ,70), 291(14), 276 (8) 144 (100), 116
(19).
4.3.9. (E)-N'-(4-Hydroxybenzylidene)-1H-indole-2-carbohydrazide (9)
Yield: 92%. m.p. 270-271 °C. Gold crystals, UV (MeOH) λmax(nm) 332; IR (KBr):
3449 cm-1 (OH-str), 3213 cm-1 (2° amine N-H Str), 3050 cm-1 (Ar CH str), 1607 cm-1
(Ar C=C), 1512 cm-1 (N-H Bend), 1229 cm-1 (C-N str), 1164 cm-1 (C-O str). 1H NMR
(500 MHz, DMSO-d6):  11.76 (br. s, 3 H, 2×NH, OH), 8.35 (s, 1H, ArCH=N), 7.68
(d, 1H, J = 7.5 Hz, H-4), 7.60 (d, 2H, J = 8.0 Hz, H-6′, H-2′), 7.48 ( d, 1H, J = 8.0 Hz,
H-7), 7.28 (s, 1H, H-3), 7.23 (t, 1H, J = 7.5 Hz, H-5), 7.08 (t, 1H, J = 8.0 Hz, H-6),
6.87 (d, 2H, J = 7.5 Hz, H-5′, H-3′); 13C NMR (125 MHz, DMSO-d6): 160.70,
157.50, 146.70, 139.70, 138.40, 131.20, 130.40, 130.40, 126.20, 121.60, 120.60,
119.70, 116.10, 116.10, 114.80, 111.10; Anal. Calcd for C16H13N3O2, C = 68.81, H =
13

4.69, N = 15.05, Found C = 68.82, H = 4.68, N = 15.06; EI MS m/z (% rel. abund.):
279 (M+ ,38), 261 (10), 144 (100), 116 (12).
4.3.10. (E)-N'-(2-Hydroxybenzylidene)-1H-indole-2-carbohydrazide (10)
Yield: 88%. m.p. 270-272 °C; White milky powder; UV (MeOH) λmax(nm) 334; IR
(KBr): 3324 cm-1 (OH-str), 3213 cm-1 (2° amine N-H Str), 3050 cm-1 (ArCH str), 1650
cm-1 (C=O), 1613 cm1 (Ar C=C), 1537 cm-1 (N-H Bend), 1203 cm-1 (C-N), 1147 cm-1
(C-O str), 753 cm-1 (ortho-subst.opp). 1H NMR (500 MHz, DMSO-d6):  12.18 (s,
1H, NH), 11.83 (s, 1H, NH), 11.27 (s, 1H, broad OH), 8.65 (s, 1H, ArCH=N), 7.70 (d,
1H, J = 8.0 Hz, H-4), 7.60 (d, 1H, J = 7.0 Hz, H-6′), 7.49 ( d, 1H, J = 8.5 Hz, H-7),
7.31-7.30 (m, 2H, H-3, H-3′), 7.26 (t, 1H, J = 7.0 Hz, H-5), 7.10 (t, 1H, J = 7.5 Hz, H-
6), 6.93 (s, 2H, H-4′,H-5′); 13C NMR (125 MHz, DMSO-d6): 157.20, 157.10,
146.10, 139.60, 138.80, 132.40, 131.10, 127.40, 121.60, 121.20, 120.60, 119.60,
118.40, 117.60, 114.80, 111.00; Anal. Calcd for C16H13N3O2, C = 68.81, H = 4.69, N
= 15.05, Found C = 68.81, H = 4.67, N = 15.05; EI MS m/z (% rel. abund.): 279 (M+
,58), 261 (20), 144 (100), 116 (18), 75 (19).
4.3.11. (E)-N'-(3-Hydroxy-4-methoxybenzylidene)-1H-indole-2-carbohydrazide
(11)
Yield: 90%. m.p 150-152 °C; Orange needles; UV (MeOH) λmax(nm) 333; IR (KBr):
3335 cm-1 (OH-str), 3260 cm-1 (2° amine N-H Str), 3043 cm-1 (Ar C-H str), 1617 cm-1
(Ar C=C), 1560 cm-1(N-H Bend), 1275 cm-1 (C-N str), 1125 cm-1 (C-O str). 1H NMR
(500 MHz, DMSO-d6):  11.77 (s, 1H,NH), 11.76 (s, 1H, NH), 9.38 (s, 1H, OH),
8.30 (s, 1H, ArCH=N), 7.67 (d, 1H, J = 7.5 Hz, H-4), 7.48 (d, 1H, J = 8.0 Hz, H-7),
7.30-7.29 ( m, 2H, H-3, H-2′), 7.24 (t, 1H, J = 7.5 Hz, H-5), 7.10-7.06 (m, 2H, H-6,
13
H-5′), 7.00 (d, 1H, J = 8.5 Hz, H-6′), 3.82 (s, 3H, OCH3); C NMR (125 MHz,
DMSO-d6): 157.50, 152.30, 147.20, 146.90, 139.70, 138.40, 131.20, 131.10,
122.70, 121.60, 120.60, 119.70, 115.70, 114.60, 112.10, 111.00, 56.30; Anal. Calcd
for C17H15N3O3, C = 66.01, H = 4.89, N = 13.58, Found C = 66.00, H = 4.90, N =
13.56; EI MS m/z (% rel. abund.): 309 (M+ , 64), 291(18), 276 (11), 144 (100), 116
(20).
4.3.12. (E)-N'-(3-Bromo-4-hydroxybenzylidene)-1H-indole-2-carbohydrazide (12)
14

