U.S. patent number 4,883,801 [Application Number 06/898,748] was granted by the patent office on 1989-11-28 for xanthine derivative pest control agents.
This patent grant is currently assigned to The General Hospital Corporation. Invention is credited to James A. Nathanson.
United States Patent |
4,883,801 |
Nathanson |
November 28, 1989 |
Xanthine derivative pest control agents
Abstract
The use of xanthine derivatives having the general formula:
##STR1## as pesticidal and pestistatic agents is disclosed, as well
as pesticidal and pestistatic compositions containing same.
Inventors: |
Nathanson; James A. (Wellesley,
MA) |
Assignee: |
The General Hospital
Corporation (Boston, MA)
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Family
ID: |
27095315 |
Appl.
No.: |
06/898,748 |
Filed: |
August 18, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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648086 |
Sep 7, 1984 |
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Current U.S.
Class: |
514/263.33;
514/263.34 |
Current CPC
Class: |
A01N
43/90 (20130101) |
Current International
Class: |
A01N
43/90 (20060101); A01N 043/90 () |
Field of
Search: |
;514/263,265 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
King, Chemicals Evaluated as Insecticides and Repellents, pp. 1-21,
100-101 and 322-323 (1954). .
Moffett, et al., Comp. Biochem. Physiol., vol. 75C, pp. 305-310,
1983. .
Janzen, et al., Phytochem., vol. 16, pp. 223-227 (1977). .
Clark, Ent. Exp. & Appl., vol. 29, pp. 189-197 (1981). .
McDaniel, et al., J. Insect Physiol., vol. 20, pp. 245-252 (1974).
.
Targa, et al., Brazil J. Genetics, vol. 4, pp. 669-677 (1982).
.
Srinivasan et al., J. Toxicol. & Envir. Health, vol. 2, pp.
569-576 (1977). .
Srinivasan et al., Toxicology Letters, vol. 3, pp. 229-232 (1979).
.
Srinivasan et al., Toxicology Letters, vol. 3, pp. 101-105 (1979).
.
Sittig, Pesticide Mfg. & Toxic Mat'ls. Control Encyclopedia,
pp. 1-10 (1980). .
Pojakovick et al., Pesticide Biochem. and Physiology, vol. 6, pp.
10-19 (1976)..
|
Primary Examiner: Robinson; Douglas W.
Assistant Examiner: Fay; Zohreh A.
Attorney, Agent or Firm: Saidman, Sterne, Kessler &
Goldstein
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of U.S. application Ser. No. 648,086
filed Sept. 25, 1984, now abandoned, all subject matter of which is
herein incorporated by reference.
Claims
What is claimed and desired to be covered by letters patent is:
1. A method of controlling a phosphodiesterase-containing
invertebrate pest which comprises bringing into contact with said
pest a pest-controlling amount of a xanthine derivative having the
general formula: ##STR5## or the acid addition salts thereof,
wherein X is oxygen or sulfur; and
R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are selected from
hydrogen; aliphatic hydrocarbons having 1-8 carbon atoms and
cycloaliphatic hydrocarbons having 3-8 carbon atoms; aliphatic
hydrocarbons having 1-8 carbon atoms and cycloaliphatic
hydrocarbons having 3-8 carbon atoms substituted with 1-3 halogen
atoms, C.sub.1 -C.sub.4 alkyl, or hydroxy; alkoxy having 1-6 carbon
atoms; phenyl; naphthyl; halo, hydroxy, or C.sub.1 -C.sub.4
alkyl-substituted phenyl or naphthyl; or phenoxy;
with the proviso that for compound I, at least one of R.sup.1,
R.sup.2,R.sup.3 and R.sup.4 is other than hydrogen, methyl and
ethyl, and
with the further proviso that said compound has a V.sub.max of more
than 50 and an EC.sub.50 of no more than 3, where V.sub.max is
expressed as the percent inhibition of feeding at a 3% (gm/100 ml)
concentration of spray and EC.sub.50 is defined as the spray
concentration (gm/100 ml) required to cause a 50% inhibition of
feeding.
2. A method of inhibiting the feeding of a
phosphodiesterase-containing invertebrate pest which comprises
bringing into contact with said pest a feed-inhibiting amount of a
xanthine derivative having the general formula: ##STR6## or the
non-hydrogen fluoride acid addition salts thereof, wherein X is
oxygen or sulfur; and
R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R5 are selected from
hydrogen; aliphatic hydrocarbons having 1-8 carbon atoms and
cycloaliphatic hydrocarbons having 3-8 carbon atoms; aliphatic
hydrocarbons having 1-8 carbon atoms and cycloaliphatic
hydrocarbons having 3-8 carbon atoms, substituted with 1-3 halogen
atoms, C.sub.1 -C.sub.4 alkyl, or hydroxy; alkoxy having 1-6 carbon
atoms; phenyl or naphthyl; halo, hydroxy, or C.sub.1 -C.sub.4
alkyl-substituted phenyl or naphthyl; or phenoxy;
with the proviso that for compound I, at least one of R.sup.1,
R.sup.2,R.sup.3 and R4 is other than hydrogen, methyl and ethyl;
and
with the further proviso that, said compound has a V.sub.max of
more than 50 and an EC.sub.50 of no more than 3, where V.sub.max is
expressed as the percent inhibition of feeding at a 3% (gm/100 ml)
concentration of spray and EC.sub.50 is defined as the spray
concentration (gm/100 ml) required to cause a 50% inhibition of
feeding.
3. The method of claim 1, wherein said xanthine derivative is
selected from the group consisting of 1,3-dipropylxanthine;
1,3-diallyl-xanthine; 1,3-dibenzyl-xanthine;
1-methyl-3-isobutyl-xanthine; 1-isoamyl-3-isobutyl-xanthine;
1-phenethyl-3-ethyl-xanthine;
1,3-dimethyl-7-(2-chloroethy-1)-xanthine;
1,3-dimethyl-7-beta-hydroxypropyl)-xanthine;
1,3,7-trimethyl-8-methoxy-xanthine; 1,3-dipropyl-7-methyl-xanthine;
1,3,7-tripropyl-xanthine; 1,3-dipropyl-7-benzyl-xanthine; and
1,3-dibutyl-xanthine.
4. The method of claim 2, wherein said xanthine derivative is
selected from the group consisting of 1,3-dipropyl-xanthine;
1,3-diallyl-xanthine; 1,3-dibenzyl-xanthine;
1-methyl-3-isobutyl-xanthine; 1-isoamyl-3-isobutyl-xanthine;
1-phenethyl-3-ethyl-xanthine;
1,3-dimethyl-7-(2-chloroethyl)-xanthine;
1,3-dimethyl-7-beta-hydroxypropyl)-xanthine;
1,3,7-trimethyl-8-methoxy-xanthine; 1,3-dipropyl-7-methyl-xanthine;
1,3,7-tripropyl-xanthine; 1,3-dipropyl-7-benzyl-xanthine; and
1,3-dibutyl-xanthine.
