Quantitative structure-activity relationships in the inhibition of photosystem II in chloroplasts by phenylureas

Kakkis, Emil; Palmire, Vincent C.; Strong, Cynthia D.; Bertsch, Walter F.; Hansch, Corwin; Schirmer, Ulrich

doi:10.1021/jf00121a034

Cited by 38 publications

(41 citation statements)

References 13 publications

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“…Furthermore, the effects are not reduced by treatment with DCMU, in contrast to paraquat. The fact that DPEI is a very much poorer inhibitor of non-cyclic photosynthetic electron transport than DCMU (1500.24 gM (12) (23). However, H202 accumulation does not appear to be the primary agent in DPE toxicity (14,29).…”

Section: Discussionmentioning

confidence: 99%

Mode of Action Studies on Nitrodiphenyl Ether Herbicides

Bowyer¹,

Smith²,

Camilleri³

et al. 1987

Plant Physiol.

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5-12-Chloro-4-(trifluoromethyl)phenoxyl-2-nitroacetophenone oximeo-(acetic acid, methyl ester) (DPEI), is a potent nitrodiphenyl ether herbicide which causes rapid leaf wilting, membrane lipid peroxidation, and chlorophyll destruction in a process which is both light-and r2-dependent. These effects resemble those of other nitrodiphenyl ether herbicides. Unlike paraquat, the herbicidal effects of DPEI are only slightly reduced by pretreatment with the photosynthetic electron trans- The herbicidal effects of DPE2 herbicides (rapid leaf wilting followed by necrosis) are caused by a light-and 02-dependent peroxidation of unsaturated membrane lipids (13,17,20,22,28). However, the exact nature of the interactions which give rise to this activity are not yet understood. There are three principal hypotheses. The first hypothesis proposes that the DPE is reduced to a radical species by chloroplast PSI and the radical initiates lipid peroxidation. Evidence for this hypothesis is based largely on studies with the alga Scenedesmus obliquus (14, 15).Pretreatment ofthe alga with the PSII electron transport inhibitor DCMU protects the algal cells from the herbicidal effects of the DPE oxyfluorfen. The interpretation of this result is that by blocking photosynthetic electron transfer, reduction of the DPE by PSI is inhibited as in the case with the known PSI electron acceptor, paraquat. However, DCMU is only moderately effec-'Supported by a studentship from the Science and Engineering Research Council, United Kingdom, and Shell Research Limited.2 Abbreviations: DPE, p-nitrodiphenyl ether, oxyfluorfen, 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4(trifluoromethyl) benzene; acifluorfen, 5-(2-chloro-4-trifluoromethyl) phenoxy-2-nitrobenzoate; DPEI, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitroacetophenone oxime-o-(acetic acid, methyl ester).tive at protecting higher plants and the alga Chlamydomonas eugametos from DPEs (6, 17, 22), even though very high levels of protection against paraquat are observed. It has also been shown that chlorodiphenyl ether analogs in which the p-nitro group is replaced by p-chloro have similar in vivo herbicidal effects to the parent nitro compounds, although their in vitro redox properties are very different and probably preclude radical formation by the herbicide molecule (6,7,25).The DPE acifluorfen does not inhibit photosynthetic electron transport to artificial electron acceptors but it does inhibit C02-dependent 02 evolution in intact chloroplasts (29). The site of this inhibition appears to be linked to an effect on the activation of stromal enzymes involved in CO2 fixation. The second hypothesis, proposed by Wettlaufer et al. (29) is that an inhibition of CO2 fixation would result in an accumulation of NADPH and a shunting of electron transport to 02 generating superoxide, resulting ultimately in lipid peroxidation.The third hypothesis proposes that carotenoids are involved in the activation of the nitrodiphenyl ethers, in a process independent of photosynthetic electron transfer, and whic...

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Section: Discussionmentioning

confidence: 99%

Mode of Action Studies on Nitrodiphenyl Ether Herbicides

Bowyer¹,

Smith²,

Camilleri³

et al. 1987

Plant Physiol.

