Crystal Engineering: A Remedy To Tailor the Biopharmaceutical

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Crystal Engineering: A Remedy to Tailor the Biopharmaceutical Aspects of Glibenclamide Parnika Goyal, Dimpy Rani, and Renu Chadha Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b00933 • Publication Date (Web): 07 Nov 2017 Downloaded from http://pubs.acs.org on November 8, 2017

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Crystal Growth & Design

Crystal Engineering: A Remedy to Tailor the Biopharmaceutical Aspects of Glibenclamide Parnika Goyal, Dimpy Rani, Renu Chadha* University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh-160014, INDIA

Corresponding Author: Dr Renu Chadha Professor (Pharmaceutical Chemistry) University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh- 160014, India e-mail: [email protected] Mobile: 91-9316015096.

ACS Paragon Plus Environment


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Abstract New

co-crystals

of

glibenclamide

(GCM),

namely glibenclamide-hippuric

acid

(GCM-HA),

glibenclamide-nicotinic acid (GCM-NA), glibenclamide-theophylline (GCM-TP) and glibenclamidesuccinic acid (GCM-SA) were prepared using solvent assisted grinding. The formation of new crystalline phase was preliminary characterized by Differential Scanning Calorimetry (DSC), and Powder X-Ray diffraction (PXRD) which was further supported by Fourier Transform Infra Red (FT-IR) spectroscopy and

13

C Solid State NMR (ssNMR) analysis. The crystal structures of these co-crystals

were determined from PXRD using BIOVIA material studio software. The data revealed existence of new hydrogen bond interactions between -NH and oxygen atom of sulphamoyl group of GCM with carboxylic -C=O, aromatic N (Naromatic), imidazolic -NH and carboxylic -OH of co-crystal coformers (CCF). Equilibrium solubility and intrinsic dissolution rate studies of co-crystals in phosphate buffer of pH 7.4 showed almost 1.5-3.5 times higher solubility as compared to that of pure of GCM. This further led to improvement in both rate and extent of absorption thereby improving bioavailability and remarkable enhancement in anti-diabetic activity. These results, therefore, demonstrates that cocrystallization was able to overcome the poor water solubility of GCM and provides a remedy for tuning its biopharmaceutical aspects. Introduction Glibenclamide (GCM, figure 1a) (also known as glyburide) is a second-generation sulfonylurea that is used orally as a hypoglycemic agent to treat non-insulin dependent (type II) diabetes mellitus.

1, 2

It is a

3

Class II drug based on the Biopharmaceutics Drug Classification System (BCS) due to its low 4

aqueous solubility (~ 0.018 mg/mL at 37 °C) and high permeability.

5

6

7

8,9

Many scientific approaches like cyclodextrincomplexation , micronisation , solid dispersion , use of 10

surfactants , spray drying and milling

11-13

have been previously attempted by different group of 14

researchers with an intention to improve the solubility of GCM.

However, all these approaches have

one or more limitation. Use of surfactants increases the chances of instability of drug molecule and may cause gastrointestinal irritation. Solid dispersions and cyclodextrin complexes no doubt have improved solubility and dissolution rate but suffer from a drawback of increased bulk of formulations. Moreover, the cyclodextrin complexes have associated toxicological profile. The more recent and emerging field embraced by the pharmaceutical industry, to tailor the biopharmaceutical parameters of an active pharmaceutical ingredient (API) in the crystalline state is 15-17

crystal engineering.

It is defined by Desiraju as “the understanding of intermolecular interactions in

the context of crystal packing and in the utilization of such understanding in the design of new solids 18

with desired physical and chemical properties”. These intermolecular interactions of particular interest are non-covalent interactions such as hydrogen bonding, electrostatic interactions (ion-ion, ion-dipole and dipole-dipole interactions), metal coordination bonds, halogen bonds, π-π stacking and 16

Van der Waals interactions. Derivatives synthesized from these non-covalent interactions involvecocrystals, polymorphs, solvates, and eutectics.As far as polymorphs/solvates are concerned, few group of workers have worked upon GCM crystal form and have narrated polymorphs, solvates, amorphous 11, 19-21

form and a glassy form of GCM.

However, the marketed form of drug and the most stable form


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11

is Form I. Recently, Nangia et al prepared sodium and potassium salts of GCM with an aim to 22

improve its solubility and stability. Regarding co-crystals, not much of literature is available except for one report of its co-crystal with oxalic acid using the solvent drop grinding method

23

, furnishing no

information regarding the crystal structure and evaluation. Co-crystal is a multi-component crystal in which all the components (molecular or ionic compounds) are present in the same crystal lattice in a 24, 25

definite stoichiometric ratio, stabilized by non-covalent interactions.

If at least one of the

components is API and the other is pharmaceutically acceptable, then it is a pharmaceutical co26

crystal , which provides a remedy for improvement in drug solubility, dissolution and consequently the bioavailability, whilst maintaining its intrinsic activity.

27

During the co-crystallization experiments,

molecular adducts such as salts, eutectics, co-crystals, solid solutions can be formed which depends on the nature of components and the type of interactions among them. It was conceptualized that when adhesive (heteromolecular) interaction between components outweigh cohesive (homo/self) interactions, co-crystal if formed vis-à-vis eutectics which are formed by strong cohesive interactions.

28

The presence of potential hydrogen acceptor and donor functional groups in GCM likechlorine, secondary amides and sulphonamide, increases the likelihood of forming non-covalent interactions with various co-crystal coformers (CCF). Hence, making it a promising candidate for co-crystallization. The present manuscript describes the co-crystallization of GCM using FDA’s generally regarded as safe (GRAS) status CCF, hippuric acid (HA, Figure 1b), nicotinic acid (NA, Figure 1c), theophylline (TP, figure 1d) and succinic acid (SA, figure 1d) by solvent assisted grinding. These four nontoxic CCFs possess an inherent therapeutic profile and have high aqueous solubility and physical stability.Whereas HA is obtained from the urine of horses and its biological evaluation shows that is has limited antimicrobial activity at acidic pH

29

and can be used for urinary tract infections because of

30

its antibacterial action , NA, being vitamin B3 (niacin) has broad spectrum lipid modifying and anti31

artherosclerotic properties , TP, a xanthine derivative is useful in treatment of asthma due its bronchodilating effects and has diuretic effect in heart failure

32

and SA, a dicarboxylic acid, found in

small amounts in several fruits and vegetable, is an approved flavor enhancer and is an intermediate in the Krebs cycle.

