Experimental design
Materials.
Diclofenac sodium was received as a gift from Beacon Pharmaceuticals (Ahmedabad, India). The leaves of Hibiscus rosa-sinensis Linn were collected from the medicinal garden of the C.K. Pithawala Institute of Pharmaceutical Science and Research in Surat,
India. Guar gum Indian Pharmacopoeia (IP) grade, ispaghula husk, sodium carboxymethyl cellulose IP, lactose IP, talc IP, and magnesium stearate IP were received
from Atul Chemicals (Anand, India). All other solvents and chemicals were of analytical-reagent grade. Deionized double distilled
water was used throughout the study.
Methods.
The fresh leaves of Hibiscus rosa-sinensis Linn were collected, washed with water to remove dirt and debris, and dried. The powdered leaves were soaked in water for 5–6
h, boiled for 30 min, and kept aside for 1 h for complete release of the mucilage into water. The material was squeezed from
an eight-fold muslin cloth bag to remove the marc from the solution. Acetone was added to the filtrate to precipitate the
mucilage in a quantity of three times the volume of the total filtrate. The mucilage was separated, dried in an oven at a
temperature < 50 °C, collected, dried-powdered, passed through a sieve (number 80), and stored for further use in desiccators
(32).
Physicochemical properties of dried powdered mucilage.
Dried- powdered mucilage was studied for percentage yield, particle size, mass loss on drying, viscosity, swelling index,
bulk density, angle of repose, and compressibility.
Particle size.
The microscopic method was used (in triplicate) to determine the particle size of the dried mucilage.
Mass loss on drying.
The mass loss on drying was determined for an appropriate quantity of dried mucilage at 105 °C for 2 h in a hot-air oven.
Swelling ratio.
The study was carried out in a 100-mL stoppered graduated cylinder. The initial bulk volume of 1 g of dried mucilage was
measured, and water was added in sufficient quantity to yield a 100-mL uniform dispersion. The sediment volume of the swollen
mass was noted after 24 h in storage at room temperature. The swelling ratio was calculated by determining the ratio of the
swollen volume to the initial bulk volume. The swelling ratio was evaluated in distilled water, simulated gastric fluid (0.1
N HCl), and phosphate buffer (pH 6.8) (33).
Viscosity.
Rheological studies of dried mucilage were carried out using various concentrations of solution (0.1–0.5% weight/volume
(w/v) in distilled water. The viscosity was measured using an Ostwald viscometer and compared with the viscosity of sodium
carboxymethylcellulose.
Bulk and tapped density.
A preweighed and presieved quantity of dried mucilage was poured into a graduated cylinder, and the volume recorded. The
cylinder was tapped until the powder bed volume reached a minimum value, and the tapped volume was recorded. The bulk and
tapped densities were calculated. Carr's index and Hausner ratio. Carr's index and Hausner ratio were calculated from the
bulk and tapped densities.
Angle of repose.
The angle of repose (θ) was determined using the fixed-height funnel method and calculated as follows:
in which h is the height of the powder heap and r is the radius of the powder heap. Comparisons were made between dried mucilage, guar gum, and ispaghula husk.
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