The best introduction I have found is
http://www.nutritionj.com/content/13/1/11
The cell apoptosis described in the paper 17th Nov kicks in at 20uM and the highest range tested in above paper are 20ng/ml. Ohh for standard units! I get 20ng/ml to be 80uM.
My conclusions were that for apoptosis 100 mg must be dissolved in the blood and a reasonable “maintenance” was 20mg dissolved. I much prefer the concept of hydrophilic solid dispersion so make pills from 20mg of pure curcumin with 150mg of polyvinylpyrollidone, much along lines of above mentioned paper. I do the same with green tea and milk thistle extract using 20mg of each as there are many papers indicating a synergy with the three.