RESEARCH PAPER

Supramolecular Cocrysta ls of Gl ic laz ide: Synthes is ,Characterization and Evaluation

Renu Chadha1 & Dimpy Rani1 & Parnika Goyal1

Received: 25 September 2016 /Accepted: 28 November 2016 /Published online: 29 December 2016# Springer Science+Business Media New York 2016

ABSTRACTPurpose To prepare the supramolecular cocrystals ofgliclazide (GL, a BCS class II drug molecule) via mechano-chemical route, with the goal of improving physicochemicaland biopharmaceutical properties.Methods Two cocrystals of GL with GRAS status coformers,sebacic acid (GL-SB; 1:1) and α-hydroxyacetic acid (GL-HA;1:1) were screened out using liquid assisted grinding. Theprepared cocrystals were characterized using thermal and an-alytical techniques followed by evaluation of antidiabetic ac-tivity and pharmacokinetic parameters.Results The generation of new, single and pure crystal formswas characterized by DSC and PXRD. The crystal structuredetermination from PXRD revealed the existence of bothcocrystals in triclinic (P-1) crystal system. The hydrogen bond-ed network, determined by material studio was well supportedby shifts in FTIR and SSNMR. Both the new solid formsdisplayed improved solubility, IDR, antidiabetic activity andpharmacokinetic parameters as compared to GL.Conclusions The improvement in these physicochemical andbiopharmaceutical properties corroborated the fact that thesupramolecular cocrystallization may be useful in the devel-opment of pharmaceutical crystalline materials with interest-ing network and properties.

KEY WORDS biopharmaceutical . cocrystals . crystalstructure . gliclazide . physicochemical

ABBREVIATIONSANOVA Analysis of varianceAPI Active pharmaceutical ingredientDSC Differential scanning calorimetryFTIR Fourier transform infraredGL GliclazideGOD-POD Glucose oxidase peroxidaseGRAS Generally regarded as safeHA α-hydroxyacetic acidIDR Intrinsic dissolution rateLAG Liquid assisted grindingPXRD Powder X-ray diffractionSB Sebacic acidSEM Standard error meanSSNMR Solid-state nuclear magnetic rasonanceUSP United states pharmacopoeia

INTRODUCTION

Supramolecular interactions lie at the very heart of crystallinepharmaceutical solids and are fundamental in controlling thesolid forms and their properties (1). Designing of thesupermolecules by utilizing andmodifying the supramolecularinteractions has emerged as a new frontier in the research (2).The basic tenet of building the supramolecular assembly isdirectional molecular recognition, which is ‘the strategy bywhich a molecule bears supramolecular functions’ (3).Supermolecules accounts for the isotropic and anisotropicnon covalent molecular interactions that are weak and revers-ible in nature such as hydrogen bonds, van der Waals forces,metal coordination or pi-pi interactions. The characteristicproperties of supermolecules are not the outcome of additivebut of cooperative interactions and thus, are superior anddifferent than the parent molecules (1,4). The concept ofsupermolecules has been proved a boon to the pharma worldwhich can be sensed by the blooming of supramolecular

Electronic supplementary material The online version of this article(doi:10.1007/s11095-016-2075-1) contains supplementary material, which isavailable to authorized users.

* Renu Chadharenukchadha@rediffmail.com

1 University Institute of Pharmaceutical Sciences, Panjab University,Chandigarh 160014, India

Pharm Res (2017) 34:552–563DOI 10.1007/s11095-016-2075-1

therapeutics. In the recent era, cocrystals, the supramolecularstructures, are thriving in pharmaceutical industries becauseof the lucrative opportunities offered by it. Pharmaceuticalcocrystals are the homogeneous solid crystalline complexesof two or more neutral molecular constituents (in which oneis API), bound through noncovalent interactions in the crystallattice in specific stoichiometry (1,5,6). The essence of buildingthe cocrystals relies on the intermolecular interactions amongthe complementary functionalities of parent componentswhich witness the dominance of supramolecular heteromericinteractions over the homomeric (7). The strategy ofcocrystallization is an attractive alternative which not onlyprovide the drug candidate with desired physicochemicalproperties but also caters the right of intellectual property(IP) protection (8).

