**4. Conclusion**

The continuous use of plant protection products has led to the contamination of different environmental compartments, such as water, soil and air, being water contamination of great concern due to the risks for human consumption.

The synthetic research of herbicides in the last decades has shifted from long-life compounds to less persistent and more polar compounds, in order to avoid their accumulation in the environment. However, the low persistence of these compounds does not imply their completely mineralization but they are going to degrade to smaller molecules with different physicochemical properties than the active substances. In fact, it has been demonstrated that some of their transformation products are more mobile, persistent and/or more toxic than the parent molecule. Therefore, the knowledge of the fate of herbicides in the environment is underestimated if we do not take into account their transformation products whose behaviour and agro-environmental fate is in many cases unknown.

Besides, the lack of data on the phytotoxic effects of herbicide residues has been highlighted. In this sense, it is necessary to study and develop simple methods for evaluating the environmental impact of these products based on hard scientific data. Furthermore, it is also important not only study the phytotoxicity of the herbicide by means of bioassays, but also of their degradation by-products. From these studies should be able to derive recommendations for agricultural practices for the use of these products are environmentally friendly in general and in particular the agricultural environment capable of guaranteeing the future productivity of farms in the context of sustainable agriculture.

Cyclohexanedione oxime herbicides have been developed for the post-emergence control of grasses in dicotyledonous agricultural crops. These herbicides are unstable in aqueous solution and are very sensitive to pH and sunlight. These properties are highly relevant to their environmental fate. Degradation is so rapid that degradation products apparently could contribute to the activity of the parent molecule. Until now, some of these degradation products and the degradation pathways have been identified. However, the fate, significance and phytotoxicity of their degradation products is not fully known and future research is still need to attain a complete understanding of the fate of cyclohexanedione herbicides in the environment.

#### **5. Acknowledgment**

This work was supported by the CICYT project RTA2008-00027-00-00.

#### **6. References**

94 Herbicides – Properties, Synthesis and Control of Weeds

only ACCase-inhibiting herbicides applied to fields in which resistant plants were identified. In whole-plant dose–response experiments, resistant *S. faberi* was 134-fold resistant to sethoxydim (Stoltenberg & Wiederholt, 1995), but showed low levels of resistance to the cyclohexanedione herbicide clethodim. Similarly, Table 5 summarizes the weed species that are known to have developed resistance to ACCase-inhibiting herbicides

The development of resistance to ACCase-inhibiting herbicides in several grass weeds is an increasing problem in several parts of the world. Resistance to these herbicides can arise easily following selection pressure with cyclohexanedione herbicides for six to ten years. The judicious use of ACCase-inhibiting herbicides in combination with herbicides from other classes and methods of non-chemical weed control will be important for prolonging

The continuous use of plant protection products has led to the contamination of different environmental compartments, such as water, soil and air, being water contamination of

The synthetic research of herbicides in the last decades has shifted from long-life compounds to less persistent and more polar compounds, in order to avoid their accumulation in the environment. However, the low persistence of these compounds does not imply their completely mineralization but they are going to degrade to smaller molecules with different physicochemical properties than the active substances. In fact, it has been demonstrated that some of their transformation products are more mobile, persistent and/or more toxic than the parent molecule. Therefore, the knowledge of the fate of herbicides in the environment is underestimated if we do not take into account their transformation products whose behaviour and agro-environmental fate is in many cases

Besides, the lack of data on the phytotoxic effects of herbicide residues has been highlighted. In this sense, it is necessary to study and develop simple methods for evaluating the environmental impact of these products based on hard scientific data. Furthermore, it is also important not only study the phytotoxicity of the herbicide by means of bioassays, but also of their degradation by-products. From these studies should be able to derive recommendations for agricultural practices for the use of these products are environmentally friendly in general and in particular the agricultural environment capable of guaranteeing the future productivity of farms in the context of sustainable agriculture.

