Metabolism of acetaminophen (paracetamol) in plants—two independent pathways result in the formation of a glutathione and a glucose conjugate

Abstract

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...

Effects of acetaminophen in Brassica juncea L. Czern.: investigation of uptake, translocation, detoxification, and the induced defense pathways

“…In the case of glutathionyl acetaminophen the MS/MS fragmentation pattern showed the loss of the glutamic acid residue of glutathione (129 Da) resulting in the formation of a fragment of m/z 328 (data not shown) as described in the literature (Mutlib et al 2000;Huber et al 2009). In case of the acetaminophen glycoside conjugate, we detected the pseudomolecular ion ([M+ H] + ) of m/z 314.…”

“…In analogy with this scheme, a similar detoxification pathway has recently been postulated in plants (Huber et al 2009). According to the so called "green-liver" concept (Sandermann 1994;Schröder and Collins 2002), plant detoxification cascades show strong similarities with the mammalian liver functions.…”

“…LC-MS analysis was carried out on a HPLC system (Varian ProStar 210) that was coupled to an ion trap mass spectrometer (Varian 500-MS), as described by Huber and coworkers (Huber et al 2009). The HPLC eluent was introduced to the mass spectrometer using a pneumatically assisted electrospray source.…”

Sub-lethal effects induced by a mixture of three non-steroidal anti-inflammatory drugs (NSAIDs) on the freshwater bivalve Dreissena polymorpha

“…Lastly, IBU is readily metabolised through phase I and phase II pathways; in human and rat liver, CYP 450 isoforms contribute to the majority of its phase I biotransformation (Jacqz-Aigrain and Anderson 2006). Accordingly, there is also evidence of the formation of CYP-induced metabolites of DCF (Mehinto et al 2010), IBU (Gomez et al 2011) and PCM (Huber et al 2009) in non-target species. Considering that several isoforms or encoding gene sequences of CYP 450 belonging to the 2, 4 and 6 families have been described in mussels (Chaty et al 2004), the activation of zebra mussel phase I enzyme complex could produce reactive metabolites of the tested NSAIDs.…”

New Perspectives on the Metabolism and Detoxification of Synthetic Compounds in Plants

“…Rapid GST-mediated detoxification appears to account for the tolerance of several crops toward important herbicide classes, notably the chloroacetanilides, chlorotriazines, diphenylethers and AOPPs. GSTs also detoxify other agrochemicals, including the safeners benoxacor, dichlormid and fenclorim (Brazier-Hicks et al 2008) and can act on drugs entering the environment as pollutants, such as the antibiotic chlortetracycline (Farkas et al 2007) and the painkiller paracetamol (Huber et al 2009). Occasionally, GST activity can increase xenobiotic toxicity.…”