5. The method of claim 1, wherein said xanthine derivative is
selected from the group consisting of 1,3-dipropylxanthine,
1,3,7-tripropylxanthine, 1,3-dipropyl-7-benzylxanthine,
1,3-dibutylxanthine and 1-methyl-3-isobutylxanthine.
6. The method of claim 2, wherein said xanthine derivative is
selected from the group consisting of 1,3dipropylxanthine,
1,3,7-tripropylxanthine, 1,3-dipropyl-7-benzylxanthine,
1,3-dibutylxanthine and 1-methyl-3isobutylxanthine.
7. The method of claims 1 or 2 wherein said xanthine derivative is
1,3-dipropyl-xanthine.
8. The method of claim 1 wherein said xanthine derivative has a
K.sub.i of not greater than 0.1, where K.sub.i is defined as the
concentration in mM of said xanthine derivative required to produce
a 50% inhibition of enzyme activity for hornworm nerve cord
phosphodiesterase.
9. The method of claim 2 wherein said xanthine derivative has a
K.sub.i of not greater than 0.1where K.sub.i is defined as the
concentration in mM of said xanthine derivative required to produce
a 50% inhibition of enzyme activity for hornworm nerve cord
phosphodiesterase.
10. A composition useful for controlling a
phosphodiesterase-containing invertebrate pest comprising the
following ingredients:
(1) a pest-controlling amount of an agent selected from xanthine
derivatives having the general formula: ##STR7## or the acid
addition salts thereof, wherein X is oxygen or sulfur; and
R.sub.1, R.sub.2,R.sub.3, R.sub.4 and R.sub.5 are selected from
hydrogen; aliphatic hydrocarbons having 1-8 carbon atoms and
cycloaliphatic hydrocarbons having 3-8 carbon atoms; aliphatic
hydrocarbons having 1-8 carbon atoms and cycloaliphatic
hydrocarbons having 3-8 carbon atoms, substituted with 1-3 halogen
atoms, C.sub.1 -C.sub.4 alkyl, or hydroxy; alkoxy having 1-6 carbon
atoms; phenyl; naphthyl; halo, hydroxy, or C.sub.1 -C.sub.4
alkyl-substituted phenyl or naphthyl; or phenoxy;
with the proviso that for compound I, at least one of R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 is other than hydrogen, methyl and
ethyl, and
with the further proviso that, said compound has a V.sub.max of
more than 50 and an EC.sub.50 of no more than 3, where V.sub.max is
expressed as the percent inhibition of feeding at a 3% (gm/100 ml)
concentration of spray and EC.sub.50 is defined as the spray
concentration (gm/100 ml) required to cause a 50% inhibition of
feeding together with a dust carrier; and
(2) a carrier selected from a dust carrier, a granule or pellet
carrier form, a liquid form or an aerosol.
11. The composition of claim 10, wherein said xanthine derivative
is selected from the group consisting of 1,3-dipropyl-xanthine;
1,3-diallyl-xanthine; 1,3-dibenzylxanthine;
1-methyl-3-isobutyl-xanthine; 1-isoamyl-3-isobutylxanthine;
1-phenethyl-3-ethyl-xanthine;
1,3-dimethyl,7-(2-chloroethyl)-xanthine;
1,3-dimethyl-7-beta-hydroxypropyl)-xanthine;
1,3,7-trimethyl-8-methoxy-xanthine; 1,3-dipropyl-7-methyl-xanthine;
1,3,7-tripropyl-xanthine; 1,3-dipropyl-7-benzyl-xanthine; and
1,3-dibutyl-xanthine.
12. The method of claim 10, wherein said xanthine derivative is
selected from the group consisting of 1,3dipropylxanthine,
1,3,7-tripropylxanthine, 1,3-dipropyl-7-benzylxanthine,
1,3-dibutylxanthine and 1-methyl-3-isobutylxanthine.
13. The composition of claim 10 wherein said carrier is a dust
carrier.
14. The composition of claim 13 wherein said dust carrier is
selected from the group consisting of sulfur, silicon oxides, lime,
gypsum, talc, pyrophyllite, bentonite, kaolin, attapulgite, and
volcanic ash.
15. The composition of claim 10 wherein said carrier is granule or
pellet, carrier form.
16. The composition of claim 15 wherein said granule- or-
pellet-forming carrier is selected from the group consisting of
sulfur, silicon oxides, lime, gypsum, talc, pyrophyllite,
bentonite, kaolin, attapulgite and volcanic ash.
17. The composition of claim 10 wherein said carrier is an
aerosol
18. The composition of claim 10 wherein said carrier is a liquid.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method for controlling a
pest comprising bringing into contact with the pest a
pest-controlling amount of a compound from the group comprising
derivatives of xanthine.
2. Description of the Background Art
Despite the recent development and great promise of such . advanced
pest-controlling compositions as chemical sterilants, pheromones or
ecologically-based insect control strategies, it is doubtless that,
at present, the use of chemical pesticides still plays a
predominant role. The use of insecticides often represents the
difference between profitable crop production for farmers and no
marketable crop at all, and the value of insecticides in
controlling human and animal diseases has been dramatic.
Therefore, in parallel to the aforementioned newer technologies for
pest control, there has been active research and investigation into
the detailed biochemical modes of action of existing known chemical
pesticides. Thus, for example, Nathanson, et al., Molecular
Pharmacology, 20: 68-75 (1981), presented evidence indicating that
the formamidine pesticides chlordimeform (CDM) and
N-demethylchlordimeform (DCDM) may affect octopaminergic
neurotransmission. CDM and DCDM have been reported to mimic the
effects of octopamine in stimulating light emission in the firefly
lantern (Hollingworth, R. M., et al., Science, 208: 74-76 (1982))
and in effecting nerve-evoked muscle responses in the locust leg
(Evans, P. D., Nature, 287: 60-62 (1980)). Nathanson, et al.,
supra, found that DCDM, which is the probable in vivo metabolite of
CDM is about six-fold more potent than octopamine itself as a
partial agonist of light organ octopamine-stimulated adenylate
cyclase. Stimulation by the formamidines resulted in increased
formation of the intracellular messenger, cyclic AMP (cAMP). This
stimulation was blocked by cyproheptadine, clozapine, fluphenazine
and phentolamine compounds, also known to block the octopamine
receptor. Nathanson, et al., concluded that DCDM is the most potent
octopaminergic compound described.
Similar results were observed by Hollingworth, et al. (reported in
the Scientific Papers of the Institute of Organic and Physical
Chemistry of Wroclaw Technical University, No. 22, Conference 7
(1980)). These authors demonstrated that certain formamidines act
on octopamine receptors to induce the synthesis of cyclic AMP, and
that this response is blocked by both phentolamine and
cyproheptadine, which are known to act as octopaminergic
antagonists in insects. The authors also suggested that these
formamidines are potent stimulators of the octopamine sensitive
adenylate cyclases in the thoraxic ganglia of Periplaneta
americana, and in the ventral nerve cord and fat body of M. sexta.