The present research describes the preparation and evalu-ation of two new cocrystals of GL (Fig. 1a) with GRAScoformers, sebacic acid (SB, Fig. 1b) and α-hydroxyacetic acid(HA, Fig. 1c) with the aim to improve biopharmaceuticalproperties. It is in the continuation of our previous work (9)in which two novel cocrystals of GL with succinic acid and

malic acid, with improved dissolution limited bioavailabilityhave been discussed.

MATERIALS AND METHODS

Materials

A gift sample of GL (≥99%) was procured from ConsernPharma Pvt Ltd, Ludhiana, India and used as received. Allthe chemicals were purchased from Sigma-Aldrich, India andsolvents from E. Merck Ltd, India.

Cocrystal Preparation

GL-SB (1:1) and GL-HA (1:1) cocrystals were screened outusing solvent assisted mechanochemical route. A 1:1 M mix-ture of GL (32.34 mg) with SB (20.23 mg) and 1:1 molarmixture of GL (32.34 mg) with HA (7.61 mg) were groundin a mortar and pestle, along with drop-wise addition of

Fig. 1 Chemical structure of (a) GL, (b) SB, and (c) HA.

Fig. 2 DSC thermograms of GL, coformers and cocrystals.

Supramolecular Cocrystals of Gliclazide 553

acetone (10 ml) over 60 minutes of grinding at room temper-ature. The efforts to re-crystallize the prepared cocrystals fromdifferent solvents were also attempted but none of the exper-iment yields the suitable crystals for single crystal X-ray dif-fraction analysis.

DSC

DSC Q 20 (TA-Instruments Inc., USA) with a refrigeratedcooling system, which was calibrated with indium (99.99%purity, mp 156.6°C) was used for recording thermograms.The crimped aluminium pans with 2–4 mg of samples wereheated at the rate of 10°C/min in the dry nitrogen atmo-sphere (flow rate of 50 ml/min) in the temperature range of25–250°C. The peaks were integrated by Universal Analysis2000 software (TA Instruments Inc.).

PXRD

Powder X-ray diffractometer PANalytical X’Pert Pro, oper-ated at 40 kV voltage and 45 mA current was used to collectthe data of samples at room temperature in the range of 5–45°(2θ) at the scan rate of 0.00085°/sec and high resolution. Theobtained data were interpreted by X’PERT high Scoresoftware.

FTIR

FTIR spectra were obtained using spectrum two IR spectrom-eter (Perkin Elmer, England). The prepared samples (KBrpellet technique) were scanned (4 accumulative scans) in therange of 400–4000 cm-1 with 4 cm-1 resolution.

Crystal Structure Determination from PXRD

Reflux Plus module of Material studio (BIOVIA 7.0) was usedto elucidate the crystal structure of prepared cocrystals fromPXRD. The diffraction peaks were indexed from 5° to 45° 2θ,to depict the crystal unit cell and lattice parameters using X-CELL and pawley refinement. Geometrically optimizedstructure (using DMol3) of GL and coformers were incorpo-rated into the empty unit cell, created by pawley refinementand then subjected to Powder solve to optimize the positionand conformation of the structures using simulated annealingalgorithm. In the end, the structure was refined by Rietveldrefinement to obtain the best solution of the structure ofcocrystal.

SSNMR

Solid-state 13C NMR spectra were obtained from a Jeol-ECX400 MHz spectrometer, at 100 MHz resonating frequency.The data was collected at 273 K with 1024 complex data

points, acquisition time 29.1 s, contact time of 2 ms and re-laxation delay of 5s for cross polarization. 13C NMR spectrawere referenced to the methylene carbon of glycine(δglycine = 43.3 ppm) and then recalibrated to the TMS scale.

Equilibrium Solubility Studies

The data of the equilibrium solubility was obtained by shakeflask method (10). In this study, an excess amount of thecocrystals was placed in vials containing 10 ml phosphatebuffer (pH 7.4; recommended media in USP XXV) and

Fig. 3 PXRD pattern of (a) GL (9), (b) SB, (c) GL-SB, (d) HA, and (e) GL-HA.

