Pentanedioic acid, compd. with (1S,4R)-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol (1:1)

Biodegradation in soil

Description of key information

1592U89 succinate did not readily undergo aerobic biodegradation in any of the soils examined with 15.3%, 16.8% and 11.4% of the applied test material recovered as carbon dioxide in the clay loam, sandy loam and sandy silt loam soils respectively.

Additional information

Introduction

A study has been carried out to determine the aerobic soil biodegradation of the test material in three soil types (clay loam, sandy loam and sandy silt loam) in compliance with Section 3.12 of the Food and Drug Administration (FDA) Environmental Assessment Technical Assistance Handbook.

The characteristics of the soil used in the study were as follows :

Soil classification (USDA)	Clay loam	Sandy loam	Loam
(UKMAFF)	Clay loam	Sandy loam	Sandy silt loam
Location	Buntingford Hertfordshire	Bicton Devon	Levington Suffolk
%Sand	37	64	52
%Silt	31	21	37
%Clay	32	15	11
%Organic carbon	1.4	1.0	0.8
%Organic matter	2.4	1.7	1.4
pH (1:1 H2O)	7.5	6.1	4.5
Cation exchange capacity (meq/100 g) Microbial biomass (mg C/l00 g)	22.3	10.9	8.6
Start:	25.5	13.8	ND
End:	23.7	8.5	13.7

ND : Not detected

[¹⁴C]-1592U89 succinate or [¹⁴C]-glucose was applied to triplicate samples of each soil type at a nominal application rate of 18.7 mg/50 g soil or 25 mg/50 g soil respectively, equivalent to 10 mg C/50 g of soil (dry weight equivalent). Triplicate, non-fortified samples of each soil type were also included as controls. Each soil type was incubated at 20 ± 1°C, with regular aeration, for 64 days.

Biodegradation of the test material or glucose was evaluated by determination of the carbon dioxide (CO₂) evolved as a result of complete mineralisation of the organic chemical to CO₂and water. At each sampling point the Carbosorb (CO₂absorbant) trapping solution was removed, mixed with Permafluor E scintillation cocktail and the radioactivity determined by liquid scintillation counting. Similarly, the Lumagel (volatile organic material absorbant) trapping solution was removed and the radioactivity determined directly by liquid scintillation counting. The untreated soil controls allowed correction for background radioactivity.

The levels of biodegradation of [¹⁴C]-1592U89 and [¹⁴C]-g1ucose obtained over the 64 days ofthe test were as follows:

Soil type	Biodegradation over 64days (% applied radioactivity recovered as [^14C]-CO2)
	1592U89	Glucose
Clay loam	15.3	50.7
Sandy loam	16.8	51.4
Sandy silt loam	11.4	57.7

1592U89 underwent partial biodegradation in all three soil types examined, with 15.3%, 16.8% and 11.4% of the applied test material mineralised to carbon dioxide, in the clay loam, sandy loam and sandy silt loam soils respectively, over the 64 day period of the study.

All three soil types fortified with glucose readily mineralised the reference material, with at least 50.7% biodegradation measured over the period of the study. The viability of the soils was confirmed by these results, as well as the microbial biomass determinations and the continual CO₂production from all three soil types throughout the period of the study.