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.
Table V: Results of regression analysis for dependent variables.
The dissolution data of batch HL6 were compared with the ideal release profile using f2 statistics. An f2value of 87.86 indicates that the release profile of batch HL6 was comparable with the ideal batch. A value of f2 ≥ 50 is necessary for similarity in dissolution profile at 10% difference. Table V shows the results of multiple linear regression
for the response Y60, Y300, and t80. The high values of r2 indicate good fit. The drug release of the best batch HL6 was also conducted in phosphate buffer (pH 6.8). The dissolution
data of batch HL6 in distilled water were compared with the dissolution data in phosphate buffer (pH 6.8). An f2 of 89.68 indicated that the release profile of batch HL6 in distilled water and phosphate buffer were comparable. Lastly,
the dissolution of batch HL6 was compared with the market preparation of the drug in distilled water. The dissolution data
of both were compared using f2 statistics. An f2 of 90.48 indicates that the release profile of batch HL6 and the market preparation of the drug were comparable.
Kinetics of drug release. The methods of Bamba and Puisieux were adopted as the most appropriate model for studying the kinetics of the drug release
(37). The dissolution data of the best batch (HL6) were fitted to zero order, first order, Higuchi, Hixson-Crowell, Korsemeyer
and Peppas, and Weibull models. The results of F-statistics were used for selecting the most appropriate model. The release profile of the best batch (HL6) fitted best to
the zero-order equation (F = 16.13), showing the least residual sum of square compared with Higuchi (F = 27.93) and Korsmeyer and Peppas (F = 21.80) models. This superiority, however, is statistically insignificant among these three models, as shown by the goodness
of fit test (F-ratio test). The priority should be given to the model with the lowest F-value. The drug release from the hydrophilic matrix of diclofenac sodium tablets, therefore, may be best explained by the
zero-order model. The values of slope and intercept for the zero-order models are 0.1259 and 11.7007, respectively.
Hydration capacities and erosion. Figure 1 shows the percentage increase in the weight of the hydrated pure gum matrices at various time intervals up to 6 h.
There is a strong degree of water uptake by the mucilage powder (≈ 1107% weight increase after 6 h. It is noteworthy, however,
that there is little difference in water uptake of the mucilage powder at different agitation speeds (< 10% weight difference
at 100 and 50 rpm after 6 h). Hydration is independent of agitation. The large increase in weight resulted from the very strong
hydration capacity of the mucilage powder, coupled with very little simultaneous weight loss because of erosion. Erosion was
greatly influenced by the agitation speed. Figure 2 shows that only 54% of the mucilage material remained after 6 h at 50
rpm, whereas after the same time period at 100 rpm, the amount remaining was ≈ 74%. Erosion occurred readily from compressed
mucilage matrices that were highly influenced by agitation speed. The weight difference with time was clearly a measure of
both the hydration and erosion processes occurring simultaneously.