SAFENING ACTIVITY OF NATURAL HYDROXAMIC ACIDS AND ANALOGOUS COMPOUNDSAGAINST HERBICIDE INJURY TO MAIZE

Safening activities of natural compounds DIMBOA, DIBOA, and MBOA, as w ell as synthetic 1,4-benzoxazin-3-ones were tested against acetochlor and EPTC injuries to maize. No safening activities of natural products and from low to moderate activity of synthetic benzoxazinones were ob served. In order to explain inefficacy of natural compounds we studied the influence of these molecules on enzymes participating in metaboli c detoxication of acetochlor and EPTC. Pretreatment with DIMBOA elevat ed maize cytochrome P450 levels. Pretreatments with chemicals containi ng 1,4-benzoxazin-3-one backbone did not alter glutathione S-transfera se enzyme activities. However, all natural products inhibited glutathi one S-transferase activity of roots and shoots in vitro after addition to the enzyme. Safening ineffectiveness of natural hydroxamic acids m ay be explained by their inhibitory effects on GST enzymes due to thei r reaction with sulfhydryl groups on the enzyme.