Novel potentially antibacterial naphthalimide-derived metronidazoles: Design, synthesis, biological evaluation and supramolecular interactions with DNA, human serum albumin and topoisomerase II

Article abstract of DOI:10.1016/j.cclet.2017.04.002

A series of novel naphthalimide-derived metronidazoles as new type of antimicrobial agents were for the first time designed, synthesized and characterized by NMR, IR and HRMS spectra. Experimental results revealed that most of them displayed moderate to good antibacterial activity towards Gram-positive and negative bacteria. Especially, compound 7b was able to not only exhibit effective inhibition towards the growth of P. vulgaris (MIC?=?0.002?μmol/mL) and S. dysenteriae (MIC?=?0.01?μmol/mL), but also have rapidly killing effect and prevent the development of bacterial resistance. Further research revealed that the highly active molecule 7b could not only intercalate into calf thymus DNA to form a steady supramolecular complex and thus might block DNA replication to exert the powerful bioactivities, but also be effectively transported by human serum albumin (HSA) via the formation of the 1:1 supramolecular complex, in which hydrogen bonds and hydrophobic effect played important roles in the association of compound 7b with HSA. Molecular docking indicated that the supramolecular interactions between 7b and topoisomerase II were driven by hydrogen bonds.

Full text of DOI:10.1016/j.cclet.2017.04.002

Accepted Manuscript
Title: Novel potentially antibacterial naphthalimide-derived
metronidazoles: Design, synthesis, biological evaluation and
supramolecular interactions with DNA, human serum albumin
and topoisomerase II
Authors: Jie Kang, Vijai Kumar Reddy Tangadanchu, Lavanya
Gopala, Wei-Wei Gao, Yu Cheng, Han-Bo Liu, Rong-Xia
Geng, Shuo Li, Cheng-He Zhou
PII:
S1001-8417(17)30131-6
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.cclet.2017.04.002
CCLET 4038
To appear in:
Chinese Chemical Letters
Received date:
Revised date:
Accepted date:
20-1-2017
15-3-2017
4-4-2017
Please cite this article as: Jie Kang, Vijai Kumar Reddy Tangadanchu,
Lavanya Gopala, Wei-Wei Gao, Yu Cheng, Han-Bo Liu, Rong-Xia Geng,
Shuo Li, Cheng-He Zhou, Novel potentially antibacterial naphthalimide-derived
metronidazoles: Design, synthesis, biological evaluation and supramolecular
interactions with DNA, human serum albumin and topoisomerase II, Chinese Chemical
Lettershttp://dx.doi.org/10.1016/j.cclet.2017.04.002
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.

Original article
Novel potentially antibacterial naphthalimide-derived metronidazoles: Design,
synthesis, biological evaluation and supramolecular interactions with DNA, human
serum albumin and topoisomerase II
Jie Kang1, Vijai Kumar Reddy Tangadanchu1,†, Lavanya Gopala1,‡, Wei-Wei Gao1, Yu Cheng1, Han-Bo Liu1,
1
2,
1,


Rong-Xia Geng , Shuo Li , Cheng-He Zhou
1Institute of Bioorganic & Medicinal Chemistry, Key Laboratory of Applied Chemistry of Chongqing Municipality, School of Chemistry and Chemical
Engineering, Southwest University, Chongqing 400715, China
2School of Chemical Engineering, Chongqing University of Technology, Chongqing 400054, China
 Corresponding authors.
E-mail addresses: zhouch@swu.edu.cn (C.-H. Zhou); lishuo@cqut.edu.cn (S. Li)
† Postdoctoral researcher from CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India.
‡ Postdoctoral researcher Sri Venkateswara University, Tirupati 517502, India.
Graphical Abstract
A series of novel naphthalimide-derived metronidazoles as new antibacterial agents were developed. Relational supramolecular interactions with
DNA, human serum albumin and topoisomerase II were investigated for the evaluation of antibacterial potentiality.
ARTICLE INFO
ABSTRACT
A series of novel naphthalimide-derived metronidazoles as new type of antimicrobial agents
were for the first time designed, synthesized and characterized by NMR, IR and HRMS
spectra. Experimental results revealed that most of them displayed moderate to good
antibacterial activity towards Gram-positive and negative bacteria. Especially, compound 7b
was able to not only exhibit effective inhibition towards the growth of P. vulgaris (MIC =
0.002 μmol/mL) and S. dysenteriae (MIC = 0.01 μmol/mL), but also have rapidly killing effect
and prevent the development of bacterial resistance. Further research revealed that the highly
active molecule 7b could not only intercalate into calf thymus DNA to form a steady
supramolecular complex and thus might block DNA replication to exert the powerful
bioactivities, but also be effectively transported by human serum albumin (HSA) via the
formation of the 1:1 supramolecular complex, in which hydrogen bonds and hydrophobic
effect played important roles in the association of compound 7b with HSA. Molecular docking
indicated that the supramolecular interactions between 7b and topoisomerase II were driven by
hydrogen bonds.
