IBUPROFEN METABOLISM IN Lemna gibba L. UNDER CONTROLLED CONDITIONS

At the end of the 8-day IBU exposure test, only about 5% IBU was found in the growth solution (Fig. 1A); this result is in agreement with Dordio et al. (2011) and Zhang et al. (2015). IBU was subjected to physical-chemical transformation (12.6%) whereas only about 0.4% of IBU added to the growth solution accumulated in the plant. Results highlighted that most part of IBU was transformed along time. The photodegradation and/or hydrolysis of IBU was expected, as the experiment was conducted simulating the ambient light exposure (Pietrini et al. 2015). Several studies to date show that various PPCPs can be taken up by plants from nutrient solution or soil. After being taken up by plants, PPCPs are metabolised with the generation of transformation products. In L. gibba L. exposed to 1 mg L-1 IBU for 8 days, in addition to IBU, 11 different IBU metabolites were detected, and their percent distribution is shown in Fig. 2B. It is worth underlining that the lack of carboxyl-IBU allows to hypothesise in this plant species a different metabolic pathway compared to humans and microbes. Apart from the IBU, the most concentrated IBU metabolites in L. gibba L. are hydroxyl-IBU and hydroxyl- IBU acetyl hexoside. Further, the formation of IBU- glucuronide and hexoside conjugates suggests the induction of detoxification processes in plants. The identification of such metabolites and the study of their physico-chemical properties and release in the environment will help to understand the real ecotoxicological effects of IBU in the aquatic ecosystem.