554 Chadha, Rani and Goyal

Fig. 4 FTIR spectra of (a) GL (9),(b) SB, (c) GL–SB, (d) HA, and (e)GL–HA.

Fig. 5 (a) ORTEP diagram of GL-SB and (b) alignment of the planes of GL (red) and SB (light purple) in asymmetric unit.

Supramolecular Cocrystals of Gliclazide 555

agitated with 200 rpm for 24 hours, at 37°C in water bathshaker (MSW-275 Macroscientific works, Delhi). Theresulting slurry was filtered through 0.45 μmmembrane filterand the concentration was analyzed at 228 nm by WatersAlliance HPLC system (Photodiode Array Detector).

Intrinsic Dissolution Studies

Intrinsic dissolution study was performed using rotating diskdissolution test apparatus, (DS 8000, Lab India Analyticals) inphosphate buffer pH 7.4 (recommendedmedia in USPXXV)at 37°C with 100 rpm for 4 hours. A pellet of the sample wasattached to dissolution apparatus holder and immersed indissolution media. The withdrawn buffer (5 ml) was replacedwith fresh buffer at different intervals of time and filteredthrough 0.45 μm membrane filter. The concentration was

determined at 228 nm with Waters Alliance HPLC system(Photodiode Array Detector).

In Vivo Studies

The pharmacokinetic study (11) of GL-SB andGL-HA (dose 40mg/kg; suspension in normal saline) was performed on the nor-mal rats by administering a single dose and sampling was donefor 24 hours, at different intervals of time. The plasma sampleswere analyzed by HPLC and the pharmacokinetic parameterswere calculated by PKSolver: An Add–in program (12), whichdoes the calculation based on the linear trapezoidal method.

For the pharmacodynamic studies, diabetic male wistarrats (150–200 g; 3–4 week old) were used, in which diabeteswas induced by injecting streptozotocin plus nicotinamide so-lution (45 mg/kg; prepared in citrate buffer (0.1 M; pH 4.4))intraperitoneally (13,14). GL-SB andGL-HA (dose 40mg/kg)

Fig. 6 Hydrogen bonded interactions in GL-SB.

Fig. 7 crystal packing pattern in GL-SB (a) along the b axis (b) along the a axis (c) along the a-15° axis (green and blue colour represents GL and SB moleculesrespectively).

556 Chadha, Rani and Goyal

were suspended in citrate buffer (0.1 M; pH 4.4) and admin-istered orally, once in a day, for 7 days. The plasma glucoselevel, after 7 days was checked by enzymatic GOD—POD(glucose oxidase peroxidase) method. The blood was collectedfrom retro-orbital plexus and the data was represented bymean ± SEM. Statistically the data were compared with con-trol groups (diabetic rats in pharmacodynamic study and nor-mal rats in pharmacokinetic study) by One-way ANOVAfollowed by Dunnett’s test and Student’s t-test usingGraphPad Prism 6.0 software at 95% confidence interval.

HPLC Method

Waters Alliance HPLC system which includes a waters 2996Photodiode Array Detector and a 4.6 mm×150 mm×5 μm

SunFireTMC18 columnwas used for the analyses. 10μl of all thesamples was injected in the column and analyzed by isocraticmobile phase, acetonitrile: water (50:50) of pH 3 (pH was ad-justed with orthophosphoric acid) with flow rate 1.2 ml/min.The procedure for analysis was same as in our previous work (9).

RESULTS AND DISCUSSION

DSC

GL-SB and GL-HA showed a single, sharp and unique endo-thermic transition at 153.62°C and 148.86°C respectively(Fig. 2), which is different from and amid the melting of GL(171.04°C) (9) and used coformers (SB: 134.67°C, HA:75.86°C). Besides this, the endotherms are also different fromtheir physical mixtures (supplementary data; Figure S1). Thisimplied the generation of a new crystal phase without thetraces of either of the parent components. The thermal be-havior shown by both the newly formed solid forms indicateda change in the molecular arrangement in the crystal lattice ofGL by the replacement of strong homomeric supramolecularinteractions with the heteromeric synthons and thus, the pos-sibility of cocrystal formation. Beside this, both forms withdifferent melting points also evidenced the direct effect ofcoformers in tailoring the solid state properties, and thus, af-fecting physicochemical properties.