33

The formation of co-crystals was confirmed using characterization analytical techniques like DSC, PXRD, FT-IR spectroscopy and ssNMR. Thecrystal structuresof the prepared co-crystals were determined using BIOVIA material studio software. The co-crystals have been studied for the improvement in solubility profile, anti-diabetic activity on streptozotocin (STZ) induced diabetic wistar rats. The pharmacokinetic parameters were also studied and compared to GCM.



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Figure 1: Chemical Structure of (a) GCM, (b) HA, (c) NA, (d) TP, (e) SA Experimental Materials GCM (≥99%, Abbott Healthcare Pvt. Ltd., Baddi, India), HA, NA and TP (Himedia Labs, India), SA (≥98%, Central Drug House Ltd, New Delhi, India), ethanol, acetone, HPLC grade methanol and HPLC grade acetonitrile (≥99.8%, E. Merck Ltd, Mumbai, India), were purchased and used as received. Designing of co-crystals The preliminary step for the synthesis of co-crystals is its strategically designing which involves analyzing the existing related crystal structures. This search is aided by depository of crystal structure present in the Cambridge Structural Database (CSD). The database of existing synthons of chloride, secondary amide and sulphonamide groups estimates the probability of these functional groups to form homo or hetero synthons with the complementary groups. This search was performed using ConQuest software (version 1.7) that provides the stats of existing organic crystal structures in Cambridge Structural Database (CSD, version 5.36, 2014). The query of hydrogen bonded complementary functional were built and searched for the hits. Based on the resulted hits, suitable CCFs were selected to prepare the co-crystals. Synthesis Four co-crystals, GCM-HA, GCM-NA, GCM-TP and GCM-SA were prepared via solvent assisted grinding. GCM-HA was prepared by grinding 1:1 stoichiometric ratio of GCM (98.8 mg) with HA (35.8 mg) in a pestle mortar by drop-wise addition of ethanol, at room temperature, until dry. Similarly, a 1:1 mixture of GCM (98.8 mg) with NA (24.62 mg), SA (23.62 mg) and TP (36.03 mg) was ground in pestle mortar, respectively, by drop-wise adding acetone at room temperature, until dry. The prepared samples were dried and kept in desiccator under controlled conditions. Attempts to isolate the suitable crystal were made using slow evaporation method from different solvents. Unfortunately, the crystals obtained were not of sufficient diffraction quality and size for single-crystal X-ray diffraction analysis. Identification and Characterization Differential Scanning Calorimetry (DSC) DSC thermograms of all the prepared samples were recorded on DSC Q20 (TA Instruments-Waters


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LLC, USA). The instrument was calibrated using the melting of pure indium (mp 156.6°C and ΔH of 28.45 Jg-1). Samples (3-5 mg) were taken in the aluminium pans and DSC curves were obtained under a nitrogen purge (flow rate of 50 mL per minute), at a heating rate of 10°C per minute in the temperature range of 50-250°C. The collated data was integrated using Universal Analysis 2000 software (TA Instruments Inc.). Powder X-ray Diffraction (PXRD) X-ray diffractometer PANalytical X'Pert Pro X-ray powder diffractometer (The Netherlands, Holland) was used to obtain PXRD diffraction patterns using Cu Kα radiation at 40 kV and 45 mA. The samples were analyzed from 5°-45° (2θ), angular range 5, fixed divergence slit at the scan rate of 0.00085°/sec with high resolution. The experimental data were analyzed using X’PERT high Score software. Fourier Transform Infrared Spectroscopy (FT-IR) A Spectrum RX I FT-IR spectrometer (Perkin Elmer, UK) was used to collect FT-IR spectra. The KBr pellet technique was used to prepare the samples and were analyzed over the range of 400–4000 cm

−1

−1

with 4 accumulative scans having resolution of 4 cm .

Solid-State NMR (ssNMR) The solid-state

13

C NMR of the samples was obtained from IISC, Bangalore, India using a Joel

Resonance JNM-CCX400II instrument and the spectra obtained were analyzed.The data was collected at 273 K with 1024 complex data points, acquisition time 29.1 s, contact time of 2 ms and relaxation delay of 5s for cross polarization.

13

C NMR spectra were referenced to the methylene

carbon of glycine (δglycine = 43.3 ppm) and then recalibrated to the TMS scale. Crystal structure determination The PXRD pattern of the prepared samples was used to determine the crystal structure of the cocrystals employing Reflux Plus module of Material Studio software (BIOVIA 7.0) as crystals of good quality were not obtained. The peaks in PXRD pattern at position 5°-40° 2θ were indexed using X-cell to obtain the crystal unit cell, which was further refined using Pawley refinement to optimize lattice constants and the cell parameters with minimum Rwp. The molecular structures of GCM and the respective CCF were drawn andoptimized using DMol3 module. These geometrically optimized structureswere imported into the refined empty unit cell (with lowest Rwp) and then together they were subjected to Powder Solve module using simulated annealing algorithm (10 cycles, 21000000 iterations in each cycle). The final structure solution was obtained by Rietveld refinement and geometry optimization. The similarity between the experimental and the simulated diffraction patterns was confirmed by the Rwp values.



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Evaluation Equilibrium Solubility Studies The equilibrium solubility study was done by shaking an excess amount of samples (approx 20 mg) in 34-37

10 ml phosphate buffer of pH 7.4

, in water bath shaker MSW-275 Macroscientific works, Delhi at

37°C at 200 rpm. The solubility of GCM and its co-crystals was determined at various time intervals for a period of 6 hours to ensure that the solution has reached equilibrium.The aliquots of slurry were filtered through 0.45μm membrane filter the concentration of GCM was determined by measuring the absorbance at 230 nm with Lambda 25 UV/VIS spectrometer. The residual material was then analyzed by FT-IR, after a period of 24 hours. Intrinsic Dissolution Studies This study was done using rotating disk dissolution test apparatus, DS 8000 (Lab India Analyticals) in phosphate buffer pH 7.4 at 37°C with 100 rpm for 1 hour. With the aid of die and punch and tablet compressing press, a pellet of all the samples was formed and attached to dissolution apparatus holder, which was then immersed in dissolution media. 10 ml of phosphate buffer pH 7.4 with replacement was withdrawn at different intervals of time and filtered through 0.45μm membrane filter. The concentration of GCM was determined by measuring absorbance at 230 nm with Lambda 25 UV/VIS spectrometer. Intrinsic dissolution rate was expressed in ± SD values. In Vivo Studies Male Wistar rats (150-250 g) were procured, kept in the Central Animal House and provided with standard pellet diet and water ad libtum. Diabetes was induced by a single dose of streptozotocin plus nicotinamide solution (45 mg/kg) prepared in citrate buffer (pH 4.4, 0.1 M) intraperitoneally.

