Heterocycles from marine organisms

In our ongoing search for bioactive metabolites from marine organisms, several novel heterocyclic alkaloids, such as pinnatoxins, norzoanthamine, pinnaic acids, zamamistatin, and symbioimine, have been isolated. This work features the structures, biological activities, and biogenesis of these bioactive heterocyclic marine alkaloids, along with up-to-date topics. 

New bioactive O- and N-heterocycles from Chinese marine organisms 99PAC1147. 

In our ongoing study on the plant extracts and their pure compounds from Turkish medicinal plants, we have so far screened a number of plant extracts and pure components for their antimicrobial and antiviral activities. In this chapter, we intend to cover the recent results obtained from our antimicrobial and antiviral studies on heterocyclic compounds isolated from several Turkish medicinal plants and marine organisms. 

A wide variety of natural toxins, from small heterocyclic molecules to large proteins, occurs in marine organisms. The phyletic diversity of plants in the ocean is far less than on land, while the number of marine animal phyla significantly exceeds that on land. Thus, it is not surprising that many of the known marine toxins are of animal origin. In this article, we will not only focus upon the toxins of unicellular organisms and marine animals, but also consider a few seaweed toxins. 

Most alkaloids have basic properties coimected with a heterocyclic tertiary nitrogen. Notable exceptions are colchicine, caffeine, and paclitaxel. Most alkaloids are biosynthetically derived from amino acids such as phenylalanine, tyrosine, tryptophan, ornithine, and lysine. Alkaloids represent a wide variety of chemical structures. About 20000 alkaloids are known, most being isolated from plants. But alkaloids have also been found in microorganisms, marine organisms such as algae, dinoflagellates, and puffer fish, and terrestrial animals such as insects, salamanders, and toads. 

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