Article history:
Received 22 January 2017
Received in revised form 15 March 2017
Accepted 22 March 2017
Available online
Keywords:
Metronidazole
Naphthalimide
Antibacterial
Supramolecular
DNA
1. Introduction
———

Metronidazole is a widely used clinical drug for the treatment of infectious diseases. Despite of its long term clinical use, there is
less report about the incidence of its resistance. Therefore, much research has been directing towards its derivatives, so far many
metronidazole derivatives as drugs like ornidazole, secnidazole, tinidazole and nimorazole have been successfully developed and
extensively used in clinic [1]. This encourages continuous exploration to investigate metronidazole derivatives with potential medicinal
application. It has been found that the formed reactive intermediates in microorganisms via the reduction of nitro group in
metronidazole can covalently bind with DNA and trigger the adverse effects [2], so the sterical protection of nitro group is necessary to
improve the metabolism and physicochemical property [3]. Our previous work revealed the introduction of a large structural fragment
such as berberine and quinolone into metronidazole nucleus can not only exhibit good antimicrobial activities, but also broaden the
antimicrobial spectrum [4]. However, to our best knowledge, the combination of metronidazole with napthalimide skeleton was seldom
reported.
Naphthalimides have large π-deficient aromatic backbone with cyclic double imides and a naphthalene framework. The special
structure makes naphthalimides readily interact with biological active sites via supramolecular interactions such as π-π stacking, cation-
π, coordination bonds, hydrogen bonds, ion-dipole, hydrophobic effect, van der Waals and so on, thus exhibiting various biological
activities [5]. In particular, some naphthalimide-based compounds like amonafide, mitonafide, elinafide and bisnafide have already
shown large potentiality in the treatment of cancers by supramolecular interactions with biological molecule DNA or topoisomerase II
(Top II) [6]. Recently, much literature showed that naphthalimides should also have quite large possibility as new type of antimicrobial
agents [7]. Imidazolyl, 1,2,3-triazolyl and benzimidazolyl naphthalimides were found to display comparable or even superior
antimicrobial activities to the standard drugs Norfloxacin, Chloromycin and Fluconazole [8]. Therefore, it is worth further studying
naphthalimide derivatives as new antimicrobial agents.
Fig. 1. Design of novel naphhtalimide-derived metronidazoles
In view of the above observations, as an extension of our research on metronidazole-based derivatives as new antimicrobial agents,
herein a series of novel naphthalimide-derived metronidazoles were designed for the first time (Fig. 1). The introduction of large
structural fragment might not only be beneficial to the sterical protection of nitro group to produce the reactive intermediates in
microorganisms via the reduction of nitro group in metronidazole, and to avoid triggering the adverse effects, thus overcoming drug
resistance, but also be helpful to excellent antimicrobial activity via multiple binding of supramolecular interactions with DNA or Top
II by the use of π-π stacking, hydrophobic effect, hydrogen bonds and so on. Furthermore, the amino group at the C-4 position of
naphthalimide was capable to improve the affinity and water solubility of the target molecules by forming hydrogen bonds and
coordination interaction etc. The aliphatic chain was reported to be capable of regulating physico-chemical properties, so a series of
alkyl substituents were incorporated into the target compounds in order to investigate their effect on biological activities [9].
All the prepared compounds would be screened against Gram-positive bacterial, Gram-negative bacterial and fungal strains
including Methicillin-resistant Staphylococcus aureus (MRSA). To further evaluate the prospective of the most active compound as
new antibacterial drug, time-kill kinetic assay, and bacterial resistance development research would be done. Moreover, with an aim to
explore the possible antibacterial mechanism of the prepared target compounds, the supramolecular interactions with DNA and Top II,
which are the targets of many antibacterial drugs, would be performed towards the highly active compound. The supramolecular
transportation behavior of the highly active compound by HSA would also be investigated to understand the distribution, deposition,
metabolism and efficacy.
2. Results and discussion
2.1. Chemistry
The target compounds 7a–g were synthesized via multi-step reactions from commercially available 4-bromo-1,8-naphthalic
anhydride 1. The synthetic process was outlined in Scheme 1. Commercial naphthalic anhydride 1 was treated with aqueous ammonia
to produce intermediate 2 in excellent yield of 92%, and was further reacted with chloroacetone in DMF under the presence of
potassium carbonate as base to afford compound 3 with a yield of 62%. The latter was brominated to generate the corresponding
o
compound 4 in the yield of 53%. The prepared bromide 4 was coupled with 2-methyl-5-nitroimidazole in DMF at 40 C using
potassium carbonate as base to give the desired nitroimidazole 5 in the 64% yield. The reduction of compound 5 by sodium
borohydride afforded the metronidazole derivative 6 in moderate yield. The further N-alkylation of compound 6 with various alkyl
amines in dimethyl sulphoxide using potassium carbonate as base and copper(I) oxide as catalyst under nitrogen atmosphere produced
a series of amino type of substituted naphthalimide metronidazoles 7a–g in the moderate yields ranging from 40% to 60%. All the new
compounds were confirmed by NMR, IR and HRMS spectra.