Cyclohexanedione oxime herbicides have been developed for the post-emergence control of grasses in dicotyledonous agricultural crops. These herbicides are unstable in aqueous solution and are very sensitive to pH and sunlight. These properties are highly relevant to their environmental fate. Degradation is so rapid that degradation products apparently could contribute to the activity of the parent molecule. Until now, some of these degradation products and the degradation pathways have been identified. However, the fate, significance and phytotoxicity of their degradation products is not fully known and future research is still need to attain a complete understanding of the fate of cyclohexanedione

around the world (Delye et al., 2005; Hatzios, 2001).

the usefulness of the cyclohexanedione herbicides.

great concern due to the risks for human consumption.

**4. Conclusion** 

unknown.

herbicides in the environment.


Chemical Behaviour and Herbicidal Activity of Cyclohexanedione Oxime Herbicides 97

Foy, C.L. & Witt, H.L. (1992). Annual grass control in alfalfa (*Medicago sativa*) with

García-Repetto, R., Martínez, D. & Repetto, M. (1994). The fluence of pH on the degradation

Green, P.G. & Young, T.M. (2006). Loading of the herbicide diuron into the California water

Harwood, J.L. (1999). Graminicides which inhibit lipid synthesis, *Pesticide Outlook,* Vol. 10,

Hashimoto, Y., Ishihara, K. & Soeda, Y. (1979a). Nature of the residue in soybean plant after treatment of alloxydim-sodium, *Journal of Pesticide Science,* Vol. 4, pp. 375-378. Hashimoto, Y., Ishihara, K. & Soeda, Y. (1979b). Fate of alloxydim-sodium on or in soybean

Hatzios, K.K. (2001). Cases and mechanisms of resistance to ACCase-inhibiting herbicides,

Horowitz, M. (1980). Herbicidal treatments for control of Papaver somniferum L, *Bulletin on* 

Hsiao, A.I. & Smith, A.E. (1983). A root bioassay procedure for the determination of

Hu, J.-Y., Aizawa, T. & Magara, Y. (1999). Analysis of pesticides in water with liquid

Ibáñez, M., Sancho, J.V., Pozo, O.J. & Hernández, F. (2004). Use of quadrupole time-of-flight

Iwataki, I. (1992). Cyclohexanedione herbicides: their activities and properties, *In* Draber, W.

Iwataki, I. & Hirono, Y. (1978). The chemical structure and herbicidal activity of alloxydim-

Junghans, M., Backhaus, T., Faust, M., Scholze, M. & Grimme, L.H. (2006). Application and

Kolpin, D.W., Schnoebelen, D.J. & Thurman, E.M. (2004). Degradates provide insight to

*agrochemicals,* pp. 397-426, CRC Press, Boca Raton (USA).

mixtures, *Aquatic Toxicology,* Vol. 76, pp. 93-110.

*Chemicals,* pp. 235-243, Pergamon Press, Zurich (Switzerland).

*In* Clark, J.M. & Yamaguchi, I. (Eds.), *Agrochemical Resistance: Extent, Mechanism, and Detection (ACS Symposium),* pp. 135-149, Oxford University Press, Washington D.C.

chlorsulfuron, diclofop acid and sethoxydim residues in soils, *Weed Research,* Vol.

chromatography/atmospheric pressure chemical ionization mass spectrometry,

mass spectrometry in environmental analysis: elucidation of transformation products of triazine herbicides in water after UV exposure, *Analytical Chemistry,*

& Fujita, T. (Eds.), *Rational approaches to structure, activity and ecotoxicology of* 

sodium and related compounds, *In* Geissbühler, H., Brooks, G.T. & Kearney, P.C. (Eds.), *Advances in Pesticide Science, Fourth International Congress on Pesticide* 

validation of approaches for the predictive hazard assessment of realistic pesticide

spatial and temporal trends of herbicides in ground water, *Ground Water,* Vol. 42,

kinetics of some organophosphorous pesticides in aqueous solutions, *Veterinary and* 

postemergence graminicides, *Weed Technology,* Vol. 6, pp. 938-948.

system, *Environmental Engineering Science,* Vol. 23, pp. 545-551.

plants, *Journal of Pesticide Science,* Vol. 4, pp. 299-304.

