evaluation of material properties and compression characteristics of assam bora ...

1. Introduction

2. Materials and methods

3. Results

4. Discussion

5. Conclusion

Original Research

Evaluation of material propertiesand compression characteristics ofAssam Bora rice flours as a directlycompressible vehicle in tabletformulationMohammad Zaki Ahmad†, Sohail Akhter, Ishita Dhiman, Poonam Sharma &Reena Verma†Department of Pharmaceutics, Dreamz College of Pharmacy, Mandi, India

Aim: The mechanical properties and compaction characteristics of different

varieties of Assam Bora rice flours (ABRFs) were evaluated and compared

with those of official Starch 1500�.

Methods: The material properties and compression characteristics of Assam

Bora rice flours were studied by Heckel and Kawakita analysis. The influences

of physical and geometrical properties of ABRFs were evaluated with regard

to their compression properties. The mechanical properties, such as toughness

and Young’s modulus of ABRFswere also compared with that of Starch 1500�.

Results: The novel ABRFs reflect better physical characteristics such as higher

bulk and tap densities, less porosity, better powder packing ability, large

surface area, and improved flowability. ABRFs were the least sensitive mate-

rial to magnesium stearate, and blending time did not affect its compacti-

bility. Their onset of plastic deformation and strain rate sensitivity as

compared to that of Starch 1500� demonstrate its potential use as a directly

compressible vehicle for tablet.

Conclusions: The experimental ABRFs showed superior properties to official

Starch 1500� in many cases and could serve as suitable alternatives for

particular purposes.

Keywords: Assam Bora rice, brittle fracture index, direct compression, excipients, natural

polymer, plastic deformation

Expert Opin. Drug Deliv. (2013) 10(2):163-171

1. Introduction

The manufacture of tablets using wet granulation or dry granulation methods, inlight of the requirement for a series of unit operations, is both time-consumingand potentially costly. A potentially more attractive option for the manufacture oftablets is direct compression (DC). The accessibility of novel excipients, newergrades of prevailing excipients has led to a perceptible shift of DC process towardthe tablet compression technology. Several directly compressible excipients (DCE)with uniform flow and improved compaction properties have been establishedin recent years [1-5] and still many others are under study for better enactment.On responding to this investigation toward various natural starches, rice starcheshave proved to be much better tableting properties [1,6]. Recently our grouphas reported the compactibility and compressibility characteristics of Assam Borarice starch [1].

Assam Bora rice, locally known as Bora Chaval, is widely distributed throughoutAssam in North East region of India, is characterized by its high amylopectin

10.1517/17425247.2013.736963 © 2013 Informa UK, Ltd. ISSN 1742-5247, e-ISSN 1744-7593 163All rights reserved: reproduction in whole or in part not permitted

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contents, and was first introduced in Assam from Thailandor Myanmar by Thai-Ahoms [7-11]. The potential use ofAssam Bora rice starch in the formulation of matrix tablet,compression coated tablet, and mucoadhesive microspherefor colon targeting has been previously reported by ourgroup [8,9,11,12]. The aim of this study was to investigate thematerial properties and compaction characteristics of differentvarieties of Assam Bora rice flours (ABRFs) in contrast to thecommercially available direct compression excipient.

2. Materials and methods

2.1 MaterialsDifferent varieties of Assam Bora rice (fruits of Oryza sativa,family Gramineae), that is, Kola Bora (KB), Ghiu Bora (GB),Pakhi Bora (PB), Ronga Bora (RB), and Aghuni Bora (AB)were procured from local farmers of different parts ofAssam. Starch 1500� was supplied by Anshul Agencies,Mumbai as a gift sample. All other chemicals were ofanalytical reagent grades.

2.2 MethodsThe collected Assam Bora rice was washed properly with tapwater followed by double distilled water and was sun-dried for 10 days. It was then ground in mixer grinder. Aftergrinding, all the powder samples were passed through ASTM(American Society of Testing and Materials) 22 and 44 meshsieves. Final samples were collected which passed through thesieves # 22 and retained on sieve # 44.

