Investigating the inclusion of the Ag(I)-nimesulide complex into b-cyclodextrin: Studies in solution and in the solid state

Article abstract of DOI:10.1007/s10847-013-0348-4

The present work describes the preparation and characterization of inclusion systems involving b-CD and the silver(I) nimesulide coordination complex (Ag-NMS), prepared by kneading (K) and co-evaporation (CE) methods. Solid state characterization by DSC, XRD and IR vibrational spectroscopic measurements provided remarkable evidences of the formation of true inclusion systems. Solution measurements provided information about the inclusion mode. The UV-Vis spectroscopy was used to obtain the association constants by the Scatchard method, and the value obtained was 370 ± 2 L mol-1. The 1H NMR spectroscopic measurements indicate a total inclusion of the guest into the cavity. A 2D NOESY experiment was carried out for the inclusion complex. The spectrum shows that hydrogens 3-6 of the cyclodextrin clearly correlate with the protons of the phenoxy ring of nimesulide in the Ag-NMS coordination compound, which confirms the formation of the inclusion complex. The antibacterial activities of the Ag-NMS and CE-[(Ag-NMS)b-CD] inclusion system were evaluated by the well diffusion method over Escherichia coli and Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Grampositive) pathogenic bacterial strains. The observed data shows the significant antibacterial activity of the Ag-NMS coordination complex, and no activity for the inclusion complex under the same considered conditions. Springer Science+Business Media Dordrecht 2013.

Full text of DOI:10.1007/s10847-013-0348-4

J Incl Phenom Macrocycl Chem
DOI 10.1007/s10847-013-0348-4
ORIGINAL ARTICLE
Investigating the inclusion of the Ag(I)-nimesulide complex
into b-cyclodextrin: studies in solution and in the solid state
•
Raphael E. F. de Paiva Camilla Abbehausen
•
•
Fernando R. G. Bergamini Andre L. Thompson
•
•
Danilo A. Alves Marcelo Lancellotti Pedro P. Corbi
•
Received: 14 May 2013 / Accepted: 15 June 2013
Ó Springer Science+Business Media Dordrecht 2013
Abstract The present work describes the preparation and
characterization of inclusion systems involving b-CD and
the silver(I) nimesulide coordination complex (Ag-NMS),
prepared by kneading (K) and co-evaporation (CE) meth-
ods. Solid state characterization by DSC, XRD and IR
vibrational spectroscopic measurements provided remark-
able evidences of the formation of true inclusion systems.
Solution measurements provided information about the
inclusion mode. The UV–Vis spectroscopy was used to
obtain the association constants by the Scatchard method,
and the value obtained was 370 2 L mol-1. The 1H
NMR spectroscopic measurements indicate a total inclu-
sion of the guest into the cavity. A 2D NOESY experiment
was carried out for the inclusion complex. The spectrum
shows that hydrogens 3–6 of the cyclodextrin clearly cor-
relate with the protons of the phenoxy ring of nimesulide in
the Ag-NMS coordination compound, which confirms the
formation of the inclusion complex. The antibacterial
activities of the Ag-NMS and CE-[(Ag-NMS)ꢀb-CD]
inclusion system were evaluated by the well diffusion
method over Escherichia coli and Pseudomonas aerugin-
osa (Gram-negative) and Staphylococcus aureus (Gram-
positive) pathogenic bacterial strains. The observed data
shows the significant antibacterial activity of the Ag-NMS
coordination complex, and no activity for the inclusion
complex under the same considered conditions.
Keywords Silver(I) ꢀ Nimesulide ꢀ b-Cyclodextrin ꢀ
Inclusion chemistry ꢀ NOESY NMR
Abbreviations
NMS
Nimesulide
Ag-NMS Silver(I) coordination complex with nimesulide
CD
Cyclodextrin
DSC
XRD
IR
Differential scanning calorimetry
X-ray diffractometry
Infrared
NMR
NOESY
Nuclear magnetic resonance
Nuclear overhauser effect spectroscopy NMR
spectroscopy
UV–Vis
TMS
DMSO
DMF
HG
Ultraviolet–Visible spectroscopy
Tetramethylsilane
Electronic supplementary material The online version of this
article (doi:10.1007/s10847-013-0348-4) contains supplementary
material, which is available to authorized users.
Dimethyl sulfoxide
Dimethylformamide
Host–guest inclusion complex
Molar extinction coefficient
Molar extinction coefficient of the host molecule
Molar extinction coefficient of the guest molecule
Molar extinction coefficient of the host–guest
inclusion complex
R. E. F. de Paiva ꢀ C. Abbehausen ꢀ F. R. G. Bergamini ꢀ
A. L. Thompson ꢀ P. P. Corbi (&)
e
eH
eG
eHG
Inorganic Chemistry Department, Institute of Chemistry,
University of Campinas—UNICAMP, P.O. Box 6154,
Campinas, SP 13083-970, Brazil
e-mail: ppcorbi@iqm.unicamp.br
ATCC
MH
American type collection cell
Mueller-Hinton agar
R. E. F. de Paiva
e-mail: raphael.enoque@gmail.com
BHI
Brain-heart infusion medium
Colony forming unit
D. A. Alves ꢀ M. Lancellotti
CFU
MIC
Laboratory of Biotechnology, Institute of Biology, University of
Campinas, UNICAMP, Campinas, SP 13083-970, Brazil
Minimum inhibitory concentration
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J Incl Phenom Macrocycl Chem
Introduction
was included into the cavity of a-CD and b-CD forming 1:1
and 1:2 (guest/host) complexes, respectively [33]. Braga et al.
reported the interaction studies of b-CD and permethylated b-
CD with a chloride 2,20-bipyridine trithiacyclononane ruthe-
nium(II) coordination compound [34]. This complex was
designed to be used as a DNA intercalator in order to act as an
antitumoral agent.
Silver complexes have been extensively studied as anti-
bacterial agents since the discovery of the antibacterial
activities of silver(I) sulphadiazine (Ag-SD) in 1960s
[1, 2]. The Ag-SD compound has a broad spectrum of
activity against pathogenic bacterial strains, and it has been
used in the treatment of severe burns. This aspect has stim-
ulated the search of new and more effective silver(I) com-
pounds for the treatment of multi-resistant bacterial strains
as an alternative to commercial antibiotics [3–5].
Other systems dealing with coordination compounds
bonded to modified cyclodextrin moieties were also repor-
ted in the literature. Legrand et al. [35] recently reported the
synthesis of a new silver(I) organometallic compound based
on a b-cyclodextrin-imidazolium salt, which has been
considered as a catalyst in the Suzuki cross-coupling reac-
tion. The silver(I) coordination compounds presented the
coordination through to the C-1 carbon of the imidazolium
moiety of the b-cyclodextrin salt.