*Human Toxicology,* Vol. 36, pp. 202-204.

pp. 154-158.

(USA).

23, pp. 231-236.

Vol. 76, pp. 1328-1335.

pp. 601-608.

*Narcotics,* Vol. 32, pp. 33-43.

*Water Research,* Vol. 33, pp. 417-425.


Chow, P.N.P. & MacGregor, A.W. (1983). Effect of ammonium sulfate and surfactants on activity of the herbicide sethoxydim, *Journal of Pesticide Science,* Vol. 8, pp. 519-527. Christoffers, M.J. & Kandikonda, A.V. (2006). Mechanisms of weed resistance to inhibitors of

Clark, J.R., Lewis, M.A. & Pait, A.S. (1993). Pesticide inputs and risks in coastal wetlands,

Curtin, D.Y., Grubbs, E.J. & McCarty, C.G. (1966). Uncatalysed syn-anti isomerization of

Dannenberg, A. & Pehkonen, S.O. (1998). Investigation of the heterogeneously calalyzed

Delye, C., Straub, C., Chalopin, C., Matejicek, A., Michel, S. & Le Corre, V. (2003a).

Delye, C., Zhang, X.-Q., Chalopin, C., Michel, S. & Powles, S.B. (2003b). An isoleucine

not to cyclohexanedione inhibitors, *Plant Physiology,* Vol. 132, pp. 1716-1723. Delye, C., Zhang, X.-Q., Michel, S., Matejicek, A. & Powles, S.B. (2005). Molecular bases for

Devine, M.D. & Shimabukuro, R.H. (1994). Resistance to acetyl-coenzyme A carboxylase

Dimou, A.D., Sakkas, V.A. & Albanis, T.A. (2005). Metolachlor photodegradation study in

Elazzouzi, M., Bensaoud, A., Bouhaouss, A., Guittonneau, S., Dahchour, A., Meallier, P. &

Falb, L.N., Bridges, D.C. & Smith, A.E. (1990). Effects of pH and adjuvants on clethodim photodegradation, *Journal of Agricultural and Food Chemistry,* Vol. 38, pp. 875-878. Falb, L.N., Bridges, D.C. & Smith, A.E. (1991). Separation of clethodim herbicide from acid

Foy, C.L. (1993). Progress and developments in adjuvant use since 1989 in the USA, *Pesticide* 

*Journal of Environmental Analytical Chemistry,* Vol. 84, pp. 173-182.

substances, *Fresenius Environmental Bulletin,* Vol. 8, pp. 478-485.

*of Official Analytical Chemists,* Vol. 74, pp. 999-1002.

*Environmental Toxicology and Chemistry,* Vol. 12, pp. 2225-2233.

San Francisco (USA), pp. AGRO-107.

*Chemistry,* Vol. 46, pp. 325-334.

*Végétaux,* Vol. 564, pp. 18-22.

*Physiology,* Vol. 137, pp. 794-806.

*Food and Chemistry,* Vol. 53, pp. 694-701.