2.2.1 Micromeritic properties of powder2.2.1.1 Particle size, size distribution, and morphologyThe particle size and size distribution of the ABRFs and Starch1500� were determined by optical microscopy (OlympusOptical, Japan). Approximately 500 particles were pickedrandomly in the optical field of powders, from which valueof mean projected diameter (dp) was calculated. Heywooddiameter (de) was determined using an image processor(Image Hyper 700 II, Japan) by calculating the diameter ofcircle whose area was equivalent to the actual projected areaA of a particle, as shown by Equation (1) [1,13]

Diameter( ) =4

Area(A)de π

ð1Þ

Geometric mean diameters (dg) were determined from thelog-normal distribution plot of particles mean diameter versuscumulative percent frequency [14,15]. Surface areas of theparticles were determined by Quantasorb surface area analyzer(Model QS-7). Helium gas was used as carrier and diluentgas, while nitrogen gas was used as adsorbate. Studies wereconducted at relative pressure (P/Po) ranging from 0.05 to0.30 and specific surface areas (SSABET) were obtained byBET equation [14,15].

Morphology of the ABRFs was studied by scanning electronmicrographs (SEM) taken with a scanning electron microscope(Hitachi S-300N, Germany). The samples were gold coated(about 100 A) in KSE24M high vacuum evaporator and onmetal stabs with the aid of double-sided adhesive tape.Scanned-in selected region depicting distinct morphologicalfeature was photographed.

2.2.1.2 Fundamental and derived properties of powderThe flow properties of the samples were studied by the angleof repose, bulk density, and tapped density measurements [14].The data generated from bulk densities and tapped densitieswere used in computing the Carrr’s index (CI) and Hausner’sratio (HR) for the powder samples [14]. True density wasobtained on a helium pycnometer (Ultrapyc 1200e Quan-tachrome Instruments, USA). The data generated from bulkdensity and true density were utilized for calculating theporosity of powder mass. Moisture content was determinedby official method of USP32-NF27 in a hot air oven (RemiScientific, Bangalore) at 105oC.

2.2.2 Preparation of tabletsCompaction of 400 mg powder into flat-faced tablets, witha diameter of 9 mm, was carried out on a mechanical hydrau-lic press (ESH Tablet Compaction Simulator, HuxleyBertram Engineering Ltd). To secure equal frictions betweendie wall and powder bed for compacts, the die was alwayspre-lubricated with dispersion of magnesium stearate in1:1 mixture of ethanol--ether with help of brush before eachcompression. Tablets were prepared under conditionswhere maximum compression pressure P ranged from 15 to300 MPa at dwell time of 3 s and 30 s. In the similar fashionanother batch of tablets with hole of 1.25 mm diameter attheir centre were compressed using an upper punch with ahole through the centre and a lower punch fitted withpin [16,17]. After ejection, the tablets were stored over silicagel in controlled humidity of 30% RH for 48 h to allowelastic recovery and hardening and to prevent falsely lowyield values [18].

2.2.3 Compactibility analysisAfter 36 h, final thickness (Tt) and diameter (Dt) of the nor-mal tablet and the tablets with hole (To, Do) was measuredand the results obtained were used to determine tablet tensilestrength (sT or sTo) by diametric compression test (TBH30,Erweka, Heusenstamm, Germany) and by applying theEquation (2) [19,20]

spT

t t

H

D T=

2 ð2Þ

where H is applied load needed to cause the fracture.Results were taken only from those tablets that showed no

sign of lamination or capping and split cleanly into twohalves.

M. Z. Ahmad et al.

164 Expert Opin. Drug Deliv. (2013) 10(2)

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The results obtained from tensile strength versus the productof the solid fraction and the compression pressure were fittedaccording to the Leuenberger model [19-21] in Equation (3)

s s g rT Tmax

Pe c r= × − − × ×( )( )1 ð3Þwhere sTmax is the theoretical tensile strength at infinite com-pression pressure; gc is the compression susceptibility parame-ter (MPa--1); P is compression pressure; and rr is the relativedensity of compact. Data fitting was performed employingthe Statgraphic� software (Stat Point Technologies).

2.2.4 Mechanical propertiesAfter 48 h of storage period over the silica gel in controlledhumidity of 30% RH, the resulting stress-strain curves wereobtained on a universal stress-strain analyzer (Q-test-I�,Material testing system NC, USA). The Young’s modulus(E) was obtained from the slope of the stress-strain curves. Itmeasures the stiffness of the material. The toughness of thematerial was obtained by measuring the area under curves ofthe resulting stress-strain curves [22,23]. The brittle fractureindex (BFI) was calculated from the Equation (4) [20,24]

BFI =⎛⎝⎜

⎞⎠⎟

−⎡

⎣⎢

⎤

⎦⎥0 5 1.

ss

T

To

ð4Þ

where sT the tensile strength of normal tablet and sTo is thetensile strength of the tablet with hole.