11, 12

The

animals were diabetic within 48 hours after injection. The rats were divided into 7 groups, each group with n=6. For pharmacodynamic study of GCM, GCM-HA, GCM-NA, GCM-TP and GCM-SA (dose 3.6 mg/kg) were suspended in citrate buffer (pH 4.4, 0.1 M) and administered orally for 7 days. The plasma glucose level was checked in protein free plasma by enzymatic GOD- POD (glucose oxidase peroxidase) method after 7 days. Concentration of glucose was represented by mean ± SEM and pharmacodynamic data of co-crystals were compared with drug, non-diabetic control and diabetic control group. 13

Pharmacokinetic study

was performed on normal rats and sampling was done up to 24 hours at

different intervals. GCM, GCM-HA, GCM-NA, GCM-TP and GCM-SA (dose 3.6 mg/kg) were suspended in normal saline and a single dose was administered orally to each group. Plasma concentration at different intervals was analyzed by HPLC. The pharmacokinetic data of co-crystals were compared with GCM and control group. HPLC Studies The concentration of GCM was determined by Waters Alliance HPLC system which includes a waters 2996 Photodiode Array Detector and a 4.6 mm × 250 mm Hypersil Gold


TM

C18, 5 µm column (Thermo-

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Fisher Scientific). By spiking different concentrations of GCM in plasma, the calibration curve was plotted. All the samples of 10 µl injection size were run by isocratic mobile phase which consisted of acetonitrile: water (60:40) of pH 3 (pH was adjusted with orthophosphoric acid) with flow rate 0.8 ml/min. GCM peak was detected at 230 nm with retention time 8.1 min. Results and Discussion Design and Synthesis of Co-crystals Before starting with the synthesis of co-crystals, the CSD search was performed using ConQuest software. The query was built based upon the functional groups present in GCM, i.e.chlorine, secondary amide and sulphonamide groups. Searches were conducted on each functional group along with its hydrogen bonded complementary functional groups and the hits were obtained from the database showing the high probability to generate the multicomponent with these functional groups. Based upon this search (table 1, supplementary data), it was observed that the functional groups that are most predisposed to form hydrogen bond with chlorine of GCM are amines (88) and alcohols (48), with secondary amide of GCM are amides (721), amines (1304), whereas with sulphonamide group of GCM are amines (1106), amides (144) and alcohols (110). Hence, various CCF such as hippuric acid, glutamic acid, succinic acid, caffeine, theophylline, theobromine, nicotinic acid, isonicotinic acid, nicotinamide, isonicotinamide, malonic acid, glycolic acid, malic acid, cytosine, picolinic acid, urea, etc. were selected and tried for preparing co-crystals. Fortunately, co-crystals were obtained with HA, NA, TP and SA. These were further characterized and evaluated. Characterization of Co-crystals DSC DSC thermograms showed single, sharp melting endotherms corresponding toGCM-HA, GCM-NA, GCM-TP and GCM-SA(Figure 2, table 2). Table 2: Melting temperature (Tmax) and heat of fusion obtained from DSC of co-crystals Co-crystal

Tmax (°C)

Average heat of fusion (J/g)

GCM-HA

164.99

25.54

GCM-NA

148.11

21.10

GCM-TP

167.81

26.93

GCM-SA

135.93

26.59

They were substantially different from the melting endotherms of GCM (175. 37 °C) and respective CCF’s (HA: 190.08°C, NA: 237.39 °C, TP: 271. 54 °C and SA: 192.29 °C). Thisindicated the existence of a new crystalline phase. Since the melting endotherms are very sharp, this negates the existence of co-amorphous phase. However, the positionof melting endotherms i.e. lower than the individual components raised a questionwhether a new crystalline phase is a co-crystal or a eutectic mixture? This was resolved by the DSC thermograms of corresponding physical mixtures. Two different broad peaks were observed in each case, which refutes the formation of eutectic mixtures.



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Moreover,theformation of co-crystals wasfurther concluded by the significant changes in the characteristic peaks in spectroscopic methods.

Figure 2: DSC thermograms of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA PXRD Analysis PXRD pattern is one of the prolific characterization tools

38

to confirm the formation of the new solid

phase as suggested by DSC, as it is considered to be fingerprint of the crystal structure.The diffraction patterns of GCM, all the CCF and four co-crystals are represented in figure 3. The noteworthy modifications in the diffraction pattern(table 3) not only infer the formation of new a solid crystalline phase but also bring one step closer to the formation of co-crystals rather than eutectic mixtures. Had it been eutectic mixtures, there would have been little change in the diffraction data in comparisonto the individual components.But, to differentiate between eutectic mixtures and co-crystals, only PXRD data is not sufficient. However, methods like FT-IR and ssNMR aids in further 39

confirmation of formation of co-crystals. There can be a possibility of generation of new peaks or disappearance of old peaks in PXRD pattern because of polymorphic changes. To rule out this 20

possibility, PXRD pattern of known polymoprhs/solvates (figure S1, supplementary data) were compared and found to be different from that of co-crystals. Hence, ruling out the polymorphic transition. Had it been coamphorous phase, there would have been absence of characteristic crystalline peaks in diffraction pattern of sample. Besides this, to validate the formation of co-crystals by solvent assisted grinding other cocrystallization technique such as slurry crystallization was used. The co-crystals were obtained by adding equimolar quantities of drug and respective CCF in 10 ml of ethanol and stirred for 2 hours on magnetic stirrer. The solvent was evaporated under vacuum. The solid obtained wasdried and stored in airtight vials in a desiccator. This was further characterized using DSC and PXRD. The DSC thermograms and diffraction patterns of the co-crystals obtained through the slurry crystallization and


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liquid-assisted grinding matched in their peak positions (figure S2, S3 supplementary data). Thus, validating the formation of co-crystals. Table 3: Changes observed in the diffraction pattern of co-crystals