Yield: 87%. m.p. 274-276 °C; Light yellow powder; UV (MeOH) λmax(nm) 317; IR
(KBr): 3440 cm-1 (OH-str), 3260 cm-1 (2° amine N-H Str), 1656 cm-1 (C=N str), 1617
cm-1(Ar C=C), 1545 cm-1 (N-H Bend), 1270 cm-1 (C-N str), 1143 cm-1 (C-O str), 1038
1
cm-1 (C-Br str). H NMR (500 MHz, DMSO-d6):  12.12 (s, 1H, NH), 11.81 (s, 1H,
NH), 10.61 (s, 1H, OH), 8.64 (s, 1H, ArCH=N), 7.70 (d, 1H, J = 8.0 Hz, H-4), 7.49 (
d, 1H, J = 8.0 Hz, H-7), 7.33 (s, 1H, H-3), 7.25 (t, 1H, J = 8.0 Hz, H-5), 7.18 (d, 1H, J
= 2.0 Hz, H-5′), 7.10 (t, 1H, J = 7.5 Hz, H-6), 6.94 (dd, 1H, J = 9.0 Hz, H-2′), 6.89 (d,
13
1H, J = 9.0 Hz, H-6′); C NMR (125 MHz, DMSO-d6): 158.80, 157.50, 146.70,
139.60, 138.40, 131.20, 130.20, 128.40, 129.40, 121.60, 120.50, 119.60, 118.10,
114.80, 113.60, 111.10; Anal. Calcd for C C16H12BrN3O2, C = 53.65, H = 3.38, N =
11.73, Found C = 53.64, H = 3.38, N = 11.75; EI MS m/z (% rel. abund.): 359 (M+,
41), 357 (M+ -2, 40), 279 (14), 144 (100), 116 (15).
4.3.13. (E)-N'-(2-Hydroxy-5-methoxybenzylidene)-1H-indole-2-carbohydrazide
(13)
Yield: 90%. m.p. 256-257 °C. Gray crystals; UV (MeOH) λmax(nm) 333; IR (KBr):
3543 cm-1 (OH-str), 3420 cm-1 (2° amine N-H Str), 1627 cm-1 (C=O str), 1596 cm-1
(Ar C=C), 1561 cm-1 (N-H Bend), 1248 cm-1 (C-N str), 1129 cm-1 (C-O str). 1H NMR
(500 MHz, DMSO-d6):  11.84 (s, 1H, NH), 11.79 (s, 1H, NH), 10.81 (s, 1H, OH),
8.32 (s, 1H, ArCH=N), 7.89 (s, 1H, H-6′), 7.68 (d, 1H, J = 7.5 Hz, H-4), 7.60 (d, 1H,
J = 8.5 Hz, H-7), 7.48 (d, 1H, J = 8.5 Hz, H-3′), 7.30 (s, 1H, H-3), 7.24 (t, 1H, J = 7.5
Hz, H-5), 7.09 (t, 1H, J = 8.0 Hz, H-6), 6.97 (d,1H, J = 8.5 Hz,H-5′), 3.82 (s, 3H,
OCH3); 13C NMR (125 MHz, DMSO-d6): 157.50, 153.20, 153.10, 146.00, 139.70,
138.40, 131.20, 121.60, 120.60, 119.70, 119.40, 118.20, 117.10, 114.60, 113.20,
111.00, 55.60; Anal. Calcd for C17H15N3O3, C = 66.01, H = 4.89, N = 13.58, Found C
= 66.01, H = 4.89, N = 13.59; EI MS m/z (% rel. abund.): 309 (M+ ,44), 291(16), 276
(15) 144 (100), 116 (14).
4.3.14.
(E)-N'-(3-Hydroxy-2-iodo-4-methoxybenzylidene)-1H-indole-2-
carbohydrazide (14)
Yield: 87%. m.p. 256-258 °C; Cream crystals; UV (MeOH) λmax(nm) 340; IR (KBr):
3405 cm-1 (OH-str), 3292 cm-1 (2° amine N-H Str), 3057 cm-1 (Ar CH str), 1660 cm-1
(C=N str), 1620 cm-1 (C=O str), 1589 cm-1 (N-H Bend), 1274 cm-1 (C-N str), 1136
15

1
cm-1 (C-O str), 645 cm-1 (C-I str); H NMR (500 MHz, DMSO-d6):  12.04 (s, 1H,
NH), 11.79 (s, 1H, NH), 8.70 (s, 1H, ArCH=N), 7.69 (d, 1H, J = 8.0 Hz, H-4), 7.50 (
d, 1H, J = 8.5 Hz, H-7), 7.48 (d, 1H, J = 8.5 Hz, H-5′), 7.34 (s, 1H, H-3) ,7.25 (t, 1H,
13
J = 7.5 Hz, H-5), 7.11-7.06 (m, 2H, J = 7.5 Hz, H-5, H-6′), 3.84 (s, 3H, OCH3); C
NMR (125 MHz, DMSO-d6): 157.40, 155.10, 151.80, 143.20, 139.60, 138.40,
133.60, 131.20, 124.30, 121.60, 120.60, 119.60, 114.80, 111.10, 111.00, 84.20, 56.20;
Anal. Calcd for C17H14IN3O3, C = 46.92, H = 3.25, N = 9.66, Found C = 46.93, H =
3.24, N = 9.67, EI MS m/z (% rel. abund.): 435 (M+ ,24), 307(26), 144 (100), 116
(14).
4.3.15. (E)-N'-(3,5-Dimethoxybenzylidene)-1H-indole-2-carbohydrazide (15)
Yield: 82%. m.p. 204-207 °C; White powder; UV (MeOH) λmax(nm) 327; IR ʋ cm-1
(KBr disk): 3299 cm-1 (NH stretch), 3072 cm-1 (Ar.C-H stretch), 1636 cm-1 (C=O),
1591 cm-1 (C=N), 1555 cm-1 (C-N), 1452 cm-1 (C=C), 677 (1,3,5-Ar); 1H NMR (500
MHz, DMSO-d6):  11.94 (s, 1H, NH), 11.79 (s, 1H, NH), 8.37 (s, 1H, ArCH=N),
7.69 (d, 1H, J = 8.0 Hz, H-7), 7.49 (d, 1H, J = 8.5 Hz, H-4), 7.32 (s, 1H, H-3), 7.25
(t, 1H, J = 6.0 Hz, H-5), 7.09 (t, 1H, J = 7.0 Hz, H-6), 6.92 (d, 2H, J = 2.0 Hz, H-2
13
′/H-6′), 6.58 (d, 1H, J = 2.0 Hz, H-4′), 3.81 (s, 6H,2×OCH3); C NMR (125 MHz,
DMSO-d6): 161.60, 161.60, 157.50, 146.70, 139.60, 138.40, 135.60, 131.20,
121.50, 120.60, 119.70, 114.80, 111.00, 103.40, 103.40, 102.60, 55.60, 55.60; Anal.
Calcd for C18H17N3O3, C = 66.86, H = 5.30, N = 13.00, Found C = 66.87, H = 5.31, N
= 13.01; EI MS m/z (% rel. abund.): 323 (M+ ,65), 294 (18), 144 (100), 116 (19).
4.3.16. (E)-N'-(3,4-Dimethoxybenzylidene)-1H-indole-2-carbohydrazide (16)
Yield: 84%. m.p. 249-251 °C; White powder; UV (MeOH) λmax(nm) 336; IR ʋ cm-1
(KBr disk): 3325 cm-1 (NH stretch), 3043 cm-1 (Ar.C-H stretch), 1631 cm-1 (C=O),
1568 cm-1 (C=N), 1510 cm-1 (C-N), 1421 cm-1 (C=C), 828 (1,3,4-Ar); 1H NMR (500
MHz, DMSO-d6):  11.81 (s, 1H, NH), 11.77 (s, 1H, NH), 8.37 (s, 1H, ArCH=N),
7.68 (d, 1H, J = 7.5 Hz, H-7), 7.48 (d, 1H, J = 8.5 Hz, H-4), 7.39 ( s, 1H, H-2 ′), 7.30
(s, 1H, H-3) 7.24 (m, 2H, H-5'/6'), 7.09 (t, 2H, J = 7.5 Hz, H-5/H-6) 3.84 (s, 3H,
OCH3), 3.82 (s, 3H, OCH3); 13C NMR (125 MHz, DMSO-d6): 157.50, 152.00,
149.60, 146.70, 139.60, 138.40, 131.20, 130.40, 122.30, 120.60, 121.60, 119.70,
16

