TABLE 3.
Thermodynamic parameters of linagliptin‐bovine serum albumin, rabeprazole sodium‐bovine serum albumin, and 1:1 drug–drug complex‐bovine serum albumin systems at three different temperatures (pH 7.4)
| System | T (K) | 1/T (K–1) | r 2 | Ea (kJ/mol) | ∆H (kJ/mol) | ∆S (J/mol/K) | ∆G (kJ/mol) |
|---|---|---|---|---|---|---|---|
| LG‐BSA | 298 | 0.0033 | –26.15 | –26.15 | –52.44 | –10.52 | |
| 308 | 0.0032 | 0.9906 | –26.15 | –26.15 | –52.44 | –9.99 | |
| 318 | 0.0031 | –26.15 | –26.15 | –52.44 | –9.47 | ||
| RS‐BSA | 298 | 0.0033 | –16.84 | –16.84 | –24.96 | –9.40 | |
| 308 | 0.0032 | 0.8290 | –16.84 | –16.84 | –24.96 | –9.15 | |
| 318 | 0.0031 | –16.84 | –16.84 | –24.96 | –8.90 | ||
| (LG+RS)‐BSA | 298 | 0.0033 | –39.28 | –39.28 | –106.06 | –7.67 | |
| 308 | 0.0032 | 0.9961 | –39.28 | –39.28 | –106.06 | –6.61 | |
| 318 | 0.0031 | –39.28 | –39.28 | –106.06 | –5.55 |
Abbreviations: BSA, bovine serum albumin; LG, linagliptin; RS, rabeprazole sodium.
Note: The listed thermodynamic factors like change of enthalpy (∆H) and entropy (∆S) were unique in all three temperatures. Both parameters (∆H and ∆S) were calculated from the slope and intercept obtained from the linear regression line (ln Ka vs. 1/T) plotted by utilizing the van ’t Hoff equation. The temperature‐dependent parameter, free energy change (∆G), was interpolated by utilizing the obtained thermodynamic parameters (∆H and ∆S) at three different temperatures. The value of ∆G for all the systems was varied due to temperature variation. According to the Arrhenius equation, the activation energy (Ea ) was calculated from plotted the regression line (ln kq vs. 1/T). The activation energy was constant despite the temperature rising. The observed Ea value of the drug–drug complex was found higher than the mother compounds.