Abstract
Metabolism studies with selected test substances have shown that a model on the basis
of the incubated hen’s egg is suitable as a supplement to animal experimentation.
Because of its 3,4-dimethoxyphenyl structure veratric acid (3,4-dimethoxybenzoic acid),
a known human metabolite of mebeverine, was chosen as model substance for the present
investigations and the parent compound as well as 4-hydroxy-3-methoxybenzoic acid
were identified as main metabolites. The absence of 3-hydroxy-4-methoxybenzoic acid
lets conclude that the O-demethylation takes place exclusively at the p-methoxyl function. In addition, 3,3’,4,4’-tetramethoxy-l-ornithuric acid (2,5-bis-(3,4-dimethoxybenzoylamino)pentanoic
acid) and its O-desmethyl derivative could be characterized as further metabolites. So far an amino
acid conjugate has not been described after veratric acid administration in a vertebrate.
There were no indications for the appearance of 3,4-dihydroxybenzoic acid in the veratric
acid metabolism. This was confirmed by corresponding studies having the isomeric guaiacol
acids as precursor. Furthermore, it could be proved that in ovo the O-methylation of 3,4-dihydroxybenzoic acid occurs regioselective at the m-hydroxyl group. The results which broaden the knowledge on the metabolic fate of
veratric acid are discussed in comparison with those in mammals. The metabolites were
identified by GC-MS, ESI-HRMS and LC/ESI-MS/MS. The structure of the synthesized reference
substance was confirmed by MS, 1H and 13C NMR spectral data.
Key words
complementary method to animal testing - 3,4-dimethoxyphenyl moiety - guaiacol acids
-
O-demethylation -
O-methylation - amino acid conjugation