2.2.5 Lubricant sensitivityLubricant sensitivity analysis was performed by the methoddescribed by Rojas et al. [20] with slight modification. Starchpowders and magnesium stearate (1% w/w) were mixed usinga double cone blender for 10 to 60 min. After mixing, thepowder mass was passed through ASTM 22 mesh sieves. Tab-lets of 400 mg were compressed at 70 MPa compression pres-sure. In the similar fashion another batch of tablets wereprepared without lubricants. Lubricant sensitivity (LS) wasdetermined by the Equation (5)

LS =−H H

Ho lub

o

ð5Þ

where Hlub and Ho are the hardness of the tablets preparedwith and without lubricants.

2.2.6 Compressibility analysisCompression behavior of powders was characterized byHeckel analysis [25] (Equations 6 & 7).

ln1

1−⎛⎝⎜

⎞⎠⎟ = +

DKP A ð6Þ

e = −1 D ð7Þwhere D is the relative density of the compact at pressure P, "is the porosity of powders, and K and A are constants. Itrepresents the powder densification by die filling and particlerearrangement before deformation and bonding of discreteparticles take place. The slope of the straight line, K is

reciprocal of the mean yield force, PY of the material and "is the porosity of powder bed.

The strain rate sensitivity (SRS) was determined from theEquation (8) [19,26]

SRS =−⎛

⎝⎜

⎞

⎠⎟ ×

P P

Py y

y

2 1

2

100 ð8Þ

where Py1 and Py2 are yield pressure at lowest and highestcompression speed, respectively.

The Kawakita analysis was used to study the powdercompression using the degree of volume reduction (C ) [16]

CV V

V

abP

bPCP b

a

=−

=+

= −0

0 11,

rr

ð9Þ

In the above equation, V0 denotes the initial volume ofpowder bed and VP is volume of the powder columnunder the applied pressure P. Terms a and b are constants;“a” is equal to minimum porosity of the material beforecompression representing the compressibility index and isrelated to the total volume reduction for the powder bed,while “b” represents the plasticity of material and is relatedto the resistant forces (friction/cohesion) to compression [20];rb and ra are bulk density and apparent density compact,respectively.

2.2.7 Statistical analysisThe student t test was used to find the statistical significance.A value of p < 0.05 was considered statistically significant. Alltests were performed in the replicate of six independentsamples.

3. Results

3.1 Micromeritic properties of powders3.1.1 Particle size distribution and morphologyThe particle size distribution of the different varieties ofABRFs varies from 20 -- 100 µm for KB, 25 -- 100 µm forGB, 20 -- 100 µm for PB, 20 -- 110 µm for RB,25 -- 120 for AB, and 30 -- 150 µm for Starch 1500�. Theresults of physical and geometric properties of the ABRFsand Starch 1500� are presented in Table 1. The projecteddiameter of the ABRF is 11 ± 0.320 µm for KB, 11 ±0.982 µm for GB, 11 ± 0.023 µ for PB, 11 ± 0.560 µm forRB, 11 ± 0.849 µm for AB whereas for Starch 1500� thisvalue is 12 ± 0.193 µm. The result was found to be statisticallysignificant (p < 0.01). Electron photomicrographs for ABRFsare presented in Figure 1. Particles were spherical to polygonalin shape. The surfaces of particles were relatively smooth withsome evidence of crack and indentations.

3.1.2 Fundamental and derived properties of powderThe flow properties of the samples were investigated by theangle of repose, bulk density, and tapped density measure-ments, Carr’s compressibility index, Hausner’s Ratio, and

Evaluation of material properties and compression characteristics of Assam Bora rice flours

Expert Opin. Drug Deliv. (2013) 10(2) 165

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porosity (Table 1). The result was found to be statisticallysignificant (p < 0.01).