Co-crystal

New Peaks

Peaks Disappeared (D)/

Shift in peak position

Appeared

Merged (M)

of GCM to

Shift in peak position of CCF to

GCM-HA

16.87, 18.77,

M: 21.98 (HA) with 21.53

11.11, 11.93, 16.42,

20.98, 22.49,

(GCM) to 21.82

19.16, 19.67, 21.20,

23.70

13.22

23.08, 23.39, 24.81, 28.26

GCM-NA

14.7, 16.21,

D: 21.3, 23.50, 24.93

10.86, 11.71, 12.22,

20.73,

M: 20.30, 27.21 and

15.23, 15.89, 18.55,

22.85and

27.93 (NA) with 20.39 and

18.91, 19.42°, 20.96,

24.58

27.99 (GCM) to 20.32°

21.88, 25.12, 28.05

29.32

and 27.66 GCM-TP

16.28, 24.16,

M: 12.62 and 25.86 (TP)

10.94, 11.80, 16.74,

29.02

with 12.62 and 25.47

23.22, 24.66, 27.76

14.46

(GCM) to 12.74 and 25.76 GCM-SA

14.75, 16.20,

D: 23.49

10.83, 11.70, 12.21,

20.69, 21.87,

M: 26.62 (SA) with 26.65

18.54, 18.91, 19.41,

24.56, 26.09

(GCM) to 26.58

20.94, 21.37, 22.83


19.92


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Figure 3: Diffraction patterns of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA where * represents new peaks and # represents shift in peaks

FT-IR Analysis The formation of co-crystals was further analyzed by change in the vibrational frequencies by infrared spectroscopy. The changes in the vibrational frequencies of the major functional groups of both GCM and the respective CCFsare due to the formation of hydrogen bonding interaction between them.These shifts not only confirm the formation of new crystalline phase but also confirm the position of hydrogen bonding and the functional groups involved. The FT-IR spectrum of GCM-HA showed shifts in the peaks of -NH stretch of sulfamoyl group of GCM from 3364 cm

−1

and 3315 cm

of HA shifted to 1742 cm

−1

−1

to 3358 cm

from 1749 cm

−1

−1

−1

and 3312 cm , respectively,while peaks of -CO stretch

implying interaction in these two regions of GCM-HA. In

case of spectrum of GCM-NA, considerable shift was observed from 3364 cm stretch of sulfamoyl group of GCM) to 3355 cm stretch of NA shifted from 1415 cm

−1

−1

−1

−1

and 3315 cm (-NH

−1

and 3310 cm , respectively, while -C=N and -C-N

and 1304 cm

−1

to 1411 cm

−1

−1

and 1300 cm , correspondingly,

inferring formation of hydrogen bond in these regions of GCM-NA. Similarly, broadening and shifting in peak of -NH of TP from 3121 cm

−1

to 3118 cm

−1

while 1342 cm

−1


and 1156 cm

−1

(-SO2 stretch) of

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GCM to 1339 cm

−1

−1

and 1153 cm , respectively, concluded the interaction in GCM-TP. Likewise in −1

−1

case of GCM-SA, shifts in the hydroxyl region of SA (3209 cm to 3200cm ) and sulfamoyl region (SO2 stretch: 1342 cm

−1

and 1156 cm

−1

to 1336 cm

−1

−1

and 1149 cm ) implied the interaction between

these two regions (figure 4).

Figure 4: FT-IR spectra of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA

ssNMR Analysis This analytical tool provides valuable information regarding the existence of co-crystals asis it provides information pertaining to the chemical environment of organic nuclei and issensitive to 40

hydrogen bonding. The ssNMR patterns of GCM, all the CCF and four co-crystals are represented in figure 5. Perturbations at carbon atom 16 of GCM and carbon atom 24 of HA, leads to shift in it position from158.20 ppm and 170.75 ppm to 157.82 ppm and 171.36 ppm, respectively, in GCM-HA. This substantiates the existence of hydrogen bonding between the carbon atom of carboxylic acid of HA with either of the nitrogen atoms (N2 and N3) of the sulfonylurea group of GCM. Likewise in GCM-NA, variations are also observed in C16 of GCM from158.20 ppm to 157.11 ppm and in carbon atoms adjacent to nitrogen of pyridine ring (Naromatic) (C26 and C27) from 151.53 ppm to 152.08 ppm. This supports for the hydrogen bond between Naromaticof NA with either N2 or N3 of the sulfonylurea group of GCM. Involvement of N3 in hydrogen bonding was ruled out, as there was no change in peak at 51.46 ppm corresponding to carbon atom 17 of GCM. This credits for hydrogen bonding between amide group (N2H2A) of GCM and carboxyl group of HA forming N-H⋯O synthon in GCM-HA and



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between amide group (N2H2a) of GCM and Naromaticof NA forming N-H⋯Naromaticsynthon, respectively. Similarly, peak C13 of GCM at 140.33 ppm and the peaks at 140.93 ppm and 155.12 ppm corresponding to carbon atoms adjacent to Naromaticin the imidazole ring (C25 and C28) of TP, shifted to 140.87 ppm, 140.87 ppm and155.78 ppm, respectively. The high intensity peak at 140.87 ppm is probably due to superimposition of peak of GCM at C13 and C28of TP. This indicates the hydrogen bond between the sulfonyl group (SO) of GCM andNaromaticof imidazole ring of TP, resulting in NH⋯Naromaticsynthon. In case of GCM-SA shift in peak of C13 of GCM from 140.33 ppm to 140.76 ppm and peak corresponding to carbon atoms of carboxylic group of SA (C24 and C27) from 180.50 ppm to 181.12 ppm. This illustrates the involvement of sulfonyl group (SO) of GCM and acidic hydroxyl group of SA in hydrogen bonding forming O-H⋯O synthon. These changes in the position of major peaks in ssNMR spectra gives the evidence for the atoms involved in hydrogen bonding in the co-crystals. It also corroborates with PXRD and FT-IR analysis. On conglomerating all the spectroscopic data, the dilemma between the co-crystals and eutectic mixtures was solved. And the answer to this is co-crystals, as the formation of adhesive interactions was obvious.

Figure 5: ssNMR patterns of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA where * represents shift in peaks


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Crystal structure determination The non-covalent derivatives prepared were further confirmed to be co-crystals by the determination of their crystal structures. Several attempts were made to recrystallize the prepared co-crystals. However, a single crystal of suitable size or stability for single crystal X-ray diffraction was not obtained. This may be due to difference in the solubility of the individual components of the co-crystal in the solvent. Auspiciously, the development of powder diffraction technique and structure solving algorithms makes it possible to 41

determine the crystal structure directly from PXRD pattern.

