Improvement in the water solubility and stability of 4ASA by the use of cyclodextrins

Article abstract of DOI:10.1007/s10847-010-9742-3

4-Aminosalicylic acid (4ASA) a non steroid anti inflammatory drug (NSAID) has been used for over 40 years in the treatment of inflammatory bowel diseases (IBDs). It is therefore an importance to assess physicochemical properties such as solubility and stability. The effect of cyclodextrins on the solubility and chemical stability of 4ASA was investigated. Inclusion complexes of 4ASA were characterized by the solubility method, differential scanning calorimetry (DSC) and Fourier transformer infrared spectroscopy (FT-IR). In addition, the influence of presence of CDs on stability was assessed at room temperature in different pH conditions. Complexation with CDs increased 4ASA aqueous solubility. The stoichiometric ratios of the inclusion complexes were 1:1 for α, β, γ and HP-CDs, respectively. Complexation with γ and HP-CDs has increased the 4ASA stability 4 fold. These observations suggest that 4ASA/CD complexes may be an attractive and practical procedure to modify drug physicochemical properties for use in delivery systems.

Full text of DOI:10.1007/s10847-010-9742-3

J Incl Phenom Macrocycl Chem (2011) 69:327–331
DOI 10.1007/s10847-010-9742-3
ORIGINAL ARTICLE
Improvement in the water solubility and stability of 4ASA
by the use of cyclodextrins
•
•
•
M. Lahiani-Skiba I. Youm F. Bounoure
M. Skiba
Received: 27 October 2009 / Accepted: 19 January 2010 / Published online: 4 February 2010
Ó Springer Science+Business Media B.V. 2010
Abstract 4-Aminosalicylic acid (4ASA) a non steroid
anti inflammatory drug (NSAID) has been used for over
40 years in the treatment of inflammatory bowel diseases
(IBDs). It is therefore an importance to assess physico-
chemical properties such as solubility and stability. The
effect of cyclodextrins on the solubility and chemical sta-
bility of 4ASA was investigated. Inclusion complexes of
4ASA were characterized by the solubility method, dif-
ferential scanning calorimetry (DSC) and Fourier trans-
former infrared spectroscopy (FT-IR). In addition, the
influence of presence of CDs on stability was assessed at
room temperature in different pH conditions. Complexa-
tion with CDs increased 4ASA aqueous solubility. The
stoichiometric ratios of the inclusion complexes were 1:1
for a, b, c and HP- CDs, respectively. Complexation with c
and HP-CDs has increased the 4ASA stability 4 fold. These
observations suggest that 4ASA/CD complexes may be an
attractive and practical procedure to modify drug physi-
cochemical properties for use in delivery systems.
Introduction
4-Aminosalicylic acid (4ASA) a non steroid anti inflam-
matory drug (NSAID) (Fig. 1) has been used for over
40 years in the treatment of inflammatory bowel diseases
(IBDs) [1]. It is therefore an importance to assess physico-
chemical properties such as solubility and stability. Cyclo-
dextrins (CDs) have lipophilic inner cavities and hydrophilic
outer surfaces. They, are capable of interacting with a large
variety of guest molecules to form non covalent inclusion
complexes. For this reason they are reported as complexing
agents who are able to improve the physicochemical prop-
erties of the guest molecule. In the present work solubility
and stability studies of 4ASA/CDs solid inclusion complexes
were conducted. Characterization was investigated by dif-
ferent analytical techniques: Differential Scanning Calo-
rimetry (DSC), Fourier Transformed Infrared spectroscopy
(FT-IR) to show if an inclusion phenomena is obtained.
Keywords 4ASA ꢀ Cyclodextrins ꢀ Stability, DSC ꢀ
Materials and methods
FT-IR
Materials
Cyclodextrins and 4ASA were commercial products pro-
vided by Wacker Fine chemicals (Burhausen, Germany)
and Bayer respectively.
M. Lahiani-Skiba ꢀ I. Youm ꢀ F. Bounoure ꢀ M. Skiba
Solubility studies
´
Laboratoire de Pharmacie Galenique ADEN EA 4311, Institute
for Biomedical Research, University of Rouen, 22, Boulevard
Gambetta, 76000 Rouen, France
Solubility studies were investigated according to the phase
solubility method described by Higuchi and Connors [2]
over 7 days. The following Eq. 1 was used to determine
the association constant (K) from the slope of the linear
portion of the curve.
M. Skiba (&)
Laboratoire Pharmacie Galenique ADEN EA 4311, UFR
´
Medecine-Pharmacie, 22, Bd Gambetta, 76183 Rouen, France
´
e-mail: Mohamed.skiba@univ-rouen.fr
123