114.80, 111.60, 111.00, 109.10, 56.10, 56.10; Anal. Calcd for C18H17N3O3, C = 66.86,
H = 5.30, N = 13.00, Found C = 66.88, H = 5.29, N = 13.02; EI MS m/z (% rel.
abund.): 323 (M+ ,74), 294 (24), 144 (100), 116 (24).
17

4.3.17. (E)-N'-(3-Methoxybenzylidene)-1H-indole-2-carbohydrazide (17)
Yield: 83%. m.p. 130-132 °C; Milky white powder; UV (MeOH) λmax(nm) 328; IR ʋ
cm-1 (KBr disk): 3234 cm-1 (NH stretch), 3058 cm-1 (Ar.C-H stretch), 1657 cm-1
1
(C=O), 1598.09 cm-1 (C=N), 1575 cm-1 (C-N), 1273 cm-1 (C-O), 740 (3- Ar); H
NMR (500 MHz, DMSO-d6):  11.94 (s, 1H, NH), 11.80 (s, 1H, NH), 8.42 (s, 1H,
ArCH=N), 7.69 (d, 1H, J = 8.0 Hz, H-7), 7.49 (d, 1H, J = 8.5 Hz, H-4), 7.41 (t, 1H, J
= 7.5 Hz, H-5), 7.33-31 ( m, 3H, H-3/ H-2′/H-5′), 7.25, (t, 1H, J = 7.5 Hz, H-6), 7.10,
(t, 1H, J = 7.5 Hz, H-6′), 7.04 (dd, 1H, J = 2.0, 7.0 Hz, H-4′), 3.84 (s, 3H, OCH3);
13C NMR (125 MHz, DMSO-d6):  160.50, 157.40, 146.70, 139.60, 138.40, 138.20,
131.20, 129.70, 121.60, 121.40, 120.50, 119.60, 116.40, 114.80, 111.10,
111.00, 55.70; Anal. Calcd for C17H15N3O2, C = 69.61, H = 5.15, N = 14.33, Found
C = 69.62, H = 5.16, N = 14.32; EI MS m/z (% rel. abund.): 293. (M+ ,80), 264 (13),
144 (100), 116 (12).
4.3.18. (Z)-N'-((Furan-2-yl)methylene)-1H-indole-2-carbohydrazide (18)
Yield: 85%. m.p. 241-242 °C; Yellowish powder; UV (MeOH) λmax(nm) 333; IR ʋ
cm-1 (KBr disk): 3368 cm-1 (NH stretch), 3056 cm-1 (Ar.C-H stretch), 1646 cm-1
1
(C=O), 1550 cm-1 (C=N), 1579 cm-1 (C-N), 1480 cm-1 (C=C), 1066 (C-O-C); H
NMR (500 MHz, DMSO-d6):  11.88 (s, 2H, 2×NH), 8.33 (s, 1H, ArCH=N), 7.86 (s,
1H, H-4′), 7.68 (d, 1H, J = 8.0 Hz, H-7), 7.47 (d, 1H, J = 8.0 Hz, H-4), 7.27 (s, 1H, H-
3), 7.25 (t, 1H, J = 7.0 Hz, H-5), 7.09 (t, 1H, J = 7.5 Hz, H-6), 6.96 ( d, 1H, J = 3.5
Hz, H-2′), 6.66 (dd, 1H, J = 1.5 Hz, J = 3.0 Hz, 3′); 13C NMR (125 MHz, DMSO-d6):
 157.30, 149.00, 144.20, 139.70, 138.20, 134.40, 131.20, 122.40, 121.50, 120.40,
119.70, 118.60, 114.80, 111.20; Anal. Calcd for C14H11N3O2, C = 66.40, H = 4.38, N
= 16.59, Found C = 66.42, H = 4.39, N = 16.60; EI MS m/z (% rel. abund.): 253 (M+
,85), 185 (12), 144 (100), 116 (14).
4.3.19. (E)-N'-(3-Bromo-4-fluorobenzylidene)-1H-indole-2-carbohydrazide (19)
Yield: 87%. m.p. 223-225 °C; Milky white powder; UV (MeOH) λmax(nm) 326; IR ʋ
cm-1 (KBr disk): 3297 cm-1 (NH stretch), 3043 cm-1 (Ar.C-H stretch), 1639 cm-1
(C=O), 1566 cm-1 (C=N), 1538 cm-1 (C-N), 1496 cm-1 (C=C), 1255 cm-1 (C-F), 578
1
cm-1 (C-Br); H NMR (500 MHz, DMSO-d6):  12.07 (s, 1H, NH), 11.82 (s, 1H,
NH), 8.41 (s, 1H, ArCH=N), 8.10 (d, 1H, J = 6.5 Hz, H-7), 7.83 (s, 1H, H-1′), 7.69 (d,
1H, J = 8.0 Hz, H-4), 7.51-7.470 ( m, 2H, H-5′/H-6′), 7.33 (s, 1H, H-3), 7.25 (t, 1H, J
18

