T.-D. Tran et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4555–4560
4559
active site. Moreover, B rings of docked chalcones formed various
hydrogen bonds with Thr382 and Gly377 (Fig. 2). Recently, the
combination between in silico approach (docking, 3D-QSAR) and
experimental results indicated the important amino acid in NBD
crucial for flavonoids derivatives interacted with human P-gp bind-
ing affinity and this hydrophobic site is related to NBD of
Sav1866 of S. aureus. The resulting tight interactions between
chalcones4, 20, 21, 25 and Sav1866 may used to explain and would
be related to the synergistic mechanism on non beta-lactam
antibiotics.
6. (a) Modzelewska, A.; Pettit, C.; Achanta, G.; Davidson, N. E.; Huang, P.; Khan, S.
R. Bioorg. Med. Chem. 2006, 14, 3491; (b) Vogel, S.; Heilmann, J. J. Nat. Prod.
2008, 71, 1237.
7.
8.
9.
Lin, Y. M.; Zhou, Y.; Flavin, M. T.; Zhou, L. M.; Nie, W.; Chen, F. C. Bioorg. Med.
Chem. 2002, 10, 795.
(a) Vogel, S.; Barbic, M.; Jürgenliemk, G.; Heilmann, J. Eur. J. Med. Chem. 2010,
4
5, 2206; (b) Doan, T. N.; Tran, T.-D. Pharmacol. Pharm. 2011, 2, 282.
3
0
(a) Sivakumar, P. M.; Prabhakar, P. K.; Doble, M. Med. Chem. Res. 2011, 20, 482;
(b) Vogel, S.; Ohmayer, S.; Brunner, G.; Heilmann, J. Bioorg. Med. Chem. 2008, 16,
4
286.
0. (a) Talia, J. M.; Debattista, N. B.; Pappano, N. B. Braz. J. Microbiol. 2011, 42, 470;
b) Eumkeb, G.; Siriwong, S.; Phitaktim, S.; Rojtinnakorn, N.; Sakdarat, S. J. Appl.
Microbiol. 2012, 112, 55; (c) Higuchi, T., Sato, Y.; Murasugi, S. U.S. patent
294,526, 2001.; (d) Sato, Y.; Shibata, H.; Arakaki, N.; Higuti, T. Antimicrob.
1
(
6
In the previous reports, the NorA efflux pump in SA extrudes a
Agents Chemother. 2004, 48, 1357; (e) Liu, M. H.; Otsuka, N.; Noyori, K.; Shiota,
S.; Ogawa, W.; Kuroda, T.; Hatano, T.; Tsuchiya, T. Biol. Pharm. Bull. 2009, 32,
489; (f) Tiwari, B.; Pratapwar, A. S.; Tapas, A. R.; Butle, S. R.; Vatkar, B. S. Int. J.
Chem. Tech. Res. 2010, 2, 499.
variety of structurally unrelated antibacterial like berberine, an
cationic antimicrobial, from bacterial cells.2
b,34
Hence, a test com-
bined activity between berbeine and a synthetic chalcone against
MRSA may be a positive proof to prove the above proposed hypoth-
esis. Resulting from our experiments indicated that synergistic ef-
fect was obtained for the combination of chalcone 21 and
berberine. The MIC values of berberine decreased in 32-fold from
11. Funiss, B. S.; Hannford, A. J.; Smith, P. W. G.; Tatchell, A. R. Vogel’s Textbook of
Practical Organic Chemistry, 5th ed.; Longman: London, 2004. pp 1032–1035.
12. Tran, T.-D.; Park, H.; Kim, H. P.; Ecker, G. F.; Thai, K.-M. Bioorg. Med. Chem. Lett.
2009, 19, 1650.
1
1
3. Kim, Y. H.; Kim, J.; Park, H.; Kim, H. P. Biol. Pharm. Bull. 2007, 30, 1450.
4. (a) Moorthi, S. S.; Chinnakali, K.; Nanjundan, S.; Unnithan, C. S.; Fun, H. K.; Yu,
X.-L. Acta Cryst. 2005, E61, 483; (b) Jasinski, J. P.; Pek, A. E.; Narayana, B.;
Kamath, P. K.; Yathirajan, H. S. Acta Cryst. 2010, E66, 1995; (c) Patil, P. S.;
Chantrapromma, S.; Fun, H. K.; Dharmaprakash, S. M.; Babu, H. B. Acta Cryst.