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J Incl Phenom Macrocycl Chem (2011) 69:327–331
Fig. 1 4ASA chemical
structure
samples were prepared weighing 3–5 mg of powder in
aluminium pan and analysis was performed in duplicate.
O
OH
Fourier transform infrared spectroscopy (ATR-FT-IR)
OH
Samples were analyzed in dried phase. The Fourier
Transform Infrared Spectra were obtained from a Perkin
Elmer IR spectrometer. Spectra were achieved from 4,000
to 650 cm-1, with H2O and CO2 signals ponderation,
8 cm-1 resolution, 0.2 cm-1 scanning speed, 16 scans.
NH2
Results and discussion
K ¼ slope=Soð1 ꢁ slopeÞ ð1Þ
where So is the intrinsic solubility of the drug studied under
Stability test and phase solubility
the conditions.
Stability results showed a protective effect of a-CD/4ASA
from chemical degradation up to 98% at pH 7.5 (Fig. 2a).
Phase solubility profiles of 4ASA/CDs are presented in
Fig. 2b. The phase solubility diagram of 4ASA/a-CD
complex could be classified as Bs-type that denotes com-
plexes of limited solubility. The first part had shown
increased drug solubility with increasing concentration of
a-CD in the range of 0–100 mM. K value of the 1:1
complex was 214.28 4.17 according to Eq. 1. However
the solubility diagram of b-CD had shown a Bi subtype that
Preparation of 4ASA/CDs complex
The complexes were prepared by mixing (at 1:1 M ratio)
4ASA and CDs according to the freeze drying procedure
described in [3].
Chemical stability
4ASA with and without a-CD were placed in buffer solu-
tions at pH 1.5, 7.0 or 7.5 and reacted for 7 days at
37 0.5 °C. The reaction mixture was centrifuged at
3,000 rpm for 5 min, and the supernatant was analyzed by
HPLC.
4ASA quantification by HPLC
The amount of 4-aminosalicylic acid (4ASA) in the
sample solution was determined by HPLC. The HPLC
system consisted of a Jasco 880 pump (Japan), a Jasco
875-UV detector (Japan), an autosampler HPLC-360
Kontron (Brehme, Germany) and a Kromasil column: C-
18 lm, 250 mm 9 4.6 mm (Chromato, France HAS),
maintained at room temperature. Detection of the analytes
was carried out at 300 nm. The optimum mobile phase
which was used in validation studies consisted of water–
formic acid–acetonitrile (67:3:30; v/v/v). Solvent delivery
was employed at a flow of 1.0 mL/min. Injection volume
of the analytes was set to a constant volume of 50 lL. All
HPLC parameters were controlled by the Azur software:
version 3.0 coupled to an acquisition box (Azur PAD).
Differential scanning calorimetry (DSC)
DSC analysis was carried out using a DT6 differential
calorimeter (Perkin Elmer, USA). Scans were performed in
the range of 30–300 °C with a gradient of 10 °C/min. All
Fig. 2 a 4ASA–a-CD complex in different pH medium and b phase
solubility diagrams of 4ASA–a, b, c, and HPb-CD
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J Incl Phenom Macrocycl Chem (2011) 69:327–331
329
indicates insoluble complexes. b-CD often gives rise to
B-type curves due to their poor water solubility [4].
Gamma-CD/4ASA phase solubility diagram shown an
An subtypes which indicated a linear increase of 4ASA
existence of interactions between 4ASA with a-CD. In
addition a dispersion phenomenon was observed with
HPb-CD by freeze drying method.
solubility.
K
value of the 1:1 complex was
FT-IR spectroscopy
35.71 2.21 M-1. In the case of HPb-CD the diagram
profile seems to be an An subtype and showed a first
ascendant part between 0 and 150 mM of HPb-CD con-
centrations. The best improvement for 4ASA solubility was
obtained with a-CD.
The FTIR spectra of wave number from 4,000 to 450 cm-1
are presented in Fig. (4a–d) and Table 1. 4ASA showed
two strong absorption bands between 3,380 and
3,483 cm-1 for amino stretching. All the binary systems of
4ASA/CD did not show any new peaks, indicating no
chemical bonds created in the formed complexes. The main
characteristic double band appeared also at the same
position in the physical mixtures with all CDs and 4ASA in
accordance with the thermal analysis results. However, in
the spectra of 4ASA/c-CD obtained by inclusion com-
plexes with CDs, the doublet peak in 3,380–3,483 cm-1
disappeared. Only OH large band of CD appeared on the