Nimesulide (NMS, Fig. 1a) is a non-steroidal anti-
inflammatory sulfonamide which exhibits benzyl and nitro
substituted rings. It has been used in the treatment of acute
or chronic inflammatory processes of the respiratory tract
and the oral cavity, tendinitis, rheumatoid arthritis and
dysmenorrhea [36].
Although effective against different bacterial strains,
one of the major problems of silver complexes, mainly
when biological systems are taken into account, are their
poor solubility in water and in other common solvents [6].
Since silver(I) ion has a closed-shell electronic configura-
tion, the insolubility of such compounds may be related to
the Ag(I) center capability to adopt diverse coordination
numbers with no strong energetic preference for any par-
ticular geometry [7]. This capability may generate exten-
ded solid structures, leading to polymeric and less soluble
compounds. In this context, several reports have been made
in which silver(I) complexes are described as extended 1D,
2D and 3D polymeric structures [8–13].
Recently, a silver complex with nimesulide (Ag-NMS,
Fig. 1b) was synthesized and characterized [37]. Nimesu-
lide coordinates to Ag(I) through the nitrogen and oxygen
atoms of the sulphonamide group. This compound is poorly
soluble in water, but is soluble in dimethyl sulfoxide
(DMSO), dimethylformamide (DMF), ethanol and metha-
nol. The poor solubility not only limits other medical
applications, but also limits the ability to study the mech-
anism of action of the Ag-NMS in biological medium.
The inclusion of nimesulide into b-CD was previously
reported, with an increase of its solubility in water [38].
The nimesulide molecule is prone to be included into the
cavity, due to its structure with two aromatic rings.
This work deals with the inclusion of the Ag-NMS
coordination compound into the cavity of b-CD and its
characterization in the solid state by differential scanning
calorimetry (DSC), X-ray diffractometry (XRD) and
infrared (IR) spectroscopic measurements and also in
solution by nuclear magnetic resonance (1H NMR, NO-
ESY) and ultraviolet–visible (UV–Vis) spectroscopies.
One of the possible approaches to increase the solubility of
such silver coordination compounds is their inclusion into the
cavity of cyclodextrins (CD) [14–17]. CD are cyclic torus-like
oligosaccharides consisting of several glucopyranose rings
a-1,4-linked through glucosidic bonds [15, 16]. The most
common CD contains six, seven and eight glucopyranose
units, being called as a-, b- and c-cyclodextrins, respectively.
These macromolecules present a hydrophobic cavity and a
hydrophilic surface, being able to form host–guest (HG)
complexes by the inclusion of apolar moieties of different
compounds into the CD cavity. The hydrophilic surface of CD
turns the guest more soluble in polar solvents [15, 16].
The inclusion phenomena is limited by the molecular
size, and it is driven by the type of interaction involved
[18]. The HG interaction is mostly due to van der Waals
forces and, especially for b-CD, the compounds that pos-
sesses benzylic rings or an adamantyl moiety were shown
to be more suitably included since they are able to over-
come the geometric restriction [19, 20].
Several coordination compounds with different classes
of organic ligands can also be considered for inclusion into
CDs. In this context, the inclusion of metallocene and
metallocene-derived coordination compounds of metals
such as Fe, Mo, Eu, Nb and Ti into the cavity of CDs have
been extensively studied [21–32].
The inclusion of other non-organometallic complexes has
also been reported. A vanadium compound with a hydrazone,
derived from the condensation of salicylaldehyde and the
biphenyl-4-carboxilic acid (salhybiph), K[VO2(salhybiph)],
Fig. 1 Structures of a NMS and b Ag-NMS [37]
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J Incl Phenom Macrocycl Chem
Kneaded systems
Antibacterial studies were also performed in order to
evaluate the effect of the inclusion over the antibacterial
activity of the Ag-NMS complex.
The kneaded systems with b-CD for both NMS and Ag-
NMS were prepared using 1:1 and 1:2 molar ratios of
compound/b-CD. The mixtures were grinded in a mortar
with 10.0 mL of a water/ethanol (1:1 v/v) solution. The
pastes were kneaded for 45 min and then dried at 45 °C.
The dried mass was finally powdered.
Experimental section
Reagents and equipments
Nimesulide ([99 %) and analytical grade silver(I) nitrate
(AgNO3) were purchased from Sigma-Aldrich laboratories.
Potassium hydroxide ([85 %) and b-cyclodextrin ([99 %)
were purchased from Fluka. The IR spectra of the com-
pounds were measured from 4,000 to 400 cm-1 using an
ABB Bomen MB Series FT-IR spectrophotometer; samples
were prepared as KBr pellets. DSC analyses were per-
formed on a TA Instruments 2910 in the range 25–225 °C
(oxidant atmosphere, 10 °C min-1 heating rate). X-ray
diffraction data of the polycrystalline samples were
acquired on a Shimadzu X-ray spectrometer XRD6000,
Co-evaporated systems
The co-evaporated systems with b-CD for both NMS and
Ag-NMS were prepared by the addition of 6.0ꢀ10-5 mol of
b-CD and 6.0ꢀ10-5 mol of NMS or Ag-NMS in 10.0 mL of
a water/ethanol (1:1 v/v) solution. The resulting mixtures
were stirred for 48 h and evaporated at 45 °C until dryness.
The dried masses were then powdered.
Determination of the association constants in solution
˚
with a Cu Ka radiation (k = 1.54060 A).
Both [(NMS)ꢀb-CD] and [(Ag-NMS)ꢀb-CD] inclusion
complexes were prepared using a fixed amount of NMS or
Ag-NMS and increasing amounts of b-CD as presented in
the Table 1. The samples were prepared suspending b-CD
and NMS or Ag-NMS in 10.0 mL of water on a series of
25 mL stoppered Erlenmeyer flasks, and then the mixtures
were shaken in a shaker water bath, at the fixed tempera-
ture of 25.0 0.1 °C. After 48 h of shaking, aliquots of
2.0 mL were filtered and the absorbances were measured at
397 nm. Samples were also taken after 60 and 72 h in order
to evaluate the extension of the inclusion. Solutions con-
taining solely the same corresponding amounts of b-CD
were used as blank for the UV–Vis measurements.