Scheme 1. Synthetic route of naphthalimide-derived metronidazoles. Reagents and conditions: (i) aqueous ammonia, 45 C, 8 h; (ii) chloroacetone, potassium
carbonate, DMF, 100 °C, 7 h; (iii) bromine, acetic acid, 60 °C, 3 h; (iv) 2-methyl-5-nitroimidazole, potassium carbonate, DMF, 40 C, 5 h; (v) sodium
borohydride, ethanol, 60 °C, 6 h; (vi) amines, copper(I) oxide, potassium carbonate, DMSO, 90 C, 4 h.
2.2. Biological activity
As shown in Table S1 in Supporting information, most of the prepared compounds gave moderate to good antibacterial activity
against the tested strains in vitro. The amino type of target compounds 7a–g possessed the better antibacterial efficacy than
intermediates 5 and bromo-substituted naphthalimide metronidazole 6, which demonstrated that positive effect of amino group on
biological activity. Especially, ethylamino deriavtive 7b showed relatively good broad-spectrum and efficient antibacterial activities in
comparison with other compounds. The anti-P. vulgaris potency of compound 7b among the target compounds was the strongest with
an excellent MIC value of 0.002 mol/mL, which was 95-fold, 50-fold and 10-fold more potent than reference drugs Metronidazole,
Chloromycin and Norfloxacin, respectively. Furthermore, S. dysenteriae and E. coli (DH52) were more sensitive to compound 7b
(MIC = 0.01 and 0.04 mol/mL, respectively) than Chloromycin (MIC = 0.05 and 0.10 mol/mL, respectively). Moreover, compound
7b also exhibited better activity against MRSA, S. aureus and B. typhi than Chloromycin. Notably, derivative 7b showed 5-fold
inhibition potency against MRSA than Metronidazole with a MIC value of 0.04 mol/mL. These indicated that naphthalimide
metronidazole 7b had large potentiality as a lead compound in the development of more effective board-spectrum antimicrobial agents.
Continual studies found that the length of the alkyl chain also had a certain effect on the antibacterial efficacy. The replacement of
ethyl group by dodecyl fragment, which yielded compound 7e, resulted in low activity towards the tested strains. Moreover, the
antibacterial activities of compounds 7a, 7c and 7d were also weaker than those of the highly active molecule 7b. These results
suggested that the appropriate alkyl chain was beneficial for the biological activity of the target compounds. In comparison with
compound 7b, the introduction of hydroxyl group into the alkyl chain, which yielded hydroxyethyl amino compound 7f, did not
improve inhibition potency. The ethylation of secondary amino group in compound 7b gave compound 7g which also did not increase
antibacterial potency, except for against B. typhi with the MIC value of 0.04 mol/mL, which was 2.5-fold more potent than
Chloromycin (MIC = 0.10 mol/mL). The antifungal results (Table S2 in the Supporting information) showed that most of the target
compounds had similar inhibitory tendency and intensity to their antibacterial activity. The antifungal activity of compound 7b was
stronger than other target compounds against all tested fungi with MICs between 0.01 and 0.04 μmol/mL. Particularly, compound 7b
showed 5-fold more active potency against B. yeast (MIC = 0.01 mol/mL) than Fluconazole, and stronger activity against C. utilis
(MIC = 0.02 mol/mL) than Fluconazole. All naphthalimide-derived metronidazoles possessed better anti-A. flavus (MIC = 0.040.29
mol/mL) efficiency than Fluconazole (MIC = 0.84 mol/mL).
2.3. Resistance study
MRSA has been challenging the effectiveness of antibiotics including Norfloxacin [10]. Herein, the ability of MRSA to develop
drug resistance against the most active compound 7b was tested and clinical drug Norfloxacin was chosen as a positive control. As can
be seen from Fig. 2, it indicated that the MIC for compound 7b showed no obvious change, whereas that of Norfloxacin began to
significantly increase after 5 passages against MRSA. It demonstrated that MRSA was more difficult to develop resistance against
compound 7b than clinical Norfloxacin.

70
60
50
40
30
20
10
7b
Norfloxacin
0
2
4
6
8
Day
10
12
14
16
Fig. 2. Evaluation of resistance development against compound 7b in bacterial strain MRSA.
