Registration Dossier

Diss Factsheets

Administrative data

Endpoint:
phototransformation in water
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:
1998
Report date:
1998

Materials and methods

Study type:
other: surface and solution phase photolysis
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
For surface phase photolysis, 10 µg of compound was applied to a PTFE surface and exposed in a UV chamber for various time points along with dark controls. The freeze dried mycelium (X633974) powder containing the active ingredient X642188 (UK-2A) was also evaluated for surface photolysis stability. Additionally the photostability of X642188 (UK-2A) was evaluated in solution (10 ppm in pH 4 buffer). In addition, X642188 was evaluated for hydrolytic stability under neutral (pH 7), acidic (pH 4) and basic (pH 10) conditions.
GLP compliance:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
(3S,6S,7R,8R)-8-benzyl-3-(3-hydroxy-4-methoxypyridine-2-amido)-6-methyl-4,9-dioxo-1,5-dioxonan-7-yl 2-methylpropanoate
Cas Number:
167173-85-5
Molecular formula:
C26H30N2O9
IUPAC Name:
(3S,6S,7R,8R)-8-benzyl-3-(3-hydroxy-4-methoxypyridine-2-amido)-6-methyl-4,9-dioxo-1,5-dioxonan-7-yl 2-methylpropanoate
Specific details on test material used for the study:
Substance name: X642188 (UK-2A)
Purity: Not specified

Study design

Radiolabelling:
no
Analytical method:
high-performance liquid chromatography
Light source:
other: UV chamber
Duration of test at given test condition
Initial conc. measured:
10 other: µg
Dark controls:
yes

Results and discussion

Dissipation half-life of parent compoundopen allclose all
Key result
DT50:
30.6 d
Test condition:
X642188 (UK-2A) (surface phase photolysis)
DT50:
22 h
Test condition:
X642190 (UK-2C/2D) (surface phase photolysis)
DT50:
15 h
Test condition:
X650872 (UK-3A) (surface phase photolysis)
DT50:
10.6 d
Test condition:
freeze dried mycelium (X633974) powder containing the active ingredient X642188 (UK-2A) (surface photolysis stability)
Key result
DT50:
1.2 h
Test condition:
X642188 (UK-2A) was evaluated in solution (10 ppm in pH 4 buffer)
Key result
DT50:
5.1 h
Test condition:
X642188 at pH 4
Key result
DT50:
6.9 h
Test condition:
X642188 at pH 7
Key result
Test condition:
X642188 at pH 10
Remarks on result:
other: hydrolysis appeared to be instantaneous. No X642188 was detectable even at the initiation of the experiment.

Applicant's summary and conclusion

Conclusions:
Several of the picolinamides investigated in this study have limited stability in sunlight on surfaces such that care will need to be taken to minimize its effect. More importantly however, is the hydrolytic instability of the primary candidate X642188. When diluted for application from the formulated material, the solution pH should be maintained acidic or neutral. From these studies it is apparent that X642188 has an extremely limited life-time under basic aqueous conditions. Additionally, UV screening of the application solution will also be necessary to maintain a consistent application due to the photolysis of X642188 in solution.
Executive summary:

Several naturally derived picolinamides received from Meiji Company were evaluated for surface and solution phase photostability. For surface phase photolysis, 10 µg of compound was applied to a PTFE surface and exposed in a UV chamber for various time points along with dark controls. Samples were exposed in triplicate for each time point. Samples were removed at predetermined intervals, extracted with acetonitrile and analyzed by HPLC to determine the extent of photodegradation. Half-lives for each compound were determined as follows: X642188 (UK-2A) 30.6 days, X642190 (UK-2C/2D) 22 hours, and X650872 (UK-3A) 15 hours. The freeze dried mycelium (X633974) powder containing the active ingredient X642188 (UK-2A) was also evaluated for surface photolysis stability. The half-life for the mixture was slightly faster than the pure isolate at 10.6 days due to the differing application technique used to apply the test solution to the PTFE disks.


Additionally the photostability of X642188 (UK-2A) was evaluated in solution (10 ppm in pH 4 buffer). Photolysis was extremely rapid in solution with an estimated half-life of 1.2 hours. In addition, X642188 was evaluated for hydrolytic stability under neutral (pH 7), acidic (pH 4) and basic (pH 10) conditions. Hydrolysis appeared to be base catalyzed. At pH 4 X642188 was relatively stable with a half life of 5.1 hours. At pH 7 the half life was determined to be 6.9 hours.


Under basic pH conditions however, hydrolysis appeared to be instantaneous. No X642188 was detectable even at the initiation of the experiment. The hydrolytic stability of the mycelium powder X633974 was evaluated as well at pH 4, 7 and 10. The half-lives for the active ingredient X642188 in the mycelium powder were somewhat longer than seen for the pure material at 11 and 16 hours for pH 4 and 7, respectively. As with the pure material at pH 10, the half-life could not be determined due to the rapid nature of the hydrolysis.