Metabolization of the Bacteriostatic Agent Triclosan in Edible Plants and its Consequences for Plant Uptake Assessment

Abstract

Persistent environmental contaminants may enter agricultural fields via the application of sewage sludge, by irrigation with treated municipal wastewater or by manuring. It has been shown that such contaminants can be incorporated into crop plants. The metabolism of the bacteriostatic agents triclocarban, triclosan, and its transformation product methyl triclosan was investigated after their uptake into carrot cell cultures. A fast metabolization of triclosan was observed and eight so far unknown phase II metabolites, conjugates with saccharides, disaccharides, malonic acid, and sulfate, were identified by liquid chromatography-mass spectrometry. Triclocarban and methyl triclosan lack a phenolic group and remained unaltered in the cell cultures. Phase I metabolization was not observed for any of the compounds. All eight triclosan conjugates identified in the cell cultures were also detected in extracts of intact carrot plants cultivated on triclosan contaminated soils. Their total amount in the plants was assessed to exceed the amount of the triclosan itself by a factor of 5. This study shows that a disregard of conjugates in studies on plant uptake of environmental contaminants may severely underestimates the extent of uptake into plants and, eventually, the potential human exposure to contaminants via food of plant origin.

Plant uptake of pharmaceutical and personal care products from recycled water and biosolids: a review

“…Podlipna et al (2013) studied the biotransfomation of two benzimidazole anthelmintics (used for killing parasitic worms), albendazole and flubendazole, in reed in vitro, and identified 10 albendazole and 5 flubendazole metabolites that were mostly phase II metabolites. Macherius et al (2012) investigated the metabolism of triclocarban, triclosan, and methyl triclosan in carrot cell cultures as well as in intact carrot plants. Although triclocarban and methyl triclosan remained unaltered in the cell cultures, fast metabolism of triclosan was observed and all metabolites were phase II metabolites (i.e., conjugates).…”

A review of measured bioaccumulation data on terrestrial plants for organic chemicals: Metrics, variability, and the need for standardized measurement protocols

“…Endophytic organisms can also contribute to the metabolism of organic chemicals within plants [21]. Plant biotransformation rates are available for a few pesticides [17,22,23], pharmaceutical chemicals [24], and plasticizers [25,26]. Furthermore, plant dissipation rates (degradation and transport loss mechanisms) can vary considerably between different plant compartments and environmental conditions [27,28].…”

Uptake and Metabolism of Phthalate Esters by Edible Plants

“…Studies on pesticides have highlighted the capacity of plant metabolism after uptake. 20 During the phase I plant metabolism, xenobiotics may undergo hydroxylation or hydrolysis, 21 where reactions such as hydrolysis lead to the formation of the corresponding MPEs from PAEs. Therefore, consideration of only the unaltered parent may result in an underestimation of plant accumulation of PAEs from soil, and consequently inaccurate prediction of potential human exposure.…”