= 8.0 Hz, H-5), 7.10 (t, 1H, J = 7.0 Hz, H-6); 13C NMR (125 MHz, DMSO-d6):
167.50, 157.60, 146.70, 139.60, 138.40, 134.20, 131.40, 131.20, 129.70, 121.40,
120.60, 119.60, 117.60, 114.80, 111.30, 110.10; Anal. Calcd for C16H11BrFN3O, C =
53.35, H = 3.08, N = 11.67, Found C = 53.36, H = 3.07, N = 11.67; EI MS m/z (% rel.
abund.): 361 (M+, 41), 359 (M+−2, 40), 341 (18), 339 (16), 279 (25), 144 (100), 116
(17).
4.3.20. (E)-N'-(4-Methoxybenzylidene)-1H-indole-2-carbohydrazide (20)
Yield: 88%. m.p. 122-125 °C; White powder; UV (MeOH) λmax(nm) 331; IR ʋ cm-1
(KBr disk): 3287 cm-1 (NH stretch), 3053 cm-1 (Ar.C-H stretch), 1634 cm-1 (C=O),
1
1604 cm-1 (C=N), 1511 cm-1 (C-N), 1422 cm-1 (C=C), 829 (4-Ar); H NMR (500
MHz, DMSO-d6):  11.80 (s, 2H, 2×NH), 8.39 (s, 1H, ArCH=N), 7.72 (d, 2H, J = 8.0
Hz, H-3′/H-5′), 7.68 (d, 1H, J = 8.0 Hz, H-7), 7.48 (d, 1H, J = 8.5 Hz, H-4), 7.29 (s,
1H, H-3), 7.24 (t, 1H, J = 7.0 Hz, H-5), 7.09 (d, 1H, J = 7.0 Hz, H-6), 7.05 ( d, 2H, J
= 8.0 Hz, H-2′/H-6′), 3.82 (s, 3H,OCH3); 13C NMR (125 MHz, DMSO-d6): 162.80,
157.50, 146.60, 139.70, 138.40, 131.20, 130.10, 130.10, 126.20, 121.40, 120.60,
119.70, 114.80, 114.20, 114.20, 111.10, 55.70; Anal. Calcd for C17H15N3O2, C =
69.61, H = 5.15, N = 14.33, Found C = 69.62, H = 5.16, N = 14.32; EI MS m/z (% rel.
abund.): 293. (M+ ,70), 264 (18), 144 (100), 116 (16).
4.3.21. (E)-N'-Benzylidene-1H-indole-2-carbohydrazide (21)
Yield: 90%. m.p. 197-199 °C; White powder; UV (MeOH) λmax(nm) 325; IR ʋ cm-1
(KBr disk): 3258 cm-1 (NH stretch), 3055 cm-1 (Ar.C-H stretch), 1656 cm-1 (C=O),
1
1528.18 cm-1 (C=N), 1374 cm-1 (C-N); H NMR (500 MHz, DMSO-d6):  11.92 (s,
1H, NH), 11.82 (s, 1H, NH), 8.46 (s, 1H, ArCH=N), 7.77 (d, 2H, J = 8.0 Hz, H-2′/H-
6′), 7.69 (d, 1H, J = 7.5 Hz, H-4), 7.49-7.46 (m, 4H, H-7, H-3′/H-4′/H-5′), 7.33 (s, 1H,
H-3), 7.25 (t, 1H, J = 7.0 Hz, H-6), 7.09 (d, 1H, J = 8.0 Hz, H-5); 13C NMR (125
MHz, DMSO-d6): 157.50, 146.60, 139.60, 138.30, 133.50, 131.20, 131.20, 129.10,
129.10, 128.50, 128.50, 121.40, 120.50, 119.60, 114.80, 111.20; Anal. Calcd for
C16H13N3O, C = 72.99, H = 4.98, N = 15.96, Found C = 72.98, H = 5.00, N = 15.95;
EI MS m/z (% rel. abund.): 263.(M+ ,82), 186 (13), 144 (100), 116 (12), 25 (77).
19

