Solid-State and Solution Characterization of Myricetin

Myricetin (MYR) is a natural compound that has been investigated as a chemopreventative agent. MYR has been shown to suppresses ultraviolet B (UVB)-induced cyclooxygenase-2 (COX-2) protein expression and reduce the incidence of UVB-induced skin tumors in mice. Despite MYR's promise as a therapeutic agent, minimal information is available to guide the progression of formulations designed for future drug development. Here, data is presented describing the solid-state and solution characterization of MYR. Investigation into the solid-state properties of MYR identified four different crystal forms, two hydrates (MYR I and MYR II) and two metastable forms (MYR IA and MYR IIA). From solubility studies, it was evident that all forms are very insoluble (<5 μg/ml) in pure water. MYR I was found to be the most stable form at 23, 35, and 56°C. Stability determination indicated that MYR undergoes rapid apparent first-order degradation under basic pH conditions, and that degradation was influenced by buffer species. Apparent first-order degradation was also seen when MYR was introduced to an oxidizing solution. Improved stability was achieved after introducing 0.1% antioxidants to the solution. MYR was found to have good stability following exposure to ultraviolet radiation (UVR), which is a consideration for topical applications. Finally, a partitioning study indicated that MYR possess a log P of 2.94 which, along with its solid-state properties, contributes to its poor aqueous solubility. Both the solid-state properties and solution stability of MYR are important to consider when developing future formulations.