As discussed in experimental section the

crystal structure was determined for all the co-crystals using powder diffraction pattern. The correctness of structure is assessed by the agreement between the experimental PXRD pattern and the simulated (Rietveld fit profile) diffraction pattern obtained from the determined structure. The Rwp values are the measure of similarity between the experimental and simulated profile and the obtained 42, 43

Rwp for all the co-crystals is acceptable (table 4).

The simulated PXRD pattern of co-crystals is

quite similar to the experimental pattern. The similarity between the two is explained by the low values of Rp and Rwp(figure 11). The structure determined from Powder Solve calculations is further in concordance with FT-IR and ssNMR spectral data. Crystallographic parameters of all the co-crystals (CCDC no 1559921-1559924) are given in table 4. Table 4: Crystallographic parameters of co-crystals Parameters

GCM-HA

GCM-NA

GCM-TP

GCM-SA

Chemical

C23H28ClN305S;

C23H28ClN305S;

C23H28ClN305S;

C23H28ClN305S;

formula

C9H9NO3

C6H5NO2

C7H8N4O2

C4H6O4

Stoichiometry

1:1

1:1

1:1

1:1

Room

Room

Room

Room

temperature

temperature

temperature

temperature

(25°C)

(25°C)

(25°C)

(25°C)

Crystal system

Monoclinic

Triclinic

Triclinic

Triclinic

Space group

P21/a

P-1

P-1

P-1

a (Å)

16.67

14.44

14.09

15.84

b (Å)

30.27

7.72

11.17

9.10

c (Å)

9.59

5.67

8.87

6.67

α (deg)

90

91.28

102.37

71.59

(deg)

109.64

95.57

98.40

92.81

(deg)

90

91.79

96.07

91.89

Z

4

2

2

2

Vol. (Å3)

4558.1

628.73

1334.64

911.29

2θ range

5°-45°

5°-45°

5°-45°

5°-45°

Rwp(%)

10.82

16.87

9.68

13.93

Temperature (K)



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Page 14 of 33

As GCM possesses both hydrogen bond donor (–NH) and acceptor (–CO, –SO2 and Cl) groups, at the microscopic level, there is competition of synthons that can be formed, and making it a potential candidate for co-crystallization. The crystal lattice of pure GCM reveals the existence of ring motif between sulfonyl NH and amide C=O groups and an additional intermolecular interaction 22

(N1H1A⋯O5) as shown in figure 6.

But, the incorporation of the CCF competedwith intermolecular

interactions present in pure GCM and resulted in the formation of new synthons.

Figure 6: Hydrogen bonded interaction present in pure GCM GCM-HA crystallizes in the monoclinic system with the space group P21/a, with one molecule of GCM and one molecule of HA in an asymmetric unit (Figure 7a). In the crystal lattice, both the components are aligned at an angle of 63.97°(Figure 7b). One molecule of GCM is connected to two other molecules of GCM via homomeric interactions, which is formed between hydrogen atom of -NH of carbamoyl group (adjacent to benzene ring) and oxygen atom of sulphamoyl group (N1H1A⋯O3) at a distance of 2.156 Å. Besides this, a heterosynthon is formed through the hydrogen bond between – NH of sulphamoyl group of GCM and -CO of carboxylic group of HA (N2H2A⋯O7) with distance 2.079 Å (figure 7c). This implies with addition of HA in crystal lattice of pure GCM, intermolecular interactions of pure GCM were disrupted and established a new N1H1A⋯O3 interaction.The packing pattern of GCM-HA is such that HA molecules areoriented approximately perpendicular to the chain of GCM molecules connected throughN2H2A⋯O7 (figure 7d).


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Figure 7: GCM-HA (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and HA (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-HA co-crystal, (d) crystal packing pattern where green and red colour represents GCM and HA molecules, respectively The structure of GCM-NA crystallizes in triclinic space group P-1. Asymmetric unit consists of one molecule each of GCM and NA with their planes subtended at an angle of 83.97° (figure 8a and 8b). Two heterosynthons between adjacent GCM molecules are formed, wherein; one is between -NH of carbomyl group (adjacent to cyclohexyl ring) and oxygen atom of sulphamoyl group (N3H3A⋯O4) and another one is between -NH of sulphamoyl group and oxygen atom of methoxy group forming motif (N2H2A⋯O2). The distance of these heterosynthons are 1.678 Å and 1.949 Å, respectively. Moreover, one heteromeric interaction is formed between -NH of sulphamoyl group of GCM and pyridine N (Naromatic) of NA (N2H2A⋯N4)with distance 1.490 Å (figure 8c).Intermolecular interactions of pure GCM have rearranged to form new heterosynthons of sulphonamide with, amide, methoxy group and aromatic nitrogen in the co-crystal.The 3-dimensional view of GCM-NA shows rippled bilayer of GCM and perpendicular stacks of NA molecules bridged through N2H2A⋯N4(figure 8d).



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Figure 8: GCM-NA (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and NA (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-NA co-crystal, (d) crystal packing pattern where green and pink colour represents GCM and NA molecules, respectively GCM-TP crystallizes in triclinic P-1 space group. One molecule each of GCM and TP is present in its asymmetric unit in such a way that they subtend an angle of 14.39° between their planes (figure 9a and 9b). Rearranging the interactions present in pure GCMresultsinto the formation of new ring motifs formed between sulphamoyl, amide and methoxy groups of GCM. Two homomeric interactions are formed wherein;-NH of carbamoyl group (adjacent to benzene ring) shows bifurcated bonding with oxygen atom of sulphamoyl group (N1H1A⋯O4) as well as with nitrogen atom of carbomyl group (adjacent to cyclohexyl ring) (N1H1A⋯N3), with distance of 1.963 Å and 2.577 Å, correspondingly. The third homomeric interactionis formed between-NH of carbomyl group (adjacent to cyclohexyl ring) and oxygen atom of methoxy group (N3H3A⋯O2) with distance 1.964 Å. -NH of imidazole ring of TP is interacting with oxygen atom of sulphamoyl group of GCM (N6H6A⋯O3, distance 1.973 Å), resulting in the generation of a new synthon(figure 9c). On viewing along a-axis, GCM molecules


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seems to exist indimer, which is linked to TP molecules, positionedat the opposite corners. The discrete unit of these four molecules is stabilized via weak non-covalent forces and thus forming the 3-dimensional network as shown in figure 9d.