4.3.22. (E)-N'-((Pyridin-3-yl)methylene)-1H-indole-2-carbohydrazide (22)
Yield: 92%. m.p. 250-252 °C; Milky white powder; UV (MeOH) λmax(nm) 328; IR ʋ
cm-1 (KBr disk): 3489 cm-1 (C-N-C), 3281 cm-1 (NH stretch), 3050 cm-1 (Ar.C-H
1
stretch), 1635 cm-1 (C=O), 1550 cm-1 (C=N), 1473 cm-1 (C-N); H NMR (500 MHz,
DMSO-d6):  12.08 (s, 1H, NH), 11.84 (s, 1H, NH), 8.90 (s, 1H, ArCH=N), 8.63 (d,
1H, J = 4.5 Hz, H-6′), 8.51 (s, 1H, H-2′), 8.19 (d, 1H, J = 7.5 Hz, H-4'), 7.70 (d, 1H, J
= 7.5 Hz, H-7), 7.53-7.49 ( m, 2H, H-4/H-5′), 7.35 (s, 1H, H-3), 7.25 (t, 1H, J = 7.0
13
Hz, H-5), 7.10 (t, 1H, J = 7.5 Hz, H-6); C NMR (125 MHz, DMSO-d6):  157.40,
151.80, 149.10, 143.20, 139.40, 138.20, 133.60, 131.20, 130.30, 123.80, 121.50,
120.60, 119.60, 114.80, 111.30; Anal. Calcd for C15H12N4O, C = 68.17, H = 4.58, N =
21.20; Found C = 68.19, H = 4.59, N = 21.21; EI MS m/z (% rel. abund.): 264. (M+
,74), 185 (16), 144 (100), 116 (11), 78 (18).
4.3.23. (E)-N'-((Pyridin-4-yl)methylene)-1H-indole-2-carbohydrazide (23)
Yield: 90%. m.p. 273-275 °C; Milky white powder; UV (MeOH) λmax(nm) 329; IR ʋ
cm-1 (KBr disk): 3437 cm-1 (C-N-C), 3173 cm-1 (NH stretch), 3068 cm-1 (Ar.C-H
1
stretch), 1643.87 cm-1 (C=O), 1594.96 cm-1 (C=N), 1519.70 cm-1 (C-N); H NMR
(500 MHz, DMSO-d6):  12.18 (s, 1H, NH), 11.87 (s, 1H, NH), 8.68 (d, 2H, J = 5.5
Hz, H-3′/H-5′), 8.45 (s, 1H, ArCH=N), 7.71 (d, 3H, J = 5.5 Hz, H-2′/H-6′/H-4), 7.50
(d, 1H, J = 8.5 Hz, H-7), 7.37 (s, 1H, H-3), 7.26 (t, 1H, J = 7.5 Hz, H-5), 7.10 (t, 1H,
J = 7.5 Hz, H-6); 13C NMR (125 MHz, DMSO-d6):  157.50, 149.10, 149.10, 146.50,
144.20, 139.70, 138.40, 131.10, 121.40, 120.60, 120.30, 120.30, 119.70, 114.80,
111.20; Anal. Calcd for C15H12N4O, C = 68.17, H = 4.58, N = 21.21, Found C =
68.19, H = 4.57, N = 21.23; EI MS m/z (% rel. abund.): 264. (M+ ,70), 185 (12), 144
(100), 116 (16), 78 (25).
4.3.24. (E)-N'-(Pyridin-2-ylmethylene)-1H-indole-2-carbohydrazide (24)
Yield: 82%. m.p. 253-254 °C; Yellowish green powder; UV (MeOH) λmax(nm) 328;
IR ʋ cm-1 (KBr disk): 3274 cm-1 (NH stretch), 3058 cm-1 (Ar.C-H stretch), 1646 cm-1
(C=O), 1587 cm-1 (C=N), 1530 cm-1 (C-N); 1H NMR (500 MHz, DMSO-d6):  12.12
(s, 1H, NH), 11.88 (s, 1H, NH), 8.64 (d, 1H, J = 4.5 Hz, H-3′), 8.50 (s, 1H, ArCH=N),
8.03 (d, 1H, J = 7.5 Hz, H-7), 7.92 (t, 1H, J = 7.5 Hz, H-5′), 7.71 (d, 1H, J = 7.5 Hz,
20

H-4) , 7.50 (d, 1H, J = 8.5 Hz, H-6′), 7.44 (t, 1H, J = 6.5 Hz, H-4′), 7.37 (s, 1H, H-3),
13
7.26 (t, 1H, J = 7.5 Hz, H-5), 7.10 (t, 1H, J = 7.5 Hz, H-6); C NMR (125 MHz,
DMSO-d6):  157.40, 153.40, 149.30, 144.80, 139.70, 138.40, 136.20, 131.20,
126.10, 121.60, 120.10, 120.40, 119.60, 114.80, 111.20; Anal. Calcd for C15H12N4O,
C = 68.17, H = 4.58, N = 21.20, Found C = 68.16, H = 4.59, N = 21.19, EI MS m/z (%
rel. abund.): 264. (M+ ,68), 185 (18), 144 (100), 116 (9), 78 (12).
4.3.25. (E)-N'-(Thiophen-2-ylmethylene)-1H-indole-2-carbohydrazide (25)
Yield: 88%. m.p. 250-251 °C; Yellowish powder; UV (MeOH) λmax(nm) 337; IR ʋ
cm-1 (KBr disk): 3394 cm-1 (NH stretch), 3283 cm-1 (Ar.C-H stretch), 1643 cm-1
1
(C=O), 1588 cm-1 (C=N), 1555 cm-1 (C-N), 1229 (C-S-C); H NMR (500 MHz,
DMSO-d6):  11.87 (s, 1H, NH), 11.79 (s, 1H, NH), 8.67 (s, 1H, ArCH=N), 7.70 (d,
1H, J = 5.0 Hz, H-7), 7.67 (s, 1H, H-5′), 7.50 (d, 1H, J = 3.5 Hz, H-3′), 7.48 (d, 1H, J
= 8.5 Hz, H-4) , 7.29 (s, 1H, H-3), 7.24 (t, 1H, J = 8.0 Hz, H-5), 7.17 (dd, 1H, J = 3.5
Hz, J = 5.0 Hz, H-4'), 7.09 (t, 1H, J = 7.0 Hz, H-6); 13C NMR (125 MHz, DMSO-d6):
 157.40, 144.6, 139.60, 138.40, 131.40, 130.10, 128.10, 127.10, 125.30, 121.60,
120.40, 119.70, 114.80, 111.20; Anal. Calcd for C14H11N3OS, C = 62.43, H = 4.12, N
= 15.60, Found C = 62.41, H = 4.13, N = 15.61; EI MS m/z (% rel. abund.): 269 (M+
,48), 185 (13), 144 (100), 116 (11), 83 (11).
4.3.26. (E)-Methyl 4-((2-(1H-indole-2-carbonyl)hydrazono)methyl)benzoate (26)
Yield: 90%. m.p. 249-251 °C; White powder; UV (MeOH) λmax(nm) 335; IR ʋ cm-1
(KBr disk): 3351 cm-1 (NH stretch), 3148 cm-1 (Ar.C-H stretch), 1698 cm-1 (O-C=O),
1
1633 cm-1 (C=O), 1547 cm-1 (C=N), 1436 cm-1 (C-N), 828 (4- Ar); H NMR (500
MHz, DMSO-d6):  12.09 (s, 1H, NH), 11.83 (s, 1H, NH), 8.51 (s, 1H, ArCH=N),
8.07 (d, 2H, J = 8.5 Hz, H-3′/ H-5′), 7.91 (d, 2H, J = 8.5 Hz, H-2′/ H-6′), 7.70 (d, 1H,
J = 7.5 Hz, H-7), 7.48 (d, 1H, J = 8.0 Hz, H-4) , 7.35 (s, 1H, H-3), 7.26 (t, 1H, J = 7.0
13
Hz, H-5), 7.10 (t, 1H, J = 7.0 Hz, H-6), 3.89 (s, 3H, OCH3); C NMR (125 MHz,
DMSO-d6):  165.50, 157.40, 146.50, 139.40, 138.40, 138.20, 132.20, 131.20,
130.20, 130.20, 129.30, 129.30, 129.00, 121.50, 120.40, 119.70, 114.60, 51.10, Anal.
Calcd for C18H15N3O3, C = 67.28, H = 4.71, N = 13.08, Found C = 67.27, H = 4.70, N
= 13.06; EI MS m/z (% rel. abund.): 321 (M+, 54), 289 (19), 261 (10), 144 (100), 135
(18), 116 (11),
21