2.4. Bactericidal kinetic assay
To determine the bactericidal potency of the synthesized compounds, the viability of exponentially growing MRSA against the most
active 7b was investigated by time–kill kinetics experiment [11]. The data revealed more than 3 log (CFU/mL) reduction in the number
of viable bacteria in one hour at a concentration of 4  MIC (refer to Fig. S1 in Supporting information). The experimental result
manifested that compound 7b had rapidly killing effect against MRSA.
2.5. Cytotoxicity
The in vitro cytotoxic activity of compound 7b was evaluated in MCF-7 (human breast adenocarcinoma) cells by Cell Counting Kit-
8 (CCK8) method. As shown in Fig. S2 in Supporting information, when the concentration of compound 7b was 6.25 g/mL, the cell
viability was 70.4%. With the increasing concentration of compound 7b, the toxicity gradually became high and the IC50 value was
8.51 g/mL, which suggested that it might be a promising candidate to treat cancer.
2.6. Supramolecular interactions with calf thymus DNA
The investigation of supramolecular interactions is a prevalent active field, especially in developing supramolecular drugs [12].
DNA is a main cellular target for antimicrobial agents. There is considerable attention in investigating the supramolecular interactions
of small molecules with DNA for the rational design of new and efficient DNA targeting drugs [13]. To explore the preliminary
mechanism of antimicrobial action, calf thymus DNA was often employed as DNA model [14]. Neutral Red (NR) is a convenient
planar phenazine dye which has been demonstrated that the binding mode of NR with DNA is intercalation [15]. Therefore, NR was
selected as a spectral probe to explore the binding model between the biological active compound 7b and calf thymus DNA on
molecular level in vitro by UV–vis spectroscopy (Supporting information).
The absorption spectra of supramolecular interactions of the most active compound 7b with DNA were shown Fig 3. With the
increasing concentration of 7b, an apparent intensity increase was observed in the developing band around 460 nm. In comparison to
the absorption around 460 nm of free NR in the presence of the increasing concentrations of DNA (Fig. S4 in Supporting information),
the absorbance at the same wavelength exhibited the reverse process (inset of Fig. 3). The results suggested that compound 7b should
intercalate into the double helix of DNA by substituting for NR in the DNA–NR complex. In addition, the increase of absorbance at
276 nm provided evidence for intercalation of compound 7b into DNA.
1.2
0.9
0.6
0.3
0.0
0.4
0.3
0.2
0.1
0.0
i
a
DNA+NR
450
i
350
400
500
Wavelength (nm)
a
DNA+NR
250 300
350
400
450
500
550
Wavelength (nm)
Fig. 3. UV absorption spectra of supramolecular interactions of the active compound 7b with DNA. c(DNA) = 4.32 × 10-5 mol/L, c(NR) = 2 × 10-5 mol/L, and
c(compound 7b) = 02.25 × 10-5 mol/L for curves ai, respectively, at increment 0.25 × 10-5.

2.7. Supramolecular interactions of compound 7b with HSA
HSA is a main carrier protein for a variety of endogenous and exogenous substances in the body, therefore assists in their
distribution and deposition [16]. It has been well accepted that the overall distribution, metabolism, and efficacy of drugs can be
changed by their affinity to HSA. So the investigation of supramolecular interactions with HSA can provide a better understanding of
the absorption, transportation, distribution, metabolism and excretion properties of drug molecules [17]. The experimental results
(Table 1) indicated that compound 7b could spontaneously interact with HSA to form 1:1 stable supermolecular complex via
hydrophobic effect and hydrogen bonds (Supporting information).
Table 1 Binding constants and sites of 7b–HSA supramolecular system
Scatchard Method
T (K)
10-4Kb (L/mol)
R
S.D.
0.029
0.005
0.020
n
286
298
310
8.34
0.992
0.999
0.996
1.05
1.04
1.06
7.57
6.95
2.8. Supramolecular interactions of compound 7b with topoisomerase II
To rationalize the observed antibacterial activity and understand the possible mechanism, the supramolecular docking investigation
of compound 7b with topoisomerase II receptor (PDB code: 1ZXN) was undertaken [18]. The mimetic results showed that compound
7b possessed a high total score (9.02) against topoisomerase II. Supramolecular interactions of compound 7b with topoisomerase II
receptor was shown in Fig. 4, the amido groups could interact with Ser149 and Lys418 residues of Top II through hydrogen bonds with
the distance of 2.4 Å and 2.7 Å, respectively. Furthermore, the hydroxyl group could form hydrogen bonds with Ala167 and Asn91
residues in nearly 2.1 Å distance. There were also hydrogen bonds between nitro group and residues of Tyr165 and Asn163 with the
distance of 1.7 Å and 2.8 Å, respectively. These multi-site bindings might be favorable to stabilize the compound 7b–topoisomerase II
supramolecular complex, which might be responsible for the good inhibitory efficacy of compound 7b against the tested strains.
