Chemical characterization of psoralens used in the National Toxicology Program research projects.

Chemical analyses of 4 psoralen derivatives were performed with the use of various techniques, including thin-layer chromatography, gas chromatography, infrared and nuclear magnetic resonance spectroscopy. 8-Methoxypsoralen, 5-methoxypsoralen, 3-carbethoxypsoralen, and 5-methylisopsoralen were determined to be 99, 93, 97, and 99% pure, respectively. A 7% contaminant in the 5-methoxypsoralen sample was identified as a dimethoxypsoralen isomer. These psoralens are being used in research projects sponsored by the National Toxicology Program.