Association of 3-O-methylquercetin with β-cyclodextrin:: complex preparation, characterization and ex vivo skin permeation studies

3-O-Methylquercetin (3-MQ) is a poorly soluble flavonoid not commercially available that presents antiviral activity. In this work, 3-MQ was isolated from Achyrocline satureioides and an inclusion complex of the flavonoid with beta-cyclodextrin (beta CD) was prepared. The complex was characterized by means of IR, H-1 NMR and molecular mechanics calculation, which suggested the insertion of the B ring of 3-MQ into the beta CD cavity. In addition, the skin permeation of 3-MQ and its associations with beta CD from hydroxypropyl methylcellulose (HPMC) hydrogels was investigated using Franz diffusion cells. For 3-MQ assay in pig ear skin, a LC method was developed and validated in the range 0.05-1.5 mu g/mL. The hydrogels presented similar behavior, although in the absence of polymeric matrix, the complexation of 3-MQ with beta CD seems to enhance its availability on skin surface, demonstrating the influence of the inclusion phenomena on 3-MQ diffusion through the gel and partition toward the stratum corneum.