The protection of nifedipin from photodegradation due to complex formation with β-cyclodextrin

Article abstract of DOI:10.2478/s11532-010-0043-x

The inclusion complex β-cyclodextrin:nifedipin was prepared in solid state by coprecipitation with 1:1 mol ratio. The structure of the obtained complex and nifedipin was characterized by use of X-ray diffraction (XR), infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) methods. The photodegradation of nifedipin and the β-cyclodextrin:nifedipin inclusion complex in solid state was monitored under natural daylight by infrared spectroscopy, whereby the free nifedipin degraded four to five times faster than the complexed nifedipin. The photodegradation products of both free and complexed nifedipin, formed during irradiation at 350 nm (with corresponding energy flux of 18 W m^-2) were monitored by liquid chromatography during various time intervals. The speed of formation of nitroso- and nitro-phenyl derivatives by nifedipin irradiation was significantly higher than those of complexed nifedipin irradiation, which indicates its increased photostability in the inclusion complex. The effect on this property is significant because it contributes both to the improvement of the therapeutic effect of nifedipin and to the safer application thereof.

Full text of DOI:10.2478/s11532-010-0043-x

Cent. Eur. J. Chem. • 8(4) • 2010 • 744–749
DOI: 10.2478/s11532-010-0043-x
Central European Journal of Chemistry
The protection of Nifedipin from
photodegradation due to complex
formation with b-cyclodextrin
Research Article
*
1
1
1
1
Vesna Nikolić , Dušica Ilić , Ljubiša Nikolić , Mihajlo Stanković ,
1
1
2
3
Milorad Cakić , Ljiljana Stanojević , Agneš Kapor , Mirjana Popsavin
1Faculty of Technology, University of Nish,
6000 Leskovac, Serbia
2Faculty of Sciences, Department of Physics, University of Novi Sad,
1000 Novi Sad, Serbia
3Faculty of Sciences, Department of Chemistry, University of Novi Sad,
1000 Novi Sad, Serbia
1
2
2
Received 19 November 2009; Accepted 26 February 2010
Abstract: The inclusion complex b-cyclodextrin:nifedipin was prepared in solid state by coprecipitation with 1:1 mol ratio. The structure
of the obtained complex and nifedipin was characterized by use of X-ray diffraction (XR), infrared spectroscopy (FTIR), nuclear
magnetic resonance (NMR), and differential scanning calorimetry (DSC) methods. The photodegradation of nifedipin and the
b-cyclodextrin:nifedipin inclusion complex in solid state was monitored under natural daylight by infrared spectroscopy, whereby
the free nifedipin degraded four to five times faster than the complexed nifedipin. The photodegradation products of both free and
-2
complexed nifedipin, formed during irradiation at 350 nm (with corresponding energy flux of 18 W m ) were monitored by liquid
chromatography during various time intervals. The speed of formation of nitroso- and nitro-phenyl derivatives by nifedipin irradiation
was significantly higher than those of complexed nifedipin irradiation, which indicates its increased photostability in the inclusion
complex. The effect on this property is significant because it contributes both to the improvement of the therapeutic effect of nifedipin
and to the safer application thereof.
Keywords: Nifedipin • Inclusion complex • b-cyclodextrin • Photodegradation • Liquid chromatography
©
Versita Sp. z o.o.
1
. Introduction
respectively – are the most frequently used for these
purposes. The glucosidal units are linked by α-1,4
Nifedipin [1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5- glycoside links to form the cyclic structures shown in
pyridinecarboxylate]isaderivativeof1,4-dihydropyridine. Fig. 2 [12,13].
It belongs to a group of active substances with
X-ray analysis proved that the glucosidal
therapeutic use as calcium channel blockers and residues in cyclodextrins are constrained to the more
coronary vasodilators [1-5]. o-Nitro derivatives of thermodynamically stable chair conformation because
1
,4-dihydropyridine are very unstable compounds, which all the substituents are in equatorial positions. As
readily oxidize under the influence of light to the nitroso a consequence of this conformation, all secondary
and nitro derivatives shown in Fig. 1 [6-8].
