However, when the 1 H NMR spectra of the non-polar extract are compared with the spectra of 2 and 3, it is evident that the extracts failed to show the characteristic signals of 2 and 3 in the 6.65 -6.75 ppm interval (Figure ). Even when the baselines from the same spectra were enlarged in Figure , there was no evidence of signals that define 2 and 3 in the 6.65 -6.75 ppm interval. The NMR spectra indicated, therefore, that the source of the declared "curcuminoids" in the investigated commercial products lacked the residual complexity associated with naturally-derived 1. The dihydro derivatives indicative of a natural CDS 3 were also absent. Inevitable residual complexity (go.uic.edu/residualcomplexity) results from the biosynthetic origin of the material and reflects the fact that a certain ("residual") amount of close analogs always accompany the major component as impurities, even after multiple large-scale enrichment or high-resolution laboratory purification steps. Fingerprint Analysis of "Curcumin"-containing Dietary Supplements (CDS). Chemical fingerprints capture the complexity of a botanical DS, which is a result of their diverse chemical composition and as the diagnostically different abundance levels of their constituents.