The UV–Vis spectra of the inclusion systems were recor-
ded on a Hewlett-Packard 8453A diode array spectropho-
tometer in the range 100–1,100 nm using 10.00 mm quartz
cuvettes. The H nuclear magnetic resonance (1H-NMR)
1
spectra of b-CD, Ag-NMS, co-evaporated NMS inclusion
system (CE-[(NMS)ꢀb-CD]) and co-evaporated Ag-NMS
inclusion system (CE-[(Ag-NMS)ꢀb-CD]) were recorded on a
Bruker Avance III spectrometer (400 MHz, 9.395 T), using a
5-mm probe at 25 °C applying a 908 excitation pulse with
duration of 8.40 ls, spectral width of 3.3 kHz, acquisition
time of 4.56 s and relaxation delay of 1 s. The 2D nuclear
overhauser effect spectroscopic data (NOESY) were acquired
for the samples CE-[(NMS)ꢀb-CD] and CE-[(Ag-NMS)ꢀ
b-CD] in the same equipment applying a 908 pulse of 8.40 ls
and a1808pulseof16.80 lswitha mixingtime of800 msand
relaxation delay of 1 s. Samples were prepared in D2O
(99.9 % deuterium content). All samples were prepared in
concentrations of 10 mg mL-1, except for Ag-NMS, which
Antibacterial assays
Five pathogenic bacterial strains, Escherichia coli ATCC
25922, Pseudomonas aeruginosa ATCC 27853, Staphylo-
coccus aureus ATCC 25923, S. aureus BEC9393 and
was prepared with a maximum concentration of 2 mg mL-1
.
Table 1 Experimental conditions for the determination of the
inclusions constants of NMS and Ag-NMS in b-CD
Synthesis of the Ag-NMS compound
Solution
Guest molecule
b-CD
The Ag-NMS coordination compound was synthesized as
previously reported in the literature [37]. Anal. Calc. for
AgC13H11N2O5S (%): C, 37.6; H, 2.7; N, 6.7. Found (%): C,
37.8; H, 2.4; N, 6.7. The yield of the synthesis was 85 %.
N1
N2
N3
N4
N5
C1
C2
C3
C4
NMS 2.7 10-5 mol
(0.0083 g)
-
7.5 10-6 mol (0.0093 g)
3.5 10-5 mol (0.0405 g)
6.4 10-5 mol (0.0723 g)
9.1 10-5 mol (0.1036 g)
-
7.5 10-6 mol (0.0093 g)
3.5 10-5 mol (0.0405 g)
6.4 10-5 mol (0.0723 g)
Preparation of the solid inclusion systems
Ag-NMS 2.7 10-5 mol
(0.0112 g)
The solid inclusion systems were prepared as previously
reported in the literature for NMS [38]. The experimental
procedures are described below.
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J Incl Phenom Macrocycl Chem
S. aureus Rib1 were selected. Stock solutions of CE-
[(NMS)ꢀb-CD] and CE-[(Ag-NMS)ꢀb-CD] were prepared
in water (10.0 mg mL-1), while Ag-NMS was previously
dissolved in 500 lL of EtOH 70 % and than diluted with
4.5 mL of water, giving a final solution with the concen-
tration of 10.0 mg mL-1. Sufficient inocula of the bacterial
strains were added to a 96 multiwell plate until the tur-
bidity equaled 0.5 McFarland (*1.5 9 108 CFU mL-1).
The tested compounds were sequencially diluted into the
multiwell plate. The negative control was obtained by
leaving one of the wells of each bacterial strain with no
addition of the considered compounds, while vancomycin
and chloramphenicol were used as positive controls against
the Gram-negative and Gram-positive bacterial strains,
respectively. The minimal inhibitory concentrations (MIC)
were estimated following the recommendations of the
Clinical and Laboratory Standards Institute (CLSI) [39]
and performed in triplicate.
Results and discussion
Evaluation of the inclusion in the solid-state
As described, the [(Ag-NMS)ꢀb-CD] solid inclusion sys-
tems were obtained by two different preparation methods,
kneading and co-evaporation. These strategies were pre-
viously reported in the preparation of NMS inclusion sys-
tems by Nalluri et al. [38], where kneaded systems in a 1:2
guest:host molar ratio generated a solid with high water
solubility. The [(Ag-NMS)ꢀb-CD] inclusion complexes
prepared by both methods presented aqueous solubility in a
concentration of 10 mg mL-1, which is desirable for
pharmaceutical formulations. In addition, the solubility
improvement is an evidence of formation of an inclusion
complex.
Fig. 2 DSC curves of (A) b-CD, (B) NMS, (C) Ag-NMS, (D)
K-[(NMS)ꢀb-CD] 1:1 system, (E) K-[(NMS)ꢀb-CD] 1:2 system, (F)
K-[(Ag-NMS)ꢀb-CD] 1:1 system, (G) K-[(Ag-NMS)ꢀb-CD] 1:2 system,
(H) CE-[(NMS)ꢀb-CD] system and (I) CE-[(Ag-NMS)ꢀb-CD] system
of NMS in b-CD. In this case, the system was prepared in
two different molar ratios. The 1:2 molar composition
(Fig. 2e) showed better results. However, it still shows two
different peaks, a sharp and a broad one. For the co-
evaporated system, CE-[(NMS)ꢀb-CD] (Fig. 2h), a single
broad peak centered at 141 °C is observed, indicating a
complete inclusion of NMS. These results are in agreement
with those previously reported [38].
Differential scanning calorimetry
For the Ag-NMS inclusion complexes, the kneading
procedure (K-[(Ag-NMS)ꢀb-CD]) was also used to prepare
systems with two different molar ratios, 1:1 and 1:2 Ag-
NMS/b-CD, and their DSC curves can be seen in Fig. 2f, g,
respectively. The shift and broadening of b-CD peak
indicate the formation of inclusion complexes. The 1:2
guest/host molar ratio seems to be a better system, due to
the presence of a sharper melting peak. The co-evaporated
system, in this case, shows no peaks and could not be
evaluated properly (Fig. 2i). Nevertheless, it is important to
emphasize that the absence of a characteristic fusion peak
does not indicate that CE method is inadequate for prepa-
ration of the [Ag-NMSꢀb-CD] system. Since the Ag-NMS
itself does not present any characteristic fusion peak, the
absence of this thermal phenomena in the inclusion system
Nimesulide, Ag-NMS and their inclusion complexes in b-
CD prepared by kneaded and co-evaporated method were
studied by DSC. The DSC curves are presented in Fig. 2.
The DSC curve for NMS presents an endothermic peak
at 151.0 °C which corresponds to the melting point, Fig. 2b
[38], No endothermic peaks are observed for Ag-NMS in
the temperature range 25–200 °C, Fig. 2c. The b-CD curve
shows a broad endothermic peak which may be related to
the dehydration process followed by its melting point,
centered at 183.3 °C, Fig. 2a.
