Identification, Characterization and Evaluation of Crystal Forms of Quinine Sulphate

Abstract

Crystal engineering concept has been utilized to modify the physico-chemical parameters of a naturally occurring alkaloid, quinine sulphate, by exploring its H-bond interactions to generate different forms. Quinine sulphate is found to exist in four different crystal forms. The Forms I and II depict endo/exo events suggesting conversion of metastable low melting forms to higher melting and stable form indicated by sharp melting endotherms. The low melting form I L is found to be monotropically related to high melting Form I H while low melting Form II L is enantiotropically related to high melting Form II H . The Form III and IV showed broad endotherms accompanied by mass loss in TGA prior to melting indicating the existence of solvatomorphism. The solvent molecules are tightly bound in the crystal lattice of the drug molecules which is shown by high values of the binding energies of the solvents in these two forms. The enthalpy of solution was found to be endothermic for all the forms which followed the order: Form O > Form II > Form III > Form I > Form IV and is further related to the lattice energy suggesting Form II to be least crystalline. The solubility for Form II was found to be highest with maximum release rate in dissolution studies. The effectiveness of new polymorphic forms was confirmed by performing in vivo antimalarial activity against P. berghei infection. The studies have shown an increase in antimalarial activity of Form IV concluding a successful development of new polymorphic form.

Preparation, Characterization, and Desolvation of 5‐Sulfoisophthalic Acid Sodium Salt Solvates

“…The solvate binding energy (enthalpy of desolvation) was calculated to quantify the stability of the solvates according to Eq. 1 29, 30: …”

“…The experimental weight loss of the three solvents was lower than the theoretical weight loss, revealing that the solvent molecules were partially lost before the TG The solvate binding energy (enthalpy of desolvation) was calculated to quantify the stability of the solvates according to Eq. ( 1) [29,30]:…”

Energetic 1H-Imidazo[4,5-d]pyridazine-2,4,7-triamine: A Novel Nitrogen-rich Fused Heterocyclic Cation with High Density

“…As can be seen from the XRPD pattern ofFigure 5, the characteristic peaks of α-4 at 2θ = 16. 19 In terms of thermal stability, it is of considerable benefit to determine whether the forms are monotropic or enantiotropic, 25 since metastable polymorphs tend to convert to stable polymorphs. Therefore, the in situ XRD technique was used to study the thermal stability of α-4 and β-4 at different temperatures.…”

Solvate Formation of Bis(demethoxy)curcumin: Screening and Characterization

“…To determine whether the solvent molecules are strongly or loosely bounded in the host lattice, the calculated binding energy was compared to the corresponding enthalpy of vaporization of the pure solvents (summarized in Table 2) [34]. The calculated values of BDMC-THF and BDMC-DMSO exceed the enthalpy of vaporization of the pure solvents, which indicates that the solvates are firmly bonded.…”