22

4.3.27. (E)-N'-(4-Chlorobenzylidene)-1H-indole-2-carbohydrazide (27)
Yield: 92%. m.p. 247-249 °C; Milky white powder; UV (MeOH) λmax(nm) 329; IR ʋ
cm-1 (KBr disk): 3304 cm-1 (NH stretch), 3080 cm-1 (Ar.C-H stretch), 1637 cm-1
1
(C=O), 1551 cm-1 (C=N), 1492 cm-1 (C-N), 1315 cm-1 (C=C), 748 cm-1 (C-Cl); H
NMR (500 MHz, DMSO-d6):  11.98 (s, 2H, 2xNH), 8.45 (s, 1H, ArCH=N), 7.8 (d,
2H, J = 8.5 Hz, H-3′/H-5′), 7.70 (d, 1H, J = 8.0 Hz, H-7), 7.56 (d, 2H, J = 8.0 Hz, H-2
′/H-6′), 7.48(d, 1H, J = 8.5 Hz, H-4), 7.33 (s, 1H, H-3), 7.25 (t, 1H, J = 6.0 Hz, H-5),
13
7.09 (t, 1H, J = 7.0 Hz, H-6); C NMR (125 MHz, DMSO-d6):  157.30, 146.40,
139.60, 138.30, 138.20, 132.00, 131.10, 130.40, 130.40, 128.70, 128.70, 121.40,
120.60, 119.50, 114.30, 111.4; Anal. Calcd for C16H12ClN3O, C = 64.54, H = 4.06, N
= 14.11, Found C = 64.56, H = 4.05, N = 14.13; EI MS m/z (% rel. abund.): 299 (M+,
30), 297 (M+ -2, 60), 341 (18), 261 (12), 144 (100), 116 (17).
4.3.28. (E)-Methyl2-((2-(1H-indole-2-carbonyl)hydrazono)methyl)-3,5-dimethoxy
-benzoate (28)
Yield: 91%. m.p. 202-203 °C; Milky white powder; UV (MeOH) λmax(nm) 335; IR ʋ
cm-1 (KBr disk): 3313cm-1 (NH stretch), 3062 cm-1 (Ar.C-H stretch), 1740 cm-1
1
(CO2), 1645 cm-1 (C=O), 1602 cm-1 (C=N), 1568 cm-1 (C-N); H NMR (500 MHz,
DMSO-d6):  11.83 (s, 1H, NH), 11.7 (s, 1H, NH), 8.64 (s, 1H, ArCH=N), 7.67 (d,
1H, J = 8.0 Hz, H-7), 7.46 (t, 1H, J = 8.5 Hz, H-4), 7.30 (s, 1H, H-3), 7.23 (t, 1H, J =
7.0 Hz, H-5), 7.08 (t, 1H, J = 7.5 Hz, H-6), 6.78 (s, 1H, H-5′), 6.63 (s, 1H, H-3′), 3.91
(s, 3H,OCH3), 3.87 (s, 3H,OCH3), 3.85 (s, 3H,OCH3); 13C NMR (125 MHz, DMSO-
d6):  168.20, 163.20, 161.10, 157.40, 143.40, 139.70, 138.60, 133.50, 131.20,
121.50, 120.4, 119.6, 114.7, 111.10, 110.10, 108.6, 105.7, 55.4, 55.4, 51.6; Anal.
Calcd for C20H19N3O5, C = 62.99, H = 5.02, N = 11.02, Found C = 62.98, H = 5.00, N
= 11.01; EI MS m/z (% rel. abund.): 381 (M+,34), 321 (19), 306 (10), 144 (100), 116
(11).
4.4 Molecular Docking Calculations
The study was designed to dock 2-indolcarbohydrazones derivatives against α-
glucosidase enzyme with the following communications; Intel(R) xenon(R) CPU
E5620@2.40GHz system having 3.8GB RAM with the open 11.4 (X 86_64)
operating platform. Protein-Ligand docking was carried out using the Molecular
23

Operating Environment (MOE 2010.11) software package. The three dimensional
structure for α-glucosidase of Saccharomyces cerevisiae has not been solved up-to
yet. Only few homology models have been reported [48-50]. In the current study we
predict 3D structure for α-glucosidase of Saccharomyces cerevisiae by using same
protocol as described by (Burke et al) of homology modeling [51]. The primary
sequence of α-glucosidase for Saccharomyces cerevisiae was retrieved from UniProt
(Access code P53341). Template search was performed using MOE-Search tools
against the PDB implemented in MOE v2010.11. The crystallographic structure of
Saccharomyces cerevisiae isomaltase (PDB code 3AJ7; Resolution 1.30 Å) with
72.4% of sequence identity with the target was selected as a template. The 3D
structure of α-glucosidase for Saccharomyces cerevisiae was predicted using MOE
homology modeling tools. The developed model was then subjected to energy
minimization up to 0.05 gradients.
The quality of the modeled structure was assessed by Ramachandran and
ProSA plot. The evaluation of backbone Psi and Phi dihedral angles for α-glucosidase
model revealed that 94.8% residues lie in favored region, 4.8% residues lie in allowed
region and only 0.3% residues lies in outlier region. Analysis of ProSA shows the Z-
value of -10.76 indicating no significant deviation from the score determined for the
protein of similar size. The results of both Ramachandran and ProSA plots reflect the
accuracy of our modeled structure to be used in docking protocol.
Before docking, ligands and protein were prepared using MOE v2010.11. 3D
structure of compound 3 was built by using Molecular Builder Module program
implemented in MOE and save as a (.mdb) file for molecular docking. Subsequently,
the energy of compound 3 was minimized up to 0.05 Gradient using MMFF 94x force
field. Energy minimization of the compound 3 was followed by the preparation of
protein for docking purposes. Most macromolecular crystal structures contain little or
no hydrogen coordinate data due to limited resolution and thus protonation was done
prior to docking using Protonate 3D tools. Protonation was followed by energy
minimization up to 0.05 Gradient using Amber 99 force field. The compound 3 was
docked into the active site of protein using the Triangular Matching docking method
and 30 conformations of compound 3 and protein complex were generated with
docking score (S). The complex was analyzed for interactions and their 3D images
were taken by using visualizing tool PyMol.
24