PXRD

The obtained PXRD patterns of GL-SB and GL-HA wasfound to be unique in comparison to GL and respectivecoformers (Fig. 3). In GL-SB, a few new peaks at 8.51°,

Fig. 8 (a) ORTEP diagram of GL-HA (b) alignment of the planes of GL (red) and HA (light purple) in asymmetric unit.

Fig. 9 Hydrogen bonded interactions in GL-HA.

Supramolecular Cocrystals of Gliclazide 557

9.58°, 13.86°, 19.43°, 22.46°, 23.18°, 28.18°, 28.66° ap-peared while some characteristic peaks at 10.06°, 14.97°,17.92°, 18.19°, 18.41°, 22.08°, 26.90° and 27.66° of GLand at 24.18° of SB have disappeared. Besides this, theshifting of a few peaks of GL from 16.81° to 16.59°,17.11° to 16.94°, 26.26° to 26.16° were also witnessedby PXRD. Apart from it, few peaks of GL and SB mergeto give either a new peak or a broad peak. The peaks ofGL at 15.93° merged with 16.24° of SB to give new peakat 16.03° while the peaks of GL at 20.82° and 21.16°merged with 21.60° of SB to give a broad peak at20.79°. Along with it, the peaks at 20.20° and 20.43°,21.90° and 22.09°, 25.09° and 25.34° of GL merged togive broader peak at 20.31°, 22.04°, and 25.74°, respec-tively. The broadening of the peaks was observed mainlyafter 30° 2θ.

In GL-HA, new peaks were observed at 14.10°, 24.59° and34.61° while some characteristic peaks of GL at 21.90° and ofHA at 13.86°, 16.95°, 20.17°, 21.09°, 21.99°, 25.23°, 25.46°,26.66°, 34.09°, 36.41° and 36.49° have disappeared. Besides

this, the shifting of a few peaks of GL from 16.81° to 16.77°,17.91° to 17.87°, 20.82° to 20.78°, 21.16° to 21.12°, 25.10° to25.01° and 27.66° to 27.60° were also noticed.

All the peaks in PXRDare due to the reflections from specificatomic planes and any changes in these reflections represent thevariation in crystal lattice (15). The dissimilarity in the pattern ofboth newly formed solid forms, from their starting material au-thenticates the formation of a novel crystal phase.

FTIR Spectroscopy

The nature of hydrogen bonding affects the vibrational fre-quency and helps to envisage which functional groups areinvolved in the formation of supramolecular synthons. In theIR spectrum of GL–SB, noteworthy changes were seen in thecarbamoyl and the hydroxyl regions of GL and SB, respec-tively. A major shift was observed in the –CO stretch of GL,from 1709 cm-1 to 1714 cm-1 and –OH of the carboxylicgroup of SB from 3314 cm-1 to 3297 cm-1, inferring theirinvolvement in the non covalent interactions in GL-SB. In

Table I CrystallographicParameters for GL-SB and GL-HA Parameters GL-SB GL-HA

Chemical formula C15H21N3O3S; C10H18O4 C15H21N3O3S; C2H4O3

Stoichiometry 1:1 1:1

Temperature Room temperature as specified 25°C Room temperature as specified 25°C

Crystal system Triclinic Triclinic

Space group P-1 P-1

a (Å) 12.1604 10.0691

b (Å) 11.8803 9.8283

c (Å) 10.0879 7.2085

α (deg) 104.7632 84.0771

β (deg) 98.9539 99.5801

γ (deg) 105.2249 118.0139

Z 2 2

Vol. (Å3) 1320.57 620.746

2θ range 5°–45° 5°–45°

Rwp 10.03% 12.56%

Fig. 10 arrangement of molecules in GL-HA (a) along b axis (b) along a axis (green and blue colour represents GL and HA molecules respectively).

