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Discovery of oxyacanthine dihydrochloride monohydrate polymorphs from obfuscated samples by MicroED
Jieye Lin1,2, Orel Paz1,3,4,2, Johan Unge5
1Department of Biological Chemistry, University of California, Los Angeles, 615 Charles E. Young Drive South, Los Angeles, California 90095, United States.
Biorxiv : the Preprint Server for Biology
|July 9, 2025
Summary
Microcrystal electron diffraction (MicroED) identified two crystal forms of oxyacanthine dihydrochloride monohydrate in mislabeled pharmaceutical samples. This technique is valuable for structural analysis and quality control in the pharmaceutical industry.
Area of Science:
- Pharmaceutical Sciences
- Crystallography
- Natural Products Chemistry
Background:
- Over 50% of pharmaceuticals originate from natural products.
- Accurate structural characterization is crucial for drug development and quality control.
- Mislabeled samples pose significant challenges in pharmaceutical analysis.
Purpose of the Study:
- To demonstrate the utility of Microcrystal Electron Diffraction (MicroED) for identifying polymorphic forms in complex natural product derivatives.
- To characterize two distinct crystal structures of oxyacanthine dihydrochloride monohydrate.
- To assess the potential for structural transformation between identified polymorphs.
Main Methods:
- Microcrystal Electron Diffraction (MicroED) was employed for structural determination.
- Computational analysis of structures, energies, and crystal packing was performed.
- Comparison of conformational differences between polymorphs was conducted.
Main Results:
- Two distinct polymorphic crystal structures of oxyacanthine dihydrochloride monohydrate were identified from mislabeled samples.
- Conformational variations were observed in the tetrahydroisoquinoline ring of the two polymorphs.
- Thermodynamic analysis suggested a preference for transformation into one specific polymorph.
Conclusions:
- MicroED is an effective tool for the structural elucidation of natural product-derived pharmaceuticals.
- The study highlights the importance of MicroED in pharmaceutical quality control and identifying mislabeled substances.
- Understanding polymorphism is critical for drug formulation and stability.