*Science,* Vol. 38, pp. 65-76.

pp. 2775-2786.

acetyl-CoA carboxylase, *Proceedings of Proceedings of 232nd ACS National Meeting,*

imines, oxime ethers, and haloimines, *Journal of American Chemical Society,* Vol. 88,

hydrolysis of organophosphorus pesticides, *Journal of Agricultural and Food* 

Résistance aux herbicides chez le vulpin. Un problème généralisé mais à gérer localement : sa gestion nationale semble peu envisageable, *Phytoma, la Défense des* 

residue within the carboxyl-transferase domain of multidomain acetyl-coenzyme A carboxylase is a major determinant of sensitivity to aryloxyphenoxypropionate but

sensitivity to acetyl-coenzyme A carboxylase inhibitors in black-grass, *Plant* 

inhibiting herbicides, *In* Powles, S.B. & Holtum, J.A. (Eds.), *Herbicide resistance in plants, biology and biochemistry,* pp. 141-169, Lewis Publishers, Boca Raton (USA). Dimou, A.D., Sakkas, V.A. & Albanis, T.A. (2004). Photodegradation of trifluralin in natural

waters and soils: degradation kinetics and influence of organic matter, *International* 

aqueous media under natural and simulated solar irradiation, *Jounal of Agricultural* 

Piccolo, A. (1999). Photodegradation of imazapyr in the presence of humic

and photodegradation products by liquid chromatography, *Journal of the Association* 


Chemical Behaviour and Herbicidal Activity of Cyclohexanedione Oxime Herbicides 99

Price, L.J., Herbert, D., Cole, D.J. & Harwood, J.L. (2003). Use of plant cell cultures to study graminicide effects on lipid metabolism, *Phytochemistry,* Vol. 63, pp. 533-541. Reckhow, D.A. & Singer, P.C. (1990). Chlorination by-products from drinking waters: from

Reineke, N., Bester, K., Huhnerfuss, H., Jastorff, B. & Weigel, S. (2002). Bioassay-directed

Richardson, S.D. (2006). Environmental mass spectrometry: emerging contaminants and

Richardson, S.D. (2007). Water analysis: emerging contaminants and current issues,

Richardson, S.D. (2009). Water analysis: emerging contaminants and current issues,

Ritz, C., Cedergreen, N., Jensen, J.E. & Streibig, J.C. (2006). Relative potency in nonsimilar

Roberts, T.R. (Ed.). (1998). *Metabolic pathways of agrochemicals,* Royal Society of Chemistry,

Rodríguez-Mozaz, S., López de Alda, M.J. & D., B. (2007). Advantages and limitations of on-

Sakkas, V.A., Lambropoulou, D.A. & Albanis, T.A. (2002a). Study of chlorothalonil

Sakkas, V.A., Lambropoulou, D.A. & Albanis, T.A. (2002b). Photochemical degradation

Sandín-España, P., González-Blázquez, J.J., Magrans, J.O. & García-Baudín, J.M. (2002).

Sandín-España, P., Llanos, S., Magrans, J.O., Alonso-Prados, J.L. & García-Baudín, J.M.

Sandín-España, P., Magrans, J.O. & García-Baudín, J.M. (2005a). Study of clethodim

water free from chlorine, *Weed Research,* Vol. 43, pp. 451-457.

line solid phase extraction coupled to liquid chromatography-mass spectrometry technologies versus biosensors for monitoring of emerging contaminants in water,

photodegradation in natural waters and in the presence of humic substances,

study of irgarol 1051 in natural waters: influence of humic and fulvic substances on the reaction, *Journal of Photochemistry and Photobiology A,* Vol. 147, pp. 135-141. Sandín-España, P. (2004). *Thesis: Estudio de la degradación y análisis de herbicidas* 

*ciclohexanodionas en agua clorada,* Universidad Autónoma de Madrid, Madrid

Determination of herbicide tepraloxydim and main metabolites in drinking water by solid-phase extraction and liquid chromatography with UV detection,

(2003). Optimization of hydroponic bioassay for herbicide tepraloxydim by using

degradation and by-product formation in chlorinated water by HPLC,

and high performance fractionation, *Chemosphere,* Vol. 47, pp. 717-723. Rendina, A.R., Craig-Kennard, A.C., Beaudoin, J.D. & Breen, M.K. (1990). Inhibition of

*of Agricultural and Food Chemistry,* Vol. 38, pp. 1282-1287.

current issues, *Analytical Chemistry,* Vol. 78, pp. 4021-4045.

dose-response curves, *Weed Science,* Vol. 54, pp. 407-412.