Fig. 4. Stereoview of conformation of compound 7b–topoisomerase II supramolecular complex
3. Conclusion
A series of novel naphthalimide-derived metronidazoles were for the first time designed and successfully synthesized as potential
antibacterial agents through a convenient and efficient procedure. All the target compounds were confirmed by NMR, IR and HRMS
spectra. The in vitro antimicrobial evaluation revealed that some of the target compounds could effectively inhibit the growth of some
tested strains. Structure–activity relationship suggested that aliphatic chains at the C-4 position of naphthalimide exerted a certain
impact on biological activity. The most active compound 7b with the ethylamino group could effectively inhibit the growth of P.
vulgaris and S. dysenteriae with MIC values of 0.002 and 0.01 μmol/mL, respectively. Importantly, compound 7b had the ability to
rapidly kill the tested strains and did not trigger development of bacterial resistance. Moreover, the most active molecule 7b could not
only intercalate into calf thymus DNA to form a steady supramolecular complex which might block DNA replication to display the
antibacterial activity, but also be effectively transported by HSA via the formation of the 1:1 biological supramolecular complex, in
which hydrogen bonds and hydrophobic effect played important roles in the association of compound 7b with HSA. Molecular docking
indicated that the supramolecular interactions between 7b and topoisomerase II were driven by hydrogen bonds. Additionally,
compound 7b showed concentration-dependent toxicity to MCF-7 cells. Further research studies including in vivo bioactivities,
structural modification alicyclic amines (morpholine, pyrrolidine, piperidine and piperazine, etc.) and heterocyclic azole rings (triazole,
benzimidazole, their derivatives, etc.) into the naphthalimide backbone as well as their corresponding metal supramolecular complexes
are now in progress. All these will be discussed in the full paper.

4. Experimental
4.1. General procedures for synthesis of compounds.
4.1.1. General procedures for synthesis of compounds 2–6 have been provided in Supporting information.
4.1.2. Synthesis of 6-(ethylamino)-2-(2-hydroxy-3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)-1H-benzo[de] isoquinoline-1,3(2H)-
dione (7b)
A mixture of compound 6 (4.59 g, 10 mmol), ethylamine (4.51 g, 100 mmol), copper(I) oxide (0.29 g, 2 mmol), potassium carbonate
o
(0.69 g, 5 mmol) in dimethyl sulfoxide (10 mL) was stirred at 90 C for 4 h (monitored by TLC, eluent, chloroform/methanol, 40:1,
v/v). After the solvent was evaporated under reduced pressure, and the resulting residue was extracted with chloroform (3  30 mL),
the organic layers were combined, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The crude product
was purified by silica gel column chromatography eluting with chloroform/methanol (50:1, V/V) to give the compound 7b (2.46 g) as
the yellow solid. Yield: 58%; mp:  250 oC; IR (KBr, cm-1) ν: 3377 (O-H), 3137 (N-H), 1675 (C=O), 1637,1580, 1500, 1456 (aromatic
frame); 1H NMR (600 MHz, DMSO-d6): δ 8.70 (d, 1H, J = 8.1 Hz, NAPH-H), 8.45 (d, 1H, J = 7.0 Hz, NAPH-H), 8.28 (d, 2H, J = 8.5
Hz, NAPH-H, Im-4-H), 7.69 (dd, 2H, J = 17.4, 9.7 Hz, NAPH-H, -NHCH2), 6.78 (d, 1H, J = 8.3 Hz, NAPH-H), 5.45 (d, 1H, J = 4.3
Hz, OH), 4.13 (tdd, 4H, J = 17.1, 11.8, 5.4 Hz, NAPH-CH2, Im-CH2), 3.95 (dd, 1H, J = 13.7, 8.9 Hz, OH-CH), 3.43 (m, 2H, -NHCH2),
2.35 (s, 3H, Im-CH3), 1.31 (t, 3H, J = 6.6 Hz, -CH2CH3); 13C NMR (151 MHz, DMSO-d6): δ 164.7, 163.8, 151.1, 146.1, 145.7, 134.8,
131.2, 130.2, 129.0, 124.7, 123.1, 122.6, 120.7, 108.3, 104.2, 68.1, 51.3, 43.5, 38.0, 14.1, 13.4; HRMS (ESI) calcd. for C21H21N5O5
[M+Na]+, 446.1440; found, 446.1443.
