Removal of dexamethasone by oxidative processes : structural characterization of degradation products and estimation of the toxicity.
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Date
2021
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Abstract
Dexamethasone (DEX) belongs to a class of steroid hormones that can potentially be harmful due to their
endocrine disrupting properties. The efficient elimination of DEX during the treatment of drinking water is
needed to ensure that the health of both human and aquatic species are protected. Thus different oxidative
processes were investigated in order to assess the effect of these procedures and conditions on DEX. Aqueous
solutions of DEX were treated by conventional chlorination ([NaClO]=10 mg L− 1
) and advanced oxidative
processes (ozonation – [O3]=8 mg L− 1
; photocatalysis – [TiO2]=120 mg L− 1 and UV-C; photolysis – UV-C). The
most and least efficient processes for DEX removal were ozonation (95%) and chlorination (54%), respectively.
In total, 16 degradation products were identified and characterized by high-resolution mass spectrometry and
only two have been proposed in previous reports. Chemical structures of the degradation products were proposed
and alcohol oxidation, ozonolysis and decarboxylation were the main chemical transformations observed. The
toxicities of DEX and its derivatives were evaluated by following methods: MTT assay (HepG2 cell), ECOSAR
(acute and chronic toxicity) and molecular docking (AutoDock). MTT assay results demonstrated that only a
mixture DEX and the chlorinated derivative were toxic at high concentrations. ECOSAR analysis showed that
products formed from dehydration and fluoride elimination were more toxic than intact DEX, mainly for fish and
Daphnid and to a lesser extent for green algae. The docking study revealed that these degradation products were
not capable of making hydrogen bonds with residual amino acids GLN570, GLN642 and CYS736, but were stable
at the glucocorticoid receptor indicating the possibility of being toxic to humans.
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Keywords
Glucocorticoid, Mass spectrometry, Molecular docking
Citation
QUARESMA, A. de V. et al. Removal of dexamethasone by oxidative processes: structural characterization of degradation products and estimation of the toxicity. Journal of Environmental Chemical Engineering, v. 9, 2021. Disponível em: <https://www.sciencedirect.com/science/article/pii/S2213343721018613>. Acesso em: 11 out. 2022.