*Journal of Chromatography A,* Vol. 1152, pp. 97-115.

*Chemosphere,* Vol. 48, pp. 939-945.

*Chromatographia,* Vol. 55, pp. 681-686.

*Chromatographia,* Vol. 62, pp. 133-137.

*Works Association,* Vol. 82, pp. 173-180.

*Analytical Chemistry,* Vol. 79, pp. 4295-4324.

*Analytical Chemistry,* Vol. 81, pp. 4645-4677.

Cambridge (UK).

(Spain).

formation potential to finished water concentrations, *Journal of the American Water* 

chemical analysis of river Elbe surface water including large volume extractions

acetyl-coenzyme A carboxylase by two classes of grass-selective herbicides, *Journal* 


Koskinen, W.C., Reynolds, K.M., Buhler, D.D., Wyse, D.L., Barber, B.L. & Jarvis, L.J. (1993).

Krogh, K.A., Halling-Sorensen, B., Mogensen, B.B. & Vejrup, K.V. (2003). Environmental

Kuk, Y.-I., Burgos, N.R. & Talbert, R.E. (2000). Cross- and multiple resistance of diclofop-

Leach, G.E., Devine, M.D., Kirkwood, R.C. & Marshall, G. (1995). Target enzyme-based

Li, H.-Y. & Foy, C.L. (1999). A biochemical study of BAS 517 using excised corn and soybean

Lykins, B.W., Koffskey, W.E. & Miller, R.G. (1986). Chemical products and toxicologic effects of disinfection, *Journal of American Water Works Association,* Vol. 78, pp. 66-75. Magara, Y., Aizawa, T., Matumoto, N. & Souna, F. (1994). Degradation of pesticides by

Marcheterre, L., Choudhry, G.G. & Webster, G.R.B. (1988). Environmental photochemistry

Marles, M.A.S., Devine, M.D. & Hall, J.C. (1993). Herbicide resistance in *Setaria viridis*

McInnes, D., Harker, K.N., Blackshaw, R.E. & Born, W.H.V. (1992). The influence of

McMullan, P.M. (1996). Grass herbicide efficacy as influenced by adjuvant, spray solution

Nalewaja, J.D., Matysiak, R. & Szelezniak, E. (1994). Sethoxydim response to spray carrier chemical properties and environment, *Weed Technology,* Vol. 8, pp. 591-597. Neilson, A.H. & Allard, A.-S. (2008). *Environmental degradation and transformation of organic* 

Ono, S., Shiotani, H., Ishihara, K., Tokieda, M. & Soeda, Y. (1984). Degradation of the herbicide alloxydim-sodium in soil, *Journal of Pesticide Science,* Vol. 9, pp. 471-480. Park, H. & Choi, W. (2003). Visible light and Fe(III) mediated degradation of acid orange 7 in

Park, K.W. & Mallory-Smith, C.A. (2004). Physiological and molecular basis for ALS inhibitor resistance in *Bromus tectorum* biotypes, *Weed Research,* Vol. 44, pp. 71-77. Peñuela, G.A., Ferrer, I. & Barceló, D. (2000). Identification of new photodegradation by-

the absence of H2O2, *Journal of Photochemistry and Photobiology A,* Vol. 159, pp. 241-

products of the antifouling agent irgarol in seawater samples, *International Journal of* 

pH, and ultraviolet light, *Weed Technology,* Vol. 10, pp. 72-77.

*Environmental Analytical Chemistry,* Vol. 78, pp. 25-40.

resistant *Lolium spp.*, *Weed Science,* Vol. 48, pp. 412-419.

*Biochemistry and Physiology,* Vol. 51, pp. 129-136.

root systems, *Weed Science,* Vol. 47, pp. 28-36.

