PhD, University of Cincinnati, 2024, Pharmacy: Pharmaceutical Sciences

Among chemical UV filters approved by the US FDA, avobenzone (AVO) is the most efficient and commonly used UVA filter in broad-spectrum sun care products. However, one pitfall of AVO is a lack of photostability leading to a decrease in its UV protection capacity. Its photostability primarily depends on the solvent system (solvents, emollients, and UV filters) and excipients in its vicinity (i.e., other UV filter molecules, and triplet or single quenchers). Moreover, when AVO and octinoxate (OCT), a UVB filter, are used in combination, it appears that the photo-instability of AVO can cause the photolysis of OCT. It has been reported that forming inclusion complexes with ß-cyclodextrins (ß-CD) enhanced the photoactive performance of AVO and OCT by improving their photostability and reducing skin permeation. However, most studies have investigated the complexes in solvents unintended for cosmetic formulations. Most importantly, the mechanism of host-guest complexation and photo-stabilization by ß-CD has not yet been revealed. Therefore, this dissertation aims to investigate the effect of macrocyclic compounds (ß-CD vs Cucurbit[7]uril (CB[7]) on the photostability of AVO and OCT in aqueous environment, which is motivated by three research questions. What are the differences in the complexation of AVO and OCT with ß-CD and CB[7]? How do forming complexes with ß-CD and with CB[7] affect the photostability, skin permeation, and efficacy of AVO and OCT? Finally, what is the impact of ethanol as a cosolvent on the complexation and photostability of AVO and OCT? To examine these questions, we prepared complexes of AVO-ß-CD, AVO-CB[7], OCT-ßCD, and OCT-CB[7] and characterized the complexes both in solution phase and solid state using several analytical techniques. We also conducted photostability studies for all complexes, skin permeation tests for AVO complexes, and evaluated the efficacy for all complexes. The findings from the research show that ß-CD and CB[7] have s (open full item for complete abstract)

Committee: Harshita Kumari Ph.D. (Committee Chair); Frank Heinrich PhD (Committee Member); Kevin Li Ph.D. (Committee Member); Gerald Kasting Ph.D. (Committee Member); Kavssery Ananthapadmanabhan (Committee Member); David Moore Ph.D. (Committee Member) Subjects: Pharmaceuticals