The NMS inclusion systems prepared by kneading
process, K-[(NMS)ꢀb-CD], (see Fig. 2d, e) shows a sharp
endothermic peak at 145 °C, which is shifted by 6 °C from
the NMS. The observed result indicates a partial inclusion
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J Incl Phenom Macrocycl Chem
is not sufficient to conclude that the inclusion did not
occurred. In order to fully evaluate the formation and the
extension of the inclusion, additional measurements by
other techniques were considered.
relative intensities. Both 1:1 and 1:2 molar ratios present
very similar diffraction patterns. The diffractogram of
NMS inclusion complex prepared by co-evaporation
(Fig. 3h) also presents some degree of crystallinity with a
similar pattern when compared to those obtained by the
kneaded method. The amorphization points to the forma-
tion of inclusion complexes. This result is in agreement
with the DSC evaluation.
X-ray powder diffraction
The diffraction patterns of the inclusion complexes are
expected to be distinct from the patterns obtained by the
simple superposition of each isolated component of the
inclusion system. The X-ray diffractograms of kneaded
systems, co-evaporated systems, b-CD, NMS and Ag-NMS
are presented in the Fig. 3.
The diffractograms of the Ag-NMS inclusion systems
prepared by kneading, on the other hand, presents different
behaviors according to the molar ratio. The K-[(Ag-NMS)ꢀ
b-CD] 1:1 formulation presents no crystallinity (Fig. 3f),
while the K-[(Ag-NMS)ꢀb-CD] 1:2 formulation presents
the diffraction pattern similar to b-CD (Fig. 3g). The
similarity between the XRD profiles of many of the for-
mulations with the free b-CD can be due to the presence of
the intermolecular forces between the host molecules,
mainly hydrogen bonds, responsible for the maintenance of
the typical packing structure of b-CD even in the inclusion
complexes. The CE-[(Ag-NMS)ꢀb-CD] systems show an
amorphous pattern (Fig. 3i). This result shows that distinct
inclusion complexes have been formed according to the
chosen procedure.
As reported by Sanphui et al. [40], nimesulide can
crystallizes in at least two forms, referred as Form I and
Form II. The XRD pattern and the relative intensities of the
NMS used in this study (Fig. 3a) matches with Form I. The
non-included Ag-NMS shows no defined diffraction peaks
(Fig. 3c).
The X-ray diffractograms of the HG systems were
compared to the free b-CD diffractogram (Fig. 3b). The
most pronounced change observed upon inclusion for all
formulations is the disappearance of the diffraction peak of
b-CD at 2h = 4.66°. Also, an amorphization process for all
formulations is observed, which is indicative of the inclu-
sion complexes formation.
Infrared spectroscopic measurements
The diffractograms of NMS inclusion complexes pre-
pared by kneading (Fig. 3d, e) show some degree of
crystallinity, with the diffraction peaks being compatible
with b-CD and with free NMS. However, the most intense
b-CD diffraction at 2h = 4.66° and the NMS intense dif-
fraction appears at 2h = 5° are observed with very low
The Fig. 4 shows the IR spectra of free b-CD, NMS, Ag-
NMS and all the solid host/guest formulations.
The NMS inclusion complexes present vibrational
modes of the polar groups almost unchanged. The sharp
(N–H) stretching mode in the free NMS at 3,284 cm-1
(Fig. 4A) appears as a small shoulder at *3,290 cm-1 in
the kneaded inclusion complexes (Fig. 4d, e). The broad
OH stretching mode due to aggregation of b-CD and water
almost covers this absorption. Both mas(O=S=O) and
ms(O=S=O) vibration modes appear in K-[(NMS)ꢀb-CD]
1:1 (Fig. 4d) and K-[(NMS)ꢀb-CD] 1:2 (Fig. 4e) in the
same position of the free guest. The two intense charac-
teristic bands of the nitro (NO2) group, mas(NO2) at
1,522 cm-1 and ms(NO2) at 1,317 cm-1 in the free NMS,
remain unchanged in the inclusion complexes. Regarding
the b-CD, the d(C–O–H) remains almost unchanged, along
with both m(C–O–C) asymmetrical and symmetrical
stretching modes. The IR spectrum of CE-[(NMS)ꢀb-CD]
system (Fig. 4h), on the other hand, shows no significant
changes with reference to the inclusion. Therefore, the IR
data in this case is not conclusive concerning the formation
of an inclusion system.
The IR spectra of the kneaded Ag-NMS inclusion systems
(Fig. 4f, g) present particular changes. The mas(O=S=O) and
ms(O=S=O) of the sulfonamide group in the free Ag-NMS
(Fig. 4c) appears at 1,342 and 1,153 cm-1 respectively. Upon
Fig. 3 XRD profiles of (A) b-CD, (B) NMS, (C) Ag-NMS, (D)
K-[(NMS)ꢀb-CD] 1:1 system, (E) K-[(NMS)ꢀb-CD] 1:2 system, (F)
K-[(Ag-NMS)ꢀb-CD] 1:1 system, (G) K-[(Ag-NMS)ꢀb-CD] 1:2 system,
(H) CE-[(NMS)ꢀb-CD] system and (I) CE-[(Ag-NMS)ꢀb-CD] system
inclusion, these bands are shifted to 1,292 and 1,157 cm-1
,
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J Incl Phenom Macrocycl Chem
HOMO–LUMO p–p* transition [37]. Apart for small
energy shifts, calculations confirm that the coordination of
NMS to Ag(I) does not change the nature of the transitions.
Upon inclusion, the UV–Vis spectra show two phe-
nomena. First, the p–p* transition is shifted to *397 nm.
Since this transition is assigned to the HOMO–LUMO
transition, the bathochromic shift suggests that the inclu-
sion reduces the energy difference between the frontier
orbitals for both NMS and Ag-NMS. Furthermore, the
molar extinction coefficient (e) of the HOMO–LUMO
transition is enhanced upon the inclusion, which means that
eHG is higher than both eH and eG.
