INTRODUCTION:

In recent years, researchers have become increasingly interested in the utilization of natural biopolymers due to their wide ranging advantages over synthetic polymers. Polysaccharide gums are the materials of choice because they are naturally abundant, biocompatible, biodegradable, and nonimmunogenic.

Gum is obtained from fruits of Tamarindus indica belonging to family Leguminosae is indigenous to India. The pulp contains organic acids, such as tartaric acid, acetic acid, citric acid, formic acid, malic acid, and succinic acid; amino acids; invert sugar (25-30%); pectin; protein; fat; some pyrazines (trans-2-hexenal); and some thiazoles (2-ethylthiazole, 2-methylthiazole) as fragrant; and the seed polysaccharides are found with a main chain consisting of β-1,4-connected glucose molecules together with xylose (alpha-1,6) and galactose; total protein; lipids with fatty oils; and some keto acids. In the leaves of the plant, two triterpenes, lupanone and lupeol were found . The chemical composition of amino acids, fatty acids, and minerals of tamarind plant parts have been reported.

Phytochemical investigation carried out on T. indica revealed the presence of many active constituents, such as phenolic compounds, cardiac glycosides, l-(-)mallic acid, tartaric acid, the mucilage and pectin, arabinose, xylose, galactose, glucose, and uronic acid.[3,6,10]

In the present investigation mucoadhesive property of T. indica gum has been evaluated using diclofenac (as a model drug).

Mucoadhesion, or the attachment of a natural or synthetic polymer to a biological substrate, is a practical method of drug immobilization or localization and an important new aspect of controlled drug delivery. While the subject of mucoadhesion is not new, there has been increased interest in recent years in using mucoadhesive polymers for drug delivery. Substantial effort has recently been focused on placing a drug or a formulation in a particular region of the body for extended periods of time. This is needed not only for targeting of drugs but also to better control of systemic drug delivery. Drugs that are absorbed through the mucosal lining of tissues can enter directly into the blood stream and not be inactivated by enzymatic degradation in the gastrointestinal tract. Several polymeric bioadhesive drug delivery systems have been fabricated and studied in the past.[20,21]

Tablets prepared in this study shows simple drug release behaviour, on the surface, but the drug release pattern is a complex phenomenon, at the molecular level, it involves water penetration, polymer swelling, as well as drug dissolution, diffusion, swelling, and polymer erosion process. As shown by Matrix tablets, which can be used to control the release of both water soluble and water insoluble drugs.[1,2.4]

MATERIALS AND METHOD:

Diclofenac sodium was gifted by PANACEA Biotech, Punjab. Microcrystalline Cellulose (FMC Biopolymer), Sodium Carboxyl ethyl Cellulose, Magnesium stearate (Samar Chemicals). All other reagents and chemicals used were of analytical reagent grade.

Method: Isolation of TSP

TSP was isolated following the method reported by Rao et al (1973).[10,15]. To 20g of tamarind kernel powder, 200 ml of cold distilled water was added and slurry was prepared. The slurry was poured into 800ml of boiling distilled water. The solution was boiled for 20 minutes under stirring condition in a water bath. The resulting thin clear solution was kept overnight so that most of the proteins and fibers settled out. The solution was then centrifuged at 5000 rpm for 20 minutes. The supernatant was separated and poured into twice the volume of absolute ethanol by continuous stirring. The product was filtered through muslin cloth and was pressed between felt. The precipitate was washed with absolute ethanol, isopropanol and methanol and then dried at -50-60⁰C under freeze dryer. The dried material was ground and sieved to obtain granules of different particle size range and stored in a desiccator until further use.[11,16]

Purification and standardization of Gum

The Gum was standardized for following properties.

Loss on drying:

The 5 gm gum was dried at 105 ± 5 ºC till the constant weight of gum was obtained. The loss on drying was found to be less than 7 % w/w

Ash value:

1gm of gum was accurately weighed and evenly distributed it in the crucible. It was dried at 105 ºC for one hour and ignited in muffle furnace at 70⁰± 25 ºC. Percentage of ash content was found to be less than 6 % w/w.The binder gum is natural and have ph between 7.0 - 7.5. This gum was also tested for flow properties as per I.P. and shown in table 1.

