DETERMINATION OF GLUTATHIONE IN PLANT-EXTRACTS AS THE 1-CHLORO-2,4-DINITROBENZENE CONJUGATE IN THE PRESENCE OF GLUTATHIONE-S-TRANSFERASE

A spectrophotometric method is described for the detection of total gl utathione (oxidized and reduced) in plant extracts based on the conjug ation of reduced glutathione with 1-chloro-2,4-dinitrobenzene (CDNB) i n the presence of dithioerythritol and glutathione S-transferase (EC 2 .5.1.18) at pH 6.5. Glutathione S-transferase also supported a reactio n with homoglutathione at about 5% of the rate with glutathione but, a t equilibrium, the absorbance change for the two substrates was simila r. The glutathione content of acidic extracts of wheat (Triticum aesti vum var. Condor) roots as determined by the 1-chloro-2,4-dinitro-benze ne (CDNB) method was 6.5% less than that obtained by the HPLC method b ased on the fluorescence of the monobromobimane derivative. The recove ry of exogenous glutathione, added to the extracts, exceeded 90%. The method is suited to the specific determination of glutathione in poaec ean species which also contain hydroxymethyl-glutathione since glutath ione S-transferase reportedly does not support a reaction with this co mpound.