Formation mechanism of precipitation in Huanglian Jiedu Decoction based on molecular thermodynamic characteristics / 中草药

ABSTRACT

Objective To explore all sources of precipitation, parameters of interaction and binding abilities of different Chinese materia medica (CMM) combinations during the formation process of the precipitation in Huanglian Jiedu Decoction (HJD) using the thermodynamic method. The study was aim to reveal the mechanism of the formation of precipitation in CMM decoction. Methods First, the possible CMM combinations which had obvious precipitation phenomenon when combined were determined by the research on decomposed recipes. Then isothermal titration calorimetry (ITC) was used to determine the binding heat and thermodynamic parameters of binding reactions, thermodynamic parameters contents binding constant (Ka), dissociation constant (Kd), estimate of stoichiometric ratio (n), enthalpy change (ΔH), entropy change (ΔS), Gibbs free energy change (ΔG), these data were used to explain the differences in binding abilities between different CMM combinations. Results The original decomposed recipes experiment indicated the CMM combinations that could produce obvious precipitate when they were mixed were Scutellariae Radix-Coptidis Rhizoma and Scutellariae Radix-Phellodendri Chinensis Cortex. Precipitation amount of Scutellariae Radix-Coptidis Rhizoma was the most. There was no precipitate in Scutellariae Radix-Gardeniae Fructus, Coptidis Rhizoma-Phellodendri Chinensis Cortex, Coptidis Rhizoma-Gardeniae Fructus or Phellodendri Chinensis Cortex-Gardeniae Fructus. In ITC, the thermodynamic parameters of the three experience groups were the same, ΔH 0, ΔG |-TΔS|, indicating the three reactions were all enthalpy-driving reactions. The Ka of Scutellariae Radix decoction titrated Coptidis Rhizoma decoction was 1.283 × 104, Scutellariae Radix decoction titrated Phellodendri Chinensis Cortex deccotion was 4.680 × 103, Scutellariae Radix decoction titrated Gardeniae Fructus decoction was 1.973 × 103. The value decreased gradually. The binding heat of Scutellariae Radix and Gardeniae Fructus was much smaller than the binding heats of Scutellariae Radix and Coptidis Rhizoma, Scutellariae Radix and Phellodendri Chinensis Cortex. Conclusion During the formation process of the precipitation in HJD, the main source of acid-base complex-precipitation were Scutellariae Radix-Coptidis Rhizoma and Scutellariae Radix-Phellodendri Chinensis Cortex; Analysis of molecular thermodynamic indicates the binding energy of Scutellariae Radix and Coptidis Rhizoma was larger than that of Scutellariae Radix and Phellodendri Chinensis Cortex, compared with them, the binding energy of Scutellariae Radix and Gardeniae Fructus is tiny.