Table 1: Flow properties of dried Tamarind gum

S.No.	Parameter	Value
1.	Bulk density(g/cm3)	0.50 ± 0.4
2.	Tapped density(g/cm3)	0.35 ± 0.8
3.	Carr’s index(%)	25.82 ± 0.4
4.	Angle of repose(0)	28.0 ± 0.26
No. of experiments (n) = 3

Swelling property of mucoadhesive materials [12-14]

Natural mucoadhesive material obtained from the fruits of Tamarindus indica linn is nontoxic. 250 mg of Tamarindus indica gum was allowed to hydrate in 25ml of distilled water at 250C in a 25 ml graduated cylinder. and volume measured at 5 min. intervals until there was no further hydration observed. The swelling property was determined at different time intervals (Table 2).

Table 2: Swelling property of Tamarindus indica gum.

Natural

gum

After

Min

(ml)

After

Min

(ml)

After

Min

(ml)

After

Min

(ml)

After

Min

(ml)

After

Min

(ml)

After

Min

(ml)

Tamarindus

indica

0.7

0.9

1.0

1.1

1.2

1.3

1.5

Shear stress method[17,20,21]

Two smooth, polished plexi glass blocks were selected; one block was fixed with adhesive 'Araldide' on a glass plate, which fixed on leveled table. To the upper block a thread was tied and the thread was passed down through a pulley. At the end of the thread a beaker was fixed. The length of the thread from pulley to beaker was 7 cm. The weight of the beaker was counteracted. 0.75% w/v solution of Tamarindus indica gum was prepared using purified water I.P. as solvent. A fixed volume (0.5 ml) of 0.75% w/v solution of Tamarindus indica gum were kept on the centre of the fixed block with a pipette, and then second block was placed on the first block and pressed by applying 100 g of weight, so that the drop of synthetic polymer and natural bioadhesive material solutions spreads as a uniform film in between the two blocks. After keeping it for a fixed time intervals of 5, 10, 15, and 20 min., purified water was added into the beaker gradually, the weight of purified water just sufficient to pull the upper block or to make it slide down from the base block was recorded. This weight was considered as the adhesion strength, i.e. shear stress required to measure the adhesion. Before every experiment, care was taken so that no air bubble form in between the two Blocks, which may give erratic results, and the distance from pulley to glass block shear stress was studied.

Drug-excipients interaction studies[3,5]

Drug excipients interaction studies are very important for the successful formulation of any dosage form. Fourier Transform Infrared (FTIR) Spectroscopy studies were used for the evaluation of physicochemical compatibility and interactions, which helps in the prediction of interaction of the drug with Tamarindus indica gum, diluents and lubricants used in tablet formulations. In the present study 1:1 ratio was used for preparation of physical mixtures and analyzed for compatibility studies. FT-IR studies were carried out with a Shimadzu FTIR 8400S facility using KBr pellet.

Formulation of Sustained Release Tablets

Sustained Release tablets formulation was developed with diclofenac IP as model drug by direct compression method. Tamarindus indica gum was used as a in the concentration 0.25, 0.50, 0.75, 1.00 and 1.25 w/w. Binder level was adjusted by lowering the level of MCC in the formula. All ingredients were dried, passed through 120 mesh sieve and mixed manually in mortar. The tablet formulation was developed for 250 mg tablet weight using 100 mg of Diclofenac (drug) and varying concentration of Tamarindus indica gum (as tablet binder). The tablets were compressed by using single punch tablet machine fitted with flat faced punches. The batch size prepared was 50 tablets. The prepared tablets were stored in closed container for 30 days. No evidence of chemical change was observed. The tablets were evaluated for uniformity of weight as per I.P. method.[4,5]

Evaluation of Mucoadhesive Tablets

The properties of the mucoadhesive tablet, such as hardness, friability, weight variation and drug content were determined using reported procedure.16 Briefly, hardness was determined using Monsanto hardness tester. Friability was determined by using Roche friability testing apparatus. Weight variation and drug content was performed according to IP procedures.[16]. The drug content was determined by weighing 10 tablets individually and powdered equivalent to 100mg of drug was extracted with water. The solution was filtered and after suitable dilution its absorbance was measured at 336 nm by UV visible spectrophotometer (Shimadzu 1700).

