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Assessing Hibiscus rosa-sinensis Linn as an Excipient in Sustained-Release Tablets
Natural gums and mucilage are biocompatible, cheap, readily available, and represent a potential source of excipients. The authors examine the functionality of mucilage extracted from the leaves of Hibiscus rosa-sinensis Linn as an excipient in a sustained-release tablet formulation.
Radial and axial swelling of the tablet. The initial diameter and thickness of the tablet were measured, and the tablet was kept in dissolution media. The increase
in diameter and thickness was measured at various time intervals. To evaluate the relation, the equilibrium degree of swelling
(Q) was calculated from the radial and axial swelling ratio using the following equation:
in which Vtand Vo are volumes; Rt and Ro are radius at time t and zero, respectively; and It and Io are thickness at time t and zero, respectively (36).
Stability study. To study the effect of storage on an in vitro drug release, the stability study of the best formulation (HL6) was carried out at 40 °C and 75% relative humidity in a humidity
oven. Samples were withdrawn after a three-month interval, and in vitro drug release was performed.
Results and discussion
Table I: Rheological data of dried-powdered mucilage and sodium carboxymethylcellulose (CMC).
Various physiochemical characteristics of the extracted mucilage from Hibiscus rosa-sinensis Linn were investigated. The percentage yield was 15%, and the average particle size was 180 μm. The mass loss on drying indicated
the amount of moisture present in the material that was available to interact with other material. For dried mucilage, the
mass loss on drying was 10.61%. The swelling ratio of mucilage was 9 in distilled water, 10 in simulated gastric fluid (0.1
N HCl), and 9 in phosphate buffer (pH 6.8). The authors concluded that the swelling of mucilage is pH-independent, and the
mucilage is nonionic.
Table II: Flow properties of dried-powdered mucilage and other gums.
The viscosity of the extracted dried mucilage was compared with that of semisynthetic polymer sodium carboxymethyl cellulose
(see Table I). When dried mucilage concentration exceeded 0.2% w/v, the viscosity was very difficult to measure with the Ostwald
viscometer. The dried mucilage had higher viscosity than the sodium carboxymethylcellulose.