The authors suggest that the stimulation of octopamine receptors
underlies a number of toxic responses seen with formamidines on
insects.
It should be noted that the presence of an insect adenylate cyclase
enzyme which is sensitive to naturally occurring D(-)octopamine as
a "neuro transmitter" has been known for some time (Nathanson, et
al., Science 180: 308-310 (1973) (cockroach); Nathanson, Ibid, 203:
65-68 (1979) (firefly); Evans, J., Neurochem., 30: 1015-1022 (1978)
(cockroach)).
The study of cyclic AMP as a "second messenger" has led to the
accepted model that a hormone or neuro transmitter binds at a
cell-membrane bound receptor, which activates adenylate cyclase to
a form capable of converting ATP in the cytoplasm of the cell into
cAMP. cAMP then relays the signal brought by the hormone or neuro
transmitter from the membrane to the interior of the cell. Agonists
of the hormone or neuro transmitter are, by definition, capable of
eliciting the same response (see, for example, Nathanson and
Greengard, Scientific American, 237: 108-119 (1977)). Among other
actions, cAMP stimulates the conversion of inactive phosphorylase b
into phosphorylase a, a reaction catalysed by phosphorylase kinase.
This reaction is, in turn, catalysed by an enzyme, now called
protein kinase, which occurs in an inactive and active form. Its
active form catalyses the phosphorylation of inactive phosphorylase
kinase by ATP to yield the active phosphorylated form by a reaction
in which ATP is the phosphate-group donor.
Protein kinase, the key enzyme in linking cAMP to the phosphorylase
system and to other cyclic AMP-regulated processes, is an
allosteric enzyme, i.e., an enzyme whose reactivity with another
molecule is altered by combination with a third molecule that is
not a substrate. Its inactive form contains two types of subunits,
a catalytic (C) subunit and a regulatory (R) subunit which inhibits
the catalytic subunit. cAMP is the allosteric modulator of protein
kinase, binding to a specific site on the regulatory subunit and
causing the inactive CR complex to dissociate, yielding R-cAMP
complex, and the free C subunit, which is now catalytically active.
Thus, cAMP removes the inhibition of enzyme activity that is
imposed by the binding of the regulatory subunit (Lehninger,
Biochemistry, 2nd Ed., pp. 812-813).
The enzyme responsible for the destruction of cAMP is
phosphodiesterase, which catalyzes the hydrolytic reaction as
follows: ##STR2## It is known that phosphodiesterase activity is
inhibited by caffeine and theophylline, alkaloids present in small
amounts in coffee and tea. Both caffeine and theophylline have long
been known to prolong or intensify the activity of epinephrine,
presumably due to increased persistence of cAMP in cells stimulated
by epinephrine.
Rojakovick, A. S., et al., Pesticide Biochemistry and Physioloqy,
6:10-19 (1976), explored the interaction between insecticidal
activity and cAMP as a secondary messenger, surveying the direct
effects of a variety of different types of insecticides upon the
activities of adenylate cyclase and phosphodiesterase. The survey
of the direct effects of TEPP, methylparaoxon, DDT, Dieldrin,
Aldicarb, Dimetilan, Rotenone, Allethrin, and Oxythioquinox upon
cockroach brain adenylate cyclase in vitro led the authors to the
conclusion that the compounds have essentially no direct effects on
adenylate cyclase in vitro. The same nine insecticides were also
evaluated for their effect upon cockroach brain phosphodiesterase
in vitro. Certain of the compounds showed a general relationship of
increasing inhibition with increasing concentration of insecticide,
while DDT and Dieldrin appeared to be activators of
phosphodiesterase. Oxythioquinox proved to be the most potent
inhibitor of cockroach brain phosphodiesterase, giving over 80%
inhibition. By comparison, using identical assay techniques,
1,000-fold greater concentrations of aminophylline and
theophylline, the most widely used phosphodiesterase inhibitors in
adenylate cyclase assays, inhibited 83.2 and 73.8%, respectively.
The authors concluded that, while Oxythioquinox and other
quinoxoline dithiol derivatives were demonstrated to be potent in
vitro inhibitors of phosphodiesterases, no direct relationship of
this activity to their mode of toxic action could be determined.
Finally, the authors concluded that the broad distribution of
phosphodiesterases in the animal kingdom makes it unlikely that
phosphodiesterase inhibition is a direct cause of the selective
acaricidal activity of the compounds.
Calva, U.S. Pat. No. 2,362,614, describes fluorine-containing
insecticides. Disclosed are the hydrofluoric acid addition
compounds of ammonia-substituted compounds giving rise to primary,
secondary or tertiary amines and polyamines. Insecticidal activity
is described as derived from the direct combination of the
fluorine-nitrogen link. Caffeine is included in the patent
disclosure among the "alkylamines with or without substituent
groups."
French Pat. No. 2,138,186 to Aries discloses insecticidal
compositions of urinylphosphate esters which are stabilized by
purine derivatives. Included among the purine derivatives are
purines substituted in the 2, 4 and 8 positions. No insecticidal
activity, however, is attributed to the purine compounds, the
compounds performing the function of stabilizing the active
phosphorus compounds.
Rizvi, S. J. H., et al., Indian J. Exp. Biol., 18: 777-8 (1980),
explored the herbicidal activity of ethanolic extracts of leaves
and seeds of 49 different plants. The seed extract of Coffea
arabica proved most potent. Fractionation of the extract of Coffea
arabica in different organic solvents produced a variety of
fractions, all of which were tested for the desired activity. The
chloroform fraction completely inhibited the seed germination of
the test weed at 5,000 ppm. The authors suggested Coffea arabica as
a possible source of natural herbicide. The same authors, in Agra.
Biol. Chem., 45 (5): 1255-1256 (1981), identified the active
weedicidal ingredient as 1,3,7-trimethylxanthine (caffeine). No
insecticidal activity for caffeine, however, was disclosed. Rizvi,
S. J. H., et al., Journal of Applied Entomoloqy, Vol. 90, No. 4,
pp. 378-381 (1980), studied the 1,3,7-tri-methyl-xanthine isolate
of Coffea arabica and found it to be effective as a chemosterilant
for Callosobrucaus chinensis, causing nearly 100% sterility at a
concentration of 1.5%. No suggestion of utility as a pesticidal
agent was disclosed.
Given the continuous need for increased selectivity and
effectiveness in pest control agents, it became desirable that
pesticidal and pestistatic agents from naturally occurring products
be developed. Although certain fluorinated amines, including
fluorinated caffeine, have been suggested as pesticides (Calva,
supra), and although other xanthine derivatives unsubstituted in
the 1, 3, and 7 position (the hypoxyxanthines of Aries, supra) have
been suggested as stabilizers for phosphate insecticides, and
although caffeine has been suggested as a chemisterilant (Rizvi et
al., supra), the pesticidal and pestistatic action of substituted
xanthine derivatives has not been known prior to this
invention.
