9 Nature of Propanil Bound Residues i n Rice Plants as Measured by Plant Fractionation and Animal Bioavailability Experiments
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M. L. SUTHERLAND Monsanto Agricultural Co., 800 N. Lindbergh Blvd., Saint Louis, Mo. 63166 14
In 1968 Still applied C carbonyl labeled propanil (3,4 d i chloropropionanilide) to the roots of r i c e and 6 days later could account for only 25% of applied C. Yih applied ring C labeled propanil to leaves of rice plants and 21 days later could account for only 46% of applied C. MONSANTO employed ring C propanil i n metabolism chambers that allowed CO and other v o l a t i l e radioactive products to be trapped. Treatments consisted of 5 lb/A applications of propanil phenyl- C to: 1) rice foliage, 2) s o i l containing rice plants, and 3) s o i l only. The percent C distribution and accountabili t y at the end of 27 days is shown below: FRACTION CHAMBER NUMBER 2 3 1 (%) (%) (%) 0.3 0.2 COLDTRAP 12.5 0.5 CO 0.2 0.9 SOIL 85.8 88.5 9.3 PLANT CHCl SOLUBLE 10.2 10.5 --1.9 AQUEOUS SOLUBLE 18.1 70.4 17.0 INSOLUBLE 71.7 72.5 86.6 C ACCOUNTABILITY 91.5 92.4 The above study showed that: 1) acceptable C accountabili t y could be attained when ring labeled propanil was u t i l i z e d and all possible fractions analyzed, 2) the major portion of the v o l a t i l e C trapped from chamber 1 occurred i n days 3 through 5, 3) most of the C in rice plants harvested from propanil f o l i a r or s o i l treatments was not extractable, 4) the f o l i a r applied propanil-phenyl- C must have been absorbed by rice leaves since it appeared to have undergone a similar degree of plant insolubilization as that absorbed by rice plants harvested from propanil treated s o i l , 5) the detection of 14CO suggested the possibility that the insoluble plant C could be due to incorporation of CO by rice plants into polymeric natural products. 14
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In Bound and Conjugated Pesticide Residues; Kaufman, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1976.
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Rice p l a n t s harvested at 3 and 12 weeks a f t e r s o i l a p p l i c a t i o n s of 5 l b / A p r o p a n i l - p h e n y l - ^ C were exposed t o a p l a n t s e p a r a t i o n scheme. R a d i o a c t i v i t y was spread throughout all of the f r a c t i o n s f o r both 3 r d and 12 t h week h a r v e s t s . TLC exami n a t i o n and enzymatic h y d r o l y s i s of 3 r d week r i c e p l a n t f r a c t i o n s f a i l e d to r e v e a l the presence of any n a t u r a l products. Only t r a c e q u a n t i t i e s of low s p e c i f i c a c t i v i t y C n a t u r a l products ( s t a r c h , h e m i c e l l u l o s e , l i g i n , and c e l l u l o s e ) were found i n the 12 t h week r i c e f r a c t i o n s . Of g r e a t e r s i g n i f i c a n c e was the f a c t that a l k a l i n e h y d r o l y s i s of each p l a n t f r a c t i o n r e vealed that the major p o r t i o n of was a s s o c i a t e d w i t h the 3 , 4 - d i c h l o r o a n i l i n e - p h e n y l - l ^ C moiety. Shown below i s the d i s t r i b u t i o n of C i n the various 12 t h week p l a n t f r a c t i o n s and the percent 3 , 4 - d i c h l o r o a n i l i n e - p h e n y l - ^ C In each f r a c t i o n : FRACTION C 3.4-DICHLOROANILINE (%) (% of C) HEXANE 4.8 78.2 BLIGH/DYER CHC1. 11.0 48.4 AQUEOUS 20.6 38.8 STARCH REMOVAL ACIDIC ETHANOL 22.7 63.8 STARCH 1.6 PROTEIN 1.8 HEMICELLULOSE 8.7 48.4 LIGNIN 24.4 63.2 CELLULOSE 2.0 47.3 C ACCOUNTABILITY 97.6 The i n s o l u b l e character of the major p o r t i o n of the p r o p a n i l r i c e residue suggests that the animal d i g e s t i b i l i t y of these none x t r a c t a b l e residues would be low. I f so, such i n s o l u b l e r e s i dues would have n e g l i b l e t o x i c o l o g i c a l e f f e c t . To t h i s end b i o a v a i l a b i l i t y s t u d i e s were undertaken to determine i f monog a s t r i c animals could r e l e a s e the non-extractable i n treated