A method for evaluating the pharmaceutical deconjugation potential in river water environments

- A new assay method for evaluating deconjugation activity was developed.
- Acetaminophen glucuronide and sulphate were used as model compounds.
- The reaction conditions for deconjugation were optimized.
- The method was applied to 19 pharmaceuticals in river water.
- Glucuronide conjugates predominated in the river water environment.

A new enzymatic assay method that uses deconjugation enzymes was developed to evaluate the presence and extent of conjugated pharmaceuticals in the form of glucuronide conjugates or sulphate conjugates in river environments. First, acetaminophen glucuronide (Ace Glu) and acetaminophen sulphate (Ace Sul) were used as model conjugated pharmaceuticals to determine the appropriate combination of deconjugation enzymes and reaction conditions, including temperature, duration and pH. Next, we applied the defined method to 19 pharmaceuticals grouped into nine therapeutic classes that were chosen based on previously detected levels and frequencies in sewage and river water. The enzymatic decomposition profile varied widely depending upon the enzyme preparations available. The effect of the water reaction temperature was small between 5 and 40 °C, and the reaction proceeded in for both glucuronide conjugates and sulphate conjugates at an approximately neutral pH (corresponding to usual river water conditions) within 1 h. Application of the method to environmental samples showed that some pharmaceuticals were present in both glucuronide conjugate and sulphate conjugated forms, although glucuronide conjugates were the primary forms in the river water environment. Water treatment systems at sewage treatment plants were found to be effective for the removal of these conjugated compounds. The present results should be valuable in the environmental risk assessment of conjugated pharmaceuticals and in keeping river environments clean. To the best of our knowledge, this is the first report that enables the evaluation of the pharmaceutical deconjugation potential in a river environment.

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