Figure 9: GCM-TP (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and TP (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-TP co-crystal, (d) crystal packing pattern along a axis, where green and brown colour represents GCM and TP molecules, respectively

The co-crystal, GCM-SA exists in triclinic unit cell with P-1 space group, consisting of two independent molecules of GCM and SA that are oriented at an angle of 55.50° in an asymmetric unit (figure 10a and 10b). The dimer of GCM is formed via the bond between -NH of sulphamoyl group and chloride atom attached to benzene ring (N2H2A⋯Cl1, 2.028 Å). Another dimer of SA is formed through hydrogen bond between carboxylic -OH and -C=O, forming O9H9A⋯O7 homosynthon (1.543 Å). A heterosynthon is formed which shows hydrogen bonding between carboxylic -OH of SA and oxygen atom of sulphamoyl group of GCM (O6H6A⋯O3) with distance 1.511 Å (figure 10c), byreplacing the N-H⋯O interactions present in pure GCM. When viewed from c-axis, parallel GCM and SA layers are arranged in alternate fashion wherein;bilayer of dimers of SA is sandwiched betweenbilayer of dimers of GCM (figure 10d).



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 10: GCM-SA (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and SA (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-SA co-crystal, (d) crystal packing pattern along c axis where green and blue colour represents GCM and HA molecules, respectively

Figure 11: X-ray intensity as a function of 2θ. The simulated (best Rietveld fit profile) pattern, experimental pattern, observed reflections and the difference between simulated and experimental profiles of co-crystals


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Evaluation of Co-crystals The objective of co-crystallization was to improve the solubility and dissolution of GCM making it pharmaceutically more acceptable. This was accomplished as the co-crystals of GCM possess not only have improved solubility and dissolution but also have valuable increase in biopharmaceutical parameters. Equilibrium Solubility and Intrinsic Dissolution Study How much’ and ‘how fast’ a solute dissolves in a given solvent is measured by solubility and dissolution rate, respectively. The quantitative information on the dissolution rate is obtained by intrinsic dissolution rate (IDR) experiments. The solubility and IDR of GCM and its co-crystals were determined in phosphate buffer pH 7.4, and the results are graphically represented in figure 11. The residual material after 6 and 24 hours of the solubility study were analyzed by FT-IR analysis. (Figure S4supplementary data) to investigate any change in the co-crystals. The FT-IR analysis revealed that all the co-crystals were intact up to 6 hours. After 24 hours, the FT-IR pattern of cocrystal resembles to that of drug. Thus, inferring the conversion of co-crystals to drug after 24 hours. 2

IDR (in mcg/cm /min ± SD) of GCM-HA, GCM-NA, GCM-TP and GCM-SA were found to be 93 ± 0.1, 129.22 ± 0.2, 65.52 ± 0.1 and 155.76 ± 0.2, respectively. The results depicts the maximum increase in solubility and IDR of GCM-SA to almost 3.5 times, GCM-NA to 3 times, GCM-HA to 2.2 times and 2

GCM-TP to 1.5 times the solubility and IDR of pure GCM (10.1 mcg/ml; 41.8 ± 0.1 mcg/cm /min). This is attributed to strength of hydrogen bonding between the GCM and the corresponding CCF, melting point and solubility of CCF. The highest solubility of GCM-SA is attributed to the fact that SA has highest solubility and lowest melting point.

Figure 11: (a) Equilibrium Solubility after 6 hours and (b) Intrinsic dissolution profile of GCM, GCM-HA, GCM-NA, GCM-TP and GCM-SA

In Vivo Studies We hypothesized that the improvement in solubility and IDR of GCM would lead to improved biopharmaceutical parameters of GCM co-crystals. This was supported by pharmacokinetic and pharmacodynamic evaluation. More of GCM will be available in solution form with increase in its solubility. This directly impacts the absorption of the drug in the body, thereby influencing the bioavailability. To analyze the same, pharmacokinetic evaluation was carried out in Wistar rats and all the pharmacokinetic parameters are represented in table 5. The maximum concentration (Cmax) achieved was approximately 2.1 times for GCM-HA, 2.8 times for GCM-NA, 1.6 times for GCM-TP and 3.5 times for GCM-SA as compared to pure GCM (figure 12a). The time taken to achieve



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maximum concentration (Tmax) was reduced to 180 minutes for GCM-HA and GCM-TP and to 150 minutes for GCM-NA and GCM-SA as compared to 240 minutes for GCM. This signifies improvement in both rate of absorption as well as extent of absorption signifying improvement in bioavailability. This will lead to quick therapeutic response at lower dose. Table 5: Pharmacokinetic parameters of GCM, GCM-HA, GCM-NA, GCM-TP and GCM-SA Cmax(mcg/ml)

Tmax

AUC

(min)

(mcg/ml min)

GCM

1.45

240

2242.54

GCM-HA

3.08

180

4484.23

GCM-NA

4.18

150

6501.89

GCM-TP

2.28

180

3363.79

GCM-SA

5.08

150

7174.45

Figure 12: (a) Pharmacokinetic profile and (b) Percentage of glucose reduction of GCM-HA, GCM-NA, GCM-TP and GCM-SA in comparison to GCM

Tailoring these biopharmaceutical parameters of GCM will affects its anti-diabetic activity, which was measured as percentage of glucose reduction. The maximum percentage of glucose reduction after 4 hours (figure12b) was reached up to 69.57% for GCM-HA, 78.46% for GCM-NA, 53.68% for GCM-TP and 93.68% for GCM-SA as compared to maximum reduction of 40.68% for GCM. These remarkable enhancements in anti-diabetic activity clearly prove the advantages of co-crystals in comparison to GCM in achieving the desired pharmacological response.

