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Cyclic Dipeptides and Alpha Lipoic Acid Forms for the Design of Pharmaceutical and Nutraceutical Co-crystals

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Title: Cyclic Dipeptides and Alpha Lipoic Acid Forms for the Design of Pharmaceutical and Nutraceutical Co-crystals
Author: Tsang, Andy
Department: Department of Chemistry
Program: Chemistry
Advisor: Soldatov, Dmitriy
Abstract: This thesis explores the ability of cyclic dipeptides and α-lipoic acid forms to act as co-crystallization agents. The target co-crystals are supramolecular materials combining the molecules of an active pharmaceutical ingredient (API) and an excipient in the same crystal structure. Five cyclic dipeptides and four α-lipoic acid forms were utilized in this work as potential co-crystal co-formers. Over 120 binary combinations were tested using PXRD screening technique, 11 crystal structures were studied, 10 bulk co-crystalline materials were isolated and characterized, and phase diagrams of four binary systems were determined. The main methods included powder and single crystal X-ray diffraction, differential scanning calorimetry, IR spectroscopy, as well as various preparation and in-lab characterization techniques. The data on the molecular composition, crystal structure, stability limits and degradation behavior were compared in order to develop comprehensive understanding of the factors defining the formation of co-crystalline phases and their essential properties. Special attention was given to complementarity of the co-formers manifested in the crystal packing efficiency, hydrogen bonding network dimensionality, as well as thermal and chemical stability of the studied co-crystals. The results of this study will help to diversify the market of pharmaceuticals and nutraceuticals through the introduction of new forms with improved efficacy, stability, and shelf life, and to develop new strategies in the design of such forms. This study also contributes to the chemistry of supramolecular materials and crystal engineering of organic solids.
Date: 2017-09
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