*Biochemistry and Physiology,* Vol. 46, pp. 7-14.

*chemicals*, CRC Press, Boca Raton (USA).

*Science,* Vol. 41, pp. 634-640.

119-128.

61-126.

247.

Boca Raton (USA).

*Chemosphere,* Vol. 50, pp. 871-901.

Persistence and movement of sethoxydim residues in three Minnesota soils, *Weed* 

properties and effects of nonionic surfactant adjuvants in pesticides: a review,

resistance to acetyl-coenzyme A carboxylase inhibitors in *Eleusine Indica*, *Pesticide* 

chlorination during water purification, *Water Science and Technology,* Vol. 30, pp.

of herbicides, *Reviews of Environmental Contamination and Toxicology,* Vol. 103, pp.

conferred by a less sensitive form of acetyl-coenzyme A carboxylase, *Pesticide* 

ultraviolet light on the phytotoxicity of sethoxydim tank mixtures with various adjuvants, *In* Foy, C.L. (Ed.), *Adjuvants for agrichemicals,* pp. 205-213, CRC Press,


Chemical Behaviour and Herbicidal Activity of Cyclohexanedione Oxime Herbicides 101

Shoaf, A.R. & Carlson, W.C. (1992). Stability of Sethoxydim and its degradation products in

Shukla, A., Nycholat, C., Subramanian Mani, V., Anderson Richard, J. & Devine Malcolm, D.

Smith, A.E. & Hsiao, A.I. (1983). Persistence studies with the herbicide sethoxydim in prairie

Soeda, Y., Ishihara, K., Iwataki, I. & Kamimura, H. (1979). Fate of a herbicide 14C-alloxydimsodium in sugar beets, *Journal of Pesticide Science,* Vol. 4, pp. 121-128. Somasundaram, L. & Coats, J.R. (Eds.). (1991). *Pesticide transformation products. Fate and significance in the environment,* Oxford University Press, Washington D.C. (USA). Srivastava, A. & Gupta, K.C. (1994). Dissipation of tralkoxydim in water-soil system, *Journal* 

Stoltenberg, D.E. & Wiederholt, R.J. (1995). Giant foxtail (*Setaria faberi*) resistance to

Tal, A. & Rubin, B. (2004). Molecular characterization and inheritance of resistance to

Tchaikovskaya, O., Sokolova, I., Svetlichnyi, V., Karetnikova, E., Fedorova, E. &

Tixier, C., Meunier, L., Bonnemoy, F. & Boule, P. (2000). Phototransformation of three

Tomlin, C.D.S. (Ed.). (2006). *The pesticide manual: a world compendium,* BCPC Publications,

Tuxhorn, G.L., Roeth, F.W., Martin, A.R. & Wilson, R.G. (1986). Butylate persistence and

Vialaton, D. & Richard, C. (2002). Phototransformation of aromatic pollutants in solar light:

Walker, K.A., Ridley, S.M., Lewis, T. & Harwood, J.L. (1988). Fluazifop, a grass-selective

Walter, H. (2001). Profoxydim: development of a herbicide from laboratory to field, *In*

19-30, Servicio Publicaciones Universidad de Córdoba, Córdoba (Spain). Wiederholt, R. & Stoltenberg, D.E. (1995). Cross-resistance of a large crabgrass (*Digitaria* 

toxicity, *International Journal of Photoenergy,* Vol. 2, pp. 1-8.

aryloxyphenoxypropionate and cyclohexanedione herbicides, *Weed Science,* Vol. 43,

ACCase-inhibiting herbicides in *Lolium rigidum*, *Pest Management Science,* Vol. 60,

Kudryasheva, N. (2007). Fluorescence and bioluminescence analysis of sequential UV-biological degradation of p-cresol in water, *Luminescence,* Vol. 22, pp. 29-

herbicides: chlorbufam, isoproturon, and chlorotoluron. Influence of irradiation on

activity in soils previously treated with thiocarbamates, *Weed Science,* Vol. 34, pp.

photolysis versus photosensitized reactions under natural water conditions, *Aquatic* 

herbicide which inhibits acetyl-CoA carboxylase in sensitive plant species,

Prado, R.D. & Jorrín, J.V. (Eds.), *Uso de herbicidas en la agricultura del siglo XXI,* pp.