Acknowledgements: Authors would like to acknowledge The Ministry of Agriculture
(MOA) Malaysia and Universiti Teknologi MARA for the financial support under
MOA grant file No. 100-RMI/ MOA 16/6/2 (1/2013) and Atta-ur-Rahman Institute
for Natural product Discovery (RiND) to provide excellent designed lab and facility
for the research and all technical and non-technical staff for a lot of support for this
work.
References
1. M. Kashyap, D. Das, R. Preet, P. Mohapatra, S.R. Satapathy, S. Siddharth, C.N.
Kundu, S.K. Guchhait, Scaffold hybridization in generation of indenoindolones
as anticancer agents that induce apoptosis with cell cycle arrest at G2/M phase
Bioorg. Med. Chem. Lett. 22 (2012) 2474-2479.
2. O. Talaz, I. Gulcin, S. Goksu, N. Saracoglu, Antioxidant activity of 5,10-
dihydroindeno[1,2-b]indoles containing substituents on dihydroindeno part,
Bioorg. Med. Chem. 17 (2009) 6583-6589.
3. B. Jiang, C.G. Yang, J.J. Wang, Enantioselective synthesis for the (-)-antipode of
the pyrazinone marine alkaloid, hamacanthin A. J. Org. Chem. 66 (2001) 4865-
4869.
4. J. Maj, K. Kotodziejczyk, Z. Rogóż, G. Skuza. Roxindole, a potential
antidepressant. I. Effect on the dopamine system. J. neural transm. 103 (1996)
627-641.
5. A. Klimke, E. Klieser. Antipsychotic efficacy of the dopaminergic autoreceptor
agonist EMD 49980 (Roxindol). Pharmacopsychiatry. 24 (1991) 107-112.
6. G.D. Morse, R.C. Reichman, M.A. Fischl, M. Para, J. Leedom, W. Powderly,
L.M. Demeter, L. Resnick, Y. Bassiakos, J. Timpone, S. Cox, D. Batts,
Concentration-targeted phase I trials of atevirdine mesylate in patients with HIV
infection: dosage requirements and pharmacokinetic studies. The ACTG 187 and
199 study teams. Antiviral Res. 45 (2010) 47-58.
25

7. L.J. Scott, C.M. Perry, Delavirdine: a review of its use in HIV infection. Drugs
60 (2000) 1411-1444.
8. K.E. Andersson, Pharmacology of penile erection. Pharmacol. Rev. 53 (2001)
417-450.
9. Hall, Chapman, P.H. Rhodes, Dictionary of Organic Compounds; Chapman &
Hall: London, UK, (1996).
10. I.A. Leneva, R.J. Russell, Y.S. Boriskin, A.J. Hay, Characteristics of arbidol-
resistant mutants of influenza virus: implications for the mechanism of anti-
influenza action of arbidol. Antiviral Res. 81 (2009) 132-140.
11. E. Freidonk-Mueschenborn, A. Fox, Resolution of concentration-response
differences in onset of effect between subcutaneous and oral sumatriptan.
Headache. 45 (2005) 632-637.
12. J.A. Generali, D.J. Cada, Off-label drug uses—Ondansetron: Postanesthetic
shivering. Hosp. Pharma. 44 (2009) 670-671.
13. R. Horton, Lotronex and the FDA: a fatal erosion of integrity Lancet. 375 (2001)
1544-1545.
14. D.A. Napalkov, Therapy with perindopril: organoprotection, not just the
antihypertensive effect. Kardiologiia 52 (2012) 80-83.
15. K.M. Khan, M. Taha, F. Rahim, M.I. Fakhri, W. Jamil, M. Khan, S. Rasheed, A.
Karim, S. Perveen, M.I. Choudhary, Acylhydrazide Schiff Bases: Synthesis and
Antiglycation Activity. J. Pak. Chem Soc. 35 (2013) 929-937.
16. K.M. Khan, F. Rahim, N. Ambreen, M. Taha, M. Khan, H. Jahan, Najeebullah,
A. Shaikh, S. Iqbal, S. Perveen, M.I. Choudhary, Synthesis of
benzophenonehydrazone Schiff bases and their in vitro antiglycating activities.
Med. Chem. 9 (2013) 588-595.
26