Oxidation of nifedipin brings about the loss of
NO
2
NO
NO
2
H
its pharmacological activity, to the point that nitroso
derivatives even show some toxicity. The limiting factors
for the use of nifedipin for clinical purposes are its high
photosensitivity and poor solubility [2].
H
3
COOC
COOCH
3
H
3
COOC
COOCH
3
+
H
3
COOC
COOCH
3
h n
H
3
C
N
H
CH
3
H
3
C
N
CH
3
H
3
C
N
CH
3
Nifedipin
Nitroso phenyl derivative
Nitro phenyl derivative
Buildinginclusioncomplexeswithb-cyclodextrinscan
increase nifedipin’s stability 5- to 10-fold [9-11]. Among
the natural cyclodextrins, α-, b- and γ-cyclodextrins
Figure 1.Nifedipin degradation under the influence of light to nitroso
derivatives[4-(2-nitrosophenyl)-2,6-dimethyl-3,5-dimethoxy
carbonyl pyridine] and nitro derivative [4-(2-nitrophenyl)-
2,6-dimethyl-3,5-dimethoxy carbonyl pyridine].
–
consisting of 6, 7 and 8 D-glucopyranose units,
*
E-mail: nvesna@yahoo.com
744

V. Nikolić, et al.
HOH
2
C
O
2
HOH C
O
O
O
OH
O
HOH
O
2
C
HOH
2
C
O
HO
O
OH
HO
O
OH
O
HOH
2
C
HO
2
HOH C
OH
HOH
2
C
O
HO
OH
O
O
OH
HO
O
OH
HO
HO
O
O
CH2OH
O
HO
O
HO
OH
HO
2
HOH C
CH2OH
O
OH
O
O
O
OH
OH
CH
2
OH
O
HO
HO
O
HOH
2
C
OH
HO
HOH
2
C
OH
O
OH
OH
HO
O
O
O
OH
O
O
HO
OH
OH
O
CH
2
OH
2
HOH C
CH
2
OH
OH
HO
OH
HO
OH
HO
OH
CH
O
O
HO
O
O
O
O
CH
2
OH
O
O
HO
CH
2
OH
a)
CH
2
OH
b)
O
O
c)
2
CH OH
2
OH
O
Figure 2.Structures of cyclodextrins: a) α-cyclodextrin, b) b-cyclodextrin, and c) γ-cyclodextrin
2
.2 Preparation of inclusion complex by co-
hydroxyl groups (OH-2 and OH-3) are located on one
side of the cylindrical molecule, while all primary hydroxyl precipitation
groups (OH-6) are on the opposite side. As such, the Nifedipin (1 mmol, 346 mg) and b-cyclodextrin (1 mmol,
3
wider side of the cavity is surrounded by secondary 1135 mg) were mixed and dissolved in 150 cm of water.
hydroxyl groups, i.e., the outer side of cyclodextrin is Thelight-protectedsolutionwasmixedatroomtemperature
o
hydrophilic and, therefore, soluble in aqueous media. for 24 hours, evaporated in a vacuum evaporator at 50 C
3
Conversely, the inner cavity of cyclodextrin is much more to approx. 20 cm volume, and then dried in a desiccator
o
hydrophobic in character because the free electron pairs above concentrated sulfuric acid at 25 C. After drying,
of the glycoside bridge oxygens are within the cavity a yellow cristalline complex was obtained and used for
[
14,15]. Various organic molecules can be encapsulated further investigations in this work as such.
in the cyclodextrin cavity, forming so-called inclusion
complexes. Formation of inclusion complexes alters 2.3 Preparation of physical mixture
physical properties of the included components, such Physical mixtrures were prepared by simply blending
as solubility, photosensitivity, stability, volatility, flavor nifedipin and b-cyclodextrin with 1:1 molar ratio in a
and others [16-22]. Alterations to these characteristics mortar until uniformity.
of the active component contribute to its safer and more
efficient application, especially for the production of 2.4 X-ray crystallography
pharmaceutical formulations.
