The Collaborative International Dictionary of English v.0.48:

fraxin \frax"in\, n. [From Fraxinus.] (Chem.)
   A colorless crystalline substance (C16H18O10) found in the
   bark of the ash (Fraxinus), and along with esculin in the
   bark of the horse-chestnut. It is structurally a derivative
   of a coumarin glucoside. It shows a delicate blue-green
   fluorescence in alkaline solutions; -- called also paviin
   and fraxoside. --MI-11br/

   Syn:

        8-([beta]-D-Glucopyranosyloxy)-7-hydroxy-6-methoxy-2H-1-benzopyran-2-one;
        also,
        7,8-dihydroxy-6-methoxy-coumarin-8-[beta]-D-glucoside;
        fraxetin-8-glucoside.
        [1913 Webster +PJC]