Identification of new compounds

Liu and Hop [19] have reviewed various LC-tandem MS strategies, with or without chemical modification or derivatization, which have been successfully applied in the identification and the rational, but tentative, structural determination of drug metabolites. These techniques are equally applicable to the analysis of known plant secondary metabolites or to the de novo structural identification of new compounds. 

Identification of new compounds may start with TLC analysis of plant extracts. For instance, Jakupovic et al. [4] isolated and further identified several diterpenes from Euphorbia segetalis. Similarly, chamomile essential oil (Chamomilla reticulata) was analyzed with 11 different development systems and the authors discussed... 

Identification of new compounds may start with TLC analysis of plant extracts. For instance, Jakupovic et al. - isolated and further identified several diterpenes from Euphorbia segetalis. Similarly, chamomile essential oil (Chamomilla reticulata) was analyzed with 11 different development systems and the authors discussed both the most efficient (separation power) and the ideal way they are to be used to identify an unknown component in such a complex mixture, using the minimum number of TLC systems.This area of work still has to be investigated, considering the wide variety of the vegetal reign and of potential plant toxins. 

Combined glc and mass spectrometry provide the capability to deal with the complex mixtures of closely related compounds often found in plant cuticles. Even though identification of new compounds solely by their mass spectra cannot be considered reliable, mass spectrometry has become an invaluable tool in identifying known types of compounds in cuticular lipids. For example, methyl branches in alkanes can be located by cleavage on both sides of the substituted carbon (Fig. 5). Mass spectrometry is also the most suitable technique for identifying branched fatty acids (Tulloch, 1976 Jack-son and Blomquist, 1976 Nicolaides and Apon, 1977). Functional groups such as carbonyl groups and hydroxyl groups in the aliphatic chain can be... 

Identification of new compounds relies on the registration of mass spectra for standards. Utilization of commercial and publicly available mass spectra bases is also possible. For more precise information about the presented problems, we refer to the original papers published in the literature [22,48,52]. 

Rius Sole M.A., Garcia Regueiro J.A. Role of 4-phenyl-3-buten-2-one in boar taint identification of new compounds related to sensorial descriptors in pig fat. Journal of Agricultural and Food Chemistry, 49 5303-5309 (2001). 

Thermal analysis techniques have been applied to investigate many aspects of concrete science and technology. They include hydration kinetics, mechanism of hydration, deterioration of concrete, examination of the role of newly developed admixtures, admixture detection and estimation, composition of the products, identification of new compounds, etc. 

The means by which molecular superposition is used to interpret this type of information varies almost as much as the data to be interpreted. For methods that describe data in terms of molecular characteristics, atoms, functional groups, or physical attributes, molecular superposition is the component common to all techniques. Techniques such as comparative molecular field analysis and 3D similarity are all founded on molecular superposition. Similarities may be used in compound design, compound optimization, and the identification of new compound classes. The resulting superposition sets are often generalized and the consistent spatial information referred to as a pharmacophore. The principal difficulty faced in molecular superposition is one of combinatorics. The number of ways even a pair of molecules may be superimposed is large, making the problem inherently complex. 

LC-MS finds wide application in the analysis of compounds that are not amenable to GC-MS, i.e. compounds that are highly polar, ionic and thermo-labile, as well as (bio)macromolecules. In environmental applications, LC-MS is applied, often in combination with off-line or on-line solid-phase extraction, to identify pesticides, herbicides, surfactants and other environmental contaminants. LC-MS plays a role in the confirmation of the presence of antibiotic residues in meat, milk and other food products. Furthermore, there is a substantial role for LC-MS in the detection and identification of new compounds in extracts from natural products and the process control of fermentation broths for industrial production of such compounds, e.g. for medicinal use. LC-MS technology is also widely applied in the characterization of peptides and proteins, e.g. rapid molecular-mass determination, peptide mapping, peptide sequencing and the study of protein conformation and noncovalent interactions of drugs, peptides and other compounds with proteins and DNA. However, the most important application area... 

Armstrong RB, Kim HJ, Grippo JF, Levin A A (1992) Retinoids for the future Investigational approaches for the identification of new compounds. J Amer Acad Dermatol 27, S38-S42... 

Silverstein R M, Bassler G C and Morrill T C 1981 Spectra metric Identification of Organic Compounds (New York Wiley) oh 4 and 5... 

A very good general survey for interpreting mass spectral data is given by R. M. Silverstein, G. C. Bassler, and T. C. Morrill, Spectrometric Identification of Organic Compounds, 4th ed., Wiley, New York, 1981. 

See, for example, the following laboratory texts (a) Sorum, C. H. Lagowski, J. J. Introduction to Semimicro Qualitative Analysis, 5th ed. Prentice-Hall Englewood Cliffs, NJ, 1977. (b) Shriner, R. L. Fuson, R. C. Curtin, D. Y. The Systematic Identification of Organic Compounds, 5th ed. John Wiley and Sons New York, 1964. 

B. D. Mookherjee, "The Identification of Bihmctional Compounds ia Bergamot Oil," paper presented at the 158th National Meeting of theMmerican Chemical Society, Sept. 7—12, 1969, New York. 

Hazard identification, step one, means identification of new chemicals or other factors that may cause harmful health effects. Previously, novel hazards were usually observed in case studies or after accidents or other excessive exposures, usually in occupational environments. Today, thorough toxicity studies are required on all pesticides, food additives, and drugs. New chemicals also have to be studied for their potential toxic effects. Thus, earlier hazards were in most cases identified after they had caused harmful effects in humans. Today, most chemical products have been evaluated for their toxicity with experimental animals. Therefore, hazard identification has become a preventive procedure based on safety studies conducted before a chemical compound or product reaches the market, and before individuals are exposed to it. ... 

More recently (2006) we performed and reported quantitative structure-activity relationship (QSAR) modeling of the same compounds based on their atomic linear indices, for finding fimctions that discriminate between the tyrosinase inhibitor compounds and inactive ones [50]. Discriminant models have been applied and globally good classifications of 93.51 and 92.46% were observed for nonstochastic and stochastic hnear indices best models, respectively, in the training set. The external prediction sets had accuracies of 91.67 and 89.44% [50]. In addition to this, these fitted models have also been employed in the screening of new cycloartane compounds isolated from herbal plants. Good behavior was observed between the theoretical and experimental results. These results provide a tool that can be used in the identification of new tyrosinase inhibitor compounds [50]. 

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