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“…QSAR calculations showed no significant correlation between inhibitory activity of the 1,4-naphthoquinones and their lipophilicity. Normally, high correlation exists between lipophilicity and biological activity of other photosystem I1 inhibitors [24]. Contrary, a relatively good correlation could be obtained for the inhibitory activity of naphthoquinones using either a parabolic regression on the sum of the o-Hammett values (r = 0.669) or of the Taft steric parameters in position 2 (E: 2) or in position 3 (E: 3) (r = 0.723).…”

Section: Resultsmentioning

confidence: 99%

QSAR of 1,4‐Naphthoquinones as Inhibitors of Photosystem II Electron Transport

Oettmeier

Dierig

Masson

1986

Quant. Struct.‐Act. Relat.

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42 1,4‐naphthoquinones with substituents in the 2‐ and 3‐position were examined for their inhibitory activity on photosynthetic electron transport through photosystem II. The best ones were active in concentrations in the μM range or less. A QSAR was established, using the sum of the σ‐Hammett parameters and Taft's steric E cs parameter for the substituents in the 2‐ and 3‐position. The QSAR could be improved, if instead of the E cs, the STERIMOL parameters L (for the 2‐position) and B3 and B4 (for the 3‐position) were applied. QSAR for different types of photosystem I1 inhibitors (urea, phenolic, quinoid) were compared. The differences in between them do support the idea of nonidentical though possibly overlapping binding sites at the reaction center complex of photosystem II.

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“…'-'LogKO, values were taken from '1151, d [16], "171, f [18], E[19], h [20], "211, and "221. issued by the Medicinal Chemistry Project, Pomona College, Claremont, California, or calculated with Medchem CLOGP, Version 3.33, according to Hansch and Leo [14]. Those of compounds with complicated chemical structure, such as pentachlorobenzene, DCMU, lindane, diflubenzuron, rotenone, buprofezin, dieldrin, DDT, and fenvalerate, were obtained from the literature [15-221, where log KO, values were measured by the flask-shake method.…”

Section: Compounds and Their Log Ko Valuesmentioning

confidence: 99%

Quantitative structure‐activity relationships of nonspecific and specific toxicants in several organism species

Ikemoto

Motoba

Suzuki

et al. 1992

Enviro Toxic and Chemistry

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The toxicities to Oryzias latipes, Daphnia pulex, and Chlorella vulgaris of nonspecific toxicants (alkanols, substituted benzenes, and alkyl toluates) were well collineated with the logarithm of the octanol/water partition coefficient, log Kow. However, specific toxicants such as 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), lindane, diflubenzuron, rotenone, buprofezin, dieldrin, 1,1,1‐trichloro‐2,2‐bis(p‐chlorophenyl)ethane (DDT), and fenvalerate exhibited excess toxicities dependent on the test organism species. The species‐specific excess toxicities were much higher than those expected from log Kow and seemed to appear only when the test organisms possessed the specific sites for the toxicants. However, the toxicities of n‐butyl‐ and n‐propyl‐p‐toluates to Oryzias latipes were slightly lower than those predicted from log Kow. The toxicity alleviation corresponded well to the ester biodegradability measured in the fish toxicity assay system. Thus simple quantitative structure‐activity relationships (QSARs), using solely log Kow with an appropriate set of compounds and bioassay systems, are useful not only for predicting the environmental toxicity of nonspecific toxicants and specific toxicants, including their mechanism of action, but also for assessment of their biodegradability.

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Quantitative structure-activity relationships in the inhibition of photosystem II in chloroplasts by phenylureas

Cited by 38 publications

References 13 publications

Mode of Action Studies on Nitrodiphenyl Ether Herbicides

Mode of Action Studies on Nitrodiphenyl Ether Herbicides

QSAR of 1,4‐Naphthoquinones as Inhibitors of Photosystem II Electron Transport

Quantitative structure‐activity relationships of nonspecific and specific toxicants in several organism species

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