558 Chadha, Rani and Goyal

case of GL–HA, carbamoyl region of GL and both thecarbamoyl and the hydroxyl regions of HA were found to beconcerned with supramolecular interactions. The –COstretch of GL at 1709 cm-1 and of HA at 1730 cm-1 sub-merged to give a peak at 1716 cm-1, and a shift was alsoobserved in –OH (alcohol) of HA from 3294 cm-1 to 3285cm-1 (Fig. 4).

Crystal Structure Determination from PXRD

GL–SB crystallizes in the triclinic system with the spacegroup P-1, with one molecule of GL and one molecule ofSB in an asymmetric unit (Fig. 5a). In the crystal lattice,both drug and coformer are aligned in such a way thatthey subtend an angle of 18.96° between their planes(Fig. 5b). The solid state structure of GL-SB builds bothsupramolecular homosynthons and heterosynthons(Fig. 6). The homosynthon is resulted from the interac-tion between hydrogen atom of –NH (present between –SO2 and –CO) and oxygen atom of –SO2 in GL (N1–H1⋯O1) with distance 1.903 Å. Three one pointheterosynthons were formed through the interactions be-tween oxygen atom of –SO2 in GL and hydrogen atomof carboxylic –OH in SB (O7–H39⋯O2), between aro-matic nitrogen in GL and hydrogen atom of anothercarboxylic –OH of SB (O4–H22⋯N3) and between hy-drogen atom of –NH (present between –CO and aro-matic N) in GL and oxygen atom of –CO of carboxylicgroup in SB (N2–H2⋯O6). The corresponding distanceof these heterosynthons are 1.682 Å, 2.612 Å and 2.044Å respectively. On viewing along b axis, stacked GLmolecules form a crossed ‘X’ like shape, having S atom

at the centre and SB in the cavity formed by GL(Fig. 7a).

The molecules form a layered network along a axis inwhich asymmetric units are packed in the head to head andtail to tail fashion and two parallel layers are bonded throughO–H⋯O and O–H⋯N interactions (Fig. 7b). The same layerscan be seen as a sandwich in which two GL molecules, orient-ed opposite to each other are sandwiched between SB mole-cules. The clear sandwiched view can be seen along a-15° axis(Fig. 7c).

GL–HA also crystallizes in the triclinic system with thespace group P-1, consisting of two independent molecules ofGL and HA which are oriented at an angle of 74.87° in anasymmetric unit (Fig. 8). Hydrogen atom of –NH (presentbetween –CO and aromatic N) interacts with oxygen atomof –SO2 in another GLmolecule and results in construction ofhomosynthon (N2–H2⋯O1) with distance 1.649 Å. Besidesthis, two heterosynthons also resulted through the interactionbetween the hydrogen atom of –NH (present between –SO2

and –CO) in GL and Oxygen atom of –CO in HA (N1–H1⋯O5), between nitrogen atom of –NH (present between –CO and aromatic N) of GL and hydrogen atom of alcoholic –OH of HA (O6–H25⋯N2) with the distance of 1.655 Å and1.712 Å respectively (Fig. 9). In the cocrystal, folded conform-er of GL andHA is present in bilayer form in which HA seemsto be inserted between the ‘C’ shaped GL molecules along baxis (Fig. 10a). On viewing from a axis, these parallel bilayerconsist of alternating GL and HA molecules (Fig. 10b).

The crystallographic parameters of both the cocrystals aregiven in Table I. The simulated (Rietveld fit profile) PXRDpattern, experimental PXRD pattern, as well as the differencebetween the two has been given in the supplementary data(Figure S3). The obtained Rwp values for both the cocrystals

(a)

(b) (c)

Fig. 11 (a) Homosynthons in GL(b) heterosynthon in GL-SB (c)heterosynthon in GL-HA.

Supramolecular Cocrystals of Gliclazide 559

are acceptable and this statement is supported by the variousresearch papers, published in esteemed journals (16,17). The

cif files for both cocrystals have been deposited in CCDC (GL-SB - 1505618; GL-HA – 1505619).

Fig. 12 SSNMR spectrum of (a)GL, (b) SB, (c) GL-SB, (d) HA, and(e) GL-HA (★ denotes the majorchanges in 13C NMR chemicalshifts).