SUMMARY OF THE INVENTION
The xanthine derivatives, including caffeine and theophylline, are
found in berries, seeds, and leaves of a number of species,
including tea, coffee, cocoa and cola. Although methylxanthines are
one of the most frequently used stimulants employed by the human
population, their natural function in plants was not known up to
the present. It is known, however, that to discourage insect
feeding, many plants have evolved endogenous chemical defenses,
ranging from specific toxins and substances with pheromone-like
activity to less specific bitter-tasting aversive substances.
Based on observations by this inventor and others that the mode of
action of certain formamidine pesticides was through their
octopaminergic agonist activity on octopamine receptors present in
the pest, and that these pest control agents were acting through
generation of cAMP as a "second messenger," the inventor then
observed that the effectiveness of octopaminergic agonist pest
control agents could be greatly enhanced when the quantity and
half-life of generated cAMP was augmented by inhibiting insect
phosphodiesterase enzymes, which are capable of hydrolyzing cAMP.
This observation, coupled with the known
phosphodiesterase-inhibiting activity of the methylxanthines, led
to the discovery of the invention embodied in applicant's commonly
assigned co-pending application Serial No. 605,845, filed May 1,
1984, incorporated by reference herein.
Recognizing the critical role that the phosphodiesterase inhibitors
played in the enhancement of octopaminergic agonist pest control
agents, the present inventor then began to explore the possibility
of the use of certain phosphodiesterase inhibitors alone.
Initially, coffee and tea were investigated for pestistatic or
pesticidal activity. The results of these experiments, reported
below at Example 1, suggested that pesticidal and pestistatic
activity existed for the coffee or tea.
To investigate the possible contribution of endogenous xanthine
derivatives to the pesticidal activity described above, the action
of purified xanthine derivatives on insects, including Manduca
larvae, was examined. The results of one such experiment are
reported below at Example 2, as well as the method of
investigation. Based on the results of Example 2, it appeared that
endogenous xanthine derivatives had pesticidal activity.
Endowed with this knowledge, the inventor then set out to explore
the pesticidal and pestistatic activities of various xanthine
derivatives, leading to the present invention. The inventor
discovered that certain xanthine derivatives possess the ability to
inhibit phosphodiesterase activity, and that this ability
correlates directly with the invertebrate pest-controlling
characteristics of the compound. Thus, as a result of the present
invention, it is possible to quickly and routinely evaluate, in
vitro, potentially active compounds based on their ability to
inhibit phosphodiesterase activity. Thus, this invention comprises
a method of pest control comprising bringing into contact with said
pest a pest-controlling amount of an agent consisting essentially
of a compound having the general formula (I) or (II): ##STR3##
wherein:
X is oxygen or sulfur;
R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are selected from
hydrogen; aliphatic hydrocarbons having 1-8 carbon atoms;
cycloaliphatic hydrocarbons having 3-8 carbon atoms; substituted
aliphatic hydrocarbons having 1-8 carbon atoms and cycloaliphatic
hydrocarbons having 3-8 carbon atoms, substituted with 1-3 halogen
atoms, C.sub.1 -C.sub.4 alkyl, or hydroxy; alkoxy having 1-6 carbon
atoms; phenyl; naphthyl; halo, hydroxy, or C.sub.1 -C.sub.4
alkyl-substituted phenyl or naphthyl; phenoxy; substituted phenoxy;
and the like, and acid addition salts thereof, and further, wherein
at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.5 is other than
hydrogen. For compound I, R.sup.1, R.sup.2, and R.sup.3 are not
each methyl simultaneously.
The inventor has found that on the basis of structure alone it is
not possible to predict which xanthine derivatives will have
pesticidal activity. These findings are shown in Examples 15-47.
Therefore, as mentioned above, part of the inventor's discovery
involved the development of a procedure to determine, on the basis
of their ability to inhibit phosphodiesterase, which compounds have
pesticidal activity.
Therefore the most preferred compounds are defined as having a
K.sub.i for inhibiting phosphodiesterase of not more than 0.1,
where K.sub.i is defined as the concentration in millimoles/liter
of the xanthine derivative required to produce a 50% in vitro
inhibition of the phosphodiesterase activity in tobacco hornworm
nerve cord, using the conditions described.
Such agents are further defined, in vivo, as having a V.sub.max of
more than 50%, where V.sub.max is expressed as the inhibition of
feeding at the highest dose used, usually a 3% spray solution, and
an EC.sub.50 of less than 3% (gm/100 ml), EC.sub.50 being the spray
concentration required to cause 50% inhibition of feeding, as
calculated from dose-response curves.
As described in Example 47, using the in vitro test, it is possible
to distinguish phosphodiesterase inhibiting active or inactive
compounds that are structurally similar.
DESCRIPTION OF THE FIGURES
FIG. 1A shows the effect on tobacco hornworm body weight of
powdered coffee beans or caffeine incorporated into artificial
media.
FIG. 1B shows the dose-dependent antifeeding effect of
caffeine.
FIG. 1C is a graph quantitating the antifeeding effect of xanthine
derivatives applied as a spray to tomato leaves subsequently
exposed to tobacco hornworm larvae for 4 days.
FIG. 1D is a graph showing the effect of the same xanthine
derivatives on inhibiting cyclic AMP phosphodiesterase activity in
homogenates of tobacco hornworm nerve cord.
FIG. 2 is a graph showing the phosphodiesterase inhibiting activity
of various xanthine derivatives in tobacco hornworm nerve cord.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
By the terms "pest-controlling" or "pest-controlling activity,"
used throughout the specification and claims, are meant to include
any pesticidal (killing) or pestistatic (inhibiting, maiming or
generally interfering) activities of a composition against a given
pest. Thus, these terms not only include killing, but also include
such activities as those of chemisterilants which produce sterility
in insects by preventing the production of ova or sperm, by causing
death of sperm or ova, or by producing severe injury to the genetic
material of sperm or ova, so that the larvae that are produced do
not develop into mature progeny.
By the term "inhibiting the feeding" is meant to include both
pesticidal activity wherein the pest is killed by the compound, as
well as the situation wherein the feeding activity of the larvae is
substantially affected and limited.
