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
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
Another red tide toxin produced by dinoflagellates is okadaic acid.
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
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;
anti-inflammatory agent and pain-killer called manolide isolated
from a marine sponge.
[photo of dogfish shark, tunicate and/or marine sponge, left side]
A marine natural product that has a wide range of uses is algin.
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.
Dimedone is a chemical obtained from sea anemones. For what
Australian scientists obtain a patent on this chemical?
This completes Natural Product Chemistry from Marine
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