Manag Sci. 2001 Feb;57(2):133-42.
the background to its discovery and the basis of its
KE, Cramp SM, Little JP, Veerasekaran P, Crudace AJ,
Ongar Research Station, Fyfield Road, Ongar, Essex CM5
0HW, UK. email@example.com
paper reviews the discovery of isoxaflutole
(IFT), focusing on the chemical and physicochemical
properties which contribute to the herbicidal behaviour
of this new herbicide. IFT (5-cyclopropyl-1,2-isoxazol-4-yl
alpha alpha alpha-trifluoro-2-mesyl-p-tolyl ketone)
is a novel herbicide for pre-emergence control of a
wide range of important broadleaf and grass weeds in
corn and sugarcane. The first
benzoyl isoxazole lead was synthesised in 1989 and IFT
in 1990, and the herbicidal potential of the latter
was identified in 1991. The decision to develop
the molecule was taken after two
years of field testing in North America. The
biochemical target of IFT is 4-hydroxyphenylpyruvate
dioxygenase (HPPD), inhibition of which leads to a characteristic
bleaching of susceptible species. The inhibitor of HPPD
is the diketonitrile derivative of IFT formed from opening
of the isoxazole ring. The diketonitrile (DKN) is formed
rapidly in plants following root and shoot uptake. The
DKN is both xylem and phloem mobile leading to high
systemicity. IFT also undergoes
conversion to the DKN in the soil. The soil half-life
of IFT ranges from 12 h to 3 days under laboratory conditions
and is dependent on several factors such as soil type,
pH and moisture. The log P of IFT is 2.19 and the water
solubility is 6.2 mg litre-1, whereas the corresponding
values for the DKN are 0.4 and 326 mg litre-1, respectively.
These properties restrict the mobility of IFT, which
is retained at the soil surface where it can be taken
up by surface-germinating weed seeds. The
DKN, which has a laboratory soil half-life of 20-30
days, is more mobile and is taken up by the roots.
In addition to influencing the soil behaviour of IFT
and DKN, the greater lipophilicity of IFT leads to greater
uptake by seed, shoot and root tissues. In both plants
and soil, the DKN is converted to the herbicidally inactive
benzoic acid. This degradation is more rapid in maize
than in susceptible weed species and this contributes
to the mechanism of selectivity, together with the greater
sowing depth of the crop.
Types: Review; Review, Tutorial
11455644 [PubMed - indexed for MEDLINE]
Gent Fak Landbouwkd Toegep Biol Wet. 2002;67(3):383-91.
of 4-HPPD-inhibitors in different soil types.
L, Eelen H, Bulcke R.
of Herbology, Faculty of Agricultural and Applied Biological
Sciences, Ghent University Coupure Links 653, 9000 Gent, Belgium.
experiments carried out during the 1997-2001 period on four
different soil types (sand, sandy loam, heavy sandy loam and
clay) in Flanders (Belgium), the persistence of the three 4-HPPD
inhibiting maize herbicides mesotrione (100 and 150 g ha-1),
sulcotrione (300 and 450 g ha-1) and isoxaflutole
(75 and 125 g ha-1) was studied. Therefore, soil samples
were taken at regular intervals from application in spring and
frozen. When all samples had been taken, greenhouse bioassays
were set up to detect herbicide residues in the different soil
types. Therefore, two extremely sensitive test plants, sugarbeet
(Beta vulgaris L. spp. altissima Doell. var. saccharifera Deck.-Dill)
and red clover (Trifolium pratense L.) were sown in the soil
samples. Test plants were harvested after 2 (sugarbeet) and
3 (red clover) weeks and foliage fresh weight per plant was
determined. This parameter was expressed relatively to the average
fresh weight per plant of the plants sown in the control soil
samples taken at each sampling date. The bioassays revealed
several factors that influence the persistence of the herbicide
tested. First, there is a remarkable influence of the experimental
year due to variation in weather conditions (especially rainfall
and temperature during the first weeks after spraying). Secondly,
a different soil texture results in a highly different persistence:
the shortest biological persistence was noticed each year in
clay, followed by heavy sandy loam; the longest persistence
was recorded in sandy and sandy loam soil types. Thirdly, there
are important differences between the three herbicides tested:
isoxaflutole (a member of the isoxazole chemical family) was
shown to be less persistent than sulcotrione and mesotrione
(both members of the triketone family). Remarkably, this was
not the case in clay, where a longer persistence
could be seen for isoxaflutole compared to sulcotrione and mesotrione.