3.2 Compactibility analysisThe results from Leuenberger model for tensile strength arepresented in the Table 2. The compression susceptibility (gc)

value for all ABRFs varies from 0.076 MPa--1 to0.079 MPa--1 for KB, GB, PB, RB, and AB, respectively,whereas for Starch 1500� it was found to be 0.06 MPa--1.The compactibility expressed as the area under the tensilestrength (AUCT) of ABRFs was about two times greaterthan that of Starch 1500�. Tmax for the ABRFs are higher

Table 1. Micromeritic properties of Starch 1500� and different varieties of Assam Bora rice flour.

Properties Materials

Starch 1500� Kola Bora Ghiu Bora Pakhi Bora Ronga Bora Aghuni Bora

dp (µm) 12 ± 0.193 11 ± 0.320 11 ± 0.982 11.2 ± 0.023 11 ± 0.560 11 ± 0.849de (µm) 13.9 ± 2.02 12.1 ± 1.061 11.9 ± 1.43 12.1 ± 1.43 12.5 ± 1.561 12.3 ± 1.89dg (µm) 69.9 ± 5.09 59.4 ± 3.212 59.3 ± 3.230 57.6 ± 2.451 57.5 ± 3.672 58.9 ± 2.091SSABET (m2/g) 6.9 ± 1.450 10.5 ± 1.34 10.9 ± 1.961 10.4 ± 1.452 10.1 ± 1.629 10.6 ± 1.473True density (rp) 1.53 ± 0.07 1.56 ± 0.010 1.56 ± 0.020 1.57 ± 0.020 1.56 ± 0.010 1.57 ± 0.020Bulk density (rb) 0.564 ± 0.01 0.592 ± 0.01 0.593 ± 0.01 0.584 ± 0.03 0.5806 ± 0.02 0.583 ± 0.05Tapped density (rt) 0.689 ± 0.02 0.699 ± 0.01 0.699 ± 0.01 0.692 ± 0.01 0.690 ± 0.02 0.697 ± 0.01% Porosity (") 63.19 ± 3.43 62.03 ± 2.34 62.01 ± 2.56 62.91 ± 2.67 62.78 ± 1.98 62.83 ± 3.45Compressibility index (% CI) 18.14 ± 0.45 15.26 ± 0.02 15.22 ± 0.02 16.09 ± 0.01 15.8 ± 0.01 16.28 ± 0.03Hausner’s ratio (HR) 1.20 ± 0.002 1.18 ± 0.001 1.17 ± 0.001 1.18 ± 0.010 1.18 ± 0.002 1.19 ± 0.001Angle of repose (Degree) 27.09 ± 0.08 24.5 ± 1.23 23.09 ± 1.97 23.02 ± 1.34 23.43 ± 1.51 23.05 ± 1.62% Moisture content 10.01 ± 1.09 3.43 ± 0.009 3.03 ± 0.001 3.01 ± 0.001 3.03 ± 0.001 3.02 ± 0.001

All values are expressed as mean ± s.d, n = 6.

A. B.

D.C.

Figure 1. Scanning electron photomicrographs of ABRFs A. Kola Bora. B. Ghiu Bora. C. Pakhi Bora. D. Ronga Bora.

M. Z. Ahmad et al.


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than Starch 1500�. Effect of compression pressure on the ten-sile strength of compact is presented in Figure 2.

3.3 Mechanical propertiesBFI obtained from the Equation (4) is presented inthe Table 2. The lowest BFI was observed for ABRFs(0.182 ± 0.02 to 0.198 ± 0.02) than Starch 1500� (1.201 ±0.04). The value of Young’s modulus for ABRFs varies from0.27 ± 0.05 to 0.31 ± 0.01 respectively and for Starch1500� it was found to be 0.26 ± 0.01. The toughness of thematerials was obtained by measuring the area under curvesof the resulting stress-strain curves. Toughness value for thetablet from ABRFs varies from 854 ± 21.01 to 876 ±

12.45 MPa, respectively, and for Starch 1500� it was foundto be 786 ± 10.56 MPa.

3.4 Lubricant sensitivityLubricant sensitivity was tested against Magnesium stearate at1% w/w level. The trend for lubricant sensitivity was observedas Starch 1500� > ABRFs. Lubricant sensitivity and blendingtime of the ABRFs and Starch 1500� are presented in Figures 3

and 4 respectively.

