Dear Sir. Concerning your issue about the best solvent for curcumin . The best solvent is the organic solvent acetone , and the dilution can be carried out into aqueous buffer or isotonic saline. For more details, I think the following below link may help you in your issue:
curcumin is polyphenolic compound and also contain carbonyl groups, therefore it is polar compound therefore best solvent for curcumin will be alcohol ( e.g methanol, ethanol) or if you look for nonprotic solvent you can use chloroform or acetone.Good Luck
Curcumin is soluble in organic solvents such as acetone, ethanol, DMSO and diemethylformamide. The solubility of curcumin in these solvents is approximately 1mg/ml and in acetone it is at least 20 mg/ml.