X-ray diffraction was performed on a Phillips X’Pert
In this work, the inclusion complex of nifedipin with powder diffractometer under the following conditions:
b-cyclodextrin was prepared in order to increase its samples were exposed to monochrome CuK radiation
α
o
solubility and protect it from daylight. Nifedipin and and analyzed under angle 2θ between 5 and 55 with
o
the inclusion complex b-cyclodextrin:nifedipin were 0.05 increments and recording time, t=5 sec. The
structurally characterized by use of various methods: voltage and the strength of the electric current were
1
XR, H-NMR, FTIR and DSC. Photostability of nifedipin 40 kV and 20 mA, respectively.
and of the b-cyclodextrin:nifedipin inclusion complex in
1
solid state exposed to daylight was assessed by FTIR 2.5 H NMR spectrometry
1
spectrometry. Finally, aqueous solutions of nifedipin
H-NMR spectra of the samples were measured on a
and of b-cyclodextrin:nifedipin inclusion complex were Bruker AC 250 E NMR spectrometer with operating
subjected to UV-radiation and the degradation products frequencies of 250 MHz, in a 5 mm diameter glass
were analyzed by high-pressure liquid chromatograpy cuvette at room temperature, by pulse method with
(HPLC).
multiple pulse repetitions. D O was used as the solvent
2
for nifedipin:b-cyclodextrin complex and b-cyclodextrin,
2
. Experimental Procedure
while CDCl was used for nifedipin.
3
2
.1 Reagents
2.6 Differential scanning calorimetry (DSC)
Nifedipin,[1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)- DSC curves of the samples were recorded on a DuPont
3
,5-pyridine carboxylate], 99.67% pure, was purchased DSC differential scanning calorimeter with the scanning rate
o
-1
o
from Ipca Laboratories Limited, India, and b-cyclodextrin of 10 C min and temperature range 20-320 C. Thermal
from Merck, 98%, Darmstadt. Other solvents and propertieswerestudiedbyheatingabout5mgofthesample
reagents used were p.a. and HPLC purity.
in closed aluminum containers in nitrogen atmosphere.
7
45

The protection of Nifedipin from photodegradation
due to complex formation with b-cyclodextrin
2
.7 Fourier transformation infrared spectrometry
On the other hand, there is a great similarity between
the diffractograms of b-cyclodextrin (diffractogram
(FTIR)
KBr pellets prepared from the samples and protected 2 in Fig. 3) and the inclusion complex of nifedipin
from moisture were exposed to daylight for several days and b-cyclodextrin (diffractofram 3 in Fig. 3). These
and FTIR spactra were recorded periodically to monitor represent clear evidence that the inclusion of nifedipin
the degradation of complexed and non-complexed within the cavities of b-cyclodextrin has been achieved
nifedipin to degradation products under the influence of in the complex, so that the reflection planes originating
daylight.
from nifedipin are not visible in the diffractogram, while
they are present in the diffractogram of the physical
mixture.
2
.8 HPLC analysis
Liquid chromatography was used to analyze the water
In Fig. 4, protons of the nifedipin molecule (a) and
solutionsofnifedipinandnifedipin:b-cyclodextrincomplex the glucosidal unit of b-cyclodextrin (b) are enumerated,
1
before and after irradiation with UV-light (λ=350 nm). and the results of H-NMR testing of nifedipin,
Measurements were made on HPLCAgilent 1100 Series b-cyclodextrin and b-cyclodextrin:nifedipin complex are
apparatus under the following conditions: column Zorbax given in Table 1.
Eclipse XDB-C18 4.6x150 mm, 5 mm; mobile phase
3
-1
acetonitrile/water 85/15 v/v; flow rate 0.5 cm min ;
o
column temperature 25 C; injected volume 20 mL.
Detector DAD at 205 nm.
