The decrease of pigment concentration in red tattooed skin years after tattooing.

BACKGROUND: Tattooing entails the injection of high amounts of colourants into skin. Excepting black inks, red azo pigments are the most frequent colourant used. Part of the pigment is transported away via lymphatic system. Another part can be decomposed in skin, which might be responsible for many known adverse skin reactions. OBJECTIVE: The aim of this study was to estimate the extent of decomposition and transportation by measuring the decrease of pigment concentration in human skin under in vivo conditions. METHODS: Red pigments were extracted from nine tattooed skin specimen and attempted quantification by using HPLC technology. To optimize quantification, we synthesized five common red azo pigments with purity at 98% and used them as HPLC reference substances. RESULTS: In five of the nine skin specimens, we were able to identify and subsequently to quantify the red tattoo pigments such as Pigment Red 22 or Pigment Red 112. The mean pigment concentration in skin was 0.077 ± 0.046 mg/cm². As the pigment concentration in skin ranges from 0.60 to 9.42 mg/cm² (mean: 2.53) directly after tattooing, we estimate a decrease of 87 to 99% of pigment concentration in skin after tattooing. CONCLUSION: Millions of people have many and large tattoos, whereas a single tattoo frequently covers a skin area of more than 300 cm². Thus, the major part of more than 760 mg of azo pigments either decomposes in skin or migrates in the body. That may pose a health risk on tattooed individuals, in particular may cause severe skin reactions.

Carbonyl- and carboxyl-substituted enediynes: synthesis, computations, and thermal reactivity.

The influence of electron-withdrawing groups (carbonyl and carboxyl) at the alkyne termini on the reactivity of enediynes was investigated by a combination of experimental and computational techniques. While the general chemical reactivity of such enediynes, especially if non-benzannelated, is increased markedly, the thermal cyclization, giving rise to Bergman cyclization products, is changed little relative to the parent enediyne system. This is evident from kinetic measurements and from density functional theory (DFT, BLYP/6-31G + thermal corrections) computations of the experimental systems which show that the Bergman cyclization barriers slightly (3-4 kcal/mol) increase, in contrast to earlier theoretical predictions. The effect on the endothermicities is large (DeltaDeltaH(r) = 7-12 kcal/mol). Hence, the increased reactivity of the substituted enediynes is entirely due to nucleophiles or radicals present in solution. This was demonstrated by quantitative experiments with diethylamine and tetramethyl piperidyl oxide (TEMPO) which both give fulvenes through 5-exo-dig cyclizations.