Pigment chemistry: The red sweat of the hippopotamus

  title={Pigment chemistry: The red sweat of the hippopotamus},
  author={Yoko Saikawa and Kimiko Hashimoto and Masaya Nakata and M. Yoshihara and Kiyoshi Nagai and Motoyasu Ida and Teruyuki Komiya},
Within a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes. Here we isolate and characterize the pigments responsible for this colour reaction. The unstable red and orange pigments turn out to be non-benzenoid aromatic compounds that are unexpectedly acidic and have antibiotic as well as sunscreen activity. 
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