calculated for several plant species (cucumber, lettuce, spinach (in hydroponic
experiments) and for ryegrass and lettuce (in soil)), with a time exposure ranging
from 7 to 40 days [109, 110, 125, 127]. For all the selected cases, the applied
concentrations were relatively low (2.7–69.0 μg/L), when compared to the rest of the
studies (5.0–758.0 μg/L), which might indicate a more efficient uptake for lower
applied concentrations. For the well-studied anti-inflammatory drug diclofenac, ten
times higher average BCF > TF values were detected in hydroponic experiments
(Table 3); nonetheless, four of thirteen studies had higher BCFs (3.2–17.7) than the
rest of the studies (BCF % 0.5; Fig. 5a) [101, 111, 112, 126]. Several works therefore
reported that this pattern is caused by the hydrophobicity of diclofenac [115, 119],
but as for charged molecules, the log D OW rather than the log K OW should be
considered. Since this compound has a log D OW of 1.85 translocation should be
favoured, however it is not the case. As mentioned in the first part of the chapter, the
protein plant composition might play an important role on storage of anionic
compounds in roots, as discussed by González García and co-authors [36].
The same pattern (BCF > TF) was also obtained for gemfibrozil (lipid regulator)
in a 2-week study with old cucumber plants [109] (Table 3); this result might be
related to the high metabolism of young plants, since for different type of compounds (neutral, anionic and cationic) BCF > TF were registered in this study. In
any case, further investigation is needed to evaluate the uptake results according to
rigorous pH measurements, since this molecule dramatically changes its ionization
status (pKa 0.8 to À0.99) in a very short pH interval (5.3–6).
In contrast to the behaving of most of the anionic compounds, dilantin (anticonvulsant) presented a higher average TF (2.9) when compared to its BCF (0.9)
Table 6 Chemical properties of cationic pharmaceuticals, as well as the average BCFs and TFs
calculated per compound in soil studies
Compounds
log K OW
pH
pKa
log D OW
BCF
TF
Authors
Average values
Antibiotic
Lincomycin
0.20
7.58
0.75
À3.35
0.00
9.96
[102]
Anticonvulsant
Lamotrigine
2.57
8.10
0.18
2.70
0.03
1.93
[102]
Antidiabetic
Metformin
À2.64
na
1.01
À2.56
0.34
0.61
[126]
Beta-blocker
Atenolol
0.16
6.96
0.99
À2.60
0.39
3.51
[124]
Propranolol
3.48
6.63
0.99
0.59
2.59
1.97
[125]
Psychotropic drug
Chlordiazepoxide
2.44
6.30
0.43
À0.12
0.04
6.58
[130]
Clonazepam
2.41
6.30
0.01
3.56
0.01
16.82
[130]
Fluoxetine
4.05
6.25
1.00
1.07
0.04
0.24
[125]
Flurazepam
3.80
6.30
1.00
3.77
0.01
1.24
[130]
Symbols: na, means not available
Uptake and Translocation of Pharmaceuticals in Plants:. . .
125
experiments) and for ryegrass and lettuce (in soil)), with a time exposure ranging
from 7 to 40 days [109, 110, 125, 127]. For all the selected cases, the applied
concentrations were relatively low (2.7–69.0 μg/L), when compared to the rest of the
studies (5.0–758.0 μg/L), which might indicate a more efficient uptake for lower
applied concentrations. For the well-studied anti-inflammatory drug diclofenac, ten
times higher average BCF > TF values were detected in hydroponic experiments
(Table 3); nonetheless, four of thirteen studies had higher BCFs (3.2–17.7) than the
rest of the studies (BCF % 0.5; Fig. 5a) [101, 111, 112, 126]. Several works therefore
reported that this pattern is caused by the hydrophobicity of diclofenac [115, 119],
but as for charged molecules, the log D OW rather than the log K OW should be
considered. Since this compound has a log D OW of 1.85 translocation should be
favoured, however it is not the case. As mentioned in the first part of the chapter, the
protein plant composition might play an important role on storage of anionic
compounds in roots, as discussed by González García and co-authors [36].
The same pattern (BCF > TF) was also obtained for gemfibrozil (lipid regulator)
in a 2-week study with old cucumber plants [109] (Table 3); this result might be
related to the high metabolism of young plants, since for different type of compounds (neutral, anionic and cationic) BCF > TF were registered in this study. In
any case, further investigation is needed to evaluate the uptake results according to
rigorous pH measurements, since this molecule dramatically changes its ionization
status (pKa 0.8 to À0.99) in a very short pH interval (5.3–6).
In contrast to the behaving of most of the anionic compounds, dilantin (anticonvulsant) presented a higher average TF (2.9) when compared to its BCF (0.9)
Table 6 Chemical properties of cationic pharmaceuticals, as well as the average BCFs and TFs
calculated per compound in soil studies
Compounds
log K OW
pH
pKa
log D OW
BCF
TF
Authors
Average values
Antibiotic
Lincomycin
0.20
7.58
0.75
À3.35
0.00
9.96
[102]
Anticonvulsant
Lamotrigine
2.57
8.10
0.18
2.70
0.03
1.93
[102]
Antidiabetic
Metformin
À2.64
na
1.01
À2.56
0.34
0.61
[126]
Beta-blocker
Atenolol
0.16
6.96
0.99
À2.60
0.39
3.51
[124]
Propranolol
3.48
6.63
0.99
0.59
2.59
1.97
[125]
Psychotropic drug
Chlordiazepoxide
2.44
6.30
0.43
À0.12
0.04
6.58
[130]
Clonazepam
2.41
6.30
0.01
3.56
0.01
16.82
[130]
Fluoxetine
4.05
6.25
1.00
1.07
0.04
0.24
[125]
Flurazepam
3.80
6.30
1.00
3.77
0.01
1.24
[130]
Symbols: na, means not available
Uptake and Translocation of Pharmaceuticals in Plants:. . .
125