F. Dutka

ON THE MODE OF ACTION OF EPTC AND ITS ANTIDOTES

Direct injection techniques have shown that the phytotoxicity to corn of EPTC-sulfone, EPTC and EPTC-sulfoxide is decreasing in this order, and the mixed function oxidase inhibitors piperonyl butoxide and SKF-525A are synergists but glutathione is an antagonist for the toxic action of EPTC. From these results it is concluded that 1/ sulfoxidation and glutathione conjugation are equally important for the detoxification of EPTC, 2/ these processes play a key role in the antidote effect, 3/ phytotoxicity of EPTC to corn is not due to the action of sulfone and is only partly due to the sulfoxide metabolite. A phytotoxic mechanism of EPTC not involving the sulfoxide is suggested. An attempt to find relationship between acylation reactivity and antidote activity of amides, esters and thiolesters is described.

Biochemical mode of action of the antidote fenclorim in rice (Oryza sativa L.)

Summary Fenclorim counteracts phytotoxic effects of the herbicide pretilachlor to rice but renders no protection to the weed species barnyardgrass. Our data suggest that the antidotal efficiency of fenclorim is due to its ability to increase the levels of glutathione and of the enzyme glutathione S-transferase in rice (but not in barnyardgrass) thereby enhancing the capacity of the crop plant to detoxify the herbicide via glutathione conjugation.

Alkylation of quinolines with trialkyl phosphates. Part 2. Mechanistic studies

The mechanism of alkylation of 4-quinolone (3) by trialkyl phosphates has been studied by preparative, kinetic, and isotopic methods, as well as by u.v. spectrophotometry. In a kinetically controlled process the transient initial formation of 4-methoxyquinoline (4a) was established; this was subsequently transformed by trimethyl phosphate to a quaternary N-methyl-4-methoxyquinolinium salt (6a). The latter catalyses the transformation of (4a) by intermolecular O→N methyl transfer to the more stable N-methyl-4-quinolone (5a). The end product is a mixture of (5a) and (6a). Their ratio is shifted at higher temperature in favour of (6a). This is due partly to differences in the temperature dependence of the individual reactions and partly to alkylation of (5a) by trimethyl phosphate at higher temperature. A mechanism for the alkylation reaction is proposed.

N1-aryl-N2-dichloroacetyl glycine and alanineamides as selective safeners for corn against chloroacetanilide herbicides

Abstract Structurally new N1aryl‐N2‐dichloroacetyl glycine and alaninamides were prepared. Greenhouse experiments were conducted to determine the effectiveness of the new compounds in protecting corn seedlings from chloroacetanilide (acetochlor, alachlor, dimethachlor, metazachlor, metolachlor) injury using dichlormid and BASF‐145138 as standard safeners. High rates of chloroacetanilides caused significant injury to sensitive corn hybrids. The most acive derivatives reduced injury to corn from dimethachlor and metolachlor and lesser extent from acetochlor and metazachlor. The most effective derivatives of the new compounds displayed better safening activity than the standards. Some of the new compounds were found to be selective safeners when formulated as a tank mixture with metolachlor in a 1:33–100 safener‐to‐herbicide ratio showing the same or better activity than the standard used. Nomenclature: BASF‐145138, 1‐dichloroacetyl‐hexahydro‐3,3,8α‐trimethyl‐pyrrolo‐[1,2‐α]—pyrimidin‐6‐(2H)‐one; EPTC, S‐eth...

Safening activity of natural hydroxamic acids and analogous compounds against herbicide injury to maize

Abstract Safening activities of natural compounds DIMBOA, DIBOA, and MBOA, as well 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 observed. In order to explain inefficacy of natural compounds we studied the influence of these molecules on enzymes participating in metabolic detoxication of acetochlor and EPTC. Pretreatment with DIMBOA elevated maize cytochrome P450 levels. Pretreatments with chemicals containing 1,4‐benzoxazin‐3‐one backbone did not alter glutathione S‐transferase enzyme activities. However, all natural products inhibited glutathione S‐transferase activity of roots and shoots in vitro after addition to the enzyme. Safening ineffectiveness of natural hydroxamic acids may be explained by their inhibitory effects on GST enzymes due to their reaction with sulfhydryl groups on the enzyme.

Effects of S-Ethyl-N,N-Dipropylthiocarbamate (EPTC) on Normal and Dwarf Seedlings of Zea mays L.

Summary Gibberellin-deficient dwarf 1 maize mutant seedlings are at least ten times more sensitive to EPTC (S-ethyl-N,N-dipropylthiocarbamate) phytotoxicity than normal maize. Levels of reduced glutathione and the enzymes cytosolic and microsomal glutathione S-transferase (important in the detoxication of the herbicide) are not significantly different in dwarf and normal maize. Our data suggest that EPTC phytotoxicity is related to alterations in gibberellin metabolism in maize plants.

Crown ether salt catalysis of ester aminolysis in an aprotic solvent

The RCO2− catalyzed n-butylaminolysis of 4-nitrophenyl acetate in chlorobenzene has been studied. Logarithms of the catalytic rate constants can be linearly correlated with Taft polar substituent constants for the R groups. Product analysis as well as the lack of steric hindrance by bulky R substituents indicate that the carboxylates act as general base catalysts.AbstractБыл изучен н-бутиламинолиз 4-нитрофенилацетата в хлорбензоле. Логарифм каталитических констант скорости линейно зависит от полярных костант заместителей Тафта для групп R. Анализ продуктов, а также отсутствие стерических прерятствий оббемистыми эаместителями R указывает на то, что карбоксилаты реагируют как при катализе общими основаниями.

1‐Aminobenzotriazole increases glutathione‐s‐transferase activity of maize

Abstract Glutathione‐S‐transferase (GST) activity of maize (Zea mays L.) seedlings treated with 1‐aminobenzotriazole (ABT) derivatives and/or EPTC were measured using EPTC‐sulfoxide as substrate. Both safeners and ABT derivatives significantly elevated the GST activity in the concentrations needed for effective safening action. ABT is considered as an inhibitor of plant cytochrome P‐450 monooxygenases (P‐450) and, because of this, used to study herbicide mode of action. Our data indicate that ABT has multiple effects on plants influencing not only P‐450 but GST as well. Thus the role of ABT in herbicide metabolism needs reconsideration.

Notizen: Thiol Ester Aminolysis in Acetonitrile

The kinetics of the reactions of p-nitrophenyl thiolacetate with several amines in acetonitrile was studied. Hydrazine exhibits considerably greater nucleophilicity than expected from its pKa value. Common mechanism is suggested for the aminolysis of the thiol ester and its oxygen analogue.