560 Chadha, Rani and Goyal

Mechanism of Cocrystallization

The mechanism of cocrystallization in GL-SB and GL-HA atmacroscopic level was monitored by subjecting the ground mix-ture to the PXRD at various intervals of time (supplementarydata, Figure S4 and S5). The broadening of the peaks was ob-served in the PXRD, suggesting the existence of the amorphousphase prior to the formation of final product. The insertion ofthe coformers in the crystal lattice has the tendency to disturb thealready established supramolecular architecture (sulfonamide–sulfonamide and amide–amide homosynthons) by competingwith the pre-existing functional groups in GL. This resulted inthe generation of new homo or hetero synthons (Fig. 11).

The small amount of solvent was used to speed up thecocrystallization process and its absence in the final productwas confirmed by the DSC.

In the cocrystallization of GL-SB, the sulfonamide–sulfonamide homosynthon of GL remained intact and

three new one point heterosynthons were formed whilein GL-HA, all the pre-existing synthons of GL weredisturbed.

SSNMR Spectroscopy

SSNMR senses the perturbations in the local electronic environ-ment due to the variations in the supramolecular interactionsand conformations, which directly affect the chemical shifts. Thenoticeable differences in the cocrystals were evident in the chem-ical shift of 13C SSNMR in comparison to their parent solidcomponents (Fig. 12). The chemical shifts in 13C SSNMR ofGL are representative of homosynthons (N1–H1⋯O2, N2–H2⋯O3) (18). Although the same dimer is absent in GL-SB,the atoms N1, H1, N2, H2 and O2 are participating in theformation of new homosynthon or heterosynthon except O3,which no longer acts as an acceptor of hydrogen bond. Thisresulted in upfield shifting of C1, attached directly to O3.

Table II 13C NMR ChemicalShifts (ppm from TMS) in GL, SBand Its Cocrystal GL-SB

Group Assignment GL SB GL-SB Δ (δGL-SB – δGL or SB)

CO 1 155.46 151.23 –4.23

C 2 147.43 148.99 1.56

C 5 136.66 138.19 1.53

CH 3,4,7,8 129.82 128.03 –1.79

CH2 9, 15 65.56, 62.40 66.75, 63.51 1.19, 1.11

CH 10, 14 40.95, 40.01 40.52 –0.43, 0.51

CH2 11, 13 33.00, 29.76 33.26 0.26, 3.50

CH2 12 24.80 23.52 –1.28

CH3 6 22.24 22.66 0.42

COOH 16, 25 181.86 179.73 –2.13

CH2 17, 24 35.13 34.71 –0.42

CH2 20, 21 33.32 33.26 –0.06

CH2 19, 22 31.79 31.38 –0.41

CH2 18, 23 25.55 25.65 0.10

Table III 13C NMR ChemicalShifts (ppm from TMS) in GL, HAand its Cocrystal GL-HA

Group Assignment GL HA GL-HA Δ (δGL-HA – δGL or HA)

CO 1 155.46 152.14 –3.32

C 2 147.43 147.34 –0.09

C 5 136.66 135.40 –1.26

CH 3,4,7,8 129.82 131.53, 129.65, 128.37 1.71, -0.17, -1.45

CH2 9, 15 65.56, 62.40 65.47, 63.03 –0.09, 0.63

CH 10, 14 40.95, 40.01 40.78, 39.84 –0.17,–0.17

CH2 11, 13 33.00, 29.76 32.83, 29.60 –0.17,–0.16

CH2 12 24.80 22.58 –2.22

CH3 6 22.24 20.35 1.89

COOH 16 177.28 180.56 3.28

CH2 17 60.68 56.15 –4.53

Supramolecular Cocrystals of Gliclazide 561

Besides this, O1 and N3 also act as proton acceptor in thehydrogen bonding in GL-SB, which affected neighboring car-bon atoms (C2, C9 andC15), resulting in the variation of chem-ical shift. Moreover, O5 did not participate in hydrogen bond-ing in GL-SB, in contrast to crystal structure of SB (19), as aresult, the chemical shift deviated to lower value by 2.13 ppm.