2
.9 UV-irradiation
Continuous irradiation of samples were performed in
a cylindrical photochemical reactor “Rayonet” with 14
symmetrically placed lamps with emission maxima
at 350 nm (UV-A). Samples were irradiated in quartz
cuvettes (1×1×4.5 cm) placed on a rotating circular
holder, in the middle of the cylinder, 10 cm from the
walls. The total measured energy flux at the samples
-2
was 18 W m at 350 nm.
Figure 3.X-ray diffractograms of (1) nifedipin, (2) b-cyclodextrin,
inclusion complex of nifedipin and (3) b-cyclodextrin, and
(
4) physical mixture of nifedipin and b-cyclodextrin
3
. Results and Discussion
The diffractograms of nifedipin, b-cyclodextrin,
b-cyclodextrin:nifedipin inclusion complex, and
a
physical mixture of nifedipin and b-cyclodextrin are
shown in Fig. 3. There is a great difference between the
diffractograms of the inclusion complex (diffractogram 3
in Fig. 3) and that of the physical mixture of nifedipin
and b-cyclodextrin (diffractogram 4 in Fig. 3). The
diffractogram of the physical mixture resembles the
cumulativediffractogramsofnifedipinandb-cyclodextrin.
Figure 4. (a) Nifedipin molecule and (b) glucopyranose unit with
indicated protons which give signals in 1H-NMR spectra
Table 1. Chemical shifts (δ) and changes of proton chemical shifts (∆δ) in 1H-NMR spectra of nifedipin, b-cyclodextrin, and the complex of nifedipin
with b-cyclodextrin
C-atom, nifedipin
and 6 (6H,2xCH3)
and 5 (6H, 2xOCH3)
(1H)
(1H, NH)
’-6’ (4H, Ar)
δ
, ppm
δ
, ppm
C-atom
∆δ, ppm
2
2.28 s
3.54 s
5.68 s
5.92 s
b
-cyclodextrin
Complex
5.01 s
3
1
5.12 s
-0.110
-0.055
-0.208
-0.130
4
2 and 4
3
3.65 m
4.03 t
3.595 m
3.822 t
1
3
7.2-7.8 m
5 and 6
3.92 m
3.79 m
746

V. Nikolić, et al.
The greatest ∆δ shifts after nifedipin complexation
DSC curves of nifedipin (A), b-cyclodextrin (B),
with b-cyclodextrin were recorded at protons of the C , C5 complex of b-cyclodextrin:nifedipin (C) and the physical
3
and C atoms of the glucopyranose unit of b-cyclodextrin, mixture of nifedipin and b-cyclodextrin (D) are shown
6
indicating that these protons were those most involved in Fig. 6. DSC curves show the nifedipin melting peak
o
in the interaction with the nifedipin molecule during the at about 172 C. The peak is lower in intensity for the
inclusion.
The FTIR spectra of nifedipin (A), b-cyclodextrin (B), result of interaction during complex formation.
and the inclusion complex of nifedipin and b-cyclodextrin Shown in Fig. 7 is the chromatogram of nifedipin and
C) are given in Fig. 5. The FTIR spectra of b-cyclodextrin its nitroso derivative formed by the irradiation of nifedipin
and the inclusion complex b-cyclodextrin:nifedipin by light at 350 nm wavelength for various time intervals.
are almost identical with respect to the position and Nifedipin in the solution (Fig. 7 peak 1) was largely
complex than for the physical mixture, which is the
(
intensity of the bands. The FTIR spectrum of nifedipin converted into the nitroso derivative (Fig. 7 peak 2)
shows absorption bands originating from n (N=O) at even during the first 5 minutes of light exposure, and
as
-1
-1
-1
1
530 cm , n (N=O) at 1350 cm , n(C=O) at 1680 cm , with further exposure the remaining quantities were also
s
-1
-1
n(C-O) at 1129 cm , n(N-H) at 3332 cm that are directly converted into the nitroso derivative. When the nifedipin
related to its structure. In the FTIR spectrum of the complex solution was subjected to exposure under the
b-cyclodextrin:nifedipin complex the nifedipin absorption same condition, the transformation of nifedipin into
bands are not present with the same intensity and shape the nitroso derivative was found to be considerably
as in the FTIR spectrum of nifedipin, which indicates slower (Fig. 8 peaks 1 through 7 and 8). This indicates
covering of nifedipin within the b-cyclodextrin cavities, an increased protection of the complexed nifedipin
i.e., the forming of the inclusion-type supramolecular compared to free nifedipin.
structure.
