Antiangiogenic Effect of Curcumin in Pure Versus in Extract Forms

Curcumin isolated from turmeric (Curcuma longa L., Zingaberaceae) root was found to be anti-angiogenic in a human tissue-based angiogenesis assay. As a liposoluble compound, curcumin can be extracted from turmeric root with organic solvents such as ethanol or acetone. Curcumin in its pure form has poor solubility in water, potentially limiting its medicinal use for humans when it is taken orally or injected. This study attempted to investigate the possibility of improving curcumin’s low solubility using an extract as a carrier. This would maintain anti-angiogenic properties with improved water-solubility. Experiments were undertaken to determine the extraction efficiency of different solvents for curcumin. Anti-angiogenic activities of curcumin in its pure form and in extracts were compared as a general trend ethanol or acetone was more efficient in extracting curcumin than their aqueous counterparts. Using 50 and 70% aqueous ethanol as well as 70% aqueous acetone yielded significantly more turmeric extracts by weight than absolute acetone, which was the lowest. Conversely, turmeric extracts extracted with 95% ethanol and absolute acetone contained significantly higher curcumin concentrations than water extract, which was the lowest. Combining the higher extract yield and highest curcumin concentrations in the extract, 95% ethanol gave the highest yield of single entity curcumin. In the angiogenesis assay, pure curcumin at the concentration of 85 μM (in 1% ethanol v/v) in the culture medium totally suppressed angiogenic responses. In contrast, a curcumin concentration of 18.5 μM (in the form of 100 μg/ml turmeric extract) achieved the same total inhibition of angiogenesis in culture. This nearly 5 fold gap reflected the unaccounted involvement of other antiangiogenic compounds including curcumin derivatives, and/or enhancement of curcumin by Accepted: 11 February 2008 Address correspondence to: Zhijun Liu, School of Renewable Natural Resources, LSU Agricultural Center, Baton Rouge, LA 70803. E-mail: [email protected] non-antiangiogenic compounds in the extract. This finding suggests that curcumin in the form of extracts be potentially more pharmacologically active than pure curcumin. Further investigations of this hypothesis and possible interactions are warranted.