This study also revealed that applying a low rate results in
a shorter persistence period compared to the higher rate. All
these factors work together in a complex way which determines
the persistence of the three herbicides tested.
12696405 [PubMed - indexed for MEDLINE]
Food Chem. 2003 Jan 1;51(1):146-51.
Fate of isoxaflutole
in soil under controlled conditions.
E, Fenet H, Cooper JF, Coste CM.
de Chimie Analytique, Faculte de Pharmacie, Universite de Montpellier
I, 15 avenue Ch. Flahault, BP 14 491, France.
ketone) is a new pre-emergence proherbicide used in maize and
sugarcane. Its two main derivatives are a diketonitrile derivative,
called DKN, and a benzoic acid derivative, 2-methanesulfonyl-4-trifluoromethylbenzoic
acid, called BA. Few data are available of the factors influencing
the degradation of IFT in soil, and the purpose of the present
work was to determine the relative importance of, and factors
affecting, the degradation of IFT in soil. Experiments were
conducted on five soils with distinct physicochemical characteristics,
at different temperatures and moisture contents in biotic and
abiotic conditions. The isomerization of IFT to DKN is rapid,
increasing with higher moisture contents and higher temperatures.
It depends strongly on pH and is governed by chemical processes.
The degradation of DKN to BA appeared to be essentially due
to the biological activity of the soil.
[PubMed - indexed for MEDLINE]
Gent Fak Landbouwkd Toegep Biol Wet. 2001;66(2b):723-9.
Fate of the herbicide
isoxaflutole in the soil of corn fields.
J, Neus O, Eelen H, Bulcke R.
of Phytopharmacy, Universite Catholique de Louvain 3, Place
Croix du Sud, SCI. 15 D, 1348 Louvain-la-Neuve, Belgium.
isoxaflutole 1 (5-cyclopropyl-4-isoxazolyl)[2- (methylsulfonyl)-4-(trifluoro-methyl)phenyl]-methanone)
was applied pre-emergence at the rate of 125 g ha-1 on corn
fields located in three sites different as to their soil texture
and composition. In the 0-10 cm surface soil layer, the isoxaflutole
soil half-life (soil dissipation kinetics of second order) was
9 days in sandy loam (Melle), 15 days in clay loam (Zevekote)
and 18 days in loamy sand (Zingem) soil. The sum of the concentrations
of isoxaflutole 1 and of its herbicide active metabolite diketonitrile
2 (2-cyano-3-cyclopropyl-1-(2-methylsulfonyl-4- trifluoromethylphenyl)propane-1,3-dione)
had a soil half-life (dissipation kinetics of first order) of
45 days in sandy loam, and 63 days in the clay loam and loam
sand soils. The soil metabolism of isoxaflutole thus generated,
in the soil of field corn crops, a metabolite, the diketonitrile
2, which had an herbicide activity as high as the one of the
parent isoxaflutole, and which much extended the herbicide protection
given by isoxaflutole. At the crop harvest, isoxaflutole, the
diketonitrile 2 and the acid 3 (2-methylsulfonyl-4-trifluoromethylbenzoic
acid) were no more detected in soil. During the corn crops,
isoxaflutole, and its metabolites diketonitrile 2 and acid 3
were never detected in the 10-15 et 15-20 cm surface soil layers,
indicating the very low mobility of these compounds in soil.
12425096 [PubMed - indexed for MEDLINE]
J Agric Food Chem. 2003 Dec 31;51(27):8011-4.
Degradation of isoxaflutole (balance)
herbicide by hypochlorite in tap water.