3.5 Compressibility analysisTable 3 shows the parameters resulting from the differentcompression models employed. The values of yield pressure(Py) of ABRFs are comparable to Starch 1500�. The ABRFsand Starch 1500� show comparable strain rate sensitivity

Table 2. Mechanical properties of Starch 1500� and Assam Bora rice flours.

Materials Properties

Tmax

(Mpa)*

gc(Mpa-1)

Maximum

stress (MPa)*

Maximum

strain (%)*

Young

modulus*

Toughness

(MPa)*

AUCT

(MPa2)*

BFI* Lubricant

sensitivity*

Starch 1500� 21.69 ± 2.56 0.06 3.30 ± 0.372 1.67 ± 0.03 0.26 ± 0.01 786 ± 10.56 1665.4 ± 45.98 1.201 ± 0.04 0.59 ± 0.01Kola Bora 44.98 ± 3.47 0.079 5.01 ± 0.567 1.87 ± 0.07 0.27 ± 0.01 869 ± 45.02 3196 ± 76.16 0.198 ± 0.02 0.29 ± 0.01Ghiu Bora 43.67 ± 3.78 0.076 5.90 ± 0.056 1.87 ± 0.06 0.29 ± 0.01 872 ± 34.56 3090 ± 56.89 0.182 ± 0.01 0.29 ± 0.02Pakhi Bora 44.56 ± 2.89 0.077 5.67 ± 0.980 1.89 ± 0.02 0.27 ± 0.05 854 ± 21.01 3178 ± 89.54 0.891 ± 0.01 0.30 ± 0.01Ronga Bora 43.67 ± 3.23 0.076 5.79 ± 0.371 1.88 ± 0.07 0.30 ± 0.03 868 ± 62.89 3167 ± 54.89 0.193 ± 0.03 0.29 ± 0.01Aghuni Bora 43.97 ± 3.45 0.078 5.90 ± 0.001 1.91 ± 0.31 0.31 ± 0.01 876 ± 12.45 3173 ± 87.67 0.189 ± 0.02 0.28 ± 0.01

*All values are expressed as mean ± s.d, n = 6.

KB

GB

PB

RB

AB

Starch 1500®

KB

300250

50

225200

100

175

75

0

0

0.5

1

1.5

2

2.5

3

3.5

4.5

Ten

sile

str

eng

th (

kg/c

m2 )

Compression pressure (MPa)

4

2515

125

GB

PB

RB

ABStarch 1500®

Figure 2. Tensile strength of tablet prepared from ABRFs and Starch 1500� at different compression pressures.



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Starch1500®

AhguniBora

Ronga BoraPakhi BoraGhiu BoraKola Bora

0

0.1

0.2

0.3

0.4

0.5

0.6

Figure 3. Lubricant sensitivity of tablet prepared from ABRFs and Starch 1500�.

KBGBPBRBABStarch 1500®

KB

5040

30

20

10

60

00

0.1

0.2

0.3

0.4

0.5

0.6

Time (minutes)

Lu

bri

can

t se

nsi

tivi

ty

25

15

GB PB RB AB Starch 1500®

Figure 4. Effect of mixing time and lubricant sensitivity of ABRFs and Starch 1500�.

M. Z. Ahmad et al.


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(10 -- 11%). The compressibility index, that is, “a” for theABRFs is close to the values of its porosity. The value of “a”for the ABRFs varies from 0.63 to 0.66 whereas for Starch1500� it was found to be 0.58. The “b” parameter obtainedfrom Kawakita analysis is lower for the ABRFs.

4. Discussion

4.1 Particle size and size distributionThe specific surface area is used to describe the area ofcontact between the particles. The specific surface area obtainedby the BET analysis showed that ABRFs had larger surface areasthan Starch 1500�. The larger the specific surface area andsmaller is the particle size, the larger the area of contact betweenthe particles. This observation is true for ABRFs.

