Bioactive marine natural products

Bioactive marine natural products can be defined as biologically active products, both secondary metabolites as well as enzymes, lipids and heteropolysaccharides derived from marine sources. Marine natural products have been found to be an important source of drugs and drug leads. These natural products are secondary metabolites and enhance survival fitness and may serve as chemical weapons used against bacteria, fungi, viruses and small or large animals. Most of the natural products of interest to the pharmaceutical industry are secondary metabolites and several such compounds, derived from marine invertebrates, have been in clinical trials as experimental anti-cancer drugs. Recently, cytotoxic natural products have been extraxted from marine invertebrates in the cold waters around Iceland. Extracts from the starfish Ctenodiscus crispatus and from the sponge Isodyctia showed considerable cytotoxic activity. Extensive studies have been carried out on proteolytic digestive enzymes isolated from Atlantic cod. These proteinases have higher catalytic activitiy, even at very low temperatures, than mammalian enzymes. These coldadapted marine enzymes are also more temperature and acid sensitive than enzymes from conventional sources. The cold-active proteinases have many potential uses in industry, medicine and research. A large collection of psychrophilic and psychrotolerant bacterial strains have been studied. Many of these bacteria produce exoenzymes such as proteinases, lipases, amylases and other enzymes. Understanding the properties of such extracellular bacterial enzymes is important with regard to fish and fish products, since these enzymes are involved in fish spoilage.