Preparation of curcuminoid microemulsions from Curcuma longa L. to enhance inhibition effects on growth of colon cancer cells HT-29

The objectives of this study were to extract curcuminoid from Curcuma longa L. (C. longa), a vital medicinal plant demonstrated to possess many biological activities, and prepare the curcuminoid extract and microemulsion for studying the inhibition mechanism of HT-29 colon cancer cells. Results showed that a total of 3 curcuminoids including curcumin, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), were separated within 10 min by using an Eclipse XDB-18 column and a gradient mobile phase of 0.1% formic acid solution (A) and acetonitrile (B). The curcuminoid microemulsion composed of soybean oil, Tween 80, ethanol and water was prepared with a high stability and mean particle size of 10.9 nm, zeta-potential of −65.2 mV and encapsulation efficiency of 85.7%. Both curcuminoid extract and microemulsion were effective in inhibiting HT-29 cell growth with the IC(50) being 3.83 and 2.51 μg mL(−1) after 24 h incubation, respectively, but further reduced to 2.23 and 1.94 μg mL(−1), after 48 h incubation. Both treatments could decrease the proportion of both viable and necrosis cells and increase the proportion of both early and late apoptosis cells in a dose-dependent manner, with the cell cycle arrested at the S phase. Also, both treatments could up-regulate p53 expression and down-regulate cyclin A and CDK2 expressions through a p21-independent pathway. In addition, the expressions of Bax and cytochrome C as well as the activities of caspase-8, caspase-9 and caspase-3 increased for the curcuminoid extract, while the curcuminoid microemulsion showed the same trend with the exception that an insignificant change (p > 0.05) in Bax expression was observed. Collectively, this study demonstrated that the curcuminoid microemulsion prepared from C. longa may possess great potential for the treatment of colon cancer in the future.