4.1.3. Synthesis of compounds 7a and 7c-g according to the procedure described for compound 7b
4.2. General methods for biological assays.
The antimicrobial activity in vitro for all the target compounds were evaluated for four Gram-positive bacteria (Staphylococcus
aureus ATCC25923, Methicillin-Resistant Staphylococcus aureus N315 (MRSA), Bacillus subtilis ATCC6633 and Micrococcus luteus
ATCC4698), six Gram-negative bacteria (Escherichia coli DH52, Escherichia coli JM109, Pseudomonas aeruginosa ATCC27853,
Shigella dysenteriae, Proteus vulgaris and Bacillus typhi) and five fungi (Candida albicans ATCC76615, Candida mycoderma,
Candida utilis, Aspergillus flavus and Beer yeast) using two folds serial dilution technique in 96–well micro-test plates recommended
by National Committee for Clinical Laboratory Standards (NCCLS) with the positive control of clinically antimicrobial drugs
Chloromycin, Norfloxacin, Metronidazole and Fluconazole.
4.3. General methods for resistance, bactericidal kinetic assays have been provided in Supporting information.
4.4. General methods for supramolecular interactions with DNA, HSA, and topoisomerase II have been provided in Supporting
information.
Acknowledgment
This work was partially supported by National Natural Science Foundation of China (Nos. 21372186, 21672173), the Research
Fund for International Young Scientists from International (Regional) Cooperation and Exchange Program (No. 81650110529) and
Chongqing Special Foundation for Postdoctoral Research Proposal (No. Xm2016039).
References
[1] (a) L. Zhang, X.M. Peng, G.L.V. Damu, R.X. Geng, C.H. Zhou, Comprehensive review in current developments of imidazole-based medicinal chemistry,
Med. Res. Rev. 34 (2014) 340-437;
(b) K. Lewis, Platforms for antibiotic discovery, Nat. Rev. Drug Discovery 12 (2013) 371-387;
(c) X.M. Peng, G.X. Cai, C.H. Zhou, Recent developments in azole compounds as antibacterial and antifungal agents, Curr. Top. Med. Chem. 13 (2013)
1963-2010;
(d) L.P. Peng, S. Nagarajan, S. Rasheed, C.H. Zhou, Synthesis and biological evaluation of a new class of quinazolinone azoles as potential antimicrobial
agents and their interactions with calf thymus DNA and human serum albumin, Med. Chem. Commun. 6 (2015) 222-229.
[2] (a) H.S. Sutherland, A. Blaser, I. Kmentova, et al., Synthesis and structure-activity relationships of antitubercular 2-nitroimidazooxazines bearing
heterocyclic side chains, J. Med. Chem. 53 (2010) 855-866;
(b) L. Zhang, K.V. Kumar, S. Rasheed, R.X. Geng, C.H. Zhou, Design, synthesis, and antimicrobial evaluation of novel quinolone imidazoles and
interactions with MRSA DNA, Chem. Biol. Drug Des. 86 (2015) 648-655.
[3] (a) L. Zhang, K.V. Kumar, R.X. Geng, C.H. Zhou, Design and biological evaluation of novel quinolone-based metronidazole derivatives as potent Cu2+
mediated DNA-targeting antibacterial agents, Bioorg. Med. Chem. Lett. 25 (2015) 3699-3705;
(b) M.N. Trivedi, S.Y. Gabhe, U.D. Vachhani, R.B. Patel, C.P. Shah, Synthesis of some 2-methyl-5-nitroimidazole derivatives as potential antimicrobial
agents, J. Chem. Pharm. Res. 3 (2011) 313-319.
[4] (a) L. Zhang, J.J. Chang, S.L. Zhang, et al., Synthesis and bioactive evaluation of novel hybrids of metronidazole and berberine as new type of antimicrobial
agents and their transportation behavior by human serum albumin, Bioorg. Med. Chem. 21 (2013) 4158-4169;
(b) S.F. Cui, L.P. Peng, H.Z. Zhang, et al., Novel hybrids of metronidazole and quinolones: Synthesis, bioactive evaluation, cytotoxicity, preliminary
antimicrobial mechanism and effect of metal ions on their transportation by human serum albumin, Eur. J. Med. Chem. 86 (2014) 318-334;
(c) X.M. Peng, G.L.V. Damu, C.H. Zhou, Current developments of coumarin compounds in medicinal chemistry, Curr. Pharm. Des. 19 (2013) 3884-3930;
(d) X.M. Peng, K.V. Kumar, G.L.V. Damu, C.H. Zhou, Coumarin-derived azolyl ethanols: synthesis, antimicrobial evaluation and preliminary action
mechanism, Sci. China Chem. 59 (2016) 878-894.

