Environmental
biochemistry
Nature's
sunscreen from the Great Barrier Reef, Australia
W.C
Dunlap, B.E Chalker, W.M Bandaranayake and J.J Wu Won
Australian Institute of Marine Science
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Reef-building corals are
invertebrate animals having algal
symbionts which live in the
shallow-water environments of
tropical coral reefs, and are
typically exposed to high levels
of potentially damaging solar
radiation. |
Their problem is
further complicated by the
release of photosynthetic oxygen
by algal symbionts residing
within their tissues which, in
combination with high light
intensities, is a potential cause
of hyperoxic toxicity and
photooxidative stress to the
symbiosis.
Yet, these coral
animals are able to withstand long-term
exposure to physiologically damaging
wavelengths of ultraviolet (UV)
radiation.
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We have established that
a usual feature of
photoadaptation by many marine
organisms is to biosynthesize, or
diet accumulate, UV-absorbing
compounds (sunscreens) for
environmental light protection.
These are a group of compounds
known as mycosporine-like amino
acids (MAAs). Their common
feature is that they are a
simple, non-aromatic chromophore
with a high efficiency to absorb
UV light.
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Above:
Chemical structures
and properties
of several MAAs
commonly found in marine
organisms.
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Left:
Generic
structure of simple MAA
analogues.
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The unique
physico-chemical properties of these
natural sunscreens lend consideration for
use in health care applications and in
the formulation of cosmetic products.
 |
 |
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Typical
UV-absorption spectrum
of MAA
sunscreen analogues.
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Substituent
effects on the 3-alkylamino-
cyclohex-2-enone chromophore and
the development of
1-alkyl-3-alkanoyl-
1,4,5,6-tetrahydropyridines as
sunscreen candidates.
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Our first attempt was
to prepare simple derivatives of the
functional chromophore. We succeeded in
reproducing the sunscreen
characteristics, but failed to attain a
commercial product. Our simplified
analogues were hydrolytically unstable
for commercial consideration.
In collaboration with
scientists at ICI Australia Operations
Pty Ltd we investigated the means to
stabilize the enaminoketone chromophore
for commercial suitability. We
synthesized many structural derivatives
of the 3-alkylaminocyclohexenone
chromophore and the hydrolytic reactivity
was solved by reversing the cyclization
so that the enamine function is bound in
a closed, 6-membered ring. An additional
refinement was to add gem-dimethyl
substituents at the 4-position to improve
oxidative stability.
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Photograph
Courtesy of GBRMPA
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COMMERCIAL PLAN
The synthetic
development of this new sunscreen
class was conducted in
partnership with scientists at
ICI Australia. The project was
abandoned by ICI Australia in
1992 as a consequence of
corporate restructuring and sale
of its family health business
(including sunscreens) to Colgate
Palmolive. Joint intellectual
property held by ICI Australia
was subsequently released to AIMS
as sole assignee (completed June
1995).
International patents
have been examined and and are now deeded
in most countries of application.
Commercial activities
are presently being negotiated with a
Sydney-based investor group for
Australian and international markets.
Several candidates are currently being
tested for sunscreen acceptability.
For
further information contact
Email: Dr Walter C
Dunlap - AIMS Townsville
Telephone:
+61 (07)
47534365
 AIMS home page
web@aims.gov.au
Last updated - December 18, 2008
Copyright ©1996-2002 Australian
Institute of Marine Science
URL
http://www.aims.gov.au
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