Lin CH, Lerch RN, Garrett HE, George
Center for Agroforestry, School of Natural Resources, University
of Missouri-Columbia, Columbia, Missouri 65211, USA. Linchu@missouri.edu
Chlorine has been widely employed for the disinfection of drinking
water. Additionally, it has the capacity to oxidize many organic
compounds in water. Isoxaflutole (Balance; IXF) belongs to a
new class of isoxazole herbicides. Isoxaflutole
has a very short soil half-life and rapidly degrades to a stable
and phytotoxic metabolite, diketonitrile (DKN). Further
degradation of DKN produces a nonbiologically active benzoic
acid (BA) metabolite. In experiments using high-performance
liquid chromatography-UV spectroscopy (HPLC-UV) and HPLC tandem
mass spectrometry (HPLC-MS/MS), DKN was found to rapidly react
with hypochlorite in tap water, yielding the BA metabolite as
the major end product. One milligram per liter (19 microM) of
hypochlorite residue in tap water was able to completely oxidize
up to 1600 microg/L (4.45 micromol/L) of DKN. In tap water,
the disappearance of IXF was much more rapid than in DI water.
As soon as the IXF is hydrolyzed to DKN, the DKN quickly reacts
with the OCl(-) to form nonphytotoxic BA. As a result, the herbicide
solutions prepared with tap water at 500 microg/L will no longer
possess any herbicidal activity after 48 h of storage. However,
in agronomic settings, highly concentrated tank solutions (600-800
mg/L) may be prepared with tap water since the conversion of
IXF to BA would represent <5% of the herbicide; therefore,
any impact on the herbicide efficacy would be negligible. Results
of this study show that current chlorination disinfection protocols
in municipal water systems would completely eliminate the phytotoxic
form of this new herbicide, DKN, from drinking water supplies;
yet, farmers can use chlorinated tap water without significant
loss of efficacy.
PMID: 14690388 [PubMed - indexed for MEDLINE]
Food Chem. 2002 Sep 25;50(20):5626-33.
Effects of moisture,
temperature, and biological activity on the degradation of isoxaflutole
S, Sims GK, Wax LM.
of Crop Sciences, University of Illinois, Urbana 61801, USA.
of several environmental factors on the dissipation, transformation,
and mineralization of isoxaflutole were investigated in laboratory
incubations. In the soil, isoxaflutole hydrolyzed to a diketonitrile
derivative, which is the active form of the herbicide. The diketonitrile
was then metabolized to an inactive benzoic acid derivative
and later into two unknown products, which were found only in
small quantities. Degradation of isoxaflutole was faster in
soil maintained at -100 or -1500 kPa compared to that in air-dry
soil. At 25 degrees C, the half-lives for isoxaflutole were
9.6, 2.4, and 1.5 days in air-dry, -1500 kPa, and -100 kPa moisture
regimes, respectively. A simple Arrhenius expression described
the response of isoxaflutole transformation (mineralization
and transformation) to temperature in the range of 5 to 35 degrees
C. An activation energy value (E(a)) of 67 kJ/mol for isoxaflutole
suggested the transformation of the herbicide to the diketonitrile
derivative was primarily a chemical reaction. Moreover, biological
activity had little effect on the hydrolysis of isoxaflutole,
with half-lives of 1.8 and 1.4 days in sterile and nonsterile
soil, respectively. However, the transformation
of diketonitrile to benzoic acid and the production of the unknown
products were greatly reduced in the sterile soil, suggesting
one or more biologically mediated processes.
12236689 [PubMed - indexed for MEDLINE]
Contam Toxicol. 2002 Apr;42(3):280-5.
of isoxaflutole in corn.
J, Neus O, Eelen H, Bulcke R.
of Phytopharmacy, Catholic University of Louvain, 3, Place Croix
du Sud, SCI. 15D, 1348 Louvain-la-Neuve, Belgium.
