Response to Kurien and Scofield: Solubility and bioavailability of curcumin

Abstract

We would like to thank Kurien and Scofield for useful comments on our review. The authors acknowledge that the potential of curcumin in various diseases is limited owing to its poor bioavailability in vivo. They suggest that the limited bioavailability of curcumin in vivo is due to its lack of solubility in aqueous solvents. They have demonstrated that the solubility of curcumin can be enhanced 12-fold and that of turmeric threefold by boiling for 10 min in water [ 1 Kurien B.T. et al. Improving the solubility and pharmacological efficacy of curcumin by heat treatment. Assay Drug Dev. Technol. 2007; 5: 567-576 Crossref PubMed Scopus (240) Google Scholar ]. They found that heat had no effect on the activity of curcumin. However, 98.5% curcumin and 94.7% turmeric is still water insoluble even after heating. Maximum in solution is only 7.4 μg/ml. Authors also suggest enhancement of solubility of curcumin in aqueous solvents by mild alkali treatment. However, this treatment has been shown to destabilize curcumin [ 2 Wang Y.J. et al. Stability of curcumin in buffer solutions and characterization of its degradation products. J. Pharm. Biomed. Anal. 1997; 15: 1867-1876 Crossref PubMed Scopus (1282) Google Scholar ]. Additionally, there is no data yet provided by Kurien et al. or anybody else to suggest that heat-solubilized or alkaline-solubilized curcumin in aqueous solvent has any affect on its bioavailability in animals or human. Solubilization of curcumin in turmeric oil, however, has been shown to enhance its bioavailability in rat and in human [ 3 Antony B. et al. A pilot cross-over study to evaluate human oral bioavailability of BCM-95®CG (biocurcumax™), a novel bioenhanced preparation of curcumin. Indian J. Pharmaceutical Sci. 2008; 70: 445-450 Crossref PubMed Scopus (214) Google Scholar ]. Also, administration of liposome-encapsulated curcumin has been shown to provide higher serum levels in rodents [ 4 Wang D. et al. Liposome-encapsulated curcumin suppresses growth of head and neck squamous cell carcinoma in vitro and in xenografts through the inhibition of nuclear factor kappaB by an AKT-independent pathway. Clin. Cancer Res. 2008; 14: 6228-6236 Crossref PubMed Scopus (174) Google Scholar ]. Thus, whether heat solubilization or alkali solubilization of curcumin is a solution to the problem of bioavailability remains to be seen.