Development of self-microemulsifying liquid for oral delivery of tetrahydrocurcumin (THC)

Abstract

Curcumin, extracted from the rhizomes of turmeric, has been reported to possess anti-oxidative, anti-inflammatory and anti-carcinogenic activities. Tetrahydrocurcumin (THC) is one of curcumin metabolites. THC exhibits similar pharmacological activities as curcumin; nevertheless, it shows the more potent antioxidant than curcumin [1, 2]. However, the pharmacological effect of THC is limited due to its low aqueous solubility. Self-microemulsifying drug delivery systems (SMEDDS) have been used for the improvement of oral bioavailability of insoluble lipophilic compounds. SMEDDS are isotropic mixtures of oils and surfactants that form fine oil-in-water microemulsions upon mild agitation in aqueous media such as GI fluids [3]. The optimized SMEDDS used for THC formulations in liquid form contained 70% mixtures of two surfactants: Cremophor EL and Labrasol (1:1), and 30% mixtures of oil: Labrafac PG and Capryol 90 (1:1). The liquid THC-SMEDDS rapidly formed fine oil-in water-microemulsions, with particle size of less than 50nm. The in vitro rate and extend of release of THC from liquid-SMEDDS was about 16- fold higher than that of unformulated THC. Our studies demonstrated the potential use of self-microemulsifying drug delivery system for the delivery of hydrophobic compounds, such as THC by the oral route.