In order to investigate the stability of curcuminoids in physiological media, two samples with different composition of curcumin (CUR I), mono-demethoxycurcumin (CUR II) and bis-demethoxycurcumin (CUR III) were incubated in phosphate buffer and cell culture medium without or with fetal calf serum. The curcuminoids decomposed very rapidly (more than 90% within 12 h) when serum was omitted, but were more stable in the presence of serum. The stability differed between the curcuminoids: CUR I was the least, and CUR III was the most stable curcuminoid. Several degradation products of CUR I were detected, most of which were not yet identified; ferulic acid and vanillin were disclosed as minor products. (C) 2002 Elsevier Science Ltd. All rights reserved.