8-Chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid

Other distribution data

Administrative data

Endpoint:

other distribution data

Remarks:

Plant Uptake

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The plant uptake of test item was studied in a modified nutrient solution with cucumbers (Cucumis sativas), soybeans (Glycine max), and tomatoes (Lycopersicon esculentum).

GLP compliance:

yes

Type of study:

other: plant uptake

Test material

Test material information

1

Reference substance name:

8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid

Cas Number:

353258-35-2

Molecular formula:

C9H4ClF3N2O2

IUPAC Name:

8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid

Specific details on test material used for the study:

Radiolabeled Test Item
Test substance: [Imidazo[1,2-a]pyridine-5,8a-14C]IN-QEK31-011
Batch No.: 1572460
Radiochemical Purity: 97.8%
Specific Activity: 69.12 μCi/mg or 18.29 mCi/mmol

Non Radiolabeled Test Item
Test substance: IN-QEK31
Batch No.: IE114893-105
Purity: 98.6%

Applicant's summary and conclusion

Conclusions:

The PUF for [14C]IN-QEK31 ranged from 0.07-0.26 for cucumber, 0.07-0.20 for soybean, and 0.05-0.20 for tomato.
All treated and control plants appeared to be healthy throughout the eight-day test period. [14C]IN-QEK31 was stable in the test solution over the eight-day test period.
All three crops were phosphorimaged to determine the location of radioactivity within the plant. The images of radioactivity indicated free movement and extensive translocation of the test substance into the xylem system and continuous upward movement of IN-QEK31. Overall, the highest residues were in the roots. However, within the foliage/leaves, the highest residues tended to be found in the top of the plant canopy in all three crops based on qualitative imaging.

Executive summary:

The plant uptake of [14C]IN-QEK31 was studied in a modified nutrient solution with cucumbers (Cucumis sativas), soybeans (Glycine max), and tomatoes (Lycopersicon esculentum). The modified nutrient solution used to fill the test vessels prior to dosing had an initial pH of approximately 6.0 and consisted of half-strength Hoagland’s nutrient solution fortified with potassium dihydrogen phosphate and potassium nitrate. Plants were grown to BBCH growth stage 15-17 in sand. At this stage, the plants were removed from sand, the roots were gently washed without causing any damage, and then incubated with Hoagland’s solution containing the test substance for eight days of uptake. Intermediate samples were collected on Days 2 and 4. For the cucumber, soybean, and tomato plants, the growth chamber was maintained at a constant temperature of 21.0 ± 0.4, 21.0 ± 0.2, and 21.1 ± 0.1°C and a constant relative humidity of 53.8 ± 1.0, 53.2 ± 0.8, and 54.8 ±1.7%, respectively.

All treated plants types showed normal growth which was comparable in proportion to the control untreated plants, and there was substantial growth of both the root and foliage for each plant type.

Uptake was determined by calculating the differences in the test item concentrations in the solutions used for plant incubation and the solutions taken up by the plants. In addition, measurement of radioactivity in the plants (foliage and roots) as well as the remaining solutions was used to corroborate the plant uptake of the test substance. Plant Uptake Factors (PUF) were calculated at each sampling interval and for all three crops.

All three crop plants showed normal growth during the test, and the plant mass generally increased by ca. 40-90% over the eight days sampling period except for control tomato plants which increased by 3.7-fold. Growth of foliage as well as roots appeared to fit exponential growth curve, which could be anticipated at the growth stage of the plants used in this study. The solution uptake in in all three crops was significant, and on average ca. 350 to 786 mL of the treated solution was consumed by the plants over eight days.

On Day 8, the test substance concentration in the plant roots was significantly higher than the concentration in the foliage. The average total radioactive residues in the cucumber, soybean, and tomato roots were 0.33, 0.24, and 0.80 ppm, respectively.

The average concentration in the cucumber, soybean, and tomato foliage was 0.28, 0.11, and 0.18 ppm, respectively. The concentration of the test substance in the treatment solutions was typically 5 to 13 times the concentration of the test substance taken up by the plant at Day 8.

The average calculated plant uptake factors for cucumber, soybean, and tomato plants at Days 2, 4, and 8 ranged from 0.09-0.20, 0.07-0.15, and 0.06-0.14, respectively. Overall, an average PUF factor of 0.06-0.20 can be concluded for all three crops. Since the test substance showed a radiochemical purity of >98% for all stability samples through eight days of uptake, IN-QEK31 was stable in the modified Hoagland’s nutrient solution without a plant. Similar results were observed in all cucumber and soybean test systems. In tomato test systems, one tomato sample showed a radiochemical purity of 83.1%, but the rest were >96% radiochemically pure. Therefore, the test substance was stable for the eight days of uptake.The solution pH increased in  the stability controls and in all cucumber and soybean samples over eight days. In tomato plants, a similar trend was noted with the exception that for one replicate the pH dropped to 3.8. This was the same sample that had a radiochemical purity of 83.1% and which also had the highest PUF factor for tomato plants. Therefore, the Day 8 PUF factor for tomato plants may be suspect.

Overall, the general increase in the pH did not appear to have any influence on the plant uptake of IN-QEK31 since the PUF factors remained relatively constant throughout eight days of uptake in all three crops.

All three crops were phosphorimaged to determine the location of radioactivity within the plant. The images of radioactivity indicated free movement and extensive translocation of the test substance into the xylem system and continuous upward movement of IN-QEK31. Overall, the highest residues were in the roots. However, within the foliage/leaves, the highest residues tended to be found in the top of the plant canopy in all three crops based on qualitative imaging.