Enhanced skin permeation of verbascoside-cyclodextrin complex loaded into liposomes

The biological properties of Lippia alba extracts are related to the presence of some polar components endowed with strong antioxidant, anti-inflammatory and antibacterial activities [1,2]. Verbascoside which is the main constituent in L. alba extracts could be a good candidate for topical applications. Two conditions are required: it should permeate through the stratum corneum and reach the deeper cutaneous layers, without significant leakage into the systemic route. The main aim of this work was to enhance the in vitro percutaneous penetration of verbascoside, by complexing it with β-Cd (1:1M by colyophilization) and formulating it into liposomes. Liposomes were prepared by the ultrasonication technique and were formulated in a 3% PHMC gel. Skin permeation was evaluated across excised pig skin using Franz cells and kinetic studies were performed for 8 hours. Then, skin was adequately treated and divided in stratum corneum, epidermis and dermis. Verbascoside was extracted from each section and dosed with HPLC. Both formulations didn't show any passage through „systemic circulation“ during 8 hours. The association of liposomal formulation and β-Cd, compared to the only liposomal formulation used, showed an increase of permeation of verbascoside through the stratum corneum to the epidermal sites. In both formulations diffusion to dermis is very limited, so systemic absorption after in vivo administration could be excluded, in accordance with the absence of permeation in receptor compartment of Franz cells during 8 hours.

References: 1. Timóteo, P et al. (2008) Nat. Prod. Commun. 3: 2017–2020.

2. Fu, G. et al. (2008) Curr. Med. Chem. 15: 2592–2613.