Unmasking Phytotoxicity and Interaction Mechanism of Two Phthalate Esters in Lettuce: Evidences from Biotransformation Processes, Metabolic Response and Molecular Network Perturbations

Vegetables are considerably affected by plasticizer pollution. This study investigated the transformation process and toxic mechanisms of dimethyl phthalate (DMP) and butyl benzyl phthalate (BBP), in lettuce. Six phase I transformation products of DMP and nine phase I transformation products of BBP were screened and identified using UPLC-QTOF-MS, which were primarily generated via hydrolysis, hydroxylation, and decarboxylation. Significant alterations in metabolites and genes associated with carbohydrate and nucleotide metabolism were observed, unraveling that lettuce may respond to DMP and BBP stresses by increasing energy supply and nucleotide metabolism. Furthermore, BBP hindered the expression of l-proline, salicylic acid, β-alanine, <i>APX2</i> and <i>PAL3</i>, thereby affecting the synthesis of secondary metabolites and exacerbating oxidative damage. Our findings provide novel insights for assessing the ecological risk and food safety of lettuce contaminated with DMP and BBP, promoting the supervision of plastic usage during agricultural activities.