ABSTRACT
Indanofan and its analogs inhibited the elongation of stearoyl- or arachidoyl-CoA by [2-14C]-malonyl-CoA in leek microsomes from Allium porrum. Although the precise mode of interaction of indanofan at the molecular level is not completely clarified by the present study, it is concluded that indanofan and analogs act as inhibitor of the elongase enzyme involved in de novo biosynthesis of fatty acids with an alkyl chain longer than C18, called very-long-chain fatty acids (VLCFAs). For a strong inhibition of VLCFA formation chloro substituents at the benzene ring and the oxirane group were necessary. Furthermore, the greenhouse test showed strong activity for indanofan and its analogs, and the scores coincided with cell-free elongation inhibition. The cell-free assay, however, failed to indicate any activity for an analog having a methylene instead of the oxirane group, while both Digitaria ciliaris and Echinochloa oryzicola were killed with 1 kg a.i./ha. This finding cannot be discussed because the applied use rate of 1 kg a.i./ha is too high to allow for a score differentiation. For high concentrations of this compound additional unknown inhibitory effects may be involved besides fatty acid elongation.
Subject(s)
Allium/metabolism , Chlorobenzenes/pharmacology , Fatty Acids/biosynthesis , Herbicides/pharmacology , Indans/pharmacology , Acyl Coenzyme A/metabolism , Acyl-Carrier Protein S-Malonyltransferase , Acyltransferases/antagonists & inhibitors , Carbon Radioisotopes , Cell-Free System , Fatty Acids/chemistry , Malonyl Coenzyme A/metabolism , Stearic Acids/metabolism , Structure-Activity RelationshipABSTRACT
The effect of 2-benzylamino-1,3,5-triazines on photosynthetic electron transport (PET) was measured with thylakoids isolated from atrazine-resistant, wild-type Chenopodium album, and spinach to find novel 1,3,5-triazine herbicides bearing a strong PET inhibition. The PET inhibition assay with Chenopodium (wild-type and resistant), yielded a resistance ratio (R/W = I50 (resistant)/I50 (wild-type)) of 324 for atrazine while for benzylamino-1,3,5-triazine derivatives of diamino-1,3,5-triazines a R/W of 11 to 160 was found. The compounds having a benzylamino group at one of the amino groups in the diamino-1,3,5-triazines have a resistant ratio down to one half to 1/30 of the atrazine value. The average resistance ratio of 21 benzylamino derivatives of monoamino-1,3,5-triazines was found to be about 4.0. The inhibition of 21 benzylamino-1,3,5-triazines assayed with atrazine-resistant Chenopodium thylakoids, indicated by pI50 (R)-values, correlated well with the PET inhibition pI50 (W) of wild-type thylakoids from Chenopodium.
