Effect of pH and temperature on swelling Behaviour of tamarind gum

Braja B. Panda¹, Rudra N. Sahoo^1,2, Nilamadhab Nayak¹, Subrata Mallick¹*

¹School of Pharmaceutical Sciences, Siksha ‘O’ Anusandhan (Deemed to be University),

Bhubaneswar, Odisha, India, 751003.

²School of Pharmacy and Life Sciences, Centurion University of Technology and Management,

Odisha, India.

*Corresponding Author E-mail: profsmallick@gmail.com

ABSTRACT:

Natural gum tamarind is a plant polysaccharide extracted from seeds endosperm of the plant, Tamarindus indica Linn. Thin film of the gum was prepared by direct compression method. The prepared film was investigated for the effect of pH and temperature on solvent uptake property of film by gravimetric method. Different swelling parameters such as mass swelling ratio (MSR), equilibrium swelling ratio (ESR), equilibrium swelling ratio (E_Sw) and the equilibrium water content (E_WC) were studied. It was found that swelling parameters were influenced by different pH and temperature conditions. The results suggested that the water content in equilibrium state was similar to body fluid. The gum converted to a high viscous gel of pseudo plastic characteristics in different pH conditions and the mechanism of continuous diffusion of solvent molecules into tablet during swelling was a non fickian and followed a second order kinetics.

KEYWORDS: Swelling, Swelling degree, Mass swelling ratio, Equilibrium swelling water content.

INTRODUCTION:

Nature gives us wide varieties of natural gums from plant materials which help, improve and maintain the health of all living things either directly or indirectly^1,2. Plant based natural gums are excellent choice for formulation development for their compatibility with wide range of drugs and excipients. Natural gums originating from plants are of high molecular weight and hydrophilic in nature³. These are generally composed of monosaccharide units joined by glucocidic bonds and are generally insoluble in oils or organic solvents⁴. Gums in aqueous solvent absorb water, swell up and form viscous solution or jelly^5,6. Swelling is an important characteristic related to solvent absorption capacity and also influenced by many factors. High swelling rate indicates maximum absorption and the slow process indicates the slow diffusion of solvent into the matrix. Swelling kinetics is a study of mass transfer, ion exchange and interaction and classified as Fickian and non Fickiandiffusion^7,8.

The Tamarind gum is aqueous soluble and swells to produce mucilaginous gels of non-Newtonian pseudoplastic characteristics.

In this project tamarind gum was prepared from tamarind seeds by a simple process. A thin film of gum was prepared by direct compression method. The variation of solvent absorbing capacity of the film in different physiological solution of different pH and temperature were investigated. The parameters such as mass swelling ratio, equilibrium swelling ratio (EQR), equilibrium water content (E_WC) and kinetics of swelling were analysed through gravimetric measurement method.

EXPERIMENTAL:

Materials:

Tamarind gum extracted from locally collected seeds kernel of Tamarindus indica, Acetone.

Extraction of Gum:

The method describe here was a modification of method given by Kulkarni et al. (2008) for the preparation of gum from tamarind seeds. This method involves the use of few steps and easy to apply on a laboratory scale. Tamarind seeds of 200 g were cleaned properly with water to remove any external materials. The outermost red colour tester of the seeds was removed by heating on sand. The seeds were crushed, soaked and boiled in distilled water to get a thick viscous product. The product was filtered through muslin bag to remove marc and allowed to cool down to room temperature. Acetone was added in 1:2 ratio to precipitate the mucilage. The precipitated mucilage was collected and dried at temperature 50°C in an oven. The dried mucilage was powdered and passed through sieve number 60 and preserved in a closed container for further use.

Compact preparation of the gum

Accurately weighed amount(300mg) of gum was directly compressed in to flat faced compact at 1.0 ton pressure with 1min dwelling time using 8mm punch impregnated with a little amount of magnesium stearate for easy ejection. Swelling characteristics were evaluated in buffers at pH 4, 5.8, 7 and 8, each at 22, 30, and 37ᵒC.

Swelling study

The mass swelling ratio (MSR) was calculated according to Eq. (1) and determined as a function of time:

M_t is the weight of the swollen mass at time t, and M_o is the weight at time zero. The swelling phenomenon isa continuous process till constant weight comes and the characteristic is known as equilibrium swelling ratio (E_Sw). The amount of water absorbed by the compact at equilibrium is the equilibrium water content (E_WC) which is calculated from the following Eq(2) and(3).

M_max is the hydrogel mass at equilibrium state with the solution in contact. This is the maximum achievable mass of the hydrogel. The peak value of MSR is ESR.

Swelling kinetics study

Swelling rate was calculated from the increase in weight after immersing in the aqueous liquid. Eq (4) represents the linear form for the entire swelling period.

In different solvent the swelling rate of the film was calculated from the increase in weight after immersing in the solvent. The equation (4) represents the data in linear form for the entire swelling period.