*sanguinalis*) accession to aryloxyphenoxypropionate and cyclohexanedione

(2004). Use of resistant ACCase mutants to screen for novel inhibitors against resistant and susceptible forms of ACCase from grass weeds, *Journal of Agricultural* 

solution, in soil, and on surfaces, *Weed Science,* Vol. 40, pp. 384-389.

*and Food Chemistry,* Vol. 52, pp. 5144-5150.

soils, *Weed Research,* Vol. 23, pp. 253-257.

*of Pesticide Science,* Vol. 19, pp. 145-149.

pp. 527-535.

pp. 1013-1018.

Hampshire (UK).

*Sciences,* Vol. 64, pp. 207-215.

*Biochemical Journal,* Vol. 254, pp. 307-310.

herbicides, *Weed Technology,* Vol. 9, pp. 518-524.

961-965.

34.


Sandín-España, P., Santín, I., Magrans, J.O., Alonso-Prados, J.L. & García-Baudín, J.M.

Santín-Montanya, I., Sandín-España, P., García Baudín, J.M. & Coll-Morales, J. (2007).

Santoro, A., Scopa, A., Bufo, S.A., Mansour, M. & Mountacer, H. (2000). Photodegradation of

Santos, T.C.R., Rocha, J.C., Alonso, R.M., Martínez, E., Ibáñez, C. & Barceló, D. (1998). Rapid

Sanz-Asencio, J., Plaza-Medina, M. & Martínez-Soria, M.T. (1997). Kinetic study of the

Schwarzenbach Rene, P., Gschwend, P.M. & Imboden, M.D. (2002). *Environmental organic* 

Secor, J. & Cseke, C. (1988). Inhibition of acetyl-CoA carboxylase activity by haloxyfop and

Seefeldt, S.S., Gealy, D.R., Brewster, B.D. & Fuerst, E.P. (1994). Cross-resistance of several

Sevilla-Morán, B. (2010). *Thesis: Estudio de la fotodegradación de herbicidas ciclohexanodionas en* 

Sevilla-Morán, B., Alonso-Prados, J.L., García-Baudín, J.M. & Sandín-España, P. (2010a).

Sevilla-Morán, B., Mateo-Miranda, M., López-Goti, C., Alonso-Prados, J.L. & Sandín-España,

Sevilla-Morán, B., Mateo-Miranda, M.M., Alonso-Prados, J.L., García-Baudín, J.M. & Sandín-

Sevilla-Morán, B., Sandín-España, P., Vicente-Arana, M.J., Alonso-Prados, J.L. & García-

Shoaf, A.R. & Carlson, W.C. (1986). Analytical techniques to measure sethoxydim and

*medio acuoso,* Universidad Autónoma de Madrid, Madrid (Spain).

*chemistry* (2nd), John Wiley & Sons, New Jersey (USA).

*Agricultural and Food Chemistry,* Vol. 58, pp. 3068-3076.

*environment: fate, modelling and risk mitigation,* Piacenza (Italy).

*Photochemistry and Photobiology A,* Vol. 198, pp. 162-168.

breakdown products, *Weed Science,* Vol. 34, pp. 745-751.

tralkoxydim, *Plant Physiology,* Vol. 86, pp. 10-12.

Oregon, *Weed Science,* Vol. 42, pp. 430-437.

*Chemistry,* Vol. 90, pp. 487-496.

*Development,* Vol. 25, pp. 331-334.

*Chemosphere,* Vol. 66, pp. 1315-1322.

