Principal activity

In terms of the number of scientists and engi neers involved research and development in polymer chemistry is the principal activity of the chemical in dustry The initial goal of making synthetic materials that are the equal of natural fibers has been more than met it has been far exceeded What is also im... 

Neutralizing Lotion. The principal active ingredient of cold wave neutralizers is usually an oxidizing agent. The most popular is hydrogen peroxide [7722-84-1J, employed at a concentration of 1—2% it continues to find widespread use. Aqueous solutions of sodium bromate [7789-38-0] at a concentration of 10—20% occasionally are used and are technically preferred over the peroxide formulations because of excellent stabiUty and absence of hair bleaching. Neutralizing powders appear to be on the decline but formulations stiU in use consist of sodium perborate [7632-04-4] combined with hexametaphosphates to improve solubiUty in hard water. 

In addition to platinum and related metals, the principal active component ia the multiflmctioaal systems is cerium oxide. Each catalytic coaverter coataias 50—100 g of finely divided ceria dispersed within the washcoat. Elucidatioa of the detailed behavior of cerium is difficult and compHcated by the presence of other additives, eg, lanthanum oxide, that perform related functions. Ceria acts as a stabilizer for the high surface area alumina, as a promoter of the water gas shift reaction, as an oxygen storage component, and as an enhancer of the NO reduction capability of rhodium. 

Ephedrine is the principal active ingredient in the herb ephedra, or ma huang. It is similar in form to the appetite-control drug phenylpropanolamine (banned in the United States), which is also known as norephedrine, meaning ephedrine whose methyl group has been replaced by a hydrogen. 

FIGURE 6 A summary of the principal activities that constitute a common version of the scientific method. At each stage, the crucial activity is experiment and its comparison with the ideas proposed. 

Figure 2.6 The EMEA mission statement and principal activities (reproduced with permission of EMEA).

In summary, the development of materials for the extraction of pesticides from water samples has progressed from simple liquid-liquid extraction for the principal active compound to sophisticated SPE media capable of exclusively trapping the target pesticide and metabolites selectively. The development of alkyl bonded phase silica cartridges and extraction disks combined with on-line extraction techniques is currently the principal means used for the extraction and trace enrichment of pesticides and metabolites from water. 

Of the three organic phosphorus insecticides—hexaethyl tetraphosphate, tetraethyl pyrophosphate, and parathion—the first two have been shown to be mixtures (36) that contain tetraethyl pyrophosphate as the principal active ingredient. Several methods have been proposed for the determination of this compound in the commercial products (25, 35). All are based on the separation of the tetraethyl pyrophosphate from the related ethyl phosphates, followed by its hydrolysis to diethyl orthophosphoric acid and titration with standard alkali. Both hexaethyl tetraphosphate and tetraethyl pyrophosphate are soluble in water and are rapidly hydrolyzed to monoethyl and diethyl orthophosphoric acid. This rapid hydrolysis to nontoxic products greatly limits the duration of the in- secticidal effectiveness of tetraethyl pyrophosphate, but it also eliminates the danger of toxic residues on the crops treated. 

Another extremely important military requirement that is not usually associated with civilian requirements is stability in prolonged storage under adverse conditions. For example, the first lots of fly spray that were shipped to North Africa, in 1942, contained pyrethrum as the principal active ingredient. It was not possible to store this material under cover and much of it remained under constant exposure to the intense tropical sun, undoubtedly deteriorating very rapidly. Covered storage facilities are the exception rather than the rule in a combat theater of operations, and all insecticide compounds furnished to the military forces should withstand this type of storage. 

The development of the first effective analgesic drug, opium, was almost certainly adventitious, and occurred in prehistoric times. The use of the dried exudate from slitting the immature capsule of the opium poppy, Papaver somniferum, as an analgesic, sedative and euphoriant, has a long folkloric history. Isolation of the principal active component morphine (1) as a pure crystalline compound represented one of the early landmarks in organic chemistry. 

Recent advances in PAH carcinogenesis research over the past decade have led to identification of diol epoxide metabolites as the principal active forms of the PAH investigated to date Q,2). Benzo-(a)pyrene (BP) has been most intensively investigated, and it has been demonstrated that a diol epoxide metabolite anti-BPDE is the active intermediate which binds covalently to DNA in human and other mammalian tissues 0,4). Anti-BPDE was also demonstrated to be a powerful mutagen in both bacterial and mammalian cells (15) These findings stimulated an outpouring of research directed towards elucidation of the molecular mechanism of PAH carcinogenesis. 

Chrysene is a weak tumor initiator and is inactive as a complete carcinogen (38). The 1,2-dihydrodiol is more active as a mutagen than the 3,4- or the 5,6-dihydrodiols. The biological data support the hypothesis that the principal active metabolite of chrysene is the bay region anti-1,2-diol-3,4-epoxide (58). 