Determination of the association constants in solution
In order to obtain the association constant (Ka) for both
[(NMS)ꢀb-CD] and [(Ag-NMS)ꢀb-CD] systems in aqueous
solution, the following equilibrium must be considered:
H þ G ꢀ HG
ð1Þ
where the host (H) is b-CD, the inclusion guest (G) is NMS
or Ag-NMS and the inclusion complex (HG) is [(NMS)ꢀb-
CD] or [(Ag-NMS)ꢀb-CD]. The UV–Vis absorbance of a
system where all the three species H, G and HG are present
is given by
A ¼ ꢀHb½Hꢁ þ ꢀGb½Gꢁ þ ꢀHGb½HGꢁ
ð2Þ
The guest compound is in equilibrium with the inclusion
complex HG, so the [HG] and [G] are constrained:
Fig. 4 IR vibrational spectra of (A) NMS, (B) b-CD, (C) Ag-NMS,
(D) K-[(NMS)ꢀb-CD] 1:1 system, (E) K-[(NMS)ꢀb-CD] 1:2 system,
(F) K-[(Ag-NMS)ꢀb-CD] 1:1 system, (G) K-[(Ag-NMS)ꢀb-CD] 1:2
system, (H) CE-[(NMS)ꢀb-CD] system and (I) CE-[(Ag-NMS)ꢀb-CD]
system
A ¼ ꢀGb½Gꢁ0þDꢀHGb½HGꢁ
ð3Þ
where DꢀHG ¼ ꢀHG ꢂ ꢀH ꢂ ꢀG and ½Gꢁ0 is the starting
concentration of the guest molecule. At last, combining (3)
with the definition of Ka, a nonlinear expression is obtained,
describing absorption changes for 1:1 inclusion systems
respectively. This data suggests that the sulfonamide group of
the Ag-NMS complex in the inclusion systems present an
interaction with the hydroxyl groups of b-CD.
DA DꢀHGKa½Hꢁ½Gꢁ0
¼
ð4Þ
b
1 þ Ka½Hꢁ
One approach to linearize Eq. 4 is the Scatchard method
Studies in aqueous solution
[41]. Here, this method is used with a slight modification.
The systems described by Scatchard, and most of the b-CD
inclusion systems, present negative values of DA upon
inclusion. Both NMS and Ag-NMS, on the other hand,
presents positive values of DA. Accounting to this
phenomenon, the linearization equation obtained is
UV–Vis Spectroscopic data
The UV–Vis spectra of NMS and Ag-NMS inclusion
complexes were evaluated in order to determine their
association constants. The UV–Vis spectra were acquired
up to 72 h after the beginning of the experiment. No
absorbance changes were observed for all samples after
48 h, which means that both [(NMS)ꢀb-CD] and [(Ag-
NMS)ꢀb-CD] solution systems reaches the equilibrium in
48 h.
DA
DAKa
¼
þ DꢀHGKa½Gꢁ0
ð5Þ
b½Hꢁ
b
Therefore, with this approach, it is possible to obtain Ka
as the slope of the plotting of DA/b[H] against DA/b.
Figure 5 shows the UV–Vis spectra of the Ag-NMS
solution systems presented in Table 1. The plots of DA/b[H]
versus DA/b for both NMS and Ag-NMS are given in
Both NMS and Ag-NMS UV–Vis spectra exhibit an
electronic transition at 390 nm. This transition was previ-
ously investigated using TD-DFT, being assigned as a
123

J Incl Phenom Macrocycl Chem
3,0
2,5
2,0
1,5
1,0
0,5
0,0
C1
C2
C3
C4
Fig. 6 Structures of the glucopyranose repeating unit (for b-CD,
n = 7), and the toroidal structure of b-CD emphasizing the position
of inner hydrogens 3 and 5
1
The H NMR spectroscopic measurements also allow
inferring about the stability of the inclusion complex and
the orientation of the drug molecule. According to Great-
banks and Pickford [44], the evaluation of Dd of the inner
hydrogens of b-CD (Dd = d inclusion complex - d free
b-CD) can give relevant information about the inclusion,
allowing conclusions about the stability. When Dd 3 [ Dd
5, a partial inclusion of the guest inside the cavity is
occurring. On the other hand, when Dd 3 \ Dd 5, a total
inclusion takes place. The values reported in Table 2 show
that Dd 3 \ Dd 5, which indicates a total inclusion of the
guest in the cavity.
400
600
800
1000
Wavelenght / nm
Fig. 5 UV–Vis spectra of Ag-NMS solutions systems used to
determine Ka (concentrations described in Table 1)
Supporting Information. The calculated Ka values obtained
from those plots for NMS and Ag-NMS were 367 3 and
370 2 L mol-1, respectively. Both compounds are well
described by a single linear regression, which indicates the
existence of a single association constant for each system.
For comparative purposes, the b-CD inclusion complex of
nitrobenzene presents Ka = 154 L mol-1 (pH = 7.0) [42]
and the b-CD inclusion complex of p-nitrophenol presents
Ka = 130 L mol-1 for the neutral species [43].
The presence of two aromatic rings in the Ag-NMS
molecule (Fig. 1) turns possible the formation of 1:1 or 1:2
guest/host stoichiometries for the inclusion complexes.
Also, since one of the rings is more substituted than the
other, an inclusion preference could take place. Comparing
the 1H signals of the free Ag-NMS with the inclusion
complex, we can see that the highest shifts occur for H6
and H3 of the higher substituted ring, and for H20 and H60
of the phenoxy ring. No interaction is observed with the
exterior hydrogens 2 and 4 of cyclodextrin. One important
information is that no shift is observed for H40 of Ag-NMS,
thus indicating no interaction of this hydrogen with b-CD,
while the other protons of the same ring interact. This
result suggests a total inclusion of the phenoxy ring into the
cavity of b-CD.
1H-NMR spectroscopic studies
The nuclear magnetic resonance spectroscopy provides
structural information of supramolecular systems by direct
observation. The difference in the proton chemical shifts
between the free guest, the host species and the suggested
inclusion complex provides information about the inclu-
sion process. The protons of the host are shown in Fig. 6,
1
while the H NMR spectra of the free guest (Ag-NMS),
free host (b-CD) and the CE-[(Ag-NMS)ꢀb-CD] system can
be observed in Figs. 7 and 8. The full 1H NMR spectra are
presented in Supporting Information.
NOESY NMR spectroscopic data
The full spectrum of the inclusion complex confirms that
no free b-CD is present. The structure in Fig. 6 demon-
strates that the inner cavity hydrogens 3 and 5 are the most
affected protons in the structure of the b-CD by the for-
mation of inclusion complexes. It is possible to observe in
Fig. 7 that hydrogen atoms 3 and 5 of b-CD are both
shifted upfiled by the formation of the inclusion complex
while no shifts are observed for the other protons of the b-
CD, confirming the formation of an inclusion complex
between Ag-NMS and b-CD. The external hydrogens 2 and
4 remain unchanged upon inclusion. All 1H chemical shifts
are reported in Table 2.
In order to further confirm the binding mode in the [(Ag-
NMS)ꢀb-CD], a 2D NOESY experiment was performed for
the inclusion complex. The spectrum is presented in Fig. 9.
