Metabolism of soil-related phenolic compounds in plants and cell suspension cultures

Various specifically 14C-labelled benzoic and cinnamic acids were added to the nutrient solutions of sterile-cultured seedlings and cell suspension cultures of different plant species, and tested for metabolic reaction. On the basis of 14CO2-formation and isolated 14C-labelled metabolites, the decarboxylation and O-demethylation reactions were shown to be restricted to specific substituted groups of the aromatic ring. Decarboxylation of substituted phenolic acids could only be observed when the aromatic acids possessed a hydroxyl group in the para position. The O-demethylation reactions were shown to be specific for para methoxyl groups. The ring cleavage reaction was found to be specific for ortho dihydroxy compounds. The methoxyl group in the 4-position was also split if the carboxyl group in the para position was modified to a C3-side chain or even to an alcohol group. The C3-side chain had been split much faster than the alkyl-aryl-ether bonds by demethylation reaction. In addition, various polycyclic hydrocarbons specifically labelled with 14C were added to the nutrient solutions of seedlings and cell suspension cultures of plants, and tested for metabolic reaction. These polyaromatic compounds are absorbed only by the roots. As autoradiographic studies show, there is no transport into the sprouts, apart from anthracene which can be detected in the upper organs also. Experiments with different cell cultures indicate that the absorbed polyaromatic hydrocarbons are metabolized to a less extent. Most of the absorbed activity can be isolated as the applied compound. Compared with other cell cultures tested, those of Chenopodium rubrum behaved quite differently. Absorbed benzo(a)pyrene was not extractable with organic solvents but was mainly detected in the form of water-soluble compounds. By means of high-pressure liquid chromatography these oxygenated derivatives were detected and analysed. (author)