This review intends to summarize in a comprehensive and critical way the current
knowledge about the fate and metabolization of PPCPs in plants and to give an upto-date overview of the development of analytical approaches employed in this field.
2 Experimental Approaches for Investigating the Uptake
of Drugs by Plants
2.1 Strategies for the Growing of Plants and Their Treatment
with Drugs
Since more than a decade, studies investigating not only the uptake but also the
subsequent metabolization of drugs by plants were published [12, 33]. To achieve
this goal, different approaches were followed. In the majority of reports, plantlets
were grown hydroponically in drug-containing media [17, 34] or in a support
medium (like agar or perlite) that was wetted with drug-containing aqueous solutions. A smaller number of studies reported the uptake of drugs by plants grown in
soil [18, 19]. Here drugs were mostly added by irrigation using either lab-made drugcontaining aqueous solutions or even actual reclaimed waters. What the majority of
these studies (hydroponic and soil-based ones) have in common is that to facilitate
the detection of the parent drugs but even more importantly their metabolites, rather
high concentrations of drugs were used. Nevertheless there are a few examples
where drug concentrations employed were close to those expected in actual
reclaimed waters (e.g., a study where garden cress was treated with NSAIDs at a
concentration level as low as 0.001 mg L
À1 [35]), whereas on the other hand
Armoracia rusticana cell culture was incubated with paracetamol (PAR) at a
concentration level of >160 mg L
À1 [36].
Although, as just discussed, treatment with somewhat higher concentrations of a
drug (or drug cocktail – if the fate of more than one drug is investigated in a single
plant experiment) increases the probability to detect also the less abundant drugrelated metabolites, two aspects have to be considered. First, drug concentrations
should be below a level hampering the organic growth of the plant, and second, plant
metabolism should not be affected too much by concentration effects to keep the
study meaningful also with respect to actual environmental conditions. When
considering the treatment of a single plant with a drug cocktail (to reduce the
experimental effort when investigating the fate of several drugs), unwanted interactions between the drugs should be thoroughly observed, unless the investigation of
synergistic effects (as might be occurring when using real reclaimed waters) is the
actual aim of the study. A further factor that should be kept in mind is that the solvent
employed for preparing the drug standard solution (in many cases methanol) used for
adding the drug to the growing medium or irrigation water may also exhibit negative
effects on plant growing. Here the use of ethanol instead of methanol has proven
beneficial.
498
F. Mlynek et al.
knowledge about the fate and metabolization of PPCPs in plants and to give an upto-date overview of the development of analytical approaches employed in this field.
2 Experimental Approaches for Investigating the Uptake
of Drugs by Plants
2.1 Strategies for the Growing of Plants and Their Treatment
with Drugs
Since more than a decade, studies investigating not only the uptake but also the
subsequent metabolization of drugs by plants were published [12, 33]. To achieve
this goal, different approaches were followed. In the majority of reports, plantlets
were grown hydroponically in drug-containing media [17, 34] or in a support
medium (like agar or perlite) that was wetted with drug-containing aqueous solutions. A smaller number of studies reported the uptake of drugs by plants grown in
soil [18, 19]. Here drugs were mostly added by irrigation using either lab-made drugcontaining aqueous solutions or even actual reclaimed waters. What the majority of
these studies (hydroponic and soil-based ones) have in common is that to facilitate
the detection of the parent drugs but even more importantly their metabolites, rather
high concentrations of drugs were used. Nevertheless there are a few examples
where drug concentrations employed were close to those expected in actual
reclaimed waters (e.g., a study where garden cress was treated with NSAIDs at a
concentration level as low as 0.001 mg L
À1 [35]), whereas on the other hand
Armoracia rusticana cell culture was incubated with paracetamol (PAR) at a
concentration level of >160 mg L
À1 [36].
Although, as just discussed, treatment with somewhat higher concentrations of a
drug (or drug cocktail – if the fate of more than one drug is investigated in a single
plant experiment) increases the probability to detect also the less abundant drugrelated metabolites, two aspects have to be considered. First, drug concentrations
should be below a level hampering the organic growth of the plant, and second, plant
metabolism should not be affected too much by concentration effects to keep the
study meaningful also with respect to actual environmental conditions. When
considering the treatment of a single plant with a drug cocktail (to reduce the
experimental effort when investigating the fate of several drugs), unwanted interactions between the drugs should be thoroughly observed, unless the investigation of
synergistic effects (as might be occurring when using real reclaimed waters) is the
actual aim of the study. A further factor that should be kept in mind is that the solvent
employed for preparing the drug standard solution (in many cases methanol) used for
adding the drug to the growing medium or irrigation water may also exhibit negative
effects on plant growing. Here the use of ethanol instead of methanol has proven
beneficial.
498
F. Mlynek et al.