Stability of the 3 curcuminoids in cell culture. Curcumin degraded with a half-life of about 1.7 h in cell culture medium with cells present. a: Curcumin absorbance in culture medium with C6 cells for 4 days measured with a spectrophotometer. Inset: Absorbance during the first 24 h. b: 5 μM CUR produced fluorescence in live C6 cells within 1 h after its introduction. Scale bar = 5 μm. c: Curcuminoid fluorescence persisted in cells for at least 24 h (same scale as B). d: A representative HPLC chromatogram showing complete baseline separation of the 3 curcuminoids from cell culture medium containing 0.3 % DMSO. The first group of merged peaks near 1.6 min represents the chromophoric compounds from the media. The second peak at 6.45 min is BDMC, the peak at 7.04 min is that of DMC, and the last peak at 7.68 min is that of curcumin. (mAU = milliabsorbance units). This is the same CUR preparation used for treating the cells. e: HPLC measurements show curcuminoids DMC and BDMC persist longer than curcumin in cell culture medium and degrade even slower in DMSO. f: HPLC measurements of curcuminoids in culture medium with C6 cells present for 5 days. Inset: The same data normalized to initial levels. Line colors are as in e.