[5] (a) H.H. Gong, D. Addla, J.S. Lv, C.H. Zhou, Heterocyclic naphthalimides as new skeleton structure of compounds with increasingly expanding relational
medicinal applications, Curr. Top. Med. Chem. 16 (2016) 3303-3364;
(b) G.L.V. Damu, Q.P. Wang, H.Z. Zhang, et al., A series of naphthalimide azoles: Design, synthesis and bioactive evaluation as potential antimicrobial
agents, Sci. China Chem. 56 (2013) 952-969;
(c) S. Banerjee, E.B. Veale, C.M. Phelan, et al., Recent advances in the development of 1,8-naphthalimide based DNA targeting binders, anticancer and
fluorescent cellular imaging agents, Chem. Soc. Rev. 42 (2013) 1601-1618;
(d) Z. Chen, L. Han, M.H. Xu, et al., Rationally designed multitarget anticancer agents, Curr. Med. Chem. 20 (2013) 1694-1714.
[6] (a) M.F. Brana, M. Cacho, A. Gradillas, et al., Intercalators as anticancer drugs, Curr. Pharm. Des. 7 (2001) 1745-1780;
(b) S.Y. Tan, D.H. Sun, J.K. Lyu, et al., Antiproliferative and apoptosis-inducing activities of novel naphthalimide–cyclam conjugates through dual
topoisomerase (topo) I/II inhibition, Bioorg. Med. Chem. Lett. 23 (2015) 5672-5680.
[7] (a) Y.Y. Zhang, J.L. Mi, C.H. Zhou, X.D. Zhou, Synthesis of novel fluconazoliums and their evaluation for antibacterial and antifungal activities, Eur. J. Med.
Chem. 46 (2011) 4391-4402;
(b) Y.Y. Zhang, C.H. Zhou, Synthesis and activities of naphthalimide azoles as a new type of antibacterial and antifungal agents, Bioorg. Med. Chem. Lett.
21 (2011) 4349-4352;
(c) A.S. El-Azab, A.M. Alanazi, N.I. Abdel-Aziz, et al., Synthesis, molecular modeling study, preliminary antibacterial, and antitumor evaluation of N-
substituted naphthalimides and their structural analogues, Med. Chem. Res. 22 (2013) 2360-2375.
[8] (a) H.H. Gong, K. Baathulaa, J.S. Lv, G.X. Cai, C.H. Zhou, Synthesis and biological evaluation of Schiff base-linked imidazolyl naphthalimides as novel
potential anti-MRSA agents, Med. Chem. Commun. 7 (2016) 924-931;
(b) Y.L. Luo, B. Kishore, K.V. Kumar, C.H. Zhou, G.X. Cai, Novel benzimidazole derived naphthalimide triazoles: synthesis, antimicrobial activity and
interactions with calf thymus DNA, Sci. China Chem. 58 (2015) 483-494;
(c) J.S. Lv, X.M. Peng, B. Kishore, C.H. Zhou, 1,2,3-Triazole-derived naphthalimides as a novel type of potential antimicrobial agents: Synthesis,
antimicrobial activity, interaction with calf thymus DNA and human serum albumin, Bioorg. Med. Chem. Lett. 24 (2014) 308-313.
[9] (a) M. Verma, V. Luxami, K. Paul, Synthesis, in vitro evaluation and molecular modelling of naphthalimide analogue as anticancer agents, Eur. J. Med. Chem.
68 (2013) 352-360;
(b) H.Z. Zhang, G.L.V. Damu, G.X. Cai, C.H. Zhou, Design, synthesis and antimicrobial evaluation of novel benzimidazole type of fluconazole analogues
and their synergistic effects with chloromycin, norfloxacin and fluconazole, Eur. J. Med. Chem. 64 (2013) 329-344.
[10] (a) N. Sunduru, L. Gupta, K. Chauhan, et al., Synthesis and antibacterial evaluation of novel 8-fluoro norfloxacin derivatives as potential probes for
methicillin and vancomycin-resistant Staphylococcus aureus, Eur. J. Med. Chem. 46 (2011) 1232-1244;
(b) Y. Cheng, S.R. Avula, W.W. Gao, et al., Multi-targeting exploration of new 2-aminothiazolyl quinolones: Synthesis, antimicrobial evaluation, interaction
with DNA, combination with topoisomerase IV and penetrability into cells, Eur. J. Med. Chem. 124 (2016) 935-945;
(c) W.W. Gao, S. Rasheed, V.K.R. Tangadanchu, et al., Design, synthesis and biological evaluation of amino organophosphorus imidazoles as a new type
of potential antimicrobial agents, Sci. China Chem. doi: 10.1007/s11426-016-9009-6.
[11] L. Zhang, D. Addla, P. Jeyakkumar, et al., Discovery of membrane active benzimidazole quinolones-based topoisomerase inhibitors as potential DNA-
binding antimicrobial agents, Eur. J. Med. Chem. 111 (2016) 160-182.
