Natural Product Chemistry from Marine Organisms


Have you ever seen waves crashing at night flash a green light? This greenish glow, known as bioluminescence, is light that is emitted from dinoflagellates, a type of marine plankton. Dinoflagellates possess gonyaline [click to find out more about gonyaline], a chemical that is responsible for the bioluminescence. Bioluminescence occurs when the dinoflagellates are pounded by the force of a wave breaking, or agitated by a fish or boat moving through the water. The force causes the gonyaline to undergo a chemical reaction which produces a flash of light.

Marine plants and animals produce a wide variety of chemicals. Chemicals have allowed organisms to adapt to many different habitats in the sea by providing protection against other organisms and by aiding survival in harsh conditions. Some chemicals are used in communication between organisms or for signaling when it is time to reproduce.

Scientists have isolated and studied many of these chemicals. In the past ten to twenty years, many new compounds have been discovered. Some of them have chemical properties that make them useful to humans. As research continues, many more marine chemicals may be found to have biomedical, industrial, or nutritional value. This remains an interesting and exciting area of research for scientists studying marine natural product chemistry and marine chemical ecology. Read on to explore some of the chemistry that is currently under investigation . . .

Red Tide Toxins

Extremely toxic chemicals can be produced by some marine microorganisms. This is especially noticeable when the microorganism populations grow rapidly resulting in a phenomenon called a phytoplankton bloom or a red tide. One toxic chemical associated with red tides in some parts of the world is saxitoxin (click to see molecular structure). A very dilute amount of this chemical can kill fish and other vertebrates by disrupting the nervous system. As a result, the animal cannot breathe and dies.

Another red tide toxin produced by dinoflagellates is okadaic acid. This chemical is responsible for Diarrhetic Shellfish Poisoning, a condition that can make humans very sick if they eat seafood exposed to okadaic acid from a red tide.

These and other toxins produced by marine microorganisms have been studied by chemists to find out what chemical properties make them so toxic. They can also be tested for medicinal uses. For example, okadaic acid can kill cancer cells at extremely low concentrations. Unfortunately, it is too toxic to the body in its natural form to use as a cure for cancer.

Marine Medicines

Other marine natural products that have potential medicinal value include: squalamine, an antibiotic, obtained from dogfish sharks; Didemnin B and Cephalastatin 8, both active against cancer, found in tunicates; and an anti-inflammatory agent and pain-killer called manolide isolated from a marine sponge.

[photo of dogfish shark, tunicate and/or marine sponge, left side]

Algae products

A marine natural product that has a wide range of uses is algin. This substance is harvested from giant kelp beds along the coast of southern California. You can find it in food, such as milkshakes and beer, cosmetics, or used as an industrial lubricant. Check out Kelco's web site for more information about kelp harvesting and uses. Have you eaten your algae today?

[photo of giant kelp, right side]

Process of Discovery

These exciting discoveries take years of work by chemists and marine biologists. The compounds of interest must be isolated from the organism. This is done using purification methods and analytical instruments to characterize the compound. Experiments called bioassays are run to see if the compound is biologically active against cancer cells, viruses, fungi, or bacteria. In many cases, it is not economically or environmentally feasible to harvest enough of the organism that produces a chemical to develop a drug. Therefore, scientists may try to synthesize the chemical in the laboratory. This can be very difficult if the molecular structure of the chemical is large and complicated.

Trivia:

Dimedone is a chemical obtained from sea anemones. For what purpose did Australian scientists obtain a patent on this chemical?

ANSWER!

This completes Natural Product Chemistry from Marine Organisms


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