The reagent scheme generally used in these concentrators is presented in Table 19.9. Sodium silicate is used as the common depressant, and also acts as a dispersant together with the soda ash. In the majority of operating plants, Na2S 9H20 is used as the principal activator. Some operating plants in Zambia use NaHS as a sulphidizer. Sodium or potassium xanthates are the principal collectors used, where mercaptans are used as secondary collectors. 

Vincamine (91) is the major alkaloid of V. minor, a plant used against headache and vertigo. It exerts a sedative CNS action and produces a fall in blood pressure. The principal activity is a moderate cerebral vasodilation. Clinical studies have demonstrated that i.v. administration of 91 to humans reduces the arterial blood pressure and increases cerebral blood flow and oxygen consumption. The improved cerebral hemodynamic conditions significantly and positively affect the state of patients with advanced arteriosclerosis with beneficial effects on memory, concentration, and behavior. It has thereafter been introduced under several trade names as a pharmaceutical in many European countries (232). Vobasine (32) has been widely studied it exhibits a weak CNS depressive, analgesic, and antipyretic action (21). 

Mammalian esterases have been classified into three groups according to specificity for substates and inhibitors (110). In terms of overall hydrolytic activity in mammals, the most important class of esterases is that of the B-esterases, which are principally active with aliphatic esters and amides. A-Esterases are important for aromatic esters and organophosphorus esters, and C-esterases are active with acetyl esters. In general, the specificity of mammalian esterases is determined by the nature of substituent groups (acetyl, alkyl, or aryl) rather than the heteroatom (O, N, or S) that is adjacent to the carboxy group. That is, the same esterase would likely catalyze hydrolysis of an ester, amide, or thioester as long as the substituents were identical except for the heteroatom (110). 

It is necessary to work in a species capable of responding to the principal activity. Interferons are notorious for their species specificity, but most other lymphokines at least are more generally active. Work in a primate may be required, but it depends on the substance to be tested. There may be no point in using more than one species in pivotal studies. 

How do traditional remedies fare in such trials Some perform quite well and prove to be highly effective, but others are no better than placebos. One striking success is an extract of sweet wormwood (Artemisia annua), which Chinese physicians have prescribed for the chills and fevers of malaria for more than two thousand years. About twenty-five years ago, Chinese chemists obtained from sweet wormwood its principal active component, a compound now called artemisinin. Clinical trials on malaria patients in Southeast Asia agreed with Chinese tradition on the value of artemisinin and also identified a few even more useful drugs prepared from it in the laboratory. These compounds are effective against the deadliest form of malaria and are now frequently the therapies of choice for treating it. 

Assay of Principal Active Ingredients in Formulated Dosage Forms... 

Gardner, D.R., Molyneux, R.J., James, F.F., Panter, K.E. and Stegelmeier, B.L. (1994). Ponderosa pine needle-induced abortion in beef cattle Identification of isocupressic acid as the principal active compound, /. Agric. Food Chem., 42, 756-761. 

The principal active ingredient in ephedra is ephedrine. Synthetically produced ephedrine has been approved by the FDA for use as a drug. Under those more controlled conditions, the compound has not been associated with any adverse events of the kind reported for the natural product. 

Difenoxin is the principal active metabolite of diphenoxylate and is effective at one-fifth the dosage of diphenoxylate. 

Raising the temperature to 300 °C expectedly leads to increased conversion. However, undesired side reactions now become predominant, especially at the beginning of the run (cf. Fig. 1), and as a consequence deactivation is even much faster. The same principal activity/selectivity dilemma occurred on certain other large pore zeolites, especially on HZSM-20 and, less pronounced on HL. 

O Neill and coworkers have also sought to address the problem of the metabolically susceptible CIO acetal linkage . A series of CIO carba dimers were prepared and assayed for antitumour activity. The two most potent compounds that were prepared are two phosphate ester finked dimers 115 and 116 (Scheme 40). They are principally active against leukaemia, colon and certain melanoma and breast cancer cell lines in the NCI 60-cell line assay. 

There are three types of ionotropic glutamate receptors NMDA, a-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA), and kainate receptors (Fig. 1). Each is principally activated by the agonist bearing its name and is permeable to cationic flux hence, their activation results in membrane depolarization. Ionotropic glutamate receptors were originally classified based on three selective, synthetic agonists quisqualate, kainate and NMDA. After the discovery of metabotropic receptors, it became clear that quisqualate also interacts with them. Since that time, quisqualate-sensitive ionotropic receptors have been classified by the more selective agonist AMPA. 

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