spectra. Other bands, such as 1615, 1445, 765–814 cm-1
representing aromatic ring disappeared in the inclusion
spectrum of 4ASA/a-CD suggested the aromatic ring was
entrapped into the host cavities.
Differential scanning calorimetry studies
DSC profile of 4ASA showed a characteristic endothermic
peak at 150.2 °C. A similar behavior was observed for
4ASA in the physical mixtures with a, b, c and HPb-CD
(Fig. 3). With a-CD/4ASA complex endothermic peak
disappearance denotes an inclusion complexes. With
b-CD/4ASA complex a broad endothermic peak was
exhibited between 130 and 175 °C corresponding to
release of water molecules. A well-distinct melting peak
was obtained at 150 °C with c-CD/4ASA complex. This
should indicate that 4ASA molecule was not embedded in
the c-CD inner cavity. A different pattern was observed in
the thermogram of HPb-CD/4ASA complex (Fig. 3). The
disappearance of the melting peaks of 4ASA and HPb-CD
at 150.2 and 175 °C respectively was a proof of an inclu-
sion complexes formation. These results indicated the
Conclusion
As discussed above, the nature of carriers played an
important role in the formation of inclusion complexes
Fig. 3 DSC diagram of 4ASA/CD complexes: (1) 4ASA; (2) CD; (3) physical mixture; (4) inclusion complex. a: a-CD, b: b-CD, c: c-CD,
d: HPb-CD
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J Incl Phenom Macrocycl Chem (2011) 69:327–331
Fig. 4 a FTIR spectra of 4ASA 4ASA (1), a-CD (2), freeze-dried of
4ASA/a-CD (1:1 mol/mol), (3) and physical mixture of 4ASA/a-CD
(1:1 mol/mol) (4). b FTIR spectra of 4ASA (1), b-CD (2), freeze-dried
of 4ASA/b-CD (1:1 mol/mol) (3) and physical mixture of 4ASA/b-CD
(1:1 mol/mol) (4). c FTIR spectra of 4ASA (1), c-CD (2), freeze-dried of
4ASA/c-CD (1:1 mol/mol) (3) and physical mixture of 4ASA/c-CD
(1:1 mol/mol) (4). d FTIR spectra of 4ASA (1), HPb-CD (2), freeze-
dried of 4ASA/HPb-CD (3) (1:1 mol/mol) and physical mixture of
4ASA/HPb-CD (1:1 mol/mol) (4)
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J Incl Phenom Macrocycl Chem (2011) 69:327–331
331
Table 1 Infrared spectral data and bands assignments
CH (cm-1
)
C–C (cm-1
)
C–O–C (cm-1
)
HCH (cm-1
)
C=O (cm-1
)
H bond (cm-1
)
OH (cm-1
)
NH2 (cm-1
)
4ASA
765–814
1406
1615
–
1445
–
1650
–
–
–
3380–3483
a-CD
642, 1080
642, 1080
642, 1080
1615
1070–1152
1070–1152
1070–1152
2912
2912
2912
3200–3500
3200–3500
–
–
Complex 4ASA/CD 765–814
–
–
Physical mixture
765–814
1445
1650
3200–3500 3380–3483
4ASA
765–814
1406
700–800
642, 1080
642, 1080
642, 1080
1615
–
1445
–
1650
–
–
–
3380–3483
b-CD
1070–1152
1070–1152
1070–1152
2912
2912
2912
3200–3500
3200–3500
–
–
Complex 4ASA/CD 765–814
–
–
Physical mixture
765–814
1445
1650
3200–3500 3380–3483
4ASA
765–814
1406
700–800
642, 1080
642, 1080
642, 1080
1615
–
1445
–
1650
–
–
–
3380–3483
c-CD
1070–1152
1070–1152
1070–1152
2912
2912
2912
3200–3500
3200–3500
–
–
Complex 4ASA/CD 765–814
–
–
Physical mixture
765–814
1445
1650
3200–3500 3380–3483
4ASA
765–814
1406
700–800
642, 1080
642, 1080
642, 1080
1615
–
1445
–
1650
–
–
–
3380–3483
HPb-CD
1070–1152
1070–1152
1070–1152
2912
2912
2912
3200–3500
3200–3500
–
–
Complex 4ASA/CD 765–814
Physical mixture 765–814
–
–
1445
1650
3200–3500 3380–3483
Brewster, M.: Hot stage extrusion of p-amino salicylic acid with
EC using CO2 as a temporary plasticizer. Int. J. Pharm. 327, 45–50
(2006)
4ASA could form an inclusion with a and HPb-CD, but no
inclusion with b-CD and c-CD. Nevertheless further anal-
ysis such as NMR analysis and modeling data would be
taken to confirm or not if 4ASA aromatic ring is embedded
inside the cavity of a and HPb-CD.
2. Higuchi, T., Connors, K.A.: Phase solubility techniques. Adv.
Anal. Chem. Instrum. 4, 117–212 (1965)
´
3. Lahiani-Skiba, M., Boulet, Y., Youm, I., Bounoure, F., Verite, Ph.,
Arnaud, Ph., Skiba, M.: Interaction between hydrophilic drug
and a-cyclodextrin: physico-chemical aspects. J. Incl. Phenom.
Macrocycl. Chem. 57, 211–217 (2007)
4. Challa, R., Ahuja, A., Ali, J., Khar, R.K.: Cyclodextrins in drug
delivery: an updated review. http://www.aapspharmscitech.org
(2005). 6(2), Art 43
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