Metabolomic studies on root uptake and transformation
of bioactive
compounds, like cereal benzoxazinoids (BXs) in non-BX producing plants,
are very limited. Therefore, a targeted mass-spectrometry-based metabolomics
study was performed to elucidate the root uptake of BXs in white clover
(Trifolium repens L.) and the impact
of absorbed BXs on intrinsic clover secondary metabolites. Clover
plants grew in a medium containing 100 μM of individual BXs
(five aglycone and one glycoside BXs) for 3 weeks. Subsequently, plant
tissues were analyzed by liquid chromatography–tandem mass
spectrometry to quantify the BXs and clover secondary metabolite concentrations.
All BXs were taken up by clover roots and translocated to the shoots.
Upon uptake of 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA), 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one
(DIMBOA), 2-hydroxy-1,4-benzoxazin-3-one (HBOA), and 2-β-d-glucopyranosyloxy-1,4-benzoxazin-3-one (HBOA-glc), the parent
compounds and a range of transformation products were seen in the
roots and shoots. The individual BX concentrations ranged from not
detected (nd) to 469 μg/g of dry weight (dw) and from nd to
170 μg/g of dw in the roots and shoots, respectively. The root
uptake of BXs altered the composition of intrinsic clover secondary
metabolites. In particular, the concentration of flavonoids and the
hormone abscisic acid increased substantially in comparison to control
plants.