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Plant Assimilation Kinetics and Metabolism of 2‑Mercaptobenzothiazole Tire Rubber Vulcanizers by Arabidopsis
journal contribution
posted on 2015-12-23, 00:00 authored by Gregory
H. LeFevre, Andrea C. Portmann, Claudia E. Müller, Elizabeth S. Sattely, Richard G. Luthy2-Mercaptobenzothiazole
(MBT) is a tire rubber vulcanizer found
in potential sources of reclaimed water where it may come in contact
with vegetation. In this work, we quantified the plant assimilation
kinetics of MBT using Arabidopsis under hydroponic
conditions. MBT depletion kinetics in the hydroponic medium with plants
were second order (t1/2 = 0.52 to 2.4
h) and significantly greater than any abiotic losses (>18 times
faster; p = 0.0056). MBT depletion rate was related
to the initial
exposure concentration with higher rates at greater concentrations
from 1.6 μg/L to 147 μg/L until a potentially inhibitory
level (1973 μg/L) lowered the assimilation rate.
9.8% of the initial MBT mass spike was present in the plants after
3 h and decreased through time. In-source LC-MS/MS fragmentation revealed
that MBT was converted by Arabidopsis seedlings to
multiple conjugated-MBT metabolites of differential polarity that
accumulate in both the plant tissue and hydroponic medium; metabolite
representation evolved temporally. Multiple novel MBT-derived plant
metabolites were detected via LC-QTOF-MS analysis; proposed transformation
products include glucose and amino acid conjugated MBT metabolites.
Elucidating plant transformation products of trace organic contaminants
has broad implications for water reuse because plant assimilation
could be employed advantageously in engineered natural treatment systems,
and plant metabolites in food crops could present an unintended exposure
route to consumers.