It is clearly observed that the inner cavity hydrogens 3
and 5 of the cyclodextrin correlate with protons of the
phenoxy ring of nimesulide in the Ag-NMS complex.
There is also an interaction between the hydrogen 5 of b-
CD with H6 of Ag-NMS. The strongest correlation is
observed for hydrogens H20 and H60 of Ag-NMS with the
hydrogen 3 of the b-CD. No correlation is observed for
1
H40of Ag-NMS, thus confirming the proposition from H
123

J Incl Phenom Macrocycl Chem
Table 2 1H assignments, chemical shifts and multiplicity for Ag-
NMS, b-CD and [b-CDꢀ(NMS)]
Ag-NMS Multiplicity d Ag-NMS/ d [b-CDꢀ
Dd
ppm
(Ag-NMS)]/ppm
H5
dd
d
d
t
7.92
7.59
7.42
7.29
7.09
6.94
7.92
7.73
7.53
7.34
7.07
6.82
0.00
H6
0.14
0.11
H3
H30, H50
H40
0.05
t
-0.02
-0.12
H20, H60
d
b-CD
Multiplicity
d b-CD/
ppm
d [b-CDꢀ
Dd
(Ag-NMS)]/ppm
Fig. 7 1H NMR spectra of the a Ag-NMS, b b-CD and c CE-[(Ag-
NMS)ꢀb-CD] from 2.5 to 4.0 ppm
1
3
6
5
2
4
d
t
4.98
3.86
3.78
3.76
3.55
3.50
4.97
3.78
3.79
3.66
3.55
3.49
-0.01
-0.08
0.01
s
dt
dd
t
-0.10
0.00
NMR of the total inclusion of the phenyl ring into the
cavity with no interaction of H40 with any proton of b-CD.
-0.01
Dd is the difference (in ppm) of the chemical shifts between [b-
CDꢀ(NMS)] and Ag-NMS or between [b-CDꢀ(Ag-NMS)] and b-CD
Antibacterial assays
Antibiogram assays were carried out in order to evaluate
the antibacterial activities of the compounds Ag-NMS, CE-
[(Ag-NMS)ꢀb-CD] and CE-[(NMS)ꢀb-CD] and also to
further compare the observed results of CE-[(Ag-NMS)ꢀb-
CD] to that described for the free Ag-NMS coordination
compound [37]. The antibacterial activities were confirmed
by the MIC values. The results are shown in Table 3.
The Ag-NMS coordination compound presents MIC
values in the range 6.25–50.0 lg mL-1. The inhibition of
E. coli, S. aureus and P. aeruginosa bacterial strain are in
accordance with the previously reported activity of the
complex by the disc diffusion method [37].
Although more soluble in water, the inclusion complex
CE-[(Ag-NMS)ꢀb-CD] did not show activity under the
same bacterial strains in the same experimental conditions.
Both the free Ag-NMS and the inclusion complex CE-
[(Ag-NMS)ꢀb-CD] were assayed from 10 mg mL-1 stock
solutions. The Ag-NMS is the bioactive species, what
means that upon inclusion, the available concentration of
Fig. 8 1H NMR spectra of the
a Ag-NMS, b b-CD and c CE-
[(Ag-NMS)ꢀb-CD] from 6.0 to
8.0 ppm
123

J Incl Phenom Macrocycl Chem
Ag-NMS is lower. This can justify the lack of antibacterial
activity observed for the inclusion complex. Further studies
may be envisaged in order to confirm if the activities of
both CE-[(Ag-NMS)ꢀb-CD] and Ag-NMS compounds vary
linearly with the silver content. The inclusion complex CE-
[(NMS)ꢀb-CD] did not present activity against the con-
sidered bacterial strains, since the free nimesulide does not
show antibacterial activities as previously reported [37].
Conclusions
New inclusion complexes of NMS and Ag-NMS were
obtained. For the Ag-NMS inclusion complexes, the DSC
data show that the material obtained by kneading (K-[(Ag-
NMS)ꢀb-CD]) in 1:2 molar ratio presents a sharper melting
peak. Also, the DSC of both materials prepared by kneading
do not present the melting of the precursors (b-CD and Ag-
NMS), which is an indicative of the formation of inclusion
complexes. The Ag-NMS co-evaporated system shows no
melting peaks and could not be evaluated properly by DSC.
The XRD data show that the K-[(Ag-NMS)ꢀb-CD] 1:1
formulation presents no crystallinity, while the K-[(Ag-
NMS)ꢀb-CD] 1:2 formulation presents the diffraction pat-
tern similar to b-CD. The IR data shows that nimesulide
remains coordinated to Ag(I) by the nitrogen and oxygen
atoms of the sulfonamide group upon inclusion.
The association constants found for NMS and Ag-NMS
were of 367 3 and 370 2 L mol-1 respectively,
demonstrating the stability of the inclusion complexes. The
2D NOESY clearly shows that the phenoxy ring of ni-
mesulide in Ag-NMS interacts with the interior of the
cavity of b-CD, and also shows that there is a correlation
between the hydrogen 5 of b-CD with the H6 of Ag-NMS.
The structural information given by the NMR data lead us
to propose the structure shown in Fig. 10 for the [(Ag-
NMS)ꢀb-CD] inclusion system. Even though more soluble,
the inclusion complex CE-[(Ag-NMS)ꢀb-CD] did not
present antibacterial activity when compared to the free
Ag-NMS, which may be related to the low content of silver
in the inclusion complex.
Fig. 9 2D-NOESY spectrum of CE-[(Ag-NMS)ꢀb-CD] in D2O at
room temperature with a mixing time of 800 ms. Top full spectrum;
bottom NOE signals that demonstrate correlation between b-CD
hydrogens (3, 5 and 6) and Ag-NMS hydrogens
Table 3 Minimum inhibitory concentration of the compounds Ag-NMS, CE-[(Ag-NMS)ꢀb-CD] and CE-[(NMS)ꢀb-CD]
Sample
Minimum inhibitory concentration (lg mL-1
)
Gram-negative
Gram-positive
P. aeruginosa ATCC 27853
E. coli ATCC 25922
S. aureus BEC 9393
S. aureus Rib1
S. aureus ATCC 25923
Ag-NMS
25.0
a
6.25
a
50.0
a
25.0
a
50.0
a
CE-[(Ag-NMS)ꢀb-CD]
CE-[(NMS)ꢀb-CD]
Chloramphenicol
Vancomycin
a
a
a
a
a
50.0
–
12.5
–
–
–
–
\10.0
\10.0
\10.0
For Gram-negative and Gram-positive bacteria chloramphenicol and vancomycin were used, respectively, as positive controls
a
Did not present inhibitory activity under tested concentrations
123

J Incl Phenom Macrocycl Chem
12. Kasuga, N.C., Takagi, Y., Tsuruta, S.-I., Kuwana, W., Yoshika-
wa, R., Nomiya, K.: Synthesis, structure and antimicrobial
activities Of meso silver(I) histidinate [Ag 2(D-His)(L-His)]N
(Hhis = histidine) showing different self-assembly from those of
chiral silver(I) histidinates. Inorg. Chim. Acta 368, 44–48 (2011)
13. Kasuga, N.C., Yoshikawa, R., Sakai, Y., Nomiya, K.: Syntheses,
structures, and antimicrobial activities of remarkably light-stable
and water-soluble silver complexes with amino acid derivatives,
silver(I) N-acetylmethioninates. Inorg. Chem. 51, 1640–1647
(2012)
14. Maheshwari, A., Sharma, M., Sharma, D.: Investigation of the
binding of roxatidine acetate hydrochloride with cyclomalto-
heptaose (b-cyclodextrin) using IR And NMR spectroscopy.