Where, S is the swelling at time t, and A = (1/ksSeq²) is the reciprocal of the initial swelling rate and B (1/Seq)is the inverse of the maximum swelling constants. k_s is swelling rate constant.

The nature of diffusion of aqueous liquid into the polymeric system was determined from the following Eq5.

Where, M_t is the solvent amount transported through diffusion into the polymeric network at time t and M_∞ at infinite time respectively. K is a constant related to the network structure and n is the swelling exponent relating to the solvent transport mode. Different types of diffusion mechanism are studied depending on the rate of diffusion. Fickian diffusion corresponds to n = 0.45-0.50. To elucidate the transport mechanism, the swelling curves were fitted to the following equation:

RESULTS AND DISCUSSIONS:

Solvent absorbing capacities (swelling) of the polymer with the solvent is dependent on the nature of both the polymer and the solvent. The effects of pH on MSR as a function of time in the hydration process are being depicted in Figure 1.The MSR is achieving some limiting value as the swelling proceeds to 480 min irrespective of variation of pH (4, 5.8, 7 and 8) and temperature (22, 30 and 37 ᵒC). It was observed that swelling increased with the time and temperature and became almost constant at 480 min. Figure 2 shows the linear regression of the swelling data obtained from equation (4) for the film in the different aqueous medium. The experimental values of swelling kinetic rate constants (K) as a function of the pH and temperature are being shown in Table 1. Figure 3 represents the effect of temperature on equilibrium water content (EWC) of the film in different physiological pH.

In recent year considerable attention has been received about the mechanism of solvent diffusion in to the polymeric system because of its important applications in the pharmaceutical fields in designing a novel drug delivery system. When a polymer is brought into contact with solution, solvent diffuses into the polymer and the polymer swells^9,10. Diffusion process is the migration of solvent into spaces between polymer chains resulting in a bigger separation between the pre-existing chains¹¹. The exponents n were calculated from the slopes and values ranging from 0.53 to 0.97 (Table 1). This indicates that diffusion of solvent to the interior of the film follows an anomalous diffusion mechanism. The values of E_wc in different temperature were in between 0.64 to 0.77 which are similar to percentage of body water content 0.60 (60%). Hence, the gum is applicable for formulation of various dosage forms for drug delivery with good patient compliance. The swelling exponents (0.53 to 0.97) revealed that the diffusion mechanism of solvent into the polymer is non-Fickian type (Table 1). The swelling parameters (ESR, E_WC, ISR and K_S) are increasing with increase of temperature 22 through 37° C at a particular pH.

Fig. 1: (A, B, C, D).Effect of pH on Mass Swelling Ratio (%) in different temperatures as a function of time.

Fig. 2: Swelling kinetics curves of tamarind directly compressed film

Table 1: swelling parameters at different Temperature and pH

Swelling Parameter	pH 4.0			pH 5.8			pH 7.0			pH 8.0
	22°C	30°C	37°C	22°C	30°C	37°C	22°C	30°C	37°C	22°C	30°C	37°C
ESR	2.07	2.30	3.07	1.80	2.50	2.83	2.00	2.33	3.43	1.67	2.03	2.50
EWC	0.67	0.70	0.75	0.64	0.71	0.74	0.67	0.70	0.77	0.63	0.67	0.71
ISR (gwater/ggel min)	0.96	1.5	1.97	0.80	0.93	0.99	1.51	1.86	1.93	0.7	1.5	1.94
Ks (ggel/gwater)	5.33	15	22.33	2.67	5.33	30.91	5.33	10.66	32.67	2.66	10	11.66
n	0.80	0.53	0.62	0.79	0.94	0.91	0.97	0.56	0.77	0.77	0.58	0.70

ESR = Equilibrium swelling ratio;  E_WC = Equilibrium water content; ISR = Initial swelling rate; Ks = Swelling rate constant; n = Swelling exponent.

Fig. 3: Effect of temperature on equilibrium water content (EWC) of the film in different physiological pH

CONCLUSION:

The tamarind gum behaved differently in aqueous environment with the change of both temperature and pH. All the swelling parameters increased as the temperature increased to 37° C. Therefore, the swelling behaviour of the tamarind gum at 37° C could be explored more beneficially in transmucosal drug delivery systems such as ocular (~7.0), buccal (~7.0), nasal (~7.0), gastro mucosal (below 4.0), vaginal (4.5), colonic (above 7.0) etc. as suitable swelling excipient.

ACKNOWLEDGEMENT:

The authors are indebted to Prof (Dr.) Manoj Ranjan Nayak, President, Siksha ‘O’ Anusandhan (Deemed to be University) for supporting financial and laboratory facilities.

CONFLICT OF INTEREST:

The authors have no conflict of interest.

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Received on 19.12.2019           Modified on 08.03.2020

Accepted on 14.05.2020         © RJPT All right reserved

Research J. Pharm. and Tech. 2021; 14(10):5471-5474.

DOI: 10.52711/0974-360X.2021.00954