Identification of natural products

Sche, P. P., McKenzie, K. M., White, J. D., and Austin, D. J. (1999). Display cloning functional identification of natural product receptors using cDNA-phage display. Chem. Biol. 6, 707-716. 

LC-NMR plays a central role in the on-line identification of the constituents of crude plant extracts (Wolfender and others 2003). This technique alone, however, will not provide sufficient spectroscopic information for a complete identification of natural products, and other hyphenated methods, such as LC-UV-DAD and LC-MS/MS, are needed for providing complementary information. Added to this, LC-NMR experiments are time-consuming and have to be performed on the LC peak of interest, identified by prescreening with LC-UV-MS. NMR applied to phenolic compounds includes H NMR,13 C NMR, correlation spectroscopy (COSY), heteronuclear chemical shift correlation NMR (C-H HECTOR), nuclear Overhauser effect in the... 

IDENTIFICATION OF NATURAL PRODUCTS BY CHROMATOGRAPHIC AND SPECTROSCOPIC METHODS... 

While in the recent past it was extremely difficult, time consuming and labour intensive to build such a library from purified natural products, with the advent of newer and improved technologies related to separation, isolation and identification of natural products the situation has improved remarkably. Now, it is possible to build a high quality and chemically diverse natural product library that can be suitable for any modern HTS programmes. Natural product libraries can also be of crude extracts, chromatographic fractions or semi-purified compounds. However, the best result can be obtained from a fully identified pure natural product library as it provides scientists with the opportunity to handle the lead rapidly for further developmental work, e.g. total or partial synthesis, dealing with formulation factors, in vivo assays and clinical trials. 

A substantial listing of UV spectra of coumarins is available (71PMH(3)190) and examples of the identification of natural products based on the coumarin ring system by UV analysis, amongst other methods, have been reported (58JA3686,69MI22202). 

Natural products have been, and remain, a rich source of leads for the pharmaceutical industry and many marketed drugs are either natural products or are modifications of such substances. Hence, considerable effort is spent in isolating and characterising chemicals from natural sources which can be tested in a variety of biological screens. Often, it is necessary to carry out laborious extraction and purification steps and the advent of directly coupled HPLC-NMR has been explored as an alternative technique for natural product identification. The use of HPLC-NMR, and other hyphenated techniques such as HPLC-MS-MS, for identification of natural products from plant sources has been reviewed by Wolfender and co-workers [40,41],... 

Traditional methods of pharmaceutical analysis involve a series of multiple steps. For example, the identification of natural products traditionally involves the scale-up of fermentation broths, solvent extraction, liquid/liquid or column fractionation, chromatographic fraction collection, and spectroscopic analysis (usually NMR) of the individual components. Figure 5.2 illustrates the integration of these bench-scale steps into a dedicated LC/MS/MS system (Lee et al., 1997). Integration provides unique and powerful advantages for the on-line identification of natural products (Kerns et al., 1994 Ackermann et al., 1996a). Experiments that once required 2 weeks to perform with traditional approaches are now performed in half a... 

Fig. I Overview of the different approaches used for target identification of natural products...

Many of the same chromatographic and spectroscopic techniques were applied to the isolation and identification of natural products such as carbohydrates and glyco-lipids. The discovery, isolation, computational analysis, synthesis, and structure-activity relationship studies of antibiotics such as the aminoglycosides kanamycin and neamine are of particular note (Fig. 1.14) [157, 158],... 

Van Middlesworth, E and Cannell, R.J.P. 2008. Dereplication and partial identification of natural products. In Natural Products Isolation, Vol. 4, Methods in Biotechnology, Cannell, R.J.P., Ed. Totowa, NJ Humana Press, pp. 279-327. 

The isolation and identification of natural products for potential use in agriculture has increased sharply during the past decade. Vith few exceptions the synthesis and alteration of these compounds for further use has been slow. 

M. I. Walash, O. M. Salama, and M. M. Bishr, Use of absorbance ratios in densitometric measurements for the characterization and identification of natural products of pharmacological interest, J. Chromatogr., 469 390(1989). 

The best approach for the identification of natural product leads is a matter of debate. Some very inventive techniques have been used in the bioassay-guidedmethod for example, by spraying TLC plates with reactive media that respond by producing a color change in the presence of an active compound. An alternative is to use an ethnobotanical or ethno-pharmacologicaltechnique, whereby the accumulated wisdom of many generations of native plant users may be harnessed in the... 

Bohzin, S.C. Yang, S. Kasten, T.P. Application of liquid chromatography-nuclear magnetic resonance spectroscopy to the identification of natural products. J. Chromatogr., B, Biomed. Sci. Appl. 2000, 748, 259 -267. 

Unger, S.E. Cooks, R.G. (1979). Application of mass spectometry, mass spectometry (MS/MS) to the identification of natural products in Psilocybe cyanescens. Analytical Letters 12 (Part B), 1157-1167. 

In this chapter, we start with a brief overview of the standard methods currently used for the NMR-spectroscopic identification of natural products and other types of organic small molecules, which is followed by a section dedicated to NMR spectroscopic characterization of small molecule mixtures and a discussion of approaches to increase NMR spectroscopic sensitivity. 

Lambert, M., Wolfender, J. L., Staerk, D., Christensen, B., Hostettmann, K., Jaroszewski, J. W. Identification of natural products using HPLC-SPE combined with CapNMR. Anal. Chem. 2007, 79, 727-735. 

Sanders, M. Josephs, J., Schwartz, J. Tymiak, A. DiDonato, G. Rapid Identification of Natural Products Using a Modified Ion Trap Mass Spectrometer and MS/MS Spectral Library Searching, in Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, Texas, June 13-17, 1999. 

Franke, L., Schwarz, O., MuUer-Kuhrt, L., Hoernig, C., Fisher, L., George, S., Tamikulu, Y, Schneider, P., Werz, O., Steinhilber, D. and Schneider, G. (2007) Identification of natural-product-derived inhibitors of 5-hpoxygenase activity by ligand-based virtual screening. /. Med. Chem., 50, 2640-2646. 

Until recently, developments in plant pathology and chemistry have been out of synchrony. Field observations of plant pathogens and their etiology have been meticulously recorded as a distinct, thorough discipline. In contrast, the isolation and identification of natural products from... 

Genetic information has also been established as a good starting point to explore the biosynthetic potential of myxobacteria, through the identification of natural product biosynthetic genes (Figure This strategy... 

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