Metabolism of chlorophenylalanines in crop and weed plants in relation to the formation of potential herbicidal end products

Abstract

Metabolism of 12 synthetic d, l-chlorophenylalanines has been examined in several crop and weed plants. Twenty-five gram samples of excised shoots or leaves of bushbean, soybean, corn, pigweed, lambsquarters and giant foxtail were allowed to metabolize 10 −4 M solutions of the d, l-chlorophenylalanines for 24 hr in continuous light. The plant samples were then extracted in 80% methanol and the soluble acidic metabolites fractionated into ether. Each ether concentrate was partially purified by fractional elution from a PrepSep C18 column and then analysed by HPLC. Collected fractions were esterified with pentafluorobenzylbromide and examined by GC-MS to demonstrate the presence of PFB-esters of chlorophenylacetic, chlorobenzoic and/or chlorocinnamic acids. Since certain of these metabolites are known to be potent plant growth-regulators and herbicides, the results are discussed in relation to the potential herbicidal action of certain chlorophenylalanines by the mechanism of ‘lethal synthesis’.