1
28
lg/mL (berberine alone) to 4 lg/mL (berberine with chalcone
2
1). However, the proposed mechanism of synergistic activity of
chalcones still needs more experiments to confirm. Since flavo-
noids have potential without toxicity, this class of drugs is promis-
ing for future applications in infectious diseases as well as in tumor
diseases.
In conclusion, the present investigation has clearly shown that
certain hydroxylated chalcone derivatives moderately inhibited
against MSSA and MRSA activities when using alone and they
proved to have significantly synergistic effect with non beta-
2007, E63(5), 2612; (d) Shettigar, V.; Rosli, M. M.; Fun, H. K.; Razak, I. A.; Patil,
P. S.; Dharmaprakash, S. M. Acta Cryst. 2006, E62, 4128; (e) Patil, P. S.;
Chantrapromma, S.; Fun, H.-K.; Dharmaprakash, S. M.; Babu, H. B. R. Acta Cryst.
2007, E63, 2612.
1
5. General procedure for the synthesis of chalcones: a solution of substituted
acetophenones (5 mM) and aromatic aldehyde (5 mM) in methanol (15 mL)
was cooled to 5–10 °C in an ice bath. The cooled solution was treated with
adding a small portion of pulverized KOH (10 mM). The reaction mixture was
magnetically stirred for 60 min and then left overnight or longer, monitored by
thin layer chromatography using developing solvent n-hexane–acetone (5–1).
The resulting dark solution was diluted with ice water and carefully acidified
using dilute hydrochloric acid. The chalcone which separated as a yellow solid
was collected by filtration after washing with water and further purified by
crystallization from methanol or by silica gel column chromatography.
lactam antibiotics against MRSA. These potential analogues are
0
2
,2-dihydroxychalcone (4); 2-hydroxychalcone (20); 4-hydroxy-
0
chalcone (21) and 4 -bromo-2-hydroxychalcone (25). The potential
combinations such as (i) ciprofloxacin with 4-hydroxy-chalcone
16. Chemical physical properties: Melting points (mp, °C) were recorded on a
Gallenkamp apparatus and were uncorrected. IR spectra were recorded in KBr
on Shimadzu FTIR 8201 PC. 1H NMR spectra were measured on Bruker Avance
0
(
(
21); (ii) ciprofloxacin with 4 -bromo-2-hydroxychalcone (25);
0
iii) doxycycline with 4 -bromo-2-hydroxychalcone (25); (iv)
doxycycline with 2 ,2-dihydroxychalcone (4) and (v) gentamicin
with 2 ,2-dihydroxychalcone (4) could be investigated further to
500 MHz spectrometer. Chemical shifts are reported in ppm. Coupling
0
constants J are reported (Hz).
0
17. CLSI. Performance Standards for Antimicrobial Disk Susceptibility Test; Approved
Standard, 9th ed.; CLI document M2–A9.26:1; Clinical Laboratory Standards
Institute: Wayne, PA, 2006.
achieve new combinations in treatment infectious diseases caused
by MRSA. Related to the antibacterial mechanisms, our synthesized
chalcones could effect on SA and MRSA by damaging the bacterial
cell wall. Possible mechanism for the synergistic effect of chalcones
in combinations with non-beta-lactam antibiotics were also pro-
posed as the efflux pump inhibitors and discussed via molecular
docking studies.