In vitro drug release study [8,9,16,18]

Release of Diclofenac from the tablets was studied in phosphate buffer of pH=6.8 (900 ml) as prescribed in the dissolution rate test of tablets in USP XXIV (method A) using USP Apparatus II by the rotation of the paddle at 50 rpm. The temperature was maintained at 37⁰ C ± 0.5⁰C. 10 ml of the sample was withdrawn at different time intervals, filtered and diluted suitably and analyzed by UV spectrometer (PC-2401) at 336 nm. All the experimental units were analysed in triplicate (n=3).In order to study the exact mechanism of drug release data was analysed according to zero order, first order, higuchi square root. The criteria for selecting the most appropriate model were chosen on the basis of goodness of fit test.

Swelling studies [5,6,7,16,19]

The extent of swelling was measured by taking different formulation of tablets and their initial weight was noted. Tablet from each batch was placed in Petri plate in pH 6.8 phosphate buffer. At time interval of 2, 4, 6, 8, 10, 12 hours tablets were removed from buffer medium and excess water on their surface was carefully absorbed with filter paper. The swollen tablets were weighed and swelling index was calculated.

Swelling index = (W1-W2)/W2X 100.

Mucoadhesive studies [16,19,20,21]

The tablet was studied for Force of mucoadhesion as well as duration of mucoadhesion.

Force of mucoadhesion:

Bioadhesive strength of the tablet was determined by modified physical balance. The apparatus consist of a modified double beam physical balance in which right pan had been replaced by lighter pan and the left pan had been replaced by beaker. The left side of the balance was exactly 5 g heavier by right side. A teflon block was placed in a petri dish, which was placed below the left hand side of the balance. Bovine Intestine was used for the study and phosphate buffer pH 6.8 was used as a moistening fluid. The mucosa was washed and spread on the Teflon block using thread. Peristaltic pump was used to pump the Phosphate buffer 6.8 at the flow rate 1ml/min. Tablet was fixed to the lower side of the lighter pan and the tablet was made to adhere to the membrane. Water was added slowly with an increment of 0.5 ml till tablet just separate from the membrane.

Duration of mucoadhesion

Tablets were thereby attached to freshly excise intestinal bovine mucosa, which has been spanned on a stainless steel cylinder. (Dissolution apparatus USP I basket). The cylinder was placed in the dissolution apparatus according to USP containing phosphate buffer pH 6.8 at 370C. The fully immersed cylinder was agitated with 100 rpm. The detachment disintegration and erosion of the tablets were observed within a time period of 10 hrs.

Stability studies [2,17]

The stability studies were carried out according to ICH and WHO guidelines to assess the drug and formulation stability QC1(13). Optimized formulation was sealed in aluminum packaging having a polyethylene coating on the inside. Samples were kept in a humidity chamber maintained at 45°C and 75% RH for 3 months. At the end of the study period, samples were analyzed for drug content, dissolution studies and detachment stress.

RESULT AND DISCUSSION:

The gum isolated from Tamarindus indica pulp and pH between 7-7.5 and evaluated for flow property as per I.P. result indicates the gum have good flow property^[17]. The swelling property show good swelling of gum in 35 min which reveals, it was suitable candidate for sustained release. The gum is also evaluated for shear stress property which showed better adhesiveness (17.8 g) after 20 min.[19,20]

Sustained release tablets of Diclofenac sodium with Tamarindus indica gum were prepared by using different drug: gum ratios. All the formulation showed uniform thickness, hardness, weight and drug content and found to be within pharmacopoeial limit. The compositions of the tablets and the results of the physical characterization of tablets are summarized in Table 3 and 4. The friability value decreases with increases Tamarindus indica gum concentration and hardness of tablet increases with increases gum concentration.[9]

Table 3: Composition of tablets containing Tamarindus indica

Content of tablet	Formulation [Drug: Gum ratio]
Content of tablet	1:0.25 F1	1:0.50 F2	1:75 F3	1:1 F4	1:1.25 F5
Diclofenac sodium(mg)	100	100	100	100	100
Tamarindus indica gum(mg)	25	50	75	100	125
MCC 100(mg)	122.5	97.5	72.5	47.5	22.5
Mg. Stearate(mg)	2.5	2.5	2.5	2.5	2.5
Total wt of tablet (mg)	250	250	250	250	250