Conclusions Modifying the physical and chemical parameters of a crystalline solid by incorporating a pharmaceutically acceptable molecules (CCF) and forming a new crystal lattice is a viableprospective for pharmaceuticals. To overcome the limitations due to the poor solubility of GCM, its co-crystals were prepared using nontoxic therapeutically useful CCF. The improvement in the solubility, intrinsic dissolution rate and pharmacokinetic parameters is due to the formation of new hydrogen bond interactions between -NH and oxygen atom of sulphamoyl group of GCM with carboxylic -C=O, aromatic N (Naromatic), imidazolic -NH and carboxylic -OH of the CCF. Associated Content


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Supporting Information: Supporting information available for this manuscript contains: Table 1: CSD stats for potential functional groups of GCM. Figure S1: X-ray powder diffractograms of (a) I, (b) II, solvates (c) pentanol, (d) toluene. Figure S2: DSC thermograms of co-crystals obtained through the slurry crystallization. Figure S3: PXRD obtained experimentally from (a) solvent assisted grinding, (b) slurry crystallization, (c) after removal of Kα-2 peaks used as input file and (d) simulated from the determined crystal structure. Figure S4: FT-IR spectra of the residual material after (a) 6 hours and (b) 24 hours of the solubility study. Accession Codes: CCDC number 1559921-1559924 contains the supplementary crystallographic data for this manuscript. Acknowledgement The authors are greatly thankful to the Council of Scientific & Industrial Research (CSIR), New Delhi (02(0039)/11/EMR-II) and University Grants Commission (UGC), New Delhi (F.4-1/2006(BSR)/594/2007 dated 03-05-2013) for the financial assistance. References 1. Pearson, J.G. Am. J. Med.1985, 79, 67–71. 2. Neuvonen, P.J.; Kivisto, K.T. Br. J. Clin. Pharmacol.1991, 32, 215–220. 3. Löbenberg, R.; Amidon, G.L. Eur. J. Pharm. Biopharm. 2000, 50, 3–12. 4. Löbenberg, R.; Krämer, J.; Shah, V.P.; Amidon, G.L.; Dressman, J.B. Pharm. Res. 2000, 17, 439–444. 5. Vogelpoel, H.; Welink, J.; Amidon, G.L.; Junginger, H.E.; Midha, K.K.; Möller, H.; Olling, M.; Shah, V.P.; Barends, D.M. J. Pharm. Sci.2004, 93,1945–1956. 6. Esclusa-Díaz, M.T.; Torres-Labandeira, J.J.; Kata, M.; Vila-Jato, J.L. Eur. J. Pharm. Sci. 1994, 1, 291–296. 7. Rupp, W.; Badian, M.; Heptner, W.; Malerczyk, V. Biopharm. Pharmacokinet. Eur. Congr.1984, 2, 413–420. 8. Valleri, M.; Mura, P.; Maestrelli, F.; Cirri, M.; Ballerini, R. Drug Dev. Ind. Pharm.2004, 30, 525–534. 9. Tashtoush, B.; Al-qashi, Z.S.; Najib, N.M. Drug Dev. Ind. Pharm.2004, 30, 601–607. 10. Singh, J. Drug Dev. Ind. Pharm. 1986, 12, 851–866. 11. Hassan,

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15. Zimmet, P. J. Intern. Med.2000, 247, 301-310. 16. Amos, A.F., McCarty, D.J.; Zimmet, P. Diabetic Med.1997, 14, S1-S85. 17. Cohen, A.; Horton, E.S. Curr Med Res Opin.2007, 23, 905-17. 18. Desiraju, G. R. In Crystal Engineering. The Design of Organic Solids; Elsevier, Amsterdam, 1989. 19. El-Massik, M.A.; Darwish, I.A.; Hassan, E.E.; El-Khordagui, L.K. Int. J. Pharm.1996, 140, 6976. 20. Iwata,M.; Ueda, H. Drug Dev. Ind. Pharm.1996, 22 , 1161-1165. 21. Chauhan, B.; Shimpi, S.; Paradkar, A. Eur. J. Pharm. Sci. 2005, 26, 219–230. 22. Betageri,G.V.; Makarla, K.R. Int. J. Pharm.1995, 126, 155-160. 23. Budiman, A.; Nurlatifah, E.; Amin, S. Int. J. Curr. Pharm. Rev. Res. 2016, 7, 248-250. 24. Shan, N.; Zaworotko, M. J. Drug Discov. Today. 2008, 13, 440–6. 25. Lara-Ochoa, F.; G. ESPINOSA-PÉREZ. Supramol. Chem. 2007, 19, 553−557. 26. Duggirala, N.K.; Perry, M.L.; AlmarssonÖrn.; Zaworotko, M.J. Chem.Commun. 2016, 52, 640655. 27. Blagden, N.; Matas, M. de; Gavan, P.T.; York, P. Adv. Drug Deliv. Rev. 2007, 59, 617–630 28. Cherkuvada, S.; Guru row, T.N. Cryst. Growth Des. 2014, 14, 4187-4198. 29. Hamilton-Miller, J.M.; Brumfitt, W. Invest Urol. 1977, 14, 287-291. 30. Bodel, T.P.; Cotran, R.; Kass, E.H. J. Lab. Clin. Med. 1959, 54, 881-888. 31. Al-Mohaissen, M.A; Pun, S.C.; Frohlich, J.J. Mini Rev. Med. Chem. 2010, 10, 204-217. 32. Weinberger, M. J. Allergy Clin. Immunol. 1984, 73, 525-540. 33. Deshpande, S.S. In Handbook of Food Toxicology; Marcel Dekker Inc. 2002, New York, 2002, 263. 34. El-Massik, M.A.; Darwish, I.A.; Hassan, E.E.; El-Khordagui, L.K. Int. J. Pharm.1996, 140, 6976. 35. Iwata,M.; Ueda, H. Drug Dev. Ind. Pharm.1996, 22 , 1161-1165. 36. Chauhan, B.; Shimpi, S.; Paradkar, A. Eur. J. Pharm. Sci. 2005, 26, 219–230. 37. Betageri,G.V.; Makarla, K.R. Int. J. Pharm.1995, 126, 155-160. 38. Sanphui, P.; Babu, N.J.; Nangia, A.; Cryst. Growth Des. 2013, 13, 2208-2219. 39. Stoler, E.; Warner, J.C.;Molecules, 2015, 20, 14833-14848. 40. Vogt, F.G.; Clawson, J.S.; Strohmeier, M.; Edwards, A.J.; Pham, T.N.; Watson, S.A. Cryst. Growth Des. 2009, 9, 921–937. 41. Li, P.; Chu, Y.; Wang, L.; Wenslow Jr, R.M.; Yu, K.; Zhang, H.; Deng, Z. CrystEngComm. 2014, 16, 3141-3147. 42. Elizabé, L.; Kariuki, B.M.; Harris, K.D.M; Tremayne, M.; Epple, M.; Thomas, J.M. J. Phys. Chem. B. 1997,101,8827–8831. 43. Kariuki, B.M.; Zin, D.M.S.; Tremayne, M.; Harris, K.D.M. Chem. Mater. 1996, 8, 565–569.


