Table II.
Analytical Parameters of Phase Solubility Diagrams and Estimated Values of Solubility Enhancement Factor, S CD/S 0, and Complexation Constant, K, of PZQ–β-CD and PZQ–HP-β-CD Binary Systems at 25°C, pH 7.4
| CD | Preheatinga | Slope (b ± SD) | Intercept (a ± SD) (×10−4 M) | r 2 (n)b | S CD/S 0 c | Complexation constant, K (±SD)d |
|---|---|---|---|---|---|---|
| β-CD | No | 0.180 ± 0.002 | 5.3 ± 0.1 | 0.9997 (6) | 4.3 | 412.2 ± 5.3 |
| Yes | 0.245 ± 0.005 | 6.1 ± 0.3 | 0.999 (6) | 5.3 | 531 ± 30 | |
| HP-β-CD | No | 0.164 ± 0.002 | 5.4 ± 0.1 | 0.9994 (6) | 4.0 | 365 ± 14 |
| Yes | 0.265 ± 0.002 | 5.6 ± 0.1 | 0.9998 (6) | 5.8 | 642 ± 13 |
aPreheating was performed for 1 h at 70°C under sonication, prior to equilibration at 25°C
bNumber of replications in parenthesis
cSolubility enhancement factor calculated as the ratio of PZQ solubility in 0.01 M CD solution (S CD) versus drug solubility value measured in the absence of CD (S 0 = 0.54 × 10−3 M)
dCalculated according to Eq. 1 using the slope and intercept (predicted S 0) of the respective phase solubility plots. The calculated K values become 407, 600, 365, and 667 M−1, respectively, when the experimental S 0 = 0.54 × 10−3 M is used in Eq. 1