By the term "pest" is meant any phosphodiester-ase-containing
invertebrate. These pests include, but are not limited to, round
worms (e.g., hookworms, trichina, and ascaris); flat worms (e.g.,
liver flukes and tapeworms); jointed worms (e.g., leeches);
molluscs (e.g., parasitic snails); and arthropods (insects,
spiders, centipedes, millipedes, crustaceans (e.g., barnacles)). In
particular, included among the arthropods are ticks, mites (both
plant and animal), lepidoptera (butterflies and moths and their
larvae), hemiptera (bugs), homoptera (aphids, scales), and
coleopera (beetles). Also included are spiders, anoplura (lice),
diptera (flies and mosquitos), tricoptera, orthoptera (e.g.,
roaches), odonta, thysanura (e.g., silverfish), collembola (e.g.,
fleas), dermaptera (earwigs), isoptera (termites), ephemerids
(mayflies), plecoptera, malophaga (biting lice), thysanoptera, and
siphonaptera (dictyoptera, psocoptera, and certain hymenoptera
(e.g., those whose larvae feed on leaves)). By the term "xanthine
derivative" or "methyl xanthine derivatives" are meant compounds
having the general formula (I) or (II): ##STR4## and their acid
addition salts, wherein:
X is oxygen or sulfur;
R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are selected from
hydrogen; aliphatic hydrocarbons having 1-8 carbon atoms;
cycloaliphatic hydrocarbons having 3-8 carbon atoms; substituted
aliphatic hydrocarbons having 1-8 carbon atoms and cycloaliphatic
hydrocarbons having 3-8 carbon atoms, substituted with 1-3 halogen
atoms, C.sub.1 -C.sub.4 alkyl, or hydroxy; alkoxy having 1-6 carbon
atoms; phenyl; naphthyl; halo, hydroxy, or C.sub.1 -C.sub.4
alkyl-substituted phenyl or naphthyl; phenoxy; substituted phenoxy;
and the like, and acid addition salts thereof and further wherein
at least one of R.sup.1, R.sup.2, R.sup.3 or R.sup.5 is other than
hydrogen. For compound I, R.sup.1, R.sup.2 and R.sup.3 are not each
methyl simultaneously.
Suitable aliphatic hydrocarbon compounds include alkyl, alkenyl,
alkynyl and the like.
Among the alkyl hydrocarbons are included methyl, ethyl, propyl,
isopropyl, butyl, isobutyl, tert-butyl, pentyl, tert-pentyl, hexyl,
heptyl, octyl, and the like.
Suitable alkenyl hydrocarbons are those having 2-8 carbon atoms and
may include vinyl, allyl, isopropenyl, 1-propenyl, 2-butenyl,
3-pentenyl, 2-, 3-, or 4-hexenyl, and the like.
Suitable alkynyl hydrocarbons are those having 2-8 carbon atoms and
may include ethynyl, 2-propynyl, 2-butynyl, 3-pentynyl, 3-hexynyl,
2-, 3-, or 4-heptynyl, and the like.
Suitable cylcoaliphatic groups include those having 3-8 carbon
atoms, for example, cyclopentanyl, cycloheptanyl, cyclohexanyl,
cyclopentenyl, cyclohexynyl, and the like, as well as lower alkyl,
halo or hydroxy substituted alkoxy groups.
Suitable alkoxy groups include methoxy, ethoxy, butoxy, pentoxy,
and the like.
Suitable aromatic groups include phenyl or naphthyl. Among the
substituted aromatic groups are phenyl substituted in the ortho,
meta, and/or para positions with lower alkyl groups having 1-4
carbon atoms, halogens, and hydroxy.
Where the compounds are intended as pesticides, the fluoride salts
are generally excluded; where the compounds are intended as
pestistate, caffeine is excluded.
The preparation and/or source for the compounds are well known, see
Wells, J. N., et al., J. Med. Chem., 24: 954-958 (1981); Kramer, G.
I., et al., Biochemistry, Vol. 16, No. 15, pp. 3316-3321 (1977);
Bruns, R. F., Biochemical Pharmacology, Vol. 30, pp. 325-333
(1981); and Garst, J. E., et al., Journal of Medicinal Chemistry,
Vol. 19, No. 4, pp. 499-503 (1976).
Among the above-described xanthine derivatives, certain compounds
have been shown to be especially effective. Thus, medium to large
substitution in the 3-position (R.sup.2) increases activity
substantially. Further, substitution of small to medium (methyl,
ethyl, propyl, i-propyl, butyl, isobutyl) groups in the 1-position
(R.sup.1) increases activity. Small to medium group substitution on
the 7-position (R.sup.3) also will enhance activity, as will
certain small to medium group in the 8-position (R.sup.4) However,
chloro or bulky substituent in the 8-position (R.sup.4) decreases
activity as do certain substitutions in the 9-position
(R.sup.5).
The preferred compounds of the present invention are further
defined as those compounds having a V.sub.max of more than 50%
inhibition of feeding and an EC.sub.50 of less than a 3% (gm/100
ml) concentration of spray. V.sub.max is expressed as the percent
inhibition of feeding at the highest dose used (usually a 3% spray
solution). EC.sub.50 is the spray concentration (as calculated from
dose-response curves) required to cause 50% inhibition of feeding.
The lower the EC.sub.50, the more effective the compound is in that
less of the compound is required to achieve a 50% inhibition of
feeding. Solvents for the compound include, for example,
hydrocarbon solvents, such as isopropanol and methanol. Other
solvents are known to those skilled in the art and may be used in
the spray. The 3% (gm/100ml) concentration of spray is designed and
limited by the solubility of the compound to be tested. Typically,
above 3%, these compounds are insoluble in hydrocarbon solvents.
Further, the 3% spray concentration is typically the maximum amount
of active ingredient in a pesticidal or pestistatic composition;
more typical is 1-2% concentration of active ingredient. Pesticide
Manufacturing and Toxic Materials Control Encyclopedia (Noyes Data
Corp. 1980).
Inhibition of feeding is determined at a time when untreated leaves
show 20% of leaf area remaining. Calculation is then made by
determining the percent leaf area remaining on leaves sprayed with
drugs minus 20 divided by 80 (the maximal inhibition of feeding
possible). The inhibition of feeding determination will be
described in detail below. Basically, leaves are eaten by
first-instar Manduca sexta which are placed at 6 per leaf.
In addition to Manduca sexta, other examples of insect species
demonstrated to be affected by xanthine derivatives are Tenebrio
(mealworn) larvae (EC.sub.50 0.1-0.3%); Vanessa cardui (painted
lady butterfly) larvae (EC.sub.50 0.1-0.3%); Oncopeltus fasciatus
(milkweed bug) nymph (EC.sub.50 0.3%); and, in solution, 1-methyl-3
isobutyl xanthine (IBMX) killed Culex (mosquito) larvae (EC.sub.50
0.007%). Tribolium confusum and Tribolium castaneum (flower beetle)
adults were unaffected by IBMX doses up to 3%. However, in chronic
tests, IBMX (EC.sub.50 0.2%) inhibited reproduction of these two
species.
As mentioned above, in vertebrate tissues, methylxanthines are
known to inhibit phosphodiesterase (PDE), enzymes which hydrolyze
cAMP. Rall, T. W., Pharmacoloqical Bases of Therapeutics, A. G.