1
8. Antibiotics and antibacterial agents: Standard powder forms of vancomycin and
ciprofloxacin (Sigma Chemical Co., Ltd), chloramphenicol, doxycycline and
gentamicin (Shanghai Fine Chemicals Co., Ltd), were stored at 2 to 8 °C until
use. Antibiotics discs like gentamicin (10
vancomycin (30 g), clindamycin (2 g), doxycycline (30
(5 g) and erythromycin (15 g) were supplied by Nam Khoa Co., Ltd, Vietnam.
l
g), chloramphenicol (30
lg),
l
l
l
g), ciprofloxacin
l
l
Two standard spices of bacteria like Staphylococcus aureus ATCC 25923 and
Methicillin-resistant Staphylococcus aureus ATCC43300 preserved and
activated at our Department of Microbiology were used for this study. The
bacterial culture media were purchased from Merck, in which Tryptic Soy Agar
Acknowledgments
(
(
TSA) was used to isolate and preserve bacterial species, Tryptic Soy Broth
TSB) was used as bacteria-activating medium and Mueller-Hinton Agar (MHA)
The authors wish to thank The Vietnam National Foundation for
Science and Technology Development (NAFOSTED) for financial
support. The research was fully supported from Nafosted Grant
No. 104.01.105.09 to Thanh-Dao Tran and in part by Nafosted
Grant No. 104.01.21.09 to Khac-Minh Thai for molecular modeling
works. The authors wish to thank Pharm. Thi-Cam-Van Vo for
SciFinder searching.
was used for testing antibiotics activity.
19. (a) Bauer, A. W.; Kirby, W. M. M.; Sherris, J. C.; Turck, M. Am. J. Clin. Pathol. 1966,
36, 493; (b) Jorgensen, J. H.; Turnidge, J. D. In Manual of Clinical Microbiology;
Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., Pfaller, M. A., Eds., 9th
ed.; ASM Press: Washington, DC, 2007; pp 1152–1172.
2
0. Antibacterial susceptibility testing: The disc diffusion method was carried out for
the antimicrobial tests. Briefly: Suspension of bacterial strains (100 L)
containing 108 cfu/mL of bacteria was spread on Mueller Hinton agar (MHA)
medium. The disc (6 mm in diameter), impregnated with 10 l of the test
l
l
compound at the concentration of 102.4 mg/mL were placed on the inoculated
agar. Negative control was prepared using the same solvent (DMSO), which
was employed to dissolve the test compounds. Antibiotic (2–30 lg/disc, 6 mm
References and notes
in diameter) were used. The inoculated plates were incubated at 37 °C for 24 h.
Measure the diameter (mm) of inhibitory zones (Table 2).
1. Measurement of MIC values: The MICs of antibiotics and selectively active
chalcone were determined by the microdilution method as described by The
National Committee for Clinical Laboratory Standard (NCCLS). Each test
compound was run in duplicate. The test plates were incubated at 37 °C for
1
2
.
.
Kaye, K. S.; Engemann, J. J.; Fraimow, H. S.; Abrutyn, E. Infect. Dis. Clin. North Am.
004, 18, 467.
(a) Stavri, M.; Piddock, L. J.; Gibbons, S. J. Antimicrob. Chemother. 2007, 59, 1247;
b) Junio, H. A.; Sy-Cordero, A. A.; Ettefagh, K. A.; Burns, J. T.; Micko, K. T.; Graf,
T. N.; Richter, S. J.; Cannon, R. E.; Oberlies, N. H.; Cech, N. B. J. Nat. Prod. 2011, 74,
621.
2
2
(
1
24 h. The MIC was taken as the minimum concentration of the dilutions that
3
.
(a) Hamad, B. Nat. Rev. Drug Disc. 2010, 9, 675; (b) Corey, G. R.; Stryjewski, M.
E.; Weyenberg, W.; Yasothan, U.; Kirkpatrick, P. Nat. Rev. Drug Disc. 2009, 8,
inhibited the growth of the test microorganism. The concentration of the
solvents used in the following assays was maintained at less than 2% so that no
inhibition of organisms or interference occurred.
9
29; (c) Welte, T.; Pletz, M. W. Int. J. Antimicrob. Agents 2010, 36, 391; (d) Jean,
S. S.; Hsueh, P. R. Exp. Opin. Pharmacother. 2011, 12, 2145.
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Eur. J. Chem. 2009, 6, 196.
2
2. (a) National Committee for Clinical Laboratory Standards. Methods for Dilution
Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, 6th ed.;
Approved standard M7-A6; National Committee for Clinical Laboratory
4
5
.
.