Insight in the Metabolism of Diclofenac in Plants – P 450 Mediated Hydroxylation Is Followed by Glucosyl Transfer Reactions

Pharmaceuticals form a new class of micropollutants that poses a serious threat to our aquatic environment and its organisms. Advanced technologies in waste water treatment like membrane bioreactors (MBR) have proven better elimination of organic pollutants. But still their removal capacity might be not be sufficient to remove pharmaca and their metabolites completely. Biological wastewater treatment facilities e.g. in constructed wetlands might represent rather cost and labor saving technology for small communities. We studied the possible metabolism by plants of the intensively used nonsteroidal anti-inflammatory drug Diclofenac which causes massive problems due to its poor elimination during waste water treatment processes. In order to test phytoremediation as a tool for the removal of this drug from waste water, the uptake and metabolic pathway of the of the compound into plant tissues was addressed using Hordeum vulgare (barley) and Brassica juncea (Indian mustard) as model species. Diclofenac is taken up by all plant species and undergoes rapid metabolisation. Similar to its fate in mammalian metabolism the drug is activated in a phase I reaction resulting in the hydroxylated metabolite OH-Diclofenac which is conjugated in phase II to a glucopyranoside, a typical plant specific metabolite. This is the first study to address the fate of Diclofenac in plants. Further studies are required to investigate interand intracellular transport of the conjugates and to elucidate the potential to really incorporate the drug and its sugar conjugates into cell walls. With the present set of data available it is justified to propose the use of plants in wastewater treatment for a more efficient reduction of the effluent load with unwanted pharmaceutical residues to provide a healthier environment.