l-tryptophan , 5-hydroxytryptophan ( 5-htp ) , 5-hydroxytryptamine , and 5-hydroxyindoleacetic acid ( 5-hiaa ) from discrete regions of brain can be resolved by isocratic elution on a c-18 reversed-phase column and quantitated by native fluorescence measurement .
C0041249
l-tryptophan
C0000578
5-htp