[12] (a) C.H. Zhou, L.L. Gan, Y.Y. Zhang, Review on supermolecules as chemical drugs, Sci. China Ser. B-Chem. 52 (2009) 415-458;
(b) C.H. Zhou, F.F. Zhang, L.L. Gan, Y.Y. Zhang, R.X. Geng, Research in supramolecular chemical drugs, Sci. China Ser. B-Chem. 39 (2009) 208-252 (in
Chinese);
(c) Y. Cheng, H. Wang, D. Addla, C.H. Zhou, Current researches and applications of azole-based supermolecules as medicinal agents, Chin. J. Org. Chem.
36 (2016) 1-42 (in Chinese);
(d) H. Wang, P. Jeyakkumar, S. Nagarajan, J.P. Meng, C.H. Zhou, Current researches and applications of perylene compounds, Prog. Chem. 27 (2015)
704743 (in Chinese).
[13] (a) B.K. Paul, N. Guchhait, Exploring the strength, mode, dynamics, and kinetics of binding interaction of a cationic biological photosensitizer with DNA:
Implication on dissociation of the drug DNA complex via detergent sequestration, J. Phys. Chem. B. 115 (2011) 11938-11949;
(b) X.M. Peng, L.P. Peng, S. Li, Quinazolinone azolyl ethanols: Potential lead antimicrobial agents with dual action modes targeting MRSA DNA, Future
Med. Chem. 8 (2016) 1927-1940;
(c) J. Wen, Y.L. Luo, H.Z. Zhang, et al., A green and convenient approach toward benzimidazole derivatives and their antimicrobial activity, Chin. Chem.
Lett. 27 (2016) 391-394;
(d) X.L. Li, Y.J. Lin, Q.Q. Wang, et al., The novel anti-tumor agents of 4-triazol-1,8-naphthalimides: Synthesis, cytotoxicity, DNA intercalation and
photocleavage, Eur. J. Med. Chem. 46 (2011) 1274-1279.
[14] (a) S. Narva, S. Chitti, B.R. Bala, et al., Synthesis and biological evaluation of pyrrolo[2,3-b]pyridine analogues as antiproliferative agents and their
interaction with calf thymus DNA, Eur. J. Med. Chem. 114 (2016) 220-231;
(b) P. Jeyakkumar, L. Zhang, S.R. Avula, C.H. Zhou, Design, synthesis and biological evaluation of berberine-benzimidazole hybrids as new type of
potentially DNA-targeting antimicrobial agents, Eur. J. Med. Chem. 122 (2016) 205-215.
[15] (a) G.W. Zhang, P. Fu, L. Wang, M.M. Hu, Molecular spectroscopic studies of farrerol interaction with calf thymus DNA, J. Agric. Food Chem. 59 (2011)
8944-8952;
(b) S.Q. Wen, P. Jeyakkumar, S.R. Avula, L. Zhang, C.H. Zhou, Discovery of novel berberine imidazoles as safe antimicrobial agents by down regulating
ROS generation, Bioorg. Med. Chem. Lett. 26 (2016) 2768-2773.
[16] (a) S.M.S. Abdullah, S. Fatma, G. Rabbani, J.M. Ashraf, A spectroscopic and molecular docking approach on the binding of tinzaparin sodium with human
serum albumin, J. Mol. Struct. 1127 (2017) 283-288;
(b) J.R. Duan, H.B. Liu, P. Jeyakkumar, et al., Design, synthesis and biological evaluation of novel Schiff base-bridged tetrahydroproberberine triazoles as
new type of potential antimicrobial agents, Med. Chem. Commun. doi: 10.1039/c6md00688d;
(c) B.T. Yin, C.Y. Yan, X.M. Peng, et al., Synthesis and biological evaluation of -triazolyl chalcones as a new type of potential antimicrobial agents and
their interaction with calf thymus DNA and human serum albumin, Eur. J. Med. Chem. 71 (2014) 148-159.
[17] (a) S.F. Cui, D. Addla, C.H. Zhou, Novel 3-aminothiazolquinolones: Design, synthesis, bioactive evaluation, SARs, and preliminary antibacterial
mechanism, J. Med. Chem. 59 (2016) 4488-4510;
(b) H.Z. Zhang, P. Jeyakkumar, K.V. Kumar, C.H. Zhou, Synthesis of novel sulfonamide azoles via C-N cleavage of sulfonamides by azole ring and
relational antimicrobial study, New J. Chem. 39 (2015) 5776-5796.
[18] A. Kamal, M. Sathish, L. Nayak, et al., Design and synthesis of dithiocarbamate linked -carboline derivatives: DNA topoisomerase II inhibition with DNA
binding and apoptosis inducing ability, Bioorg. Med. Chem. 23 (2015) 5511-5526.