Gillman, L. Goodman, A. Gillman, Eds. (MacMillan, N.Y. 1980), p.
592; Sutherland, E. W., et al., J. Biol. Chem., 232: 1077 (1958);
and Butcher, R. W., et al., J. Biol. Chem., 237: 1244 (1962). It
was thus investigated as to whether xanthine derivatives could
inhibit Manduca nerve cord PDE activity and, if so, whether the
degree of such inhibition was related to observed pestistatic and
pesticidal activity. The methodology for determining PDE inhibition
is described below in Examples 8-11. These examples and FIG. 1D
demonstrate the dose-dependent inhibition of nerve cord PDE
activity by various xanthine derivatives whose inhibitory effects
on leaf consumption are shown in Examples 4-7 and FIG. 1C.
The similarity of the graphs in FIGS. 1C and 1D demonstrates a
strong correlation between PDE inhibition and pesticidal and
pestistatic activity. This correlation is further evaluated in
Examples 15 through 45 below. Based on the work to date, the most
preferred compounds according to the present invention are those
xanthine derivatives according to structural formulas (I) and (II)
which also demonstrate a K.sub.i of 0.1 mM or less, wherein K.sub.i
is defined as the concentration of xanthine derivative necessary to
produce a 50% inhibition of enzyme activity for hornworm nerve cord
PDE. Inhibition of phosphodiesterase activity for hornworm nerve
cord for the purposes of determining K.sub.i within the meaning of
this invention is determined in accordance with the methodology set
out in Examples 8-11.
The pest-controlling agents of the present invention may be
formulated as dusts, water dispersions, emulsions and solutions.
They may comprise accessory agents such as dust carriers, solvents,
emulsifiers, wetting and dispersing agents, stickers, deodorants,
and masking agents (see, for example, Encyclopedia of Chemical
Technology, Vol. 13, pp. 416 et seq.).
Dusts generally will contain low concentrations, 0.1-20%, of the
compounds, although ground preparations may be used and diluted.
Carriers commonly include sulfur, silicon oxides, lime, gypsum,
talc, pyrophyllite, bentonite, kaolins, attapulgite, and volcanic
ash. Selection of the carrier may be made on the basis of
compatibility with the desired pest control composition (including
pH, moisture content, and stability), particle size, abrasiveness,
absorbability, density, wettability and cost. The agent of the
invention, alone or in combination, and eluent is made by a variety
of simple operations such as milling, solvent impregnations, fusing
and grinding. Particle sizes usually range from 0.5-4.0 microns in
diameter.
Wettable powders may be prepared by blending the agents of the
invention in high concentrations, usually from 15-95%, with a dust
carrier such as bentonite which wets and suspends properly in
water. Twenty-two percent of a surface-active agent is usually
added to improve the wetting and suspendability of the powder.
The pest-controlling agents may also be used in granules, which are
pelleted mixtures of the agents, usually at 2.5-10%, and a dust
carrier, e.g., adsorptive clay, bentonite or diatomaceous earth,
and commonly within particle sizes of 250-590 microns. Granules may
be prepared by impregnations of the carrier with a solution or
slurry of the agents and may be used principally for mosquito
larvae treatment or soil applications.
The agent may also be applied in the form of an emulsion, which
comprises a solution of the agents in water-immiscible organic
solvents, commonly at 15-50%, with a few percent of surface active
agent to promote emulsification, wetting, and spreading. The choice
of solvent is predicated upon solubility, safety to plants and
animals, volatility, flammability, compatibility, odor and cost.
The most commonly used solvents are kerosene, xylenes, and related
petroleum fractions, methylisobutylketone, and amyl acetate. Water
emulsion sprays from such emulsive concentrates may be used for
plant protection and for household insect control.
The agents may also be mixed with baits, usually comprising 1-5% of
agents with a carrier especially attractive to insects. Carriers
include sugar for houseflies, protein hydrolysate for fruit flies,
bran for grasshoppers, and honey, chocolate, or peanut butter for
ants.
The agents may be included in slow release formulations which
incorporate non-persistent compounds, insect growth regulators and
sex pheromones in a variety of granular microencapsulated and
hollow fiber preparations.
The pest-controlling agents of the present invention may be applied
depending on the properties of the particular pest-controlling
compound, the habits of the pest to be controlled, and the site of
the application to be made. It may be applied by spraying, dusting
or fumigation.
Doses of the weight of the ingredients may typically vary between
0.001 and 100 pounds/acre, preferably between 0.001-5
pounds/acre.
Sprays are the most common means of application and generally will
involve the use of water as the principal carrier, although
volatile oils may also be used. The pest-controlling agents of the
invention may be used in dilute sprays (e.g., 0.001-10%) or in
concentrate sprays in which the composition is contained at 10-98%,
and the amount of carrier to be applied is quite reduced. The use
of concentrate and ultra-low volume sprays will allow the use of
atomizing nozzles producing droplets of 30-80 microns in diameter.
Spraying may be carried out by airplane or helicopter.
Aerosols may also be used to apply the pest-controlling agents.
These are particularly preferred as space sprays for application to
enclosures, particularly against flying insects. Aerosols are
applied by atomizing amounts of liquified gas dispersion or bomb,
but can be generated on a larger scale by rotary atomizers or
twin-fluid atomizers. Carriers used as aerosols or liquified gas
may include mineral spirits, ethanol, isopropanol, deionized water,
and hydrocarbon propellants, such as isobutane, n-butane, and
propane or nonflammable fluorinated hydrocarbon propellants, or
compressed gases, such as nitrogen, carbon dioxide, or nitrous
oxide. The aerosol composition will typically comprise 0.001-10%
pest-controlling agents of this invention, more typically 0.05-3%,
and the remainder being aerosol or liquified gas ingredients. The
Science and Technoloqy of Aerosol Packaginq (John Wiley & Sons
1974).
A simple means of pest-controlling agent dispersal is by dusting.
The pest-controlling agent is applied by introducing a finely
divided carrier with particles typically of 0.5-3 microns in
diameter into a moving air stream.
Having now generally described the invention, the same will become
better understood by reference to certain specific examples which
are included herein for purposes of illustration only and are not
intended to be limiting unless otherwise specified.
EXAMPLE 1
Various concentrations of finely powdered tea leaves or powdered
coffee beans were mixed in artificial media which was then plated
out in small petri dishes and allowed to harden. At concentrations
from 0.3-10% (wt/wt) for coffee and from 0.1-3% for tea, larvae of
Manduca sexta (tobacco hornworm) housed in these dishes showed a
dose-dependent inhibition of feeding associated with hyperactivity,
tremors and stunted growth. At concentrations greater than 10% (for
coffee) or 3% (for tea), larvae were killed within 24 hours.
EXAMPLE 2
The larvae of Manduca sexta were fed on either artificial or
natural food. When added to artificial media, caffeine (the major
methylxanthine found in tea and coffee) exerted behavioral effects
that were qualitatively similar to those of the tea and coffee
described above. In addition, as FIG. 1A shows, the concentration
of purified caffeine required for 50% inhibition of weight gain was
nearly identical to the endogenous caffeine content of the
coffee-media mixture which caused 50% inhibition of weight gain.
Further, the dried tea leaves, which contain 2-3 times the caffeine
content of dried coffee beans, were about 2-3 times as effective as
coffee beans in inhibiting weight gain. Further, the concentrations
of caffeine which are found naturally in undried tea leaves
(0.68-2.1%) or coffee beans (0.8-1.8%) were sufficient to kill most
Manduca larvae. Thus, caffeine functions as an endogenous
insecticide.
EXAMPLE 3
Various xanthine derivatives were tested on natural feeding
substrates, such as tomato leaves, the xanthine derivatives being
those compounds wherein at least one of R.sup.1, R.sup.2, R.sup.3,
and R.sup.5 are other than hydrogen. The compounds, applied as a
spray, exerted pestistatic and pesticidal effects which resulted in
leaf protection. FIG. 1B shows a typical result for caffeine.
EXAMPLES 4-7
FIG. 1C (which quantitates the amount of leaf remaining) summarizes
the dose-response curves for cafeine (Example 4), theophylline
(Example 5), and the synthetic compound, 1-methyl-
3-isobutylxanthine (IBMX) (Example 6). In Example 3 above and each
of Examples 4-6, isolated hydrated tomatoe leaves were pre-sprayed
with the compound(s) or vehicle (usually MeOH) at the concentration
shown, allowed to dry and placed in closed plexiglass containers. A
group of six, three-day old tobacco hornworm larvae (initially
reared on artificial media) were then placed on each leaf, and the
amount of leaf remaining was measured at the end of four days.
Values shown are the mean (.+-.SEM) of three separate experiments.
FIG. 1C also shows the relatively weak effects of
8-phenyltheophylline (Example 7), a known adenosine receptor
blocker (Daly, J. W., J. Med. Chem., 25: 197 (1982)).
EXAMPLES 8-11
Nerve cord was dissected from 40-60 mm long M. sexta larvae,
cleaned, and homogenized (2 mg/ml) in 6 Mm Tris-maleate, pH 7.4.
PDE activity was measured (4 min. incubation at 30.degree. C.) in
an assay system (0.1 ml) containing 80 mM Tris-maleate, pH 7.4; 6
mM Mg--SO.sub.4 ; 10.sup.-7 M.sup.3 H-cyclic AMP; and tissue
homogenate (0.02 ml). Nerve cord was evaluated in the presence and
the absence of the xanthine derivative. For purposes of the
evaluation, the rate of formation of .sup.3 H-5' AMP was measured
using the technique described in Filburn, C. R., Anal. Biochem.,
52: 505 (1973). Under these conditions, enzyme activity was linear
with respect to time and enzyme concentration. The values shown in
FIG. 1D are the mean (.+-.SEM) of three separate experiments. As
may be seen, the patterns of activity in the two graphs are quite
similar.
EXAMPLE 12
To determine if the dosage of xanthine derivatives described in
experiments 4, 7 and 8-11 and ingested by the larvae (causing
pestistatic and pesticidal activity in vivo) were actually absorbed
by the animals and were sufficient to inhibit PDE in vitro,
additional experiments were carried out in order to estimate tissue
levels of xanthine derivative following three days of feeding on
various doses of the derivative. Groups of six larvae were placed
on leaves treated with vehicle or theophylline spray. After three
days, leaf area was recorded and larvae (alive or dead) were rinsed
to remove any compound adhering to their cuticle, homogenized
whole, centrifuged, and the cell-free supernatant assayed for
theophylline content by immunoenzymatic assay (Emit-AAD
theophylline assay (Syva Company, Palo Alto, CA.)). This particular
assay shows little cross-reactivity with theophylline metabolites.
From mammalian studies, it is known that theophylline penetrates
freely into all body compartments (Rall, T. W., supra.). Larvae
feeding on leaves treated with a 1% spray (an amount causing about
50% inhibition of leaf consumption) were found to contain an
internal theophylline concentration of 4.1.+-.1.1 mM (mean
.+-.deviation for two groups of six pooled animals). This
concentration was sufficient to cause more than an 80% inhibition
of hornworm nerve cord PDE activity in vitro. This observation
tends to rule out the hypothesis wherein adenosine receptors are
involved as a mechanism for the antifeeding effects of the xanthine
derivatives, since, in vertebrates, xanthine derivatives such as
theophylline are competitive adenosine receptor antagonists, but
exert such antagonism at much lower concentrations, typically 1-25
micromoles. See Bruns, R., et al., Proc. Natl. Acad. Sci. USA, 77:
5547 (1980); Williams, M., et al., Proc. Natl. Acad. Sci. USA, 77:
6892 (1980).
EXAMPLE 13
Xanthine derivatives have been reported to have calcium mobilizing
effects (Links, J. R., et al., Circ. Res., 30: 367 (1972)).
Xanthine derivatives are known to mobilize calcium from
sarcoplasmic reticulum, an effect which is blocked by diltiazem or
procaine. IBMX was evaluated with regard to antifeeding effects in
the presence of both diltiazem and procaine, neither reversing the
observed antifeeding effects.
EXAMPLE 14
Xanthine derivatives have also been reported to affect calcium
movement across the plasma membrane (Links, J. R., et al., supra;
Saeki, K., et al., Life Sci., 32: 2973 (1983)). The pestistatic and
pesticidal effects of IBMX were evaluated in the presence of D600,
verapamil, and nimodipine, compounds which are known to block
plasma membrane calcium channels. The pestistatic and pesticidal
effects of IBMX appeared unaffected by these compounds.
Discussion
Whereas caffeine has been reported to be 10-fold weaker than
theophylline as an adenosine antagonist (Bruns, R., et al., supra),
as demonstrated by the above Examples, caffeine was somewhat more
potent than theophylline in preventing leaf eating and about
equally potent as a PDE inhibitor. See FIGS. 1C and 1D. Also,
whereas IBMX and theophylline are roughly equally potent in
blocking adenosine receptors (Bruns, R., et al., supra) IBMX was
about 10-fold more potent both in disruption of feeding and in PDE
inhibition. See FIG. 1D. Furthermore, the very potent adenosine
antagonist, 8-phenyltheophylline, (K.sub.i for adenosine receptor
(0.12-1.0 micromoles) (Daly, J. W., J. Med. Chem., 25: 197 (1982);
Bruns, R., et al., supra) exerted little antifeeding effect and was
a very weak PDE inhibitor (see FIGS. 1C and 1D). Additionally, the
non-xanthine, papavarine, was a potent inhibitor both of insect PDE
(K.sub.i =40 micromoles) and of the ability of Manducca to feed
(EC.sub.50 =0.1% spray). Unlike xanthine derivatives, papavarine is
an inhibitor of adenosine uptake, and it potentiates, rather than
blocks physiological effects on adenosine receptors (Huang, M., et
al., Life Sci., 14: 489 (1974)). Taken together, these data are
more consistent with a mechanism of action related to PDE
inhibition than to adenosine blockade.
Cumulatively, these data suggest that pestistatic and pesticidal
effects of the xanthine derivatives are mediated through an
alteration of tissue cyclic AMP levels, most likely secondarily to
an inhibition of phosphodiesterase. Thus, the naturally occurring
xanthine derivatives function as endogenous pest-controlling
agents.
EXAMPLE 15-45
Thirty-one compounds conforming to the general formula (I) or (II)
above were prepared or obtained and evaluated with regard to
pesticidal and pestistatic activity. The results of the evaluation
are reported in Table 1 below. In Table 1 below, EC.sub.50 and
V.sub.max are as described above, with active compounds being those
compounds with a V.sub.max of more than 50% inhibition of feeding
and an EC.sub.50 of less than 3% (gm/100 ml) concentration of
spray. As may be seen from Table 1, Examples 15-31 are active
compounds within the above meaning, with Examples 32-44 being
inactive compounds. Example 45 is weakly active. Of the seventeen
active compounds, twelve are more active than caffeine
(1,3,7-trimethylxanthine), Examples 16-21, 24, 26, and 28-31.
TABLE 1 ______________________________________ STRUCTURAL-ACTIVITY
RELATIONSHIPS OF XANTHINES WITH PESTICIDAL ACTIVITY Ex. Compound
EC.sub.50 V.sub.max ______________________________________ Active
Compounds 15 1,3-dimethyl-xanthine (theophylline) 1.5 94 16
1,3-diethyl-xanthine 0.33 98 17 1,3-dipropyl-xanthine 0.035 95 18
1,3-diallyl-xanthine 0.35 99 19 1,3-dibenzyl-xanthine 0.45 70 20
1-methyl,3-isobutyl-xanthine 0.3 95 21
1-isoamyl,3-isobutyl-xanthine 0.2 >52 22
1-phenethyl,3-ethyl-xanthine 0.6 96 23 1,3,7-trimethyl-xanthine
(caffeine) 0.3 98 24 1,3-dimethyl,7-(2-chlorethyl)-xanthine 0.3 95
25 1,3-dimethyl,7-(beta-hydroxypropyl- 1.5 95 xanthine) 26
1,3,7-trimethyl,8-methoxy-xanthine 0.5 86 27 3,7-dimethyl-xanthine
(theobromine) 1.0 87 28 1,3-dipropyl,7-methyl-xanthine 0.48 84 29
1,3,7-tripropyl-xanthine 0.19 95 30 1,3-dipropyl,7-benzyl-xanthine
0.08 96 31 1,3-dibutyl-xanthine 0.044 90 Inactive Compounds 32
xanthine >3 0 33 1-methyl-xanthine >3 21 34 3-methyl-xanthine
>3 8 35 7-methyl-xanthine >3 29 36 8-methyl-xanthine >3 35
37 9-methyl-xanthine >3 10 38 1,7-dimethyl-xanthine >3 30 39
1,7-dimethyl-uric acid >3 30 40 1,3,7-trimethyl-uric acid >3
40 41 1,3-dimethyl-7-acetyl-xanthine >3 18 42
1,3-dimethyl-8-phenyl-xanthine >3 38 43
1,3-dipropyl-8-phenyl-xanthine >3 0 44
1,3,7-trimethyl-8-chloro-xanthine >3 40 Weakly Active 45
1,3,9-trimethyl-xanthine >3 50
______________________________________
EXAMPLE 46
Fifteen xanthine derivatives, and xanthine itself, were evaluated
according to their ability to inhibit phosphodiesterase activity in
hornworm nerve cord using the methodology set out in Examples 8-11
above. The sixteen compounds and the identifying key for FIG. 2
appear in Table 2 below. As may be seen from FIG. 2, compounds 1-5
have a K.sub.i (K.sub.i, as defined above, being the concentration
in mM necessary to cause a 50% inhibition in PDE activity) of 0.1
or less. These same five compounds have a V.sub.max of at least 95
and an EC.sub.50 of 0.33 or less.
TABLE 2 ______________________________________ KEY FOR GRAPH OF
FIG. 2 ______________________________________ Inactive Compounds A.
1,3-dimethyl-7-acetyl-xanthine B. 1-methyl-xanthine C.
8-methyl-xanthine D. xanthine E. 7-methyl-xanthine F.
3-methyl-xanthine G. 1,3-dimethyl-8-chloro-xanthine H.
1,3-dimethyl-8-phenyl-xanthine Active Compounds 1.
1,3-dipropyl-xanthine 2. 1-methyl,3-isobutyl-xanthine 3.
1,3-diallyl-xanthine 4. 1,3-diethyl-xanthine 5.
1,3-dimethyl-7-(2-chlorethyl)-xanthine 6. 1,3-dimethyl-xanthine
(theophylline) 7. 1,3,7-trimethyl-xanthine (caffeine) 8.
1,3-dimethyl-7-(beta-hydroxypropyl)-xanthine 9.
1,3-dipropyl,7-methyl-xanthine 10. 1,3,7-tripropyl-xanthine 11.
1,3-dipropyl,7-benzyl-xanthine 12. 1,3-dibutyl-xanthine
______________________________________
This strong correlation between in vitro PDE inhibition and
pesticidal activity allows one to accurately predict the pesticidal
activity of xanthine derivatives based on PDE inhibition in tobacco
hornworm nerve cord.
EXAMPLE 47
These four structurally similar compounds were tested as described
in Example 46: 1,3,7-trimethylxanthine (caffeine);
1,7-dimethyl-xanthine; 1,3,9-tri-methyl-xanthine; and
1,3-dimethyl-xanthine.
The caffeine compound tested according to the methods disclosed in
the present invention is active. Therefore, one would predict that
the above three compounds which differ only by a single methyl
group would also be active. However, the tests show that only
1,3-dimethyl-xanthine was active. 1,7-dimethylxanthine was inactive
and 1,3,9-trimethyl-xanthine was only weakly active. These results
are not obvious and one could only predict them by knowing the
teachings of the application. More specifically, the inventor's in
vitro phosphodiesterase testing procedure correctly predicts as
shown in Examples 15-45 that, of the three compounds, only
1,3-dimethyl-xanthine is active. Thus, as a result of the present
invention, it is possible to quickly and routinely evaluate, in
vitro, potentially active compounds based on their ability to
inhibit phosphodiesterase activity.
Having now fully described this invention, it will be understood by
those of skill in the art that the same may be performed within a
wide and equivalent range of compositions, parameters, structures,
modes of application, pests, formulations, and ranges without
affecting the scope of the invention or any embodiment thereof.
* * * * *