Similarly in GL-HA, O3 did not form the hydrogen bond,in contrast to GL, which resulted in upfield shifting of C1. InHA (20), carboxylic –OH is the potential proton donor but itdid not retain the same character in GL-HA, which cause thedownfield shifting of adjacent C16. The chemical shift of C17(attached O6) in GL-HA is affected by two factors, the firstbeing the non availability of O6 as an acceptor of hydrogenbond (in contrast to HA) and formation of O–H⋯Nheterosynthon by replacing O–H⋯O synthon, resulting intoits upfielding.

The other carbon nuclei in the vicinity of supramolecularinteractions also experience the change in local environmentand appear slightly at different chemical shifts from parentcompounds (Tables II and III).

Equilibrium Solubility and Intrinsic Dissolution Studies

Our prime objective of preparing the cocrystals was to mod-ulate the solubility of GL, as its absorption is limited by disso-lution. Both the cocrystals evidenced 3 fold increment in theequilibrium solubility and approximately 1.5 fold IDR incomparison to GL (Table IV).

The solubility and IDR pattern of these cocrystals may beexplained on the basis of the packing of molecules in the crys-tal lattice, frequency and strength of supramolecular interac-tions, solubility and melting point of the coformers. The

higher solubility of GL-HA may be attributed to the fact thatthe molecules are packed in bilayer pattern in crystal latticewhile in GL-SB they are arranged in multi-layers, indicatingstrong crystal lattice. Besides this, conformer HA has highersolubility and lower melting point as compared to SB, which isalso a contributing factor towards the higher solubility andIDR of GL-HA in comparison to GL-SB.

In Vivo Studies

Both cocrystals exhibited considerable glucose level reductionin comparison to GL (F3,18 = 403, p< 0.0001; Table V), sig-nifying the enhancement in antidiabetic activity. This en-hancement may be attributed to the changes in physicochem-ical and supramolecular properties which influence the phar-macokinetic parameters (F3,18 = 396, p< 0.0001; Table V) aswell. GL-SB and GL-HA showed 1.62 and 1.68 fold increasein Cmax, respectively as compared to GL, without affectingTmax. This indicates the increase in absorption of GL withoutmuch affecting rate of absorption.

CONCLUSIONS

The supramolecular interactions are the key elementwhich influences physicochemical properties and theperformance of the crystalline solids. Supramolecularcocrystals of GL with GRAS status coformers, sebacicacid (GL-SB) and α-hydroxyacetic acid (GL-HA), pre-pared using liquid assisted grinding (LAG) were system-atically characterized using various analytical techniques.Almost 3 fold improvement was found in the solubility,accompanied with improved pharmacodynamic andpharmacokinetic parameters.

ACKNOWLEDGMENTS AND DISCLOSURES

The authors are greatly thankful to the University GrantsCommission (UGC), New Delhi (F.4-1/2006(BSR)/5-94/2007 dated 03-05-2013) and Council of Scientific &Industrial Research (CSIR), New Delhi (02(0039)/11/EMR-II) for the financial assistance.

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Table V Pharmacodynamic and Pharmacokinetic Parameters of GL, GL-SB and GL-HA [GL† : The Values for GL are Taken from Our PreviousResearch Paper, (9)]

Glucose reduction(%)± SEM

AUC0-t

(μg/ml*min)Cmax

(μg/ml)Tmax (min)

GL† 75.11± 0.2 42542.25 55.26 240

GL-SB 91.41± 0.2 83712.42 89.68 240

GL-HA 93.23± 0.2 86153.67 93.15 240

Table IV Solubility and IDR of GL and Cocrystals [GL† : The Values for GLare Taken from Our Previous Research Paper, (9)]

Solubility (mg/mL) ± SD IDR (mg/min/cm2) ± SD

GL† 2.10± 0.2 39.21± 0.1

GL-SB 5.12± 0.2 51.42± 0.1

GL-HA 6.35± 0.1 56.26± 0.2

562 Chadha, Rani and Goyal

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Supramolecular Cocrystals of Gliclazide 563

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