Bioactivity of Natural Products

Some Facile Screening Methods Used to Evaluate the Bioactivity of Natural Products... 

Biooxidation of cyclobutanones is a particularly useful transformation, as the corresponding chiral butyrolactones represent highly valuable building blocks for a large variety of natural products as well as bioactive compounds [165]. 

A rate-limiting step in the use of natural products as probes in biology is the chemical synthesis of useful bioactive probes, such as affinity reagents or fluorescent probes, that can be readily applied by biochemists and cell biologists. The ability to generate useful probes derived from natural products is completely dependent on a prior knowledge of the... 

The previous section discussed chelation enforced intra-annular chirality transfer in the asymmetric synthesis of substituted carbonyl compounds. These compounds can be used as building blocks in the asymmetric synthesis of important chiral ligands or biologically active natural compounds. Asymmetric synthesis of chiral quaternary carbon centers has been of significant interest because several types of natural products with bioactivity possess a quaternary stereocenter, so the synthesis of such compounds raises the challenge of enantiomer construction. This applies especially to the asymmetric synthesis of amino group-substituted carboxylic acids with quaternary chiral centers. 

Berry JP, Reece KS, Rein KS, Baden DG, Haas LW, Ribeiro WL, Shields JD, Snyder RV, Vogelbein WK, Gawley RE (2002) Are Pfiesteria species toxicogenic Evidence against production of ich-thyotoxins by Pfiesteria shumwayae. Proc Natl Acad Sci USA 99 10970-10975 Bhakuni DS, Rawat DS (2005) Bioactive marine natural products. Springer, New York Blunt JW, Copp BR, Munro MHG, Northcote PT, Prinsep MR (2006) Marine natural products. Nat Prod Rep 23 26-78... 

Synthetic cyclic peptides are of eminent interest not only as replicates or analogues of natural products or as conformationally restricted bioactive peptides and peptide or protein fragments, but may also serve for specific purposes as listed in the following sections. 

The relative contribution to the cup of natural products by marine and terrestrial organisms is outlined in Table 9.1. Column entries are the phylum, class or order, number of species, biogenetic class of metabolites produced, their bioactivity level, and a qualitative indication as to the average molecular complexity (Whitlock 1998). The latter property receives closer attention in Table 9.II for specific molecular skeletons. These data warrant several conclusions. First, unusual secondary metabolites on land derive mostly fi-om green plants and arthropods, while in the sea are the algae, sponges, cnidarians, bryozoans, and ascidians that give most. This is true no matter if the molecular skeleton, or the actual metabolite, or even the bioactivity, is examined. 

The raison d etre of natural product diversity, and the exploitation of natural products by man, were delineated in Chapters 12 and 13. Man went further, in an endeavor to improve on nature by making available rare bioactive compounds and synthetic analogues with a better performance (Liu 1999). 

A herbal product contains multiple constituents that might be responsible for its therapeutic effects. It is thus necessary to define as many of the constituents as possible in order to understand and explain the bioactivity. The concept of phytoequivalence has been introduced in Germany to ensure consistency of phytotherapeuticals. According to this concept, a chemical profile for a herbal product is constructed and compared with the profile of a clinically proven reference product. Since many of these preparations contain flavonoids, it is essential to have adequate analytical techniques at hand for this class of natural product. 

Wang, S., Ghisalberti, E.L., and Ridsdill-Smith, J., Bioactive isoflavonols and other components from Trifolium subterraneum. Journal of Natural Products, 61, 508, 1998. 

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