4.2 Fundamental and derived properties of powderABRFs presented higher bulk and tap densities than Starch1500�. This phenomenon is due to the lower particle sizeand higher consolidation achieved during process. Thus,ABRFs exhibit a more regular, smooth, and almost sphericalparticles, which were more compactable than Starch 1500�.Porosity of ABRFs varies from 62.03 ± 2.34 to 62.91 ±2.67 and for Starch 1500� it was found to be 63.19 ± 3.43.In this case, regular, smooth, and almost spherical shape ofthe ABRFs made packing more convenient and hence itsporosity was reduced. The compressibility index (CI) andHausner’s ratio (HR) provide an indication about the degreeof densification, which could result from vibration of hopperduring the compression of tablet [27]. The ranking for the CIand HR of the ABRFs and Starch 1500� was found to beStarch 1500� > ABRFs. Furthermore, all the flours fromdifferent varieties of Assam Bora rice had lower values of CIand HR suggesting better flowability. This is further sup-ported by the angle of repose. Moisture content of ABRFs issignificantly less as compared Starch 1500�.

4.3 Compactibility analysisThe compression susceptibility (gc) was higher for ABRFsthan Starch 1500�. The parameter gc specifies the rateat which the compact hardness sT builds-up with anincrease in applied compression stress and provides information

about compressibility [19]. A plastically deforming material willhave a high value of gc [28]. These results suggest that ABRFsundergo plastic deformation during compaction.

Further, compactibility expressed as the area under the ten-sile strength of ABRFs varies from 3035.7 ± 67.45 to 3167.3 ±75.56 and for Starch 1500� it was found to be 1663.30 ±21.67. The predicted maximum tensile strength value (Tmax)for the ABRFs are about twofold greater than that of Starch1500�, thus better compactibility than Starch 1500�.

4.4 Brittle fracture index, Young’s modulus, and

toughnessThe BFI is a measure of the ability of a tablet to relieve stressthat is caused by the presence of defective region (hole) [20].BFI is a measure of brittleness, which is the primary causeof capping and lamination. A BFI value lower than 0.2 indi-cates better compacting properties, whereas BFI values greaterthan 0.2 indicate tendencies to cap and laminate [19]; thus inthis regard ABRFs would be more useful.

Young’s modulus measures the stiffness of the material,that is, the resistant of the material to elastic deformationwhen it is compressed [20]. ABRFs had a higher Young’smodulus than Starch 1500�, indicating a high resistance toelastic deformation resulting in better compaction and hence,improved mechanical properties during compression. Thetoughness of the material represents the resistance when com-pressed until breaking [20,23]. Tablets prepared from ABRFscan withstand a minimum of 5 -- 6 MPa compression forcebefore breaking, while the value for the tablets preparedfrom Starch 1500� was 3 MPa. The large toughness valuemay indicate an increased ability of ABRFs to absorb andwithstand applied force [23].

4.5 Lubricant sensitivityMagnesium stearate is commonly used in tablet formulationsto reduce friction between the material and tooling used. Starch1500� is known for having high sensitivity to lubricants [29].These results suggest that materials with low Py value aremore sensitive to magnesium stearate, and thus sensitivitydecreases as the ductility of the material decreases. As seenin Figure 3, the trend for lubricant sensitivity ranged as Starch1500� > ABRFs. Figure 4 shows the relationship between blend-ing time and lubricant sensitivity. In case of ABRFs, a plateau insensitivity is achieved within 30 min of blending. This suggeststhat covering effect of magnesium stearate reaches a limitbetween 30 min and new available sites for particle bindingare formed afterwards. Long mixing time with lubricant hada major effect on the lubricant sensitivity of Starch 1500�.

4.6 Compressibility analysis4.6.1 Heckel analysisTable 3 lists the Heckel parameter of products evaluated. Pyis the yield pressure, which refers to the pressure at whichthe materials begins to deform plastically [20]. The Py valueof ABRFs as well as Starch 1500� below 100 MPa, suggests

Table 3. Parameter obtained from Heckel and Kawakita

analysis of ABRFs and Starch 1500�.

Materials Kawakita

parameters

Heckel

parameters

a b Py Da Db Do

Kola Bora 0.63 0.14 89 0.639 0.58 0.15Ghiu Bora 0.63 0.14 89 0.632 0.59 0.15Pakhi Bora 0.65 0.15 88 0.637 0.56 0.16Ronga Bora 0.64 0.14 89 0.629 0.58 0.15Aghuni Bora 0.63 0.15 89 0.634 0.59 0.15Starch 1500� 0.58 0.20 78 0.594 0.55 0.18



