Incorporation of emamectin benzoate (MK-0244) residues into soluble sugars of plants

The semisynthetic avermectin, emamectin benzoate (MK-0244), as well as other avermectins, is known to degrade rapidly and photolytically on plants, mostly to complex polar extractable residues. After [C-14]emamectin benzoate treatment, extractable residues from foliage of lettuce and cabbage and from fodder, kernels, and cobs of sweet corn were studied to determine the nature of a specific subfraction of these polar residues. These subfractions of polar extractable residues were water soluble and retained by aminopropyl solid phase extraction columns. HPLC analysis showed peaks of radioactivity corresponding to those of xylose, fructose, glucose, galactose, and/or sucrose standards. Several other discrete but unidentified radioactive components were also seen. This incorporation of radioactivity into simple sugars indicated that extensive fragmentation of emamectin had occurred. The formation of radioactive sugars in plants after [C-14]emamectin treatment may indicate the source of radioactivity for other classes of natural products in these treated plants for which bioincorporation has also been reported.