Topical formulation and dermal delivery of active phenolic compounds in the Thai medicinal plant - Clerodendrum petasites S. Moore

Purpose: To develop topical formulations of Clerodendrum petasites S. Moore (CP), and to optimize the skin permeability and topical bioavailability of the active phenolic compounds therein. Methods: The skin uptake and delivery of active compounds from two formulations, an oil-in-water cream and a lotion (both containing 10% w/w CP extracts), were examined (a) invitro using pig skin, and (b) invivo in human volunteers. Stratum corneum (SC) was collected by tape stripping and the compounds were detected and quantified by high performance liquid chromatography coupled with either mass spectrometry (HPLC-MS) or ultraviolet and photodiode array (HPLC-UV-PDA) detection. Results: From the invitro results, vanillic acid, verbascoside, nepetin and hispidulin, were chosen as potential phenolic actives for topical delivery optimization from the formulations. Invivo, vanillic acid, nepetin and hispidulin were appreciably taken up into the SC within 6 h, while verbascoside did not penetrate beyond the most superficial layers. No significant differences in delivery were observed between the two formulations, both of which were well tolerated. Conclusions: The detected topical absorption of hispidulin, nepetin, and vanillic acid, from the cream and lotion vehicles investigated, suggest that these compounds are potentially active compounds in Thai traditional medicine for the treatment of a wide range of skin diseases.