17. M. Taha N.H. Ismail, W. Jamil , H. Rashwan, S.M. Kashif, A.A. Sain, M.I.
Adenan, E.H. Anouar, M. Ali, F. Rahim, K.M. Khan. Synthesis of novel
derivatives of 4-methylbenzimidazole and evaluation of their biological activities.
Eur J Med Chem. 84 (2014) 731-738.
18. K.M. Khan, Z. Shah, V.U. Ahmad, M. Khan, M. Taha, F. Rahim, H. Jahun, S.
Perveen, M.I. Choudhary, Synthesis of 2,4,6-trichlorophenyl hydrazones and
their inhibitory potential against glycation of protein. Med. Chem. 7 (2011) 572-
580.
19. E. Anouar, S. Raweh, I. Bayach, M. Taha, M.S. Baharudin, F.D. Meo, M.H.
Hasan, A. Adam, N.H. Ismail, J.F. Weber, P. Trouillas, Antioxidant properties of
phenolic Schiff bases: structure-activity relationship and mechanism of action. J.
Comput. Aided Mol. Des. 27 (2013) 951-964.
20. M. Taha, N.H. Ismail, W. Jamil, S. Yousuf, F.M. Jaafar, M.I. Ali, S.M. Kashif, E.
Hussain, Synthesis, evaluation of antioxidant activity and crystal structure of 2,4-
dimethylbenzoylhydrazones. Molecules 18 (2013) 10912-10929.
21. A.N. Aziz, M. Taha, N.H. Ismail, E.H. Anouar, S. Yousuf, W. Jamil, K. Awang,
N. Ahmat, K.M. Khan, S.M. Kashif, Synthesis, Crystal Structure, DFT Studies
and Evaluation of the Antioxidant Activity of 3,4-Dimethoxybenzenamine Schiff
Bases. Molecules 19 (2014) 8414-8433.
22. a) M. Taha, M.S. Baharudin, N.H. Ismail, K.M. Khan, F.M. Jaafar, Samreen, S.
Siddiqui, M.I. Choudhary, Synthesis of 2-methoxybenzoylhydrazone and
evaluation of their antileishmanial activity. Bioorg. Med. Chem. Lett. 23 (2013)
3463-3466; b) M. Taha, N.H. Ismail, M. Ali, K.M. Khan, W. Jamil, S.M. Kashif,
M. Asraf, Synthesis of Indole-2-hydrazones in Search of Potential
Leishmanicidal Agents. Med. Chem. Res. 23 (2014) 5282–5293
27

23. A. Pandey, D. Dewangan, S. Verma, A. Mishra, R.D. Dubey, Synthesis of schiff
bases of 2-amino-5-aryl-1, 3, 4-thiadiazole and its analgesic, anti-inflammatory,
antibacterial and antitubercular activity. Int. J. Chem. Tech. Res. 3 (2011) 178-
184.
24. Y. Zhou, M. Zhao, Y. Wu, C. Li, J. Wu, M. Zheng, L. Peng, S. Peng, A class of
novel Schiff's bases: Synthesis, therapeutic action for chronic pain, anti-
inflammation and 3D QSAR analysis. Bioorg. Med. Chem. 18 (2010) 2165-2172.
25. S.M. Sondhi, N. Singh, A. Kumar, O. Lozach, L. Meijer, Synthesis, anti-
inflammatory, analgesic and kinase (CDK-1, CDK-5 and GSK-3) inhibition
activity evaluation of benzimidazole/benzoxazole derivatives and some Schiff's
bases. Bioorg. Med. Chem. 14 (2006) 3758-3765.
26. K. Rana, A. Pandurangan, N. Singh, A.K. Tiwari, A systemic review of Schiff
bases as an analgesic, anti-inflammatory. Int. J. Curr. Pharm. Res. 4 (2012) 5-11.
27. M.M. Aly, Y.A. Mohamed, K.A.M. El-Bayouki, W.M. Basyouni, S.Y. Abbas,
Synthesis
of
some
new
4(3H)-quinazolinone-2-carboxaldehyde
thiosemicarbazones and their metal complexes and a study on their
anticonvulsant, analgesic, cytotoxic and antimicrobial activities - part-1. Eur. J.
Med. Chem. 45 (2010) 3365-3373.
28. S. Kim, α-Glucosidase inhibitor from Buthus martensi Karsch. Food Chemistry,
136 (2013) 297-300.
29. E. Gallienne, T. Gefflaut, M. Lemaire, Synthesis of new nitrogen analogues of
salacinol and deoxynojirimycin and their evaluation as glycosidase inhibitors. J.
Org. Chem. 71 (2006) 894-902.
30. N. Zitzmann, A.S. Mehta, S. Carrouee, T.D. Butters, F.M. Platt, J. McCauley,
B.S. Blumberg, R.A. Dwek, T.M. Block. Imino sugars inhibit the formation and
28

secretion of bovine viral diarrhea virus, a pestivirus model of hepatitis C virus:
implications for the development of broad spectrum anti-hepatitis virus agents.
Natl. Acad. Sci. USA 96 (1999) 11878-11882.
31. J.E. Groopman, Current advances in the diagnosis and treatment of AIDS: an
introduction. Rev. Infect. Dis. 12 (1990) 908-911.
32. H. Bischoff, Pharmacology of alpha-glucosidase inhibition. Eur. J. Clin. Invest.
24 (1994) 3-10.
33. A. Trapero, A. Llebaria, A Prospect for Pyrrolidine Iminosugars as Antidiabetic
α-Glucosidase Inhibitors. J. Med. Chem. 55 (2012) 10345-10346.
34. a) A. L. Aguilar, J. Escribano, P. Wentworth, T. D. Butters, Synthetic
1‐Deoxynojirimycin N‐Substituted Peptides Offer Prolonged Disruption to
N‐Linked Glycan Processing. ChemMedChem, 9 (2014) 2809-2813; b) M. Taha,
N.H. Ismail, S. Imran, M.Q. B. Rokei, S.M. Saad, K.M. Khan. Synthesis of New
Oxadiazole Derivatives as α-Glucosidase Inhibitors. Bioorg Med chem 23 (2015)
4155-4162; c) G. Aydin, K Ally, F. Aktaş, E. Şahin, A. Baran, M. Balci,
Synthesis and α‐Glucosidase and α‐Amylase Inhibitory Activity Evaluation of
Azido‐and Aminocyclitols. Euro. J. Organ. Chem. 31 (2014) 6903-6917; d) M.
Taha, N.H. Ismail, M.S. Baharudin, S. Lalani, S. Mehboob, K.M. Khan, S.
yousuf, S. Siddiqui F. Rahim M.I. Choudhary. Synthesis crystal structure of 2-
methoxybenzoylhydrazones and evaluation of their a-glucosidase and urease
inhibition potential. Med. Chem. Res. 24 (2015) 1310-1324; e) F. Rahim, H.
Ullah, M.T. Javid, A. Wadood, M. Taha, M. Ashraf, A. Shaukat, M. Junaid, S.
Hussain, W. Rehman, R. Mehmood, M. Sajid, M. N. Khan, K. M. Khan.
Synthesis, in vitro evaluation and molecular docking studies of thiazole
derivatives as new inhibitors of α-glucosidase. Bioorg Chem 62 (2015) 62, 15-21;
29