Improving Dissolution Properties by Polymers and Surfactants: A Case Study of Celastrol

Area of Science:

• Solid-state chemistry
• Materials science
• Pharmaceutical sciences

Background:

• Celastrol, a natural compound, exists in multiple crystalline forms (polymorphs).
• Understanding polymorph properties is crucial for drug formulation and efficacy.
• Polymorphism significantly impacts solubility, dissolution rate, and bioavailability.

Purpose of the Study:

• To characterize two celastrol polymorphs.
• To investigate the influence of surfactants and polymers on celastrol solubility and wettability.
• To elucidate the mechanisms behind observed solubility differences.

Main Methods:

• X-ray powder diffraction (XRPD) for structural characterization.
• Thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) for thermal properties.
• Single-crystal X-ray diffraction for detailed structure determination.
• Solubility and wettability measurements in various media.

Main Results:

• Two celastrol polymorphs (form I and form II) were identified and structurally characterized.
• Surfactants like Tween 80 and sodium dodecyl sulfate (SDS) increased celastrol solubility by over 10^4 times.
• Form I exhibited superior wettability compared to form II across different buffer solutions.
• Form I showed higher solubility in carboxymethylcellulose (CMC) and polyvinylpyrrolidone (PVP) but lower solubility in Tween 80 and SDS solutions compared to form II.

Conclusions:

• Celastrol polymorphism significantly affects its solid-state properties, including solubility and wettability.
• Surfactants are effective in enhancing celastrol solubility and wettability.
• Abnormal solubility differences between polymorphs in different media were observed and investigated, suggesting complex interaction mechanisms.