Figure 6. DSC curves of (A) nifedipin, (B) b-cyclodextrin, the
inclusion complex of nifedipin and (C) b-cyclodextrin and
(
D) the physical mixtrure of nifedipin and b-cyclodextrin
Figure 5.FTIR spectra of (A) nifedipin, (B) b-cyclodextrin and (C) the
inclusion complex of nifedipin and b-cyclodextrin.
Figure 7. HPLC chromatogram of nifedipin: (1) nitro-derivative
of nifedipin without irradiation, (2) nitroso-derivative of
nifedipin obtained by irradiation at 350 nm for 5, 10, 15,
20, 25 and 30 min.
7
47

The protection of Nifedipin from photodegradation
due to complex formation with b-cyclodextrin
FTIR was used to monitor the effect of daylight on
the stability of solid forms of nifedipin and complexes of
nifedipin with b-cyclodextrin. Prepared KBr pellets with
nifedipin and with b-cyclodextrin:nifedipin complex were
exposed to daylight for several days (0 to 15 days) and
FTIR spectra were recorded periodically. Figs. 9 and
10 display the spectra for pure nifedipin and nifedipin
complex with b-cyclodextrin, respectively.
The bands that are indicative and can be used to
monitor nifedipin degradation to nitroso derivatives
during exposure to daylight are found at wave numbers
Figure 8.HPLC chromatogram of nifedipin and b-cyclodextrin
complex: nitro-derivative of (1) nifedipin complex without
irradiation, (2) products after complex irradiation at 350 nm
for 5 min; (3) 10 min; (4) 15 min; (5) 20 min; (6) 25 min; (7)
1
681, 1731, and 3332, and they originate from the
corresponding vibrations of the nifedipin carbonyl, the
nitroso derivative carbonyl, and the nifedipin amine,
respectively. With the increase of nifedipin exposure to
daylight, the formation of the nitroso derivatives also
increases. This conclusion is based on the absorption
bands from C=O groups in nifedipin and the nitroso
derivative, which occur at different frequencies, namely,
30 min and (8) nitroso-derivative of nifedipin from complex.
-
1
1
681 and 1731 cm , respectively. This phenomenon
can be explained by the existence of an acid proton
at the fourth carbon atom of the nifedipin molecule
that may hydrogen bond with two oxygen atoms of
the ester group, causing the C=O band to appear at a
Figure 9. FTIR spectra of nifedipin exposed to daylight for several days
-
1
lower frequency (1681 cm ). In the nitroso derivative
of nifedipin there is no acid proton, so the C=O
group frequency has the usual value, i.e., it appears
-
1
at 1731 cm . The irradiation of nifedipin also brings
about the decrease of two intensive bands at 1530
-
1
and 1350 cm , corresponding to the asymmetric and
symmetric vibrations of the nitro group of nifedipin. The
-
1
appearance of a medium intensity band (1558 cm )
during photodegradation of nifedipin corresponds to
the vibrations of N=O group in the nitroso derivative
of nifedipin. The incomplete stability of nifedipin in the
complex is indicated by the decreased intensity of the
Figure 10. FTIR spectra of nifedipin complex with b-cyclodextrin
exposed to daylight for several days
-
1
band at 3392 cm , resulting from the vibrations of OH 4. Conclusion
groups of b-cyclodextrin and NH groups of nifedipin.