Carbohydr. Res. 346, 1809–1813 (2011)
Fig. 10 Schematic representations of the phenoxy ring of Ag-NMS
complex included into b-CD cavity
15. Szejtli, J.: Introduction and general overview of cyclodextrin
chemistry. Chem. Rev. 98, 1743–1753 (1998)
16. Szejtli, J.: Cyclodextrin technology, 1st edn. Kluwer Academic
Publishers, Dordrecht (1998)
Acknowledgments This study was supported by grants from the
Brazilian Agencies FAPESP (Sa˜o Paulo State Research Foundation,
Brazil—proc. 2012/08230-2), CAPES and CNPq. Professor Corbi is
17. Wenz, G.: Cyclodextrins as building blocks for supramolecular
structures and functional units. Angew. Chem. Int. Ed. Engl. 33,
803–822 (1994)
´
also grateful to Professors Celso A. Bertran and Andre L. B. Formiga
from the Campinas State University, UNICAMP, Brazil, for technical
support.
18. Harata, K., Kawano, K.: Crystal structure of the cyclomalto-
hexaose (a-cyclodextrin) complex with isosorbide dinitrate.
Guest-modulated channel-type structure. Carbohydr. Res. 337,
537–547 (2002)
References
19. Meindersma, G.W., van Schoonhoven, T., Kuzmanovic, B.,
Haan, A.B.: Extraction of toluene, o-xylene from heptane and
benzyl alcohol from toluene with aqueous cyclodextrins. Chem.
Eng. Process. 45, 175–183 (2006)
20. Wintgens, V., Layre, A.-M., Hourdet, D., Amiel, C.: Cyclodex-
trin polymer nanoassemblies: Strategies for stability improve-
ment. Biomacromolecules 13, 528–534 (2012)
21. McCormack, S., Russel, N.R., Cassidy, J.F.: Cyclic voltammetry
of ferrocene carboxylic acid cyclodextrin inclusion complexes.
Electrochim. Acta 11, 1939–1944 (1992)
22. Ferreira, P., Gonc¸alves, I.S., Pillinger, M., Rocha, J., Santos, P.,
Teixeira-Dias, J.J.C.: Modification of b-cyclodextrin with ferr-
ocenyl groups by ring opening of an encapsulated [1]ferroceno-
phane. Organometallics 19, 1455–1457 (2000)
23. Braga, S.S., Gonc¸alves, I.S., Ribeiro-Claro, R., Lopes, A.D.,
Pillinger, M., Teixeira-Dias, J.J.C., Rocha, J., Roma˜o, C.C.:
Encapsulation of cyano(cyclopentadienyl) complexes of iron with
beta-cyclodextrin. Supramol. Chem. 14, 359–366 (2002)
24. Cunha-Silva, L., Gonc¸alves, I.S., Pillinger, M., Xue, W.-M.,
Rocha, J., Teixeira-Dias, J.J.C., Ku¨hn, F.E.: Synthesis and char-
acterization of the inclusion compound of a methyltrioxorhe-
nium(VII) adduct of 4-ferrocenylpyridine with beta-cyclodextrin.
J. Organomet. Chem. 656, 281–287 (2002)
25. Fernandes, J.A., Lima, S., Braga, S.S., Pillinger, M., Ribeiro-
Claro, P., Rodriguez-Borges, J.E., Lopes, A.D., Teixeira-Dias,
J.J.C., Gonc¸alves, I.S.: Inclusion complexation of dimeric and
trimeric oligo(ferrocenyldimethylsilanes) with gamma-cyclodex-
trin. Organometallics 24, 5673–5677 (2005)
1. Fox, C.L.J.: Silver sulfadiazine-a new topical therapy for pseu-
domonas in burns. Arch. Surg. 96, 184–188 (1968)
2. Fox, C.L., Modak, S.M.: Mechanism of silver sulfadiazine action
on burn wound infections. Antimicrob. Agents Chemother. 5,
582–588 (1974)
3. Demain, A.L., Sanchez, S.: Microbial drug discovery: 80 years of
progress. J. Antibiot. 62, 5–16 (2009)
4. Nishaminy, K.: Tigecycline: A new glycylcycline antimicrobial
agent. Am. J. Health Syst Pharm 63, 1235–1243 (2006)
5. Bergamini, F.R.G., Ferreira Jr, M.A., de Paiva, R.E.F., Gomes,
A.F., Gozzo, F.C., Formiga, A.L.B., Corbi, F.C.A., Mazali, I.O.,
Alves, D.A., Lancellotti, M., Corbi, P.P.: A binuclear silver
complex with L-buthinonine sulfoximine: Synthesis, spectro-
scopic characterization, DFT studies and antibacterial assays.
RSC Adv. 2, 10372–10379 (2012)
6. Pettinari, C., Marchetti, F., Lupidi, G., Quassinti, L., Bramucci,
M., Petrelli, D., Vitali, L.A., da Silva, M.F.C.G., Martins,
´
L.M.D.R.S., Smolenski, P., Pombeiro, A.J.L.: Synthesis, antimi-
crobial and antiproliferative activity of novel silver(I) tris(pyraz-
olyl) methanesulfonate and 1,3,5-triaza-7-phosphadamantane
complexes. Inorg. Chem. 50, 11173–11183 (2011)
7. Hao, H.-J., Sun, D., Li, Y.-H., Huang, R.-B., Zheng, L.-S.: Effect
of different carboxylates on a series of Ag(I) coordination com-
pounds with benzoguanamine ligand. Cryst. Growth Des. 11,
3564–3578 (2011)
8. Jin, S., Wang, D., Shen, B., Li, Y., Yu, F., Ji, S., Su, M.J.:
Synthesis and structural characterization of three saccharinate-
metal complexes with exo-bidentate bis(imidazole) derivatives.
