Bm. Lange et al., CHLOROANILINE LIGNIN CONJUGATES AS MODEL SYSTEM FOR NONEXTRACTABLE PESTICIDE-RESIDUES IN CROP PLANTS/, Environmental science & technology, 32(14), 1998, pp. 2113-2118
In vitro lignins formed by the peroxidase/H2O2-mediated polymerization
of coniferyl alcohol in the presence of 3,4-dichloroaniline or [N-15]
aniline were studied by H-1, C-13 and N-15 NMR spectroscopy. The anili
nes were >95% bound to the benzylic a-position of lignin side chains.
Mild acid hydrolysis under simulated stomach conditions (0.1 M HCl, 37
degrees C) was studied as a first estimate of animal bioavailability.
The two extremes,of facile or slow acid hydrolysis that are known for
chloroaniline/lignin-comelexes could be reproduced by using low or hi
gh incorporation ratios of aniline to coniferyl alcohol (10 or 40 mol
%, respectively). The case of facile a cid hydrolysis and high animal
bioavailability may be due to the high; mole ratios used and may not b
e relevant for pesticidal crop plant residue levels of 3,4-dichloroani
line. The latter are typically in the parts per million range. On the
basis of N-15 NMR spectre I fine structure; we propose that the acid-l
abile linkage may be due to anchimeric assistance in conformers formed
at the high aniline molar ratio. The;optimized methods represented he
re allow the use; of in vitro lignin copolymers as a reference system
for the structural features. and the bioavailability of nonextractable
pesticide residues in crop plants.