Fate of [14C]diphenylamine in stored apples

The nature add magnitude of residues in apples treated with [C-14]diphenylamine (DPA) was investigated following treatment and storage at reduced temperature. Additional apples were treated with a mixture of [C-14]DPA and deuterium-labeled DPA (D-10-DPA) for use in metabolite identification. Stored apples were sampled at 16 different intervals throughout a 40-week period. Total radioactive residue levels remained constant over the entire testing interval. The parent chemical and several metabolites were identified on the final harvest peel and pulp samples by quantitative and qualitative analytical methods. A majority of the terminal residue, which was confined largely in the peel, consisted of unmetabolized DPA. Residues in pulp, however, were largely composed of glycosyl conjugates of several hydroxylated diphenylamine (OH-DPA) metabolites. The major polar metabolite identified in stored apples was a glucose conjugate of 4-hydroxy-diphenylamine (4-OH-DPA). Additional metabolites, characterized as glycosyl conjugates of 2-OH-DPA, 3-OH-DPA, 4-OH-DPA, or dihydroxy-DPA, were also detected along with their intact (i.e., nonconjugated) forms in apple pulp.