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For Table of Contents Use Only Crystal Engineering: A Remedy to Tailor the Biopharmaceutical Aspects of Glibenclamide Parnika Goyal, Dimpy Rani, Renu Chadha* University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh-160014, INDIA

Synopsis Cocrystallization provides a remedy for improvement biopharmaceutical aspects GCM, a poorly soluble drug. Exploiting this technique, the new cocrystals formed, GCM-HA, GCM-NA, GCM-TP and GCM-SA, showed noteworthy improvement in solubility, IDR and efficacy in comparison to GCM.



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Figure 1: Chemical Structure of (a) GCM, (b) HA, (c) NA, (d) TP, (e) SA

Table 2: Melting temperature (Tmax) and heat of fusion obtained from DSC of co-crystals Co-crystal GCM-HA GCM-NA GCM-TP GCM-SA

Tmax (°C) 164.99 148.11 167.81 135.93

Average heat of fusion (J/g) 25.54 21.10 26.93 26.59

Figure 2: DSC thermograms of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA

Table 3: Changes observed in the diffraction pattern of co-crystals


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Co-crystal

New Peaks Appeared

Peaks Disappeared (D)/ Merged (M)

Shift in peak position of GCM to

GCM-HA

16.87, 18.77, 20.98, 22.49, 23.70

M: 21.98 (HA) with 21.53 (GCM) to 21.82

GCM-NA

14.7, 16.21, 20.73, 22.85and 24.58

GCM-TP

16.28, 24.16, 29.02

GCM-SA

14.75, 16.20, 20.69, 21.87, 24.56, 26.09

D: 21.3, 23.50, 24.93 M: 20.30, 27.21 and 27.93 (NA) with 20.39 and 27.99 (GCM) to 20.32° and 27.66 M: 12.62 and 25.86 (TP) with 12.62 and 25.47 (GCM) to 12.74 and 25.76 D: 23.49 M: 26.62 (SA) with 26.65 (GCM) to 26.58

11.11, 11.93, 16.42, 19.16, 19.67, 21.20, 23.08, 23.39, 24.81, 28.26 10.86, 11.71, 12.22, 15.23, 15.89, 18.55, 18.91, 19.42°, 20.96, 21.88, 25.12, 28.05

Shift in peak position of CCF to 13.22

29.32

10.94, 11.80, 16.74, 23.22, 24.66, 27.76

14.46

10.83, 11.70, 12.21, 18.54, 18.91, 19.41, 20.94, 21.37, 22.83

19.92

Figure 3: Diffraction patterns of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA where * represents new peaks and # represents shift in peaks



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Figure 4: FT-IR spectra of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA


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Figure 5: ssNMR patterns of GCM, all the CCF, GCM-HA, GCM-NA, GCM-TP and GCM-SA where * represents shift in peaks Table 4: Crystallographic parameters of co-crystals Parameters

GCM-HA

GCM-NA

GCM-TP

GCM-SA

Chemical

C23H28ClN305S;

C23H28ClN305S;

C23H28ClN305S;

C23H28ClN305S;

formula

C9H9NO3

C6H5NO2

C7H8N4O2

C4H6O4

Stoichiometry

1:1

1:1

1:1

1:1

Room

Room

Room

Room

temperature

temperature

temperature

temperature

(25°C)

(25°C)

(25°C)

(25°C)

Crystal system

Monoclinic

Triclinic

Triclinic

Triclinic

Space group

P21/a

P-1

P-1

P-1

a (Å)

16.67

14.44

14.09

15.84

b (Å)

30.27

7.72

11.17

9.10

c (Å)

9.59

5.67

8.87

6.67

α (deg)

90

91.28

102.37

71.59

β (deg)

109.64

95.57

98.40

92.81

γ (deg)

90

91.79

96.07

91.89

Z

4

2

2

2

Temperature (K)



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Vol. (Å3)

4558.1

628.73

1334.64

911.29

2θ range

5°-45°

5°-45°

5°-45°

5°-45°

Rwp(%)

10.82

16.87

9.68

13.93

Figure 6: Hydrogen bonded interaction present in pure GCM


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Figure 7: GCM-HA (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and HA (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-HA co-crystal, (d) crystal packing pattern where green and red colour represents GCM and HA molecules, respectively

Figure 8: GCM-NA (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and NA (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-NA co-crystal, (d) crystal packing pattern where green and pink colour represents GCM and NA molecules, respectively



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Figure 9: GCM-TP (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and TP (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-TP co-crystal, (d) crystal packing pattern along a axis, where green and brown colour represents GCM and TP molecules, respectively


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Figure 10: GCM-SA (a) ORTEP diagram, (b) alignment of the planes of GCM (pink) and SA (light purple) in asymmetric unit, (c) Hydrogen bonded interaction in GCM-SA co-crystal, (d) crystal packing pattern along c axis where green and blue colour represents GCM and HA molecules, respectively

Figure 11: X-ray intensity as a function of 2θ. The simulated (best Rietveld fit profile) pattern, experimental pattern, observed reflections and the difference between simulated and experimental profiles of co-crystals



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Figure 11: (a) Equilibrium Solubility after 6 hours and (b) Intrinsic dissolution profile of GCM, GCM-HA, GCM-NA, GCM-TP and GCM-SA Table 5: Pharmacokinetic parameters of GCM, GCM-HA, GCM-NA, GCM-TP and GCM-SA Cmax(mcg/ml)

Tmax

AUC

(min)

(mcg/ml min)

GCM

1.45

240

2242.54

GCM-HA

3.08

180

4484.23

GCM-NA

4.18

150

6501.89

GCM-TP

2.28

180

3363.79

GCM-SA

5.08

150

7174.45

Figure 12: (a) Pharmacokinetic profile and (b) Percentage of glucose reduction of GCM-HA, GCM-NA, GCM-TP and GCM-SA in comparison to GCM


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For Table of Contents Use Only

Crystal Engineering: A Remedy to Tailor the Biopharmaceutical Aspects of Glibenclamide Parnika Goyal, Dimpy Rani, Renu Chadha*

Synopsis Cocrystallization provides a remedy for improvement biopharmaceutical aspects GCM, a poorly soluble drug. Exploiting this technique, the new cocrystals formed, GCM-HA, GCM-NA, GCM-TP and GCM-SA, showed noteworthy improvement in solubility, IDR and efficacy in comparison to GCM.


Crystal Engineering: A Remedy To Tailor the Biopharmaceutical

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