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that they are less brittle and deform mainly by plastic defor-mation [30] Do, Da, and Db are related to initial powder pack-ing/densification, total compact densification and particlerearrangement, fragmentation at the initial compactionstage, respectively [31]. The value of Do, Da, and Db forABRFs were higher than Starch 1500�, indicating thatABRFs exhibited higher total degree of packing both duringdie filling and at low compression pressure. Since in all casesof ABRFs Db were larger than Do, densification throughparticle rearrangement was more prevalent than die fillingat low compaction pressure. Strain rate sensitivity measuresthe plastic deforming properties of the material. Strainrate sensitivity increases as the plastic deformation becomesthe more dominant mechanism during the compactionprocess [19].Kawakita analysis showed comparable total compressibility

“a” values from ABRFs and Starch 1500�. Furthermore, “b”parameter showed that ABRFs are the materials with lowestcohesive forces to compression. Thus compressibility rangefollow the order ABRFs > Starch 1500�. Since ABRFs havehigh volume reduction, they also had highest compactibilityand theoretical tensile strength. As shown in the Figure 2,compactibility range follow the order ABRFs > Starch1500�. Since friability of the tablet is inversely related tothe compactibility and ranged as Starch 1500� > ABRFs,however in all cases, friability are within the limit.

5. Conclusion

The results of the present investigation provide some insightinto the material and compaction properties of the AssamBora rice flours and Starch 1500�. Results connote the promi-sing use of ABRFs as directly compressible vehicle; on the otherhand, it would be more useful when high tensile strength of thetablet is desirable. Another advantage associated with ABRFs isthat they can be used for direct compression of amine drugswith diminishing the chance of Maillard reaction due to lowmoisture content. Thus, parameters evaluated suggest that theABRFs may be served as suitable alternatives to Starch 1500�

for particular purposes, that is, these new materials have thepotential for use as a direct compression excipient.

Acknowledgments

The authors thank N Begum from Guwahati (Assam) for pro-viding the different varieties of Assam Bora rice. Authors alsothank late A Bhattacharya from Dibrugarh University for hislong vision on natural polymer for drug delivery and forproviding important information on Assam Bora rice.

Declaration of interest

The authors state no conflict of interest and have received nopayment in preparation of this manuscript.

Bibliography

1. Ahmad MZ, Akhter S, Anwar M, et al.

Compactibility and compressibility studies

of Assam Bora rice starch.

Powder Technol 2012;224:281-6

2. Nada AH, Graf E. Evaluation of Vitacel

M80K as a new direct compressible

vehicle. Eur J Pharm Biopharm

1998;46:347-53

3. Bangudu AB, Pilpel N. Tensile strength

of paracetamol and avicel powders and

their mixtures. J Pharm Pharmacol

1984;36:717-22

4. Saha S, Shahiwala AF. Multifunctional

coprocessed excipients for improved

tabletting performance. Expert Opin

Drug Deliv 2009;6(2):197-208

5. Tho I, Bauer-Brandl A. Quality by

design (QbD) approaches for the

compression step of tableting.

Expert Opin Drug Deliv

2011;8(12):1631-44

6. Bos CE, Bolhuis GK, Van DH,

Lerk CF. Native starch in tablet

formulations: properties on compaction.

Pharm Weekbl Sci 1987;9:274-82

7. Sharma SD, Vellanki JMR, Hakim KI,

Singh RK. Primitive and current cultivars

of rice in Assam-a rich source of valuable

genes. Curr Sci 1971;40:126-8

8. Ahmad MZ, Akhter S, Rahman M, et al.

Development of polysaccharide based

colon targeted drug delivery system:

design and evaluation of Assam Bora rice

starch based matrix tablet.

Curr Drug Deliv 2011;8:575-81

9. Ahmad MZ, Akhter S, Anwar M, et al.

Feasibility of Assam Bora rice starch as a

compression coat of 5-fluorouracil core

tablet for colorectal cancer.