Since nifedipin derivatives generated by exposure to Nifedipin:b-cyclodextrin is an inclusion-type complex.
daylight lack the NH, the decreased total absorption Structuralcharacterizationofthepreparedinclusioncomplex
-
1
in the band around 3392 cm may be attributed to the was carried out by use of various methods. Nifedipin
loss of NH absorption.
photosensitivity in the inclusion complex is decreased
The stability of nifedipin in the complex is higher more in solid state than in the solution. Pure nifedipin
compared to pure nifedipin, based on the decrease in shows significantly higher photosensitivity compared to the
intensity of the aforementioned bands in the complex. inclusion complex, both in solution and in solid state. In this
-1
Thecompletelossofthebandat1681cm forcomplexed work, it was shown that the photosensitivity of solid state
nifedipin was achieved after 10 days of exposure to nifedipin, both pure and in complex, may be monitored by a
daylight, and there were no changes in peak intensities fast and simple FTIR method.
-1
at 3391 and 1733 cm under continued exposure. This
indicates an increased photostability of nifedipin in the Acknowledgements
inclusion complex compared to both solid nifedipin and This paper was supported by Ministry of Science and
the solutions of nifedipin and b-cyclodextrin:nifedipin Technological Development – Republic of Serbia,
complex.
project TR-19048
748

V. Nikolić, et al.
References
[
1] M. Shamsipur, B. Hemmateenejad, M. Akhond, [11] K.L. Andrew Chan, S.G. Kazarian, Mol. Pharm.
K. Javidnia, R. Miri, J. Pharm. Biomed. Anal. 31,
013 (2003)
1, 331 (2004)
[12] J. Szejtli, Chem. Rev. 98, 1743 (1998)
1
[
[
[
[
[
[
[
[
2] M.A. Bayomi, K.A. Abanumay, A.A. Al-Angary, Int. [13] P. Giastas, K. Yannakopoulou, I.M. Mavridis,
J. Pharm. 243, 107 (2002)
Acta Cryst. B59, 287 (2003)
3] D.L. Savigni, D. Wege, G.S. Cliff, M.L.H. Meesters, [14] M.M. Pop et al., Acta Cryst. B58, 1036 (2002)
E.H. Morgan, Biochem. Pharmacol. 65, 1215 (2003) [15] H.J. Schneider, F. Hacket, V. Rodiger, Chem. Rev.
4] V.B. Patravale, V.B. Nair, S.P. Gore, J. Pharm.
Biomed. Anal. 23, 623 (2000)
98, 1755 (1998)
[16] V.T. D’Souza, K.B. Lipkowitz, Chem. Rev. 98, 1749(1998)
5] R. Teraoka, M. Otsuka, Y. Matsuda, Int. J. Pharm. [17] T. Loftsson, J. Buldvinsdottr, A.M. Sigurdardottir,
84, 35 (1999)
Int. J. Pharm. 98, 225 (1993)
6] I.A. Majeed, W.J. Murray, D.W. Newton, S. Othman, [18] R.A. Rajewski, V.J. Stella, J. Pharm. Sci. 85, 1142
W.A. Alturk, J. Pharm. Pharmacol. 39, 1044 (1987)
(1996)
7] Y. Mastuda, R. Teraoka, I. Sugimoto, Int. J. Pharm. [19] V. Nikolić, M. Stanković, A. Kapor, Lj. Nikolić,
1
5
4, 211 (1989)
D. Cvetković, J. Stamenković, Pharmazie 59, 845
(2004)
[20] V. Nikolić, Lj. Nikolić, M. Stanković, A. Kapor,
M. Popsavin, D. Cvetković, J. Serb. Chem. Soc.
72, 737 (2007)
8] I. Matsuura, M. Imaizumi, M. Sugiyama, Chem.
Pharm. Bull. 38, 1692 (1990)
9] N. Škalko, M. Brandl, M. Bećirević-Laćan,
J. Filipović-Grčić, I. Jalšenjak, Eur. J. Pharm. Sci.
4
, 359 (1996)
[21] R. Ficarra et al., J. Pharm. Biomed.Anal. 23, 33 (2000)
[22] R. Ficarra et al. J. Pharm. Biomed.Anal. 23, 232 (2000)
[
10] J. Mielcarek, Pharmazie 51, 477 (1996)
7
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