The Collaborative International Dictionary of English v.0.48:

Umbelliferone \Um`bel*lif"er*one\, n. (Chem.)
   A tasteless white crystalline substance, C9H6O3, found in
   the bark of a certain plant (Daphne Mezereum), and also
   obtained by the distillation of certain gums from the
   Umbelliferae, as galbanum, asafetida, etc. It is analogous
   to coumarin. Called also hydroxy-coumarin. Its strong
   fluorescence under ultraviolet light makes it useful in
   analytical biochemistry, as, for example, to detect
   phosphatase activity by hydrolysis of umbelliferyl phosphate.
   [1913 Webster +PJC]