Table 4: Evaluation of tablets prepared from Aegle marmelos gum

S. No	Formulation	Hardness (kg/cm²)	Friability (%)	Drug content (%)	Thickness (mm)	Wt. variation
1	F1	6.20±1.25	0.70±0.02	100.2±4.45	5.1±0.21	249.45±0.45
2	F2	6.40±1.45	0.65±0.04	99.5±2.30	5.3±0.10	251.10±0.20
3	F3	6.50± 1.35	0.65±0.02	99.7±2.50	5.0±0.35	250.35±0.15
4	F4	7.00±1.35	0.50±0.03	100.1±5.65	5.2±0.15	250.10±0.35
5	F5	7.50±1.40	0.45±0.05	99.50±3.40	5.2±0.30	249.25±0.30

Number of trials ( n= 5)

For Wt. variation data no. of trials n=20

In vitro drug release study [12,15,16]

The results of in vitro drug release studies of different formulation are depicted in Figure 1.

Figure 1: cumulative percentage release of drug

Formulation F1, F2, F3, F4 shows significant good release for 12 hrs with low burst effect. The formulation with 1:1 drug-gum ratio (formulation F4) exhibited the extended cumulative percentage of drug release value (95.5%) after 12 hr. The initial burst release decrease with increase in concentration of gum. Other formulation did not show the results of drug release upto that extend. The drug release follows the Higuchi release pattern i.e. diffusion followed by erosion and n value (n<0.05) indicates nonfician transport mechanisms. [table 5]

Table5 : Drug release kinetic studies of tablet formulation

Formulations	Zero order kinetics	First order kinetics	Higuchi square root equation	Regression coefficient
F1	0.9213	0.9131	0.9997	0.5210
F2	0.9326	0.8968	0.9988	0.5625
F3	0.9112	0.9200	0.9951	0.6212
F4	0.9231	0.9144	0.9990	0.5176
F5	0.9416	0.9106	0.9992	0.5426

Mucoadhesive study

The swelling behaviour is important for bioadhesion. Water sorption increases with increase in the concentration of hydrophilic polymers. The Tamarindus indica gum swells slowly and dissolves in presence of water. Hence SI increases with time up to 9 hours and then decreases. The reason behind this may be that as the time passes more the dissolution of outer gelled layer of tablets in dissolution medium. With no doubt, the hydrophilic content of the hydrogel will affect the intermolecular forces responsible for diffusion and swelling. As hydrophilicity of the hydrogel increases, the interaction between water and hydrogel will increase too; this facilitates water diffusion and leads to greater swelling. In formulation F1 to F-5 showed sharp increase in swelling (figure.2).

Time [hrs]

Figure 2: Swelling index of formulated tablet

Mucoadhesion is determined by Mucoadhesive strength and duration of mucoadhesion. Formulation F1-F4 shows good mucoadhesive strength. As the viscosity gum increases swelling increases and mucoadhesion force depends on the swelling of the gum. This improves the consolidation step that increases the mobility of molecule and facilitates the interpretation with mucus layer, thus mucoadhesion increases. F4 shows maximum mucoadhesive strength i.e. 0.285 N But further F5 has least mucoadhesion strength; this is due to tremendous increase in viscosity, which leads to entangled structure of the polymer, which hinders the deep interpenetration between polymer and mucin molecules.

All the formulation except F5 passes the test of mucoadhesion. The order of mucoadhesion property among all the formulations was found as F4>F3>F2>F1 (Time = 10 hrs). The formulation F5 fails to retain due to the over hydration of the formulation .The targeting to the intestine can be achieved by the dynamic swelling behavior of cross linked Natural polymers which depend on the polymer relaxation at different pH. In intestinal pH, networks swelled by a relaxation-controlled mechanism and leads to entanglement of natural polymers with mucin.

No interaction was observed in the IR spectra. All the principle peaks were observed in the tablet formulation spectrum (figure 3 and 4). Formulation was found to be stable for 3 months in accelerated condition.

CONCLUSION:

The present study revealed that Tamarindus indica gum used as Natural polymers appears to be suitable for use as a release retardant in the manufacture of sustained release tablets because of its good swelling, good flow rate and suitability for mucoadhesion formulations. From the dissolution study, it was concluded that dried Tamarindus indica gum can be used as an excipient for making sustained release mucoadhesive tablets of diclofenac sodium.

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Received on 18.04.2014 Accepted on 28.05.2014

Asian J. Res. Pharm. Sci. 4(2): April-June 2014; Page 77-82