Tamarind seed polyose (TSP) is a polysaccharide gum extracted from the seeds of Tamarindus indica (lmli). TSP is a polymer with an average molecular weight of 52,350 and a monomer of mainly three sugars—glucose, galactose, and xylose—in a molar ratio of 3:1:2 (3). It is insoluble in organic solvents and dispersible in hot water to form a highly viscous gel such as a mucilaginous solution with a broad pH tolerance and adhesivety (4, 5). In addition, it is nontoxic and nonirritant with haemostatic activity (4). It had been previously used in some drug formulations (5, 6).

For this study, TSP was used to prepare sustained-release formulations of indomethacin (IND), an anti-inflammatory drug substance with a short half-life of 2.4 ± 0.4 h (7). Its dosage regimen is 25 mg thrice daily, with peptic ulceration as its major side effect. IND is a suitable candidate for a sustained-release formulation. Tablets were prepared using direct compression because a wet granulation method would cause an initial swelling of the polymer, thereby affecting the swelling profile of the various fractions during release testing of the matrix tablets.

Materials. TSP was extracted according to the method described by Nandi et al. (8). After extraction, the dried material was milled into powder form with a pestle and mortar. Six particle-size fractions were obtained by sieving with various mesh-number test sieves. Indomethacin was supplied by Unicure India Pvt. Ltd. (Noida, India) and magnesium stearate was obtained from Amrut Industrial Products (Lucknow, India). Indomethacin and magnesium stearate were used as supplied.

Micromeritic property study. The bulk and tapped densities of the powder were determined with a measuring cylinder, and true density was determined using a liquid pycnometer with benzene as the displacement fluid. The porosity was determined using the equation

in which E, ρ_bulk, and ρ_true are the porosity, bulk density, and true density, respectively. The flowability (indicated by the angle of repose, Hausner ratio, and Carr's index) of the powder also was studied. The angle of repose was measured using the fixed-height method. Carr's index was calculated using the equation

and

is the Hausner ratio.

Swelling profile study. The swelling profile was determined by transferring accurately weighed 1 g of each fraction into separate 100-mL stoppered measuring cylinders. These were made up to volume with distilled water and observations made for increases in volume of the TSP. Readings were taken at specified times until a constant volume was observed in each of the cylinders.