S-cysteinyl-hydroxychlorpropham: Formation of the S-cysteinyl conjugate of isopropyl-3′-chloro-4′-hydroxycarbanilate in oat (Avena sativa L.)

Isopropyl-3′-chlorocarbanilate (chlorpropham) forms phenolic metabolites, isopropyl-3′-chloro-4′-hydroxycarbanilate (I), and isopropyl-5′-chloro-2′-hydroxycarbanilate (II), in several plant species. In oat, which is a chlorpropham-susceptible plant, I was converted to an S-cysteinyl-conjugate (III). The reaction in vitro was catalyzed by a partially purified, soluble enzyme. The formation of III by the enzyme preparation and by oat shoot sections was compared. Mass spectral data indicated the presence of an aryl-thioether bond, and chloro-, hydroxy-, and isopropylcarbanilate groups in III. The results of this investigation indicate that III was isopropyl-(2-amino-2-carboxyethyl)thio]-chloro-hydroxycarbanilate (S-cysteinyl-hydroxychlorpropham).