 While
eleutherobin will have to go through years of testing to determine
its effectiveness in humans, Fenical points to it as an example
of the potential the oceans hold as a source of new pharmaceuticals.
“The ocean can contribute enormously to the cure and understanding
of human disease,” he said. “Our goal is to take advantage
of that vast resource.”
Fenical and colleague John Faulkner, also a Scripps professor of
marine chemistry, are considered pioneers of the relatively new
field of marine natural products chemistry. The field, which did
not come into its own until the 1970s, is garnering more attention
as scientists find it progressively more difficult to find new drugs
from terrestrial sources.
“Everybody
is saying, ‘We need new antibiotics, where are we going
to get them?’” |
“Everybody
is saying, ‘We need new antibiotics, where are we going to
get them?’” said Fenical. “And here is this vast
resource out there in the ocean that has been completely overlooked
despite the fact that the oceans form the majority of the surface
of Earth.”
With
so much to choose from, how do scientists know which marine organisms
to collect? The key, said Faulkner, is to look for organisms that
appear to defend themselves chemically rather than rely on the
protection of such things as shells and spines or the mobility
to run away and hide.
“There
is an inverse correlation between physical protection and chemical
protection,” said Faulkner. “So if we go out onto the
reef and we see something that looks like a large chunk of food—poorly
protected, soft-bodied, and easy to grab—and nothing is eating
it, then we assume it has chemical protection.”
The
underlying assumption is that some of the chemicals that help
protect marine organisms also may ward off disease in humans.
One of the first places scientists look for chemically defended
species are tropical reefs, where marine animals must fiercely
compete for space and nutrients.
 Faulkner’s
team of researchers, for example, often travels to such remote
places as Palau in the western Pacific to explore the island’s
reefs, mangrove-lined channels, and underwater caves in search
of new organisms. They are particularly interested in collecting
such things as sponges, tunicates, and opisthobranch molluscs
(molluscs without shells).
Immediately after each dive, Faulkner’s team sorts, numbers,
classifies, photographs, and records each specimen in field journals.
They then perform a crude screening of the organisms to determine
if they contain novel chemicals that are biologically active.
Once samples are brought back to Faulkner’s lab at Scripps,
a small portion of each specimen is extracted using an organic
solvent such as methanol. This extract is then tested in a variety
of bioassays to determine whether it is effective against bacteria,
fungi, or viruses. Other tests examine whether the agent shows
potential for inhibiting inflammation or cancer-cell growth.
If an extract shows desired activity, the remainder of the sample
is extracted and separated into its component chemicals, which
are again put through a battery of tests to determine their potential
against disease. These chemicals are then identified using a nuclear
magnetic resonance spectrometer that gives scientists information
about a chemical’s physical structure.
|