J. Coord. Chem. 64, 617–629 (2011)
26. Braga, S.S., Paz, F.A.A., Pillinger, M., Seixas, J.D., Roma˜o, C.C.,
Gonc¸alves, I.S.: Structural studies of beta-cyclodextrin and perme-
thylated beta-cyclodextrin inclusion compounds of cyclopentadi-
enyl metal carbonyl complexes. Eur. J. Inorg. Chem 2006, 1662–
1669 (2006)
9. Yaghi, O.M., Li, H.: T-shaped molecular building units in the
porous structure of Ag(4,40-bpy) NO3. J. Am. Chem. Soc. 118,
295–296 (1996)
27. Lima, S., Gonc¸alves, I.S., Ribeiro-Claro, P., Pillinger, M., Lopes,
A.D., Ferreira, P., Teixeira-Dias, J.J.C., Rocha, J., Roma˜o, C.C.:
Interactions of cationic and neutral molybdenum complexes with
beta-cyclodextrin host molecules. Organometallics 20, 2191–2197
(2001)
10. Li, B., Zang, S.-Q., Ji, C., Du, C.-X., Hou, H.-W., Mak, T.C.W.:
Syntheses, structures and properties of two unusual silver–
organic coordination networks: 1D–1D tubular intertwinement
and existence of an infinite winding water chain. Dalton Trans.
40, 788–792 (2011)
28. Braga, S.S., Marques, M.P.M., Souza, J.B., Pillinger, M., Te-
ixeira-Dias, J.J.C., Gonc¸alves, I.S.: Inclusion of molybdenocene
dichloride (Cp2MoCl2) in 2-hydroxypropyl- and trimethyl-beta-
11. Sengul, A., Kurt, O., Buyukgungor, O.: A 2D network silver
coordination polymer with the multimodal ligand 2-pyrazyl
methyl ketazine. Struct. Chem. 22, 925–929 (2011)
123

J Incl Phenom Macrocycl Chem
cyclodextrin: Structural and biological properties. J. Organomet.
Chem. 690, 2905–2912 (2005)
complexes and Suzuki coupling. New J. Chem. 35, 2061–2065
(2011)
29. Braga, S.S., Gago, S., Seixas, J.D., Valente, A.A., Pillinger, M.,
Santos, T.M., Gonc¸alves, I.S., Roma˜o, C.C.: Beta-cyclodextrin
and permethylated beta-cyclodextrin inclusion compounds of a
cyclopentadienyl molybdenum tricarbonyl complex and their use
as cyclooctene epoxidation catalyst precursors. Inorg. Chim. Acta
359, 4757–4764 (2006)
30. Braga, S.S., Ferreira, R.A.S., Gonc¸alves, I.S., Ribeiro-Claro, P.,
Pillinger, M., Rocha, J., Teixeira-Dias, J.J.C., Carlos, L.D.: Study
of the inclusion compound formed between a luminescent euro-
pium (III) beta-diketonate complex and gamma-cyclodextrin.
J. Incl. Phenom. Macrocycl. Chem. 44, 261–265 (2002)
36. Whittle, B.J.R.: Gastrointestinal effects of nonsteroidal anti-
inflammatory drugs. Fundam. Clin. Pharmacol. 17, 301–313
(2003)
37. de Paiva, R.E.F., Abbehausen, C., Gomes, A.F., Gozzo, F.C.,
Lustri, W.R., Formiga, A.L.B., Corbi, P.P.: Synthesis, spectro-
scopic characterization, DFT studies and antibacterial assays of a
novel silver(I) complex with the anti-inflammatory nimesulide.
Polyhedron 36, 112–119 (2012)
38. Nalluri, B.N., Chowdary, K.P.R., Murthy, K.V.R., Hayman, A.R.,
Becket, G.: Physicochemical characterization and dissolution
properties of nimesulide-cyclodextrin binary systems. AAPS
PharmSciTech. 4, 6–17 (2003)
´
31. Morales, A., Struppe, J., Melendez, E.: Host–guest interactions
between niobocene dichloride and a-, b-, and c-cyclodextrins:
Preparation and characterization. J. Incl. Phenom. Macrocycl.
Chem. 60, 263–270 (2008)
39. Clinical and Laboratory Standards Institute (CLSI), Performance
standards for antimicrobial susceptibility testing, 17th Informa-
tional Supplement, Wayne, PA, USA (2007)
ˇ
ˇ
32. Turel, I., Demsar, A., Kosmrlj, T.: The Interactions of titanocene
dihalides with a-, b- and c-cyclodextrin host molecules. J. Incl.
Phenom. Macrocycl. Chem. 35, 595–604 (1999)
40. Sanphui, P., Sarma, B., Nangia, A.: Phase transformation in
conformational polymorphs of nimesulide. J. Pharm. Sci. 100,
2287–2299 (2011)
¨
33. Lippold, I., Vlay, K., Gorls, H., Plass, W.: Cyclodextrin inclusion
41. Scatchard, G.: The attractions of proteins for small molecules and
ions. Ann. N. Y. Acad. Sci. 51, 660–662 (1949)
42. Chen, M., Diao, G., Zhang, E.: Study of inclusion complex of
b-cyclodextrin and nitrobenzene. Chemosphere 63, 522–529
(2006)
43. Buvari, A., Barcza, L.: Complex formation of phenol, aniline, and
their nitro derivatives with b-cyclodextrin. J. Chem. Soc. Perkin
Trans. II, 543–545 (1988)
compounds of vanadium complexes: Structural characterization
and catalytic sulfoxidation. J. Inorg. Biochem. 103, 480–486
(2009)
34. Marques, J., Anjo, L., Marques, M.P.M., Santos, T.M., Paz,
F.A.A., Braga, S.S.: Structural studies on supramolecular adducts
of cyclodextrins with the complex [Ru([9]aneS3)(bpy)Cl]Cl.
J. Organomet. Chem. 693, 3021–3028 (2008)
´
35. Legrand, F.-X., Menand, M., Sollogoub, M., Tilloy, S., Monflier,
44. Greatbanks, D., Pickford, R.: Cyclodextrins as chiral complexing
agents in water, and their application to optical purity measure-
ments. Magn. Reson. Chem. 25, 208–215 (1987)
E.: An N-heterocyclic carbene ligand based on a b-cyclodextrin–
imidazolium salt: Synthesis, characterization of organometallic
123