Chemical diversity of natural products

Natural Product Discovery, Molecular Biological Approaches to Natural Products in Microbes, Chemical Diversity of Natural Products An Overview Terpenoids in Plants... 

Marine Namral Products, Chemical Diversity of Chemical Diversity of Natural Products in Plants Pharmaceuticals Natural Products and Natural Product Models Natural Products as Anticancer Agents Chemical Ecology An Overview... 

It is well-established that the chemical diversity of nature cannot be replicated by humankind. Although only about 150000 natural products have been characterised, they represent close to 6000 carbon skeletons and most are replete with the functional groups and physical characteristics that are prevalent in the existing drugs of the world.74... 

The wide distribution of PKSs in the microbial world and the extreme chemical diversity of their products do in fact result from a varied use of the well-known catalytic domains described above for the canonical PKS systems. Taking a theoretic view of polyketide diversity, Gonzalez-Lergier et al. (41) have suggested that even if the starter and extender units are fixed, over 100,000 linear heptaketide structures are possible using only the 5 common reductive outcomes at the P-carbon position (ketone, (R- or S-) alcohol, trans-double bond, or alkane). Recently, it has become apparent that even this does not represent the upper limit for polyketide diversification. To create chemical functionalities beyond those mentioned above, nature has recruited some enzymes from sources other than fatty acid synthesis (the mevalonate pathway in primary metabolism is one example) not typically thought of as type I PKS domains. Next, we explore the ways PKS-containing systems have modified these domains for the catalysis of some unique chemistries observed in natural products. 

In summary, the marine environment contains a wealth of plants, animals and microorganisms. Due to their unique adaptations to their ocean habitat, they contain a wide diversity of natural products. These compounds have shown activity in a variety of assays which have relevance to human diseases. As our understanding of the molecular basis of disease expands, these compounds and ones yet to be discovered will provide lead compounds for human therapeutic treatment. Innovations in synthesis, fermentation of symbionts as well as in manipulation of biosynthetic genes will allow us to produce sufficient material for clinical use of the compounds. Marine organisms provide a unique opportunity for access to chemical diversity. 

Another relevant library-building concept that also emerged from the diversity of natural products assumes that such molecular scaffolds primarily hold the biological activity, and the side chains and functional groups only modify or fine-tune the interaction. Therefore, a new term was introduced by the Schreiber group, skeletal diversity (Kwon, Park, and Schreiber, 2002). Instead of increasing the overall structural diversity or dissimilarity, skeletal diversity is required in libraries involved in chemical genetics which can only be achieved by diversity-oriented synthesis (DOS) (Arya et al., 2005 Tan, 2005). 

Ecological factors such as predation contribute to marine diversity of natural products due to evolution through natural selection. The symbiosis between the microbial community and invertebrates is another factor that probably contributes to the chemical diversity of substances at the species level. There is evidence from recent studies suggesting that microbes associated with marine invertebrates may be the true producers of some of the natural products that were previously assumed to be produced by then-invertebrate host [9-11]. 

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