Your notion of the structure of hipposudoric and norhipposudoric acids, pigments of the red sweat of the hippopotamus, may need some updating. This newly published study calls for your attention:
“Refined Structure of Hipposudoric and Norhipposudoric Acids, Pigments of the Red Sweat of the Hippopotamus,” Takatoshi Matsumoto, Yoko Saikawa, Masaya Nakata, and Kimiko Hashimoto, Chemistry Letters, epub 2015. (Thanks to T Brian H McMurry for bringing this to our attention.) The authors are at Keio University, Japan.
BONUS: Video of one way to collect sweat from a hippo: