Herbicides biological

The similarity in the herbicide biology and biochemistry of the above structurally distinct compounds is interesting as well as intriguing. One of the key questions is whether these inhibitors compete for the... 

Uses Herbicide biological oxidation-reduction indicator... 

Combustion in an incinerator is the only practical way to deal with many waste streams.This is particularly true of solid and concentrated wastes and toxic wastes such as those containing halogenated hydrocarbons, pesticides, herbicides, etc. Many of the toxic substances encountered resist biological degradation and persist in the natural environment for a long period of time. Unless they are in dilute aqueous solution, the most effective treatment is usually incineration. 

CtHjCIjNS, PhC(S)NH2, a herbicide with a high level of biological activity. 

The correlations between chemical descriptors of molecular properties and biological activity, especially the activity of herbicides and/or plant growth regulators has been described (12). Several alternatives or improvements on the Hansch-Fujita QSAR system have been developed (13—15). 

Discovery. The traditional approach to new pesticide discovery was to make iatuitive changes ia the substitueats oa a promising primary chemical stmcture. Initially, materials from any source were subjected to screening for biological activity as iasecticides, herbicides, or fungicides. 

Pharmaceuticals and Agrochemicals. Thioglycohc acid and its esters are useful as a raw material to obtain biologically active molecules. In cephalosporine syntheses, (4-pyridyl)thioacetic acid [10351 -19-8] (65) and trifluoromethane (ethyl) thioglycolate [75-92-9] (66) are used as intermediates. Methyl-3-ainino-2-thiophene carboxylate can be used as intermediate for herbicidal sulfonylureas (67) and various thiophenic stmctures (68). 

Before the discovery of streptomycin, pyrazinamide (126) was one of the front runners in the treatment of tuberculosis. A broad spectrum of biological activity has been associated with pyrazine derivatives, ranging from the herbicidal activity of (127) to antibiotic activity... 

The Knorr pyrazole synthesis has been extensively utilized in the preparation of a number of pyrazoles as metal chelators, photographic dyes, herbicides, and biologically active... 

Similar to their [4,3-c] isomers [99AHC(75)243], 1,2,4-triazolo [l,5-c]pyrimidiiies displayed numerous biological and medicinal activities. In addition, the [1,5-c] isomers found useful agrochemical applications as herbicides. 

According to Urbanski et al. biological activity of 1,3-oxazine derivatives is due to the active CH2 group in the 2-position. Tne use of tetrahydro-l,3-oxazines was also suggested against some infections in veterinary service. The suggested use of tetrahydro-l,3-oxa-zines as herbicides did not seem to be a success. 

Polarographic methods can be used to examine food and food products biological materials herbicides, insecticides and pesticides petroleum and petroleum products pharmaceuticals. The examination of blood and urine samples is frequently carried out to establish the presence of drugs and to obtain quantitative results. 

A large number of 1,2,4-triazines that are condensed with one or more heterocycles are well known and a wide variety of synthetic methods for their preparations are available. Compounds containing the 1,2,4-triazine moiety are in use as pharmaceuticals, dyes, pesticides, herbicides, etc., and a great number of reports have been directed to the synthesis of the title heterocycles having potentially useful biological properties. 

Encelia farinosa (27), and rmw-cinnamic acid from guayule (Par-thenium argentatum) 5). Some chemical and biological properties of natural herbicides from Thanmosma montana are described in this... 

The total amount of pesticide applied worldwide, as mentioned, is estimated to be 2.5 million tons. Of this 50 to 60% are herbicides, 20 to 30% are insecticides, and 10 to 20% are fungicides. Interestingly, less than one-third of all the agricultural cropland in the world is treated with some kind of pesticide. This illustrates the fact that a significant portion of crops receive no pesticide and, therefore, are protected to some extent by nonchemical biological controls. 

Since 1945 the use of synthetic pesticides in the United States has grown 33-fold. The amounts of herbicides, insecticides, and fungicides used have changed with time due, in large part, to changes in agricultural practices and cosmetic standards (14, 15). At the same time, the toxicity and biological effectiveness of these pesticides have increased at least 10-fold (15). For example, in 1945 DDT was applied at a rate of about 2 kg/ha. With the more potent insecticides available now, similar effective insect control is achieved with pyrethroids and aldicarb applied at 0.1 kg/ha and 0.05 kg/ha, respectively. 

The herbicide activity ascribed to the 1,2,4-oxadiazole derivative 67 (60) has prompted the search for other biologically active derivatives. This example was prepared from the corresponding 5-chloromethyl-1,2,4-oxadiazole 63 via conversion to the HHT 65 through the aminomethyl analog 64. Reaction of the HHT 65 with diethyl phosphite under neat conditions produced the desired diethyl ester intermediate 66, which was hydrolyzed to 67. 

More controversially, endocrine disruption as a consequence of exposure to the herbicide atrazine (2-chloro-4-ethylamine-6-isopropylamine-s-triazine), one of the most widely used herbicides in the world, has also been hypothesized to explain various adverse biological effects in frog populations in the United States. Exposure to atrazine in the laboratory at high concentrations, far exceeding those found in the natural environment, has been reported to induce external deformities in the anuran species Rana pipiens, Rana sylvatica, and Bufo americanus (Allran and Karasov 2001). Studies by Hayes et al. have suggested that atrazine can induce hermaphroditism in amphibians at environmentally relevant concentrations (Hayes et al. 2002 Hayes et al. 2003). Laboratory studies with atrazine also indicated the herbicide... 

---