*Toxicology,* Vol. 64, pp. 475-480.

Vol. 32, pp. 3479-3484.

194.

(2005b). Degradation of alloxydim in chlorinated water, *Agronomy for Sustainable* 

Optimal growth of *Dunaliella primolecta* in axenic conditions to assay herbicides,

the triazole fungicide hexaconazole, *Bulletin of Environmental Contamination and* 

degradation of propanil in rice crop fields, *Environmental Science and Technology,*

degradation of ethiofencarb in aqueous solutions, *Pesticide Science,* Vol. 50, pp. 187-

diclofop-resistant wild oat (*Avena fatua*) biotypes from the Willamette Valley of

Indirect photodegradation of clethodim in aqueous media. By-product identification by quadrupole time-of-flight mass spectrometry, *Journal of* 

P. (2011). Photodegradation of profoxydim in natural waters. Comparative study of the photolytic behaviour of the active substance and its formulation Aura®, *Proceedings of Proceedings of XIV Symposium in Pesticide Chemistry. Pesticides in the* 

España, P. (2010b). Sunlight transformation of sethoxydim-lithium in natural waters and effect of humic acids, *International Journal of Environmental Analytical* 

Baudín, J.M. (2008). Study of alloxydim photodegradation in the presence of natural substances: Elucidation of transformation products, *Journal of* 


**6** 

 *China* 

**1(Heterocyclyl),2,4,5-Tetrasubstituted Benzenes** 

It is well known that agrochemicals have played a important role in agricultural production that provided for about 700 million people during the past 50 years. At the same time, the increasing world population seems to be a major driving force for the need to enhance the output of food production. The agrochemical industry has been very successful in developing new herbicides and other agrochemicals. Herbicides are used widely in the world in protecting crops from undue competition from weeds (Price & Kelton, 2011).

The first commercial inhibitor of protoporphyrinogen oxidase (Protox) is the nitrofen that belongs to diphenyl ether (DPE), which was introduced in 1963 by Rohm & Hass (Now Dow AgroSciences) (Matsunaka, 1976). Some years later, the oxadiazon as the fisrt compound of the 1(heterocyclyl), 2, 4, 5-tetrasubstituted benzene (HTSB) family was introduced in 1968 by Rhone-Poulenc (Metivier et al., 1968). Nitrofen and oxadiazon represent the earliest examples of Protox inhibiting herbicides (Fig. 1). Although their chemical structures are completely different from each other, they share a common mode of action, inhibition of the protoporphyrinogen oxidase enzyme, though this was not known until the late 1980s.

Several early inventions of HTSB herbicide in 1960s had a significant impact on our understanding of the structure–activity of this kind herbicides. Rhone-Poulenc first introduced 3-(2,4-dichlorophenyl)-1,3,4-oxadiazol-2(3H)-one in 1965 (Boesch et al., 1965). Further lead optimization at the phenyl ring soon led to the discovery in 1968 of the 2,4 dichloro-5-isopropoxyphenyl substitution pattern of the herbicide oxadiazon

Fig. 1. Chemical structures of two early examples of Protox inhibitors.

**1. Introduction** 

**as Protoporphyrinogen-IX Oxidase** 

*Shenyang Research Institute of Chemical Industry Co. Ltd.* 

*State Key Laboratory of the Discovery and Development of Novel Pesticide* 

**Inhibiting Herbicides** 

Hai-Bo Yu, Xue-Ming Cheng and Bin Li

Zagnitko, O., Jelenska, J., Tevzadze, G., Haselkorn, R. & Gornicki, P. (2001). An isoleucine/leucine residue in the carboxyltransferase domain of acetyl-CoA carboxylase is critical for interaction with aryloxyphenoxypropionate and cyclohexanedione inhibitors, *Proceedings of the National Academy of Sciences of the United States of America,* Vol. 98, pp. 6617-6622.