isoxaflutole 1 (5-cyclopropyl-4-isoxazolyl)[2-(methylsulfonyl)-4-(trifluoromethyl)phenyl]-methanone)
has been applied preemergence at the rate of 125 g ha(-1) on
corn crops grown on fields located in regions different as to
their soil textures. Its metabolite diketonitrile 2 (2-cyano-3-cyclopropyl-1-(2-methylsulfonyl-4-trifluoromethylphenyl)propane-1,3-dione)-which
is the herbicide's active compound-and its nonherbicide metabolite
3 (2-methylsulfonyl-4-trifluoromethylbenzoic acid) were measured
in the 0-10 cm surface soil layer of the corn crops after the
treatment and until the harvest. At the opposite of what occurred
in plant shoots, the transformation of isoxaflutole 1 into diketonitrile
2 was not immediate in soil. In the 0-10 cm surface soil layer,
this transformation occurred progressively according to an apparent
second-order kinetics, and the soil half-lives of isoxaflutole
1 self were comprised between 9 and 18 days. The adsorption
of isoxaflutole 1 onto the solid phase of the soil and its organic
matter should explain the stabilization effect of soil, increased
by the application of fresh organic fertilizer. The sum of the
concentrations of isoxaflutole 1 and diketonitrile 2 disappeared
in the 0-10 cm surface soil layer according to an apparent first-order
kinetics, and the soil half-lives of this sum were comprised
between 45 and 65 days. The sum of the concentrations of isoxaflutole
1 and of its metabolites diketonitrile 2 and acid 3 did not
account for the amount of isoxaflutole 1 applied. The discrepancy
increased with the delay after the application, showing that
the acid 3 was further metabolized in soil into common nontoxic
products, and ultimately into CO2. The conjunction of the adsorption
of isoxaflutole and its metabolites (which reduced their mobilities)
onto the soil and its organic matter, and their further metabolism
should explain why isoxaflutole and its metabolites were not
detected in the 10-15 and 15-20 cm surface soil layers during
[PubMed - indexed for MEDLINE]
From Science Direct
Environmental Pollution; Volume 108, Issue 2 , May 2000,
Sorption and desorption of the
diketonitrile metabolite of isoxaflutole in soils
S. Mitra, P.C. Bhowmik and B. Xing
Department of Plant and Soil Sciences, Stockbridge Hall, University
of Massachusetts, Amherst, MA 01003, USA
Isoxaflutole is a new pre-emergence corn herbicide that undergoes
rapid conversion to a diketonitrile derivative (DKN) in soils.
Sorption–desorption studies were conducted in five different
soils varying in physical and chemical properties. A batch equilibration
technique was used with total initial aqueous solution concentrations
of DKN at 0.25, 0.75, 2.0, 8.0, 25, 75, 150, and 250 mg l-1.
After the sorption process, two subsequent desorptions were
conducted with an equilibration period of 7 days. A high correlation
existed between the desorption coefficient, KFd and the organic
matter content of soils (r2=0.844 for the first desorption and
r2=0.861 for the second desorption), while the clay content
did not greatly influence the desorption of DKN. Although the
sorption of DKN was generally reversible, a sorption–desorption
hysteresis was apparent in all soils. The
site energy distribution curves emphasized the fact that DKN
binds tightly to soils with higher organic matter content and
greater proportion of DKN was retained by those soils
From Toxnet at Toxline
WEED SCIENCE; 46 (4). 1998. 397-402.
Optimizing foliar activity of isoxaflutole
on giant foxtail (Setaria faberi) with various adjuvants.
YOUNG BG, HART SE
Crop Sci. Dep., Univ Ill., Urbana, IL 61801, USA.
BIOSIS COPYRIGHT: BIOL ABS. Greenhouse, laboratory, and field
studies were conducted to evaluate the potential of nonionic
surfactant (NIS), crop oil concentrate (COC), methylated seed
oil (MSO), and 28% urea ammonium nitrate (UAN) to
enhance whole plant efficacy, absorption, and spray retention
of foliar applications of isoxaflutole to giant foxtail.
In greenhouse studies, isoxaflutole at 10 g ai ha-1 reduced
giant foxtail growth 5%, whereas the addition of a spray adjuvant
reduced giant foxtail growth at least 75%. The addition of UAN
improved giant foxtail growth reduction when used in combination
with isoxaflutole plus NIS. Isoxaflutole spray retention on
the leaf surface was increased with an adjuvant and a further
increase was observed with the addition of UAN.
Isoxaflutole applied with NIS, COC, and MSO resulted in 42,
60, and 91% 14C absorption, respectively, compared to 21% absorption
from isoxaflutole applied alone 24 h after treatment
(HAT). Increased 14C absorption and entry into the c [abstract
CAS Registry Numbers:
141112-29-0 - Isoxaflutole
15978-77-5 - Nitric acid ammonium salt, mixt. with urea
to Isoxaflutole Index Page