r i c e p l a n t s . White a l b i n o r a t s were dosed w i t h p r o p a n i l - p h e n y l t r e a t e d p l a n t samples v i a gavage and maintained i n Aerospace metabolism cages. The h i g h l y r e s t r i c t i v e Aerospace metabolism cage provides good f e c e s / u r i n e s e p a r a t i o n , e l i m i n a t e s coprophagy, and allows monitoring of * C02 and other v o l a t i l e products. When 4 a l b i n o r a t s were dosed w i t h p r e - e x t r a c t e d 12 t h week r i c e p l a n t f i l t e r cake, no C 0 and other 1 4 v o l a t i l e products could be detected, w h i l e 76.1% of the i n i t i a l x appeared i n the feces w i t h only 2.4% i n the u r i n e . When the study was r e peated i n the Aerospace cages u t i l i z i n g non-extracted 12 t h week r i c e , the e x c r e t i o n of C was 6.5% i n the u r i n e and 78.2% i n the f e c e s . Since the 12 t h week r i c e contained 36% e x t r a c t a b l e 1 4 it appears t h a t the r a t was l e s s e f f i c i e n t i n removing the l ^ C p r o p a n i l residues from the r i c e p l a n t than s o l v e n t e x t r a c t i o n . To overcome the low C a c c o u n t a b i l i t y the r a t b i o a v a i l -
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In Bound and Conjugated Pesticide Residues; Kaufman, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1976.
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a b i l i t y s t u d i e s were repeated i n l e s s r e s t r i c t i v e Econo metabol i s m cages w i t h 12 t h week non-extracted r i c e . The percent recovery rose t o 88.8% i n the feces, 11.3% i n u r i n e , w i t h an a c c o u n t a b i l i t y o f 99.9%. Combustion o f t i s s u e i n all s t u d i e s conducted, revealed l e s s than 0.05 ppm i n f a t , kidney, l i v e r and muscle. The h i g h l y r e s t r i c t i v e nature o f Aerospace metabolism cages causes c o n s t i p a t i o n and/or low food i n t a k e r e s u l t i n g i n low C r e c o v e r i e s due t o incomplete passage o f the dose. Normal r a t metabolism such as e x c r e t i o n o f products v i a u r i n e i s a l s o slowed down. I t should be pointed out t h a t not all absorbed components are excreted e x c l u s i v e l y v i a the u r i n e . Some absorbed components can be e l i m i n a t e d by the feces due t o b i l e e x c r e t i o n i n t o the d i g e s t i v e t r a c t . A t the request o f FDA, b i l i a r y f i s t u l a r e c y c l i n g experiments were c a r r i e d out by Bio-Test L a b o r a t o r i e s on dog and mice. Rice p l a n t s harvested 3 weeks a f t e r 10 lb/A p r o p a n i l - p h e n y l - C s o i l treatment were e x t r a c t e d v i a B l i g h / Dyer and the r e s u l t i n g f i l t e r cake was used i n the r e c y c l i n g experiments. Bio-Test found l e s s than 0.05% of the C dose appearing i n the b i l e of dogs or mice. The d i s t r i b u t i o n of ^ C i n the u r i n e and feces was very s i m i l a r t o that found i n the r a t b i o a v a i l a b i l i t y s t u d i e s . There was no s i g n i f i c a n t t i s s u e r e t e n t i o n o f l^C by e i t h e r dogs o r mice. In summary, the r a p i d i n s o l u b i l i z a t i o n of C i n p r o p a n i l phenylt r e a t e d r i c e p l a n t s can be accounted f o r by the a s s o c i a t i o n o f the 3 , 4 - d i c h l o r o a n i l i n e moiety w i t h v a r i o u s p l a n t f r a c t i o n s . The degree o f absorption o f bound p r o p a n i l residues i n r i c e by monogastric animals can be monitored d i r e c t l y by u r i n a r y e x c r e t i o n a c t i v i t y . Due t o the low absorption by monog a s t r i c animals, the bound p r o p a n i l residues should be considered as low t o x i c o l o g i c a l concern.
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Literature Cited: 1. 2.
Still,
G. G., Science (1968) 159, 992-993.
Yih, R. Y., McRae, D. H., Wilson, H. F., Science (1968) 161, 376.
In Bound and Conjugated Pesticide Residues; Kaufman, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1976.
