Background, aim, and scope Pharmaceuticals and their metabolites are detected in the aquatic environment and our drinking water supplies. The need for high quality drinking water is one of the most challenging problems of our times, but still only little knowledge exists on the impact of these compounds on ecosystems, animals, and man. Biological waste water treatment in constructed wetlands is an effective and low-cost alternative, especially for the treatment of non-industrial, municipal waste water. In this situation, plants get in contact with pharmaceutical compounds and have to tackle their detoxification. The mechanisms for the detoxification of xenobiotics in plants are closely related to the mammalian system. An activation reaction (phase I) is followed by a conjugation (phase II) with hydrophilic molecules like glutathione or glucose. Phase III reactions can be summarized as storage, degradation, and transport of the xenobiotic conjugate. Until now, there is no information available on the fate of pharmaceuticals in plants. In this study, we want to investigate the fate and metabolism of N-acetyl-4-aminophenol (paracetamol) in plant tissues using the cell culture of Armoracia rusticana L. as a model system. Materials and methods A hairy root culture of A. rusticana was treated with acetaminophen in a liquid culture. The formation and identification of metabolites over time were analyzed using HPLC-DAD and LC-MS n techniques. Results With LC-MS technique, we were able to detect paracetamol and identify three of its metabolites in root cells of A. rusticana. Six hours after incubation with 1 mM of acetaminophen, the distribution of acetaminophen and related metabolites in the cells resulted in 18% paracetamol, 64% paracetamol-glucoside, 17% paracetamol glutathione, and 1% of the corresponding cysteine conjugate. Discussion The formation of two independently formed metabolites in plant root cells again revealed strong similarities between plant and mammalian detoxification systems. The detoxification mechanism of glucuronization in mammals is mirrored by glucosidation of xenobiotics in plants. Furthermore, in both systems, a glutathione conjugate is formed. Due to the existence of P450 enzymes in plants, the formation of the highly reactive NAPQI intermediate is possible. Conclusions In this study, we introduce the hairy root cell culture of A. rusticana L. as a suitable model system to study the fate of acetaminophen in plant tissues. Our first results point to the direction of plants being able to take up and detoxify the model substrate paracetamol. These first findings underline the great potential of using plants for waste water treatments in constructed wetlands. Recommendations and perspectives This very first study on the detoxification of a widely used antipyretic agent in plant tissues again shows the flexibility of plant detoxification systems and their potential in waste water treatment facilities. This study covers only the very first steps of acetaminophen detoxification in plants; s...

The major metabolic pathways in mammals are conjugation with activated sulfate and glucuronic acid, while a small amount of acetaminophen forms a chemically reactive and highly toxic, hydroxylated metabolite. We identified a glutathionyl and a glycoside conjugate, which refer to the similarities to mammalian detoxification. Increased GST activities in leaf tissues were observed correlated with the appearance of the acetaminophen-glutathione conjugate which shows the involvement of this enzyme group in the metabolism of acetaminophen in plants to organic pollutants and xenobiotics. High acetaminophen concentrations lead to oxidative stress and irreversible damages in the plants, which necessitates further investigations using lower drug concentrations for the deeper understanding of the induced detoxification-and defense processes.

Carbamazepine (CBZ) is a pharmaceutical frequently categorized as a recalcitrant pollutant in the aquatic environment. Endophytic bacteria previously isolated from reed plants have shown the ability to promote growth of their host and to contribute to CBZ metabolism. In this work, a horseradish (Armoracia rusticana) hairy root (HR) culture has been used as a plant model to study the interactions between roots and endophytic bacteria in response to CBZ exposure. HRs could remove up to 5% of the initial CBZ concentration when they were grown in spiked Murashige and Skoog (MS) medium. Higher removal rates were observed when HRs were inoculated with the endophytic bacteria Rhizobium radiobacter (21%) and Diaphorobacter nitroreducens (10%). Transformation products resulting from CBZ degradation were identified using liquid chromatography-ultra high-resolution quadrupole time of flight mass spectrometry (LC-UHR-QTOF-MS). CBZ metabolism could be divided in four pathways. Metabolites involving GSH conjugation and 2,3-dihydroxylation, as well as acridine related compounds are described in plants for the first time. This study presents strong evidence that xenobiotic metabolism and degradation pathways in plants can be modulated by the interaction with their endophytic community. Hence it points to plausible applications for the elimination of recalcitrant compounds such as CBZ from wastewater in CWs.

Mixed pollution is a characteristic of many industrial sites and constructed wetlands. Plants possessing an enzymatic detoxifying system that is able to handle xenobiotics seems to be a viable option for the removal of mixed persistent contaminants such organochlorines (OCs: monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB), γ-hexachlorocyclohexane (HCH)). In this study, Phragmites australis plants were exposed to sub-lethal concentrations of OCs (7 days), in single-exposure (0.8 to 10 mg l(-1)) and in mixture of OCs (0.2 mg l(-1) MCB + 0.2 mg l(-1) DCB + 2.5 mg l(-1) TCB + 0.175 mg l(-1) HCH). Studies were conducted on the detoxification phase II enzymes; glutathione S-transferases (GST), and glucosyltransferases (UGT). Measurements of GST and UGT activities revealed that OCs may be buffered by glutathione and glucose conjugation. There appeared to be a correlation between the effects on phase II enzymes and the degree of chlorination of the benzene ring with, for example, the greatest effects being obtained for HCH exposure. In the case of mixed pollution, the induction of some GST isoenzymes (CDNB, 35 % non-significant) and UGT (118 %) in leaves and the inhibition of phase II enzymes in the other organs were measured. UGTs appear to be key enzymes in the detoxification of OCs.