Comparative Evaluation of Compaction Characteristics and Flow Properties of Tamarind and Gellan Gum

 

Patil SV*1, Jadge DR1 and Dhawale SC2

 

1Shree Santkrupa College of Pharmacy, A/P Ghogaon, Tal. Karad, Dist. Satara -415111.

2Government College of Pharmacy, Karad.

* Corresponding Author E-mail: sachinpatil79@rediffmail.com.

 

ABSTRACT

Tablet compression is a process of applying pressure to materials held in die cavity. Measurement of porosity change as a function of compression pressure is widely used in describing the compression process. The heckle plot is the method, most frequently used to evaluate the volume reduction of the materials when pressure is applied. Tamarind is a seed gum with potential industrial application and was successfully used in formulation of tablet. Gellan is an exopolysaccharide generally available in two grades, high acyl gellan and low acyl gellan. Gellan gum has been used as disintegrant and also in the formulation of gastro retentive tablet. In the present study, compressibility characteristics and flow properties of gellan gum and tamarind gum were comparatively evaluated with directly compressible lactose. Compressibility properties were studied by Heckel plot study, Carrs index and Hausners ratio and flow properties were studied by angle of repose. The study showed that degree of initial packing in low acyl and high acy gellan gum was high as compared with directly compressible lactose. For tamarind gum, degree of initial packing is lower as compared with directly compressible lactose. Gum powders did not undergo extensive particle rearrangement. Also high acyl gellan gum and tamarind gum showed greater amount of plasticity than low acyl gellan gum and directly compressible lactose.

 

 KEY WORDS Compressibility, Heckel plot, Tamarind gum, Gellan gum

 

INTRODUCTION:

Polysaccharides are frequently used in drug delivery systems. When polysaccharides are used in tablet formulations, its compressibility properties are very important. Tablet compression is a process of applying pressure to materials held in die cavity. The events that occurs in process of compression are1 transitional repacking, deformation at point of contact, fragmentation and/or deformation, bonding, deformation of solid body, decompression, ejection. In pharmaceutical industry, the measurement of porosity change as a function of compression pressure is widely used in describing the above compression process. The compressibility of powder bed could be obtained from relationship between applied pressure and porosity.2

 

The Heckle plot is the method, most frequently used to evaluate the volume reduction of the materials when pressure is applied. It is assumed that the densification of the powdered column follows a first order kinetics. Thus the degree of material densification is correlated to its porosity3,4. The Heckel equation is widely used for relating the relative density ‘D’ of a powder during compression to the applied pressure ‘P’. It is written as follows: ln (1/1-D) = KP + A (1)

 

The slope of the straight-line portion ‘K’ is the reciprocal of the mean yield pressure ‘Py’ of the material. From the value of the intercept ‘A’ the relative density ‘Da’ and the relative density of powder bed at the point when the applied pressure equals to zero ‘Do’ can be calculated using following equations.

Da = 1- e-A (2) Do= 1- e-Ao (3)

Where Ao represents the intercept of the line when P = 0. The relative density ‘Db’ describes the phase of rearrangement at low pressure and is the difference between Da and Do: 5

Db = Da - Do (4)

 

Tamarind gum is obtained from endosperm of seeds of the tamarind tree (Tamarindus Indica), which is a seed gum with potential industrial application.6 Recently tamarind gum was successfully used in formulation of bioadhesive tablet of lactoferrin.7 Gellan is an exopolysaccharide produced by bacterium Spingomonas paucimobilis, formerly referred as Pseudomonas elodea. Generally gellan gum is available in two grades, high acyl gellan, which is partially deacetylated and low acyl gellan, which is highly deacetylated.8 Gellan gum is used as disintegrant9 and also for gastro retentive drug delivery system in tablet formulation10. Therefore objective of this study was to comparatively evaluate the compressibility characteristics of gellan gum and tamarind gum with directly compressible lactose.

 

MATERIALS AND METHODS:

Materials:

Tamarind kernel powder was obtained as gift sample from Balasamlca mill, Theni, Andhra Pradesh. Low acyl gellan gum (LA) and high acyl gellan gum (HA) were obtained as gift samples from CP Kelco (Burzin and Leons, Pvt. Ltd.), Bombay. Directly compressible lactose (DCL) was purchased from Rajesh Chemicals, Mumbai.

 

Methods:

Compressibility study by Heckel analysis:

Compression was performed on hydraulic press (Sammrudhi Enterprises, Mumbai.) using 13 mm flat faced punch and die set, at pressure 20, 40, 60, 80, 100 and 120 kg/sq.cm. True density of the powder was determined by compression at 120 kg/sq.cm. The weight, diameter and thickness were also determined. The data was processed using Heckel equation (Eq. 1). Mean yield pressure (M.Y.P.), Da, Db and Do were determined as per equations 1, 2, 3 and 4 respectively.

