Natural products, characterization

Lipids (Section 26.1) Biologically important natural products characterized by high solubility in nonpolar organic solvents. 

In the area of natural product characterization, Wall and colleagues utilized 3 mm NMR probe capabilities in the characterization of novel bioactive clerodane diterpenoids from the leaves and twigs of Casearia sylvestris.149 The general structure of the three new clerodanes is shown by 72, the molecules differing in the length and branching of the alkyl side-chain substituent. 

M. O Neil-Johnson, R. Withers, R. Nast, B. Potts, A. Deese, J. Pease and Y. Liu, Natural products characterization analysis of mass-limited samples using 3 mm microCryoProbe, 221st ACS National Meeting, San Diego, CA, April 1-5, 2001, Abstract MEDI-357. 

Williams, T., Blinov, K., Elyashberg, M. and Martisrosian, E. Recent Advances in the Use of NMR Prediction and Automated Structure Elucidation Software for Natural Product Characterization, presented at the SMASH NMR Conference. Argonne, IL, 2000. 

Sprogoe, K., Staek, D., Ziegler, H. L., Jensen, T. H., Holm-Moller, S. B., and Jaroszewski, J. W. (2008). Combining HPLC-PDA-MS-SPE-NMR with circular dichroism for complete natural product characterization in crude extracts Levorotatory gossypol in Thespesia danis.. Nat. Prod. 71, 516-519. 

Thin-layer chromatography has been used extensively for natural products characterization, as shown in other chapters of this handbook. However, TLC7MS is only now being applied to this important analytical area. Lemire and Busch (51) used liquid secondary ion mass spectrometry with TLC to examine some of the alkaloid compounds present in extracts of Sanguinaria canadensis. The semisynthetic alkaloid nicergoline has been analyzed in a plate cutting/elution experiment with positive ion liquid secondary ion mass spectrometry (52). A detection limit of 10 ng was complemented by a linear dynamic range of 50-l(X)0 ng for quantitative purposes. 

Inasmuch as establishing the carbon framework of a molecule overcomes a major obstacle to structure determination, carbon nuclear magnetic resonance ( C-NMR) spectroscopy is potentially the most powerful spectroscopic implement for natural products characterization. The broad range of chemical shifts are valuable in determining the presence of different functional groups (49, 84, 85, 235, 321,... 

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