Enhancement of percutaneous absorption of curcumin (turmeric pigment) by ethanol

Curcumin is the active component of Curcuma species including C. longa (turmeric). This molecule is well known for its anti-inflammatory effect, which seems to be stronger than that of hydrocortisone. Curcuma species have been used in Asian traditional medicine as topical anti-inflammatory drugs. Curcumin has poor oral bioavailability and its topical application could be of choice, particularly for local effects. However, its percutaneous absorption and enhancement, that are the subject of the present investigation, are not well studied yet. Permeation of curcumin through excised rat skin was studied at 25°C using static diffusion cells. As curcumin is not soluble in water, an aqueous solution of Tween 20 was used as the receptor phase. Dried curcumin (deposited on skin after solvent evaporation), and 50%, 75% and 96% aqueous solutions of ethanol (all containing 0.1% curcumin) were used as donor phases. Drug determination was by spectrophotometry at 424 nm. Data are presented as Mean±SD. Results showed that permeation flux of curcumin from dried system, which is at its highest thermodynamic activity, was 0.43±0.25 mg cm-2 h-1. In ethanolic systems, fluxes were higher than that of dried system and concentration-dependent. The flux was measured to be 0.75±0.07 mg cm-2 h-1 and 1.09±0.56 mg cm-2 h-1 in 50% and 75% systems respectively. When the concentration of ethanol was increased to 96%, the flux was increased to 2.3±0.79 mg cm-2 h-1, which is by about 6 times more than that of the dried system. This could be mainly due to the effects of ethanol and/or water on the lamellar liquid crystalline structure of the skin. These results show that ethanol and possibly other classes of enhancers can significantly increase permeation of curcumin. Further investigations including the effects of other classes of enhancers and vehicles on percutaneous absorption of curcumin and Curcuma extract are in progress in our laboratories.