 

Bulk density, tap density, Carrs index and Hausners ratio:

Bulk density and tap density was determined according to following method:

A 50 ml glass cylinder was weighed and filled with 30 ml of spray-dried extract and reweighed. The opening of the cylinder was secured with parafilm. The cylinder was gently reversed once and the powder was carefully leveled without compacting. Bulk volume was determined after one mechanical tap on a tap density tester (Dolphin Instruments, Mumbai.). Tap volume was measured after 2000 taps. Each analysis was repeated thrice.11 Values of bulk density and tap density used to calculate Carrs index and Hausners ratio.12, 13

 

Figure 1: Heckel plots of LA, HA, TKP and DCL.

RD: Relative density, LA: Low Acyl Gellan gum, HA: High

Acyl Gellan gum, DCL: Directly compressible lactose.

 

Flow property:

The flow behavior of TKP, LA, HA and DCL was determined by angle of repose. Fixed funnel method was used for determination of angle of repose.14

 

RESULTS AND DISCUSSION:

Heckel analysis:

Heckle plot is as given in Fig 1. The Intercept A was determined from extrapolation of the line. The values of M.Y. P, Da, Db and Do of the formulations are presented in Table 1. Do value represent the degree of initial packing in the die. Do values of LA and HA were high than DCL, which indicates that degree of initial packing in LA and HA is high as compared with DCL. For TKP, Do values are less than DCL which indicates that degree of initial packing is lower as compared with DCL. Da value represents the total degree of packing at zero and low pressure. Da values of LA and TKP were less than DCL but that of HA was more than DCL which indicates that total degree of packing of LA and TKP were less than DCL but for HA it was more. Db value represents the particle rearrangement phase in early compression stage and tends to indicate extent of particle fragmentation although fragmentation occurs at the same time as plastic and elastic deformation of constituent particles. LA, HA and TKP shows lower Db values than DCL which indicates LA, HA and TKP did not undergo extensive particle rearrangement as compared with DCL. The further arrangement may be due to fragmentation of individual particles followed by plastic deformation, so plastic deformation was a principle mechanism of compression which was also supported by relatively low M.Y. P values of HA, LA and TKP than DCL. Larger value of slope is related with greater amount of plasticity in the material.3 LA, HA and TKP shows large values of slope than DCL which has shown their greater amount of plasticity than DCL. MYP is related inversely to the ability of a material to deform plastically under pressure. MYP values of LA, HA and TKP were less than DCL which indicates that onset of plastic deformation in LA, HA and TKP occurred at lower pressure than DCL which is well correlated with results of slope and Db. Furthermore Db values of LA, HA and TKP were lower than Do indicates better particle rearrangement during die filling which is exactly opposite to that of DCL.

 

Bulk density, Tap density, Carr’s index and Hausner’s ratio:

The values of bulk density, tap density, Carr’s index and Hausner’s ratio were given in Table 2. Bulk density and tap density values of the gums were less than DCL. The Carr’s index and Hausner’s ratio were simple methods to evaluate compressibility of powders. The higher values of Carr’s index and Hausner’s ratio of gums as compared with DCL showed its poor compressibility.12, 13

 

Flowability:

Flow behavior of LA, HA, TKP and DCL was determined by Angle of repose and the values were given in Table 2. The values of angle of repose of gums showed their poor flowability as compared with DCL.14

 

CONCLUSION:

Comparative evaluation of compaction properties of LA, HA, TKP with DCL showed that except HA, LA and TKP have high degree of initial and total packing at zero and low pressure than DCL. But all gum powders showed very less extent of particle rearrangement. Also it was observed that for gum powders, plastic deformation was a principle mechanism compression which was well supported by low slope and high MYP values. It was concluded that LA, HA and TKP have poor compressibility and flowability. Thus during formulation of tablets with the LA, HA and TKP need to add additional excipients to have better compressibility and flowability.

 

Table 1: Heckel parameters of LA, HA, TKP and DCL

Sample	Slope	Intercept	M.Y.P.	Da	Do	Db
LA	0.02869	0.823	34.8472	0.5609	0.4725	0.0884
HA	0.04345	1.0126	23.0128	0.6369	0.5648	0.0721
TKP	0.04752	0.2162	20.9415	0.1943	0.1681	0.0262
DCL	0.0223	0.980	44.84	0.6247	0.2813	0.3434

LA: Low Acyl Gellan gum, HA: High Acyl Gellan gum, DCL: Directly compressible lactose

 

Table 2: Heckel parameters of LA, HA, TKP and DCL.

Sample	B. D. (g/cc)	T.D. (g/cc)	C.I. (%)	H.R.	A.O.R. (0)
LA	0.3448	0.4748	27.56	1.38	39.56
HA	0.4011	0.5263	31.21	1.31	43.52
TKP	0.4761	0.5405	11.92	1.14	51.34
DCL	0.78	0.91	14.28	1.666	24.13

B.D.: Bulk density, T.D.: Tapped Density, C.I.: Carrs Index, H.R.: Hausner’s ratio, A.O.R.: Angle of repose.

 

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Accepted on 12.08.2008   © RJPT All right reserved