TABLE 4.
Binding constant and number of binding sites of linagliptin‐bovine serum albumin, rabeprazole sodium‐bovine serum albumin, and 1:1 drug–drug complex‐bovine serum albumin systems at different temperatures
| System | pH | T (K) | r 2 | Kb (L/mol) | logK b | n |
|---|---|---|---|---|---|---|
| LG‐BSA | 7.4 | 298 | 0.9237 | 2.65 | 0.424 | ˜1.0 |
| 308 | 0.9210 | 2.05 | 0.313 | ˜1.0 | ||
| 318 | 0.9109 | 3.41 | 0.533 | ˜1.0 | ||
| RS‐BSA | 7.4 | 298 | 0.8709 | 2.11 | 0.325 | ˜1.0 |
| 308 | 0.9109 | 2.10 | 0.324 | ˜1.0 | ||
| 318 | 0.8924 | 1.58 | 0.201 | ˜1.0 | ||
| (LG‐RS)‐BSA | 7.4 | 298 | 0.890 | 0.12 | –0.905 | ˜1.0 |
| 308 | 0.915 | 1.23 | 0.092 | ˜1.0 | ||
| 318 | 0.901 | 1.00 | 0.0005 | ˜1.0 |
Abbreviations: BSA, bovine serum albumin; LG, linagliptin; RS, rabeprazole sodium
Note: The binding parameters (Kb = binding constant and n = number of binding sites) were obtained from the linear relationship between log{(F 0 – F)/ F } and log{[D]0 – n[P]0(F 0 – F)/F} for all systems at three different temperatures at pH 7.4. The binding constants (Kb ) for the drug–drug complex with BSA were found smaller than the parent compounds. The number of binding sites (n) was almost steady and approximately one.