Curr Drug Deliv 2012;9:105-10

10. Ahmad MZ, Akhter S, Ahmad I, et al.

In vitro and in vivo evaluation of Assam

Bora rice starch based bioadhesive

microsphere as drug carrier for colon

targeting. Expert Opin Drug Deliv

2012;9:141-9

11. Ahmad MZ, Akhter S, Rahman M, et al.

Colorectal cancer targeted

Irinotecan-Assam Bora rice starch based

microspheres: a mechanistic,

pharmacokinetic and biochemical

investigation. Drug Dev Ind Pharm

2012; doi: 10.3109/

03639045.2012.719906

12. Ahmad MZ, Akhter S, Anwar M,

Ahmad FJ. Assam Bora rice starch based

biocompatible mucoadhesive microsphere

for targeted delivery of 5-fluorouracil in

colorectal cancer. Mol Pharm

2012;9(11):2986-94

13. Obae K, Iijima H, Imada K.

Morphological effect of microcrystalline

cellulose particles on tablet tensile

strength. Int J Phar 1999;182:155-64

14. Sinko PJ. Micromeritics. In: Martin’s

physical pharmacy and pharmaceuticals

sciences. Lippincott, William & Wilkins,

New York; 2005. p. 53-560

15. Williams RO III, Sriwongjanya M,

Barron MK. Compaction properties of

microcrystalline cellulose using tableting

indices. Drug Dev Ind Pharm

1997;23:695-704

16. Kawakita K, Ludde KH. Some

considerations on powder compression

equations. Powder Technol

1970-714:61-8

M. Z. Ahmad et al.


Exp

ert O

pin.

Dru

g D

eliv

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f C

alga

ry o

n 03

/10/

13Fo

r pe

rson

al u

se o

nly.

17. Odeku OA, Itiola OA. Compaction

properties of three types of starch.

Iranian J Pharm Res 2007;6:17-23

18. Armstrong NA, Haines-Nutt RF. Elastic

recovery and surface area changes in

compacted powder systems.

Powder Technol 1974:9(5-6):287-90

19. Jain S. Mechanical properties of powders

for compaction and tableting:

an overview. Pharm Sci Technol Today

1999;2(1):20-31

20. Rojas J, Kumar V. Comparative

evaluation of silicified microcrystalline

cellulose II as a direct compression

vehicle. Int J Pharm 2011;416:120-8

21. Leuenberger H, Rohera BD.

Fundamentals of powder compression. I.

The compactibility and compressibility of

pharmaceutical powders. Pharm Res

1986;3:12-22

22. Alderborn G, Nystrom C.

Pharmaceutical powder compaction

technology. Marcel Dekker Inc,

New York; 1996

23. Hancock BC, Clas SD, Christensen K.

Micro-scale measurement of the

mechanical properties of compressed

pharmaceutical powders. 1. The elasticity

and fracture behaviour of microcrystalline

cellulose. Int J Pharm 2000;209:27-35

24. Hiestand E, Wells J, Peot C, Ochs J.

Physical processes of tableting.

J Pharm Sci 2006;66:510-19

25. Heckel RW. An analysis of powder

compaction phenomena.

Trans MetallSoc AIM 1961;221:1001-8

26. Roberts RJ, Rowe RC. The effect of

punch velocity on the compaction of a

variety of materials. J Pharm Pharmacol

1985;37:377-84

27. Adedokun MO, Itiola OA. Material

properties and compaction characteristics

of natural and pregelatinized forms of

four starches. Carbohydr Polym

2010;79:818-24

28. Jetzer W, Leuenberger H. Determination

of capping tendency in pharmaceutical

active ingredients and excipients.

Pharm Acta Helv 1984;59:2-7

29. Hsu SH, Tsai TR, Chuo WH,

Cham TM. Evaluation of Era-Tab as a

direct compression excipient. Drug Dev

Ind Pharm 1997;23:711-16

30. York P. Crystal engineering and particle

design for the powder compaction

process. Drug Dev Ind Pharm

1992;18:677-721

31. Chowhan CT, Chow YP. Compression

behaviour of pharmaceutical powders.

Int J Pharm 1980;5:139-48

AffiliationMohammad Zaki Ahmad†1, Sohail Akhter2,

Ishita Dhiman1, Poonam Sharma1 &

Reena Verma1

†Author for correspondence1Department of Pharmaceutics,

Dreamz College of Pharmacy,

Mandi, India

Tel: +91 9805815080;

E-mail: [email protected] of Pharmaceutics,

Faculty of Pharmacy, Jamia Hamdard,

New Delhi, 110062, India



Exp

ert O

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Dru

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eliv

. Dow

nloa

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info

rmah

ealth

care

.com

by

Uni

vers

ity o

f C

